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      11-05-2008, 04:53 AM   #67
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Originally Posted by exdos View Post
I don't see how GPS monitoring can give you figures for Volumetric Efficiency, and that's the REAL measure of assessing air-intake mods, especially to monitor ram air-intake systems.


But how can you replicate the ram effect on a static dyno unless you also replicate the movement of air over the car at the commensurate wheel speed? As you've said previously, you would require a wind tunnel to do this on a dyno like the F1 teams use, and this is not feasible. However, there is a very simple and much cheaper way of assessing ram pressure increases, and that is to actually measure the parameters that you need to calculate Volumetric Efficiency using a datalogger connected to the car's ECU whilst driving in "real world" conditions, which aren't just the replication of the environment which creates ram pressure, but IS the very environment in which your car operates. What more could you ask for? My DashDynoSPD cost me about $350, and for that one off payment I can do unlimited dyno runs for evermore, and I also get unlimited access to a free "wind tunnel" as well all the actual data I need to accurately compute Volumetric Efficiency in "real world" on-the-road conditions and a host of other useful data. Why mess around with static dynos?
GPS clearly won't give you volumetric efficiency, but you can extrapolate from the numbers that there is a difference in power can't you? Which is what it all boils down to.

I think there are many more things that can be done to get more accuracy but we are talking about a hundred dollar part here. The dyno is a great place to get an idea. Not to mention tuning is going to be done on the dyno. Most parts are tuned on the dyno, you can't drive around with body panels hanging off, open mufflers, hood opened, etc.
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      11-05-2008, 05:35 AM   #68
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Originally
I see your point, but not exactly...perhaps I just can't 'see' it.
If you have a straight river flowing south and you have a stream flowing into it from the east, then if the stream joins the river at an angle of less than 90 degrees, then the flow of water going south in the river will pull water from the stream into the river. Think about it, if the stream joins the river at angle of, say, 60 degrees, then there is absolutely no chance of the river back-flowing into the stream because the pressure of water upstream in the river, will force all the water in the river down the river and not into the tributary streams along its route. In the case of your air-intake, think of the river as being the air coming from the scoop in the bumper (Part 3 in the diagram of your car) and the stream being the air coming from your vent in the hood. Does this example help?

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Originally Posted by ace996 View Post
EXDOS said -"I think that you will find that, under WOT, the ram effect from the two vents (parts 2 and 3 in the diagram of your M3's air intake system) will provide less air to the engine, even in a completely sealed ram air-intake system, than your OEM air intake system will do."

ACE996 said - "that's the question...they may not...at any speed."
My S54 engine has a 3246cc engine and at the rev limit of 7600rpm, and at a Volumetric efficiency of 100% it consumes 12.33 cubic metres of air per minute. Your E90 M3 with a 3999cc engine and at the rev limit of 8400rpm and at a VE of 100% consumes 16.8 cubic metres per minute which is 36.25% more air than my S54 engine can consume. Now my air intake has just the scoop in the bumper and a secondary scoop behind the headlamp, which I see is equivalent to Parts 2 and 3 in the diagram of your air-intake.
I have done a total of seven individual mods and tweaks to my air intake and exhaust systems, all of which have individually, and collectively, helped me improve the Volumetric Efficiency at increasingly lower speeds. Now if you had to rely solely on Parts 2 and 3 to provide 16.8 cubic metres of air per minute, then I would suggest that you will not see a VE of anything near 100% until very high speeds. However, with your additional third intake, Part 1, your engine is able to obtain the necessary air to achieve 100%VE at realistic useful road speeds.

I am sure that if I were to cut a hole in my MC's hood and provide an additional intake to my air-filter box, to make my MC's air-intake system function similar to yours, that I would see a considerable improvement in VE at lower speeds in addition to those I've already achieved with my present 7 tweaks/mods.

Take a look at the photo below, it shows the rain marks on the bonnet of my car after I'd made a high-speed motorway journey (Germany). These marks clearly demonstrate the flow of air over the hood of my car. Notice how the lines seem to come closer together and concentrate in the region on the hood where your M3's hood vent is located. This concentration occurs on both left and right sides of the hood. In view of the fact that the pressure of air towards the rear of the hood is at positive pressure on a moving car, then it seems obvious to me, that your bonnet vent is perfectly positioned to provide the additional air required to supplement the air-intakes from Parts 2 and 3. I'm afraid that I just can't bring myself to cut a hole in my bonnet to allow my engine to benefit from this additional source of air, purely for aesthetic reasons.




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Originally Posted by ace996 View Post
pressure sensor would do it, too
Using pressure sensors will give you the picture of what is going on inside the air-intake system, and would be extremely useful and interesting to see, but they will not give you the figures for Volumetric Efficiency. Ideally they would be part of a bigger test rig which would give you time-stamped data that could be viewed alongside air-flow measurements and rpm etc. For me, the ultimate measurement in assessing mods to air-intakes and engine performance improvements/losses is Volumetric Efficiency.

If your car is parked outside in a thunderstorm, where does the rain water go that falls into the hood vent?
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      11-05-2008, 06:20 AM   #69
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GPS clearly won't give you volumetric efficiency, but you can extrapolate from the numbers that there is a difference in power can't you? Which is what it all boils down to.
That's rather a roundabout way of doing something which you can do easily in a more direct way. Also, unless you are using a perfectly level and smooth road on a perfectly windless day then your calculations for power output will contain errors, whereas, the figure for VE gives you the efficiency of engine breathing in all conditions, and that's where your engine power comes from.


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I think there are many more things that can be done to get more accuracy but we are talking about a hundred dollar part here. The dyno is a great place to get an idea. Not to mention tuning is going to be done on the dyno. Most parts are tuned on the dyno, you can't drive around with body panels hanging off, open mufflers, hood opened, etc.
I've always been a huge fan of the OEM air-intake system on my MC, because I can see that it harnesses ram-effect. BUT, I could always see ways to improve the system and I've already identified at least 7 ways that the MC's OEM air-intake could be improved, and I've performed those mods and obtained very significant gains (circa 15% power increase). Not all of my ideas have been successful but I've only been able to determine which work and which don't from the data-logging. Clearly, BMW engineers have also thought that ram air-intake systems have merit and they have used this design on all it's M cars that have come along since the S50 MC was built in 1998, and each successive M car has a more improved and refined ram air-intake system, and your M3's intake is an improvement on what I have in my MC. It's the details in the system which makes all the difference to performance. I've owned my MC for more than 5 years now and I participate on a MC internet forum, and it never ceases to amaze me the number of owners who want to ditch the MC's OEM air-intake system and replace it with what they call a "Cold Air Intake" (CAI) - I'm sure that you know all about these things. Someone has recently produced such a CAI for the S54 MC and here is a photograph of it:



They have also gone to the trouble of getting the car dynoed with the CAI fitted and they use the graph below to prove that this CAI is producing gains:




In an earlier posting in this thread, I wrote: " Air starvation on many dynos, particularly with BMW's with ram-effect air intakes, occurs because the fans placed in front of the car on the static dyno, do NOT replicate the flow (pressure) of air passing in front of the car in "real world" on-the-road conditions, therefore, an engine with a ram-air intake system cannot replicate its true performance."
And YOU seem to agree with me on this because you have written: "A dyno fan will never replicate air flow at real world speeds, certainly not at 85 mph and up as who other than a Formula 1 team has access to that kind of wind tunnel?"
The CAI in the photo above with "proven" gains claimed, as demonstrated by the dyno plot, will NOT repeat NOT show an improvement over the OEM air intake in real world conditions. Static dynos produce artefacts when used with ram air-intakes. A datalogger can be bought for less than they are selling the CAI in the photo above. Static Dynos without suitable fans are useless for testing cars equipped with genuine ram air-intakes. I wonder why your M3 hasn't been fitted with a CAI like the one being sold for my MC?
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      11-05-2008, 06:32 AM   #70
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That's rather a roundabout way of doing something which you can do easily in a more direct way. Also, unless you are using a perfectly level and smooth road on a perfectly windless day then your calculations for power output will contain errors, whereas, the figure for VE gives you the efficiency of engine breathing in all conditions, and that's where your engine power comes from.




I've always been a huge fan of the OEM air-intake system on my MC, because I can see that it harnesses ram-effect. BUT, I could always see ways to improve the system and I've already identified at least 7 ways that the MC's OEM air-intake could be improved, and I've performed those mods and obtained very significant gains (circa 15% power increase). Not all of my ideas have been successful but I've only been able to determine which work and which don't from the data-logging. Clearly, BMW engineers have also thought that ram air-intake systems have merit and they have used this design on all it's M cars that have come along since the S50 MC was built in 1998, and each successive M car has a more improved and refined ram air-intake system, and your M3's intake is an improvement on what I have in my MC. It's the details in the system which makes all the difference to performance. I've owned my MC for more than 5 years now and I participate on a MC internet forum, and it never ceases to amaze me the number of owners who want to ditch the MC's OEM air-intake system and replace it with what they call a "Cold Air Intake" (CAI) - I'm sure that you know all about these things. Someone has recently produced such a CAI for the S54 MC and here is a photograph of it:



They have also gone to the trouble of getting the car dynoed with the CAI fitted and they use the graph below to prove that this CAI is producing gains:




In an earlier posting in this thread, I wrote: " Air starvation on many dynos, particularly with BMW's with ram-effect air intakes, occurs because the fans placed in front of the car on the static dyno, do NOT replicate the flow (pressure) of air passing in front of the car in "real world" on-the-road conditions, therefore, an engine with a ram-air intake system cannot replicate its true performance."
And YOU seem to agree with me on this because you have written: "A dyno fan will never replicate air flow at real world speeds, certainly not at 85 mph and up as who other than a Formula 1 team has access to that kind of wind tunnel?"
The CAI in the photo above with "proven" gains claimed, as demonstrated by the dyno plot, will NOT repeat NOT show an improvement over the OEM air intake in real world conditions. Static dynos produce artefacts when used with ram air-intakes. A datalogger can be bought for less than they are selling the CAI in the photo above. Static Dynos without suitable fans are useless for testing cars equipped with genuine ram air-intakes. I wonder why your M3 hasn't been fitted with a CAI like the one being sold for my MC?
As I think you have indicated there are many variables. There are ways to cheat the dyno, we all know that. Whether you lower tire pressure, reset the ecu, move the fan, don't give a cool down, these all affect it.

The reason I give credit to someone like RPI is because of the way they dyno and test. The same reason I believe Active Autowerke and Evosport when they post numbers. They simply have too much at stake to inflate numbers to where they can't be reproduced. These companies have spent decades in some cases building their reputation.

I believe items like the RPI scoops make far greater gains in the real world than they do on the dyno.

As for your comment regarding the GPS and incline, the newer boxes give you the % of incline or of the decline. You will know exactly where you stand. I believe the GPS is the easiest and quickest way to see the acceleration difference. No, I won't have volumetric efficiency and exact air flow numbers, but I don't have those now, and what I am primarily concerned with is the acceleration numbers (differs for each person and their goal with the car.)

Like I said, combine all sources ideally. I'm sure even dataloggers have variables that influence them.

I would like to see where you believe you increased efficiency, some things could potentially carry over to the E92. It would at least be valuable to see.
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      11-05-2008, 07:43 AM   #71
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As I think you have indicated there are many variables. There are ways to cheat the dyno, we all know that. Whether you lower tire pressure, reset the ecu, move the fan, don't give a cool down, these all affect it.

The reason I give credit to someone like RPI is because of the way they dyno and test. The same reason I believe Active Autowerke and Evosport when they post numbers. They simply have too much at stake to inflate numbers to where they can't be reproduced. These companies have spent decades in some cases building their reputation.

I believe items like the RPI scoops make far greater gains in the real world than they do on the dyno.

As for your comment regarding the GPS and incline, the newer boxes give you the % of incline or of the decline. You will know exactly where you stand. I believe the GPS is the easiest and quickest way to see the acceleration difference. No, I won't have volumetric efficiency and exact air flow numbers, but I don't have those now, and what I am primarily concerned with is the acceleration numbers (differs for each person and their goal with the car.)

Like I said, combine all sources ideally. I'm sure even dataloggers have variables that influence them.

I would like to see where you believe you increased efficiency, some things could potentially carry over to the E92. It would at least be valuable to see.
I'm not even attempting to suggest that dyno operators are deliberately manipulating the results obtained on dynos. What I am saying is that static dynos will produce artefacts (inaccurate results) with genuine ram air-intakes unless used with appropriate variable speed fans which replicate the same air speed passing over the car as the wheel speed of the car. This is not a factor when data logging on the road.

I find it bizarre that most dyno operators give their results as "at the flywheel" figures when they actually record "at the wheels". Why not give the figures they actually accurately record? Likewise, whatever percentage they add to the "at the wheels" figure to give their "at the flywheel" values cannot be a fixed percentage to add to all cars of the same model, and even to the same vehicle with genuine engine performance improvements. For example: a OEM MC produces 325bhp "at the flywheel" and 275bhp "at the wheels" on a dyno: this represents an 18.18% increase on the "at the wheels" value. After modding my MC's air/exhaust system my car now consistently produces 321bhp at the wheels, as recorded by my datalogger, so if I add 18.18% to 321bhp, I get an "at the flywheel" value of 379.35bhp, whereas if I assume that the losses are still the same, then I should only add 50bhp to 321bhp to give 371bhp. As you can see, there's a difference of 8.35bhp (2.25%) between the two figures. Which is correct?

Again, the figures produced on dynos are generally variable upon the weather conditions at the time of the dyno run, yet many dyno operators don't attempt to standardise their results to account for altitude, barometric pressure, temperature, and humidity, and this means that dyno results, even for the same car tested on different days on the same dyno are not comparable. Whereas the results produced by my datalogger are standardised for altitude, barometric pressure, temperature, and humidity and give the "at the wheel" figure, so that someone testing a car in Mexico can produce the same standardised result that I can produce at an elevation of 100feet in cold and wet UK, so that we can accurately compare results.

Therefore if you acknowledge that a few percent here, and a few percent there, in all the potential errors that can creep into static dyno testing, as I see, then whilst you are attempting to be objective and scientific in using static dynos there are still too many possible flaws to make them as reliable as "on the road" dataloggers which use the cars ECU for their data. For me, it's a no brainer which is the most accurate method.


As for the mods to my MC that can be carried over: it seems to me that I've been unknowingly working in parallel to BMW and some of my mods have also been incorporated into later BMW's M car air intake designs. For example, the scoop in my MC's bumper is called a "brake duct" and is a straight-through funnel with a snorkel into it from the air-filter box. I discovered by taking temperature readings of my brakes, that this duct doesn't actually have any effect on brake cooling, so I decided to make a small blanking plate to almost completely block the back of the duct to make it into a genuine scoop for the air intake. I found that this increased the ram pressure inside the air-intake so that I got the same ram pressure inside my air-filter box at approximately 10mph lower than when OEM without the blanking. The first time I looked inside a Z4 MC's brake duct in late 2006, I was expecting to see a straight-through brake duct like on my MC, but in fact, there was a partial blank at the back of the Z4 MC's brake duct like mine - it's even an additional part fixed to the duct like mine, rather than a one-piece scoop.

I started modding my air-intake system when I saw that the inside of the air-filter box contained a trumpet which makes the air take an "S" shaped route inside the box before it passes through the filter (reverse-flow silencing). I cut this off so that the air can pass directly through the filter by the shortest route.

I've found the most successful mod of all though has been the gutting of the OEM silencers to remove the "reverse-flow" and make them "free-flow". This mod has allowed all my additional mods to the air-intake (pre-throttle) work better. My engine now feels so "light" and willing to pull throughout the entire rev range.

I've added an additional air intake duct into the system, so that I've now got three air intakes and not just the OEM two ducts. If you think that each of the mods might only add about 2% performance gain, since I presently have a total of seven mods to the system, you can see how I've obtained a 15% increase in power. If you think that a static dyno might have an error of around 2%, then it would be possible to miss every single one of those mods, whereas the VE can spot them all.

Hope this helps.
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      11-05-2008, 11:57 AM   #72
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,,,
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If you have a straight river flowing south and you have a stream flowing into it from the east, then if the stream joins the river at an angle of less than 90 degrees, then the flow of water going south in the river will pull water from the stream into the river. Think about it, if the stream joins the river at angle of, say, 60 degrees, then there is absolutely no chance of the river back-flowing into the stream because the pressure of water upstream in the river, will force all the water in the river down the river and not into the tributary streams along its route. In the case of your air-intake, think of the river as being the air coming from the scoop in the bumper (Part 3 in the diagram of your car) and the stream being the air coming from your vent in the hood. Does this example help?
-well, yes, but in our case the rivers are sealed and they lead to a lake...they don't "t-off" with one another which would have a scavenging/venturi effect...I understand your point I just don't think that exact situation is happening in the box.
Either way, I do appreciate you putting in the time...your posts contribute a great deal and bring another perspective on this issue.



My S54 engine has a 3246cc engine and at the rev limit of 7600rpm, and at a Volumetric efficiency of 100% it consumes 12.33 cubic metres of air per minute. Your E90 M3 with a 3999cc engine and at the rev limit of 8400rpm and at a VE of 100% consumes 16.8 cubic metres per minute which is 36.25% more air than my S54 engine can consume. Now my air intake has just the scoop in the bumper and a secondary scoop behind the headlamp, which I see is equivalent to Parts 2 and 3 in the diagram of your air-intake.
I have done a total of seven individual mods and tweaks to my air intake and exhaust systems, all of which have individually, and collectively, helped me improve the Volumetric Efficiency at increasingly lower speeds. Now if you had to rely solely on Parts 2 and 3 to provide 16.8 cubic metres of air per minute, then I would suggest that you will not see a VE of anything near 100% until very high speeds. However, with your additional third intake, Part 1, your engine is able to obtain the necessary air to achieve 100%VE at realistic useful road speeds. -yes... 'at what speed' does it happen is the answer to sealing the hood vent for good. If it's100mph, then that's not really worth doing...

I am sure that if I were to cut a hole in my MC's hood and provide an additional intake to my air-filter box, to make my MC's air-intake system function similar to yours, that I would see a considerable improvement in VE at lower speeds in addition to those I've already achieved with my present 7 tweaks/mods.yes, it effectively makes it an 'open' airbox but with only cold-air feeding it. LIke those cone filters people change their OEM airboxes forthat sit in the engine bay without a box...except in this example...you'd have that heat-shielding box.

Take a look at the photo below, it shows the rain marks on the bonnet of my car after I'd made a high-speed motorway journey (Germany). These marks clearly demonstrate the flow of air over the hood of my car. Notice how the lines seem to come closer together and concentrate in the region on the hood where your M3's hood vent is located. This concentration occurs on both left and right sides of the hood. In view of the fact that the pressure of air towards the rear of the hood is at positive pressure on a moving car, then it seems obvious to me, that your bonnet vent is perfectly positioned to provide the additional air required to supplement the air-intakes from Parts 2 and 3. I'm afraid that I just can't bring myself to cut a hole in my bonnet to allow my engine to benefit from this additional source of air, purely for aesthetic reasons.


if the pressure zone at that point is less than what is present inside the airbox(the pressure fed from the front two inlets), then air will come out of that vent. I notice this with rain/water/leaves whilst cruising.
I do not think that zone/vent is allowing any positive pressure to be added to the airbox, on the contrary, I think it acts as a true vent...allowing pressure to be released out the box. Why else would rain fly out of the box or leaves poke out through the mest on the vent when drivng?




If your car is parked outside in a thunderstorm, where does the rain water go that falls into the hood vent?
It is either the fog-light inlet or small holes in the bottom of the box..like other cars. I'll have to take the top of the box off to be certain.
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      11-05-2008, 12:07 PM   #73
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Originally Posted by exdos View Post

As for the mods to my MC that can be carried over: it seems to me that I've been unknowingly working in parallel to BMW and some of my mods have also been incorporated into later BMW's M car air intake designs. For example, the scoop in my MC's bumper is called a "brake duct" and is a straight-through funnel with a snorkel into it from the air-filter box. I discovered by taking temperature readings of my brakes, that this duct doesn't actually have any effect on brake cooling, so I decided to make a small blanking plate to almost completely block the back of the duct to make it into a genuine scoop for the air intake. I found that this increased the ram pressure inside the air-intake so that I got the same ram pressure inside my air-filter box at approximately 10mph lower than when OEM without the blanking.
So you plugged a leak in your intake system and made your ram-effect more efficient...that's what I would like to do. Increasing the amount of air that is forced into the box is not going to make as much of a difference if there is a hole in it. It's like filling that tub with two drains(air manifold and the hood vent)...block one and the water will fill up faster, just like it did when you blocked the brake-duct exit.
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      11-05-2008, 01:23 PM   #74
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Looking at the diagram of the M3's air intake as posted by Swamp2, ALL the air intakes are sited in zones of positive pressure on a moving vehicle. See this article here: http://www.autospeed.com/cms/A_2162/article.html

I think this may have answered a big question many of us have had and still seems to be overlooked (in that no one replied to this yet)
. The intake on the front bumper cover being at positive pressure is obvious. The fact that the pressure changes signs ALONG the hood going from - to + is the big surprise I think none of us realized. From my perspective I always guessed the hood intake was at a negative pressure from a simplisitic Bernouillis equation argument (high speed = low pressure). I would be very curious to know if this is a function of speed (perhaps + at some speeds and - at others). The next question is not just the absolute pressure on the hood, but the pressure differential between hood locations and the inside of the airbox. This is what really governs flow into or flow out of the box. If the M3s hood intake is indeed always under positive relative pressure this answers many questions. Unfortunately, some who have observed the situation report that there is an outward flow from this location (don't recall which speeds, but I think many). They noticed this from either debris or using a thread. This seems to be contradictory.
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      11-05-2008, 04:01 PM   #75
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-well, yes, but in our case the rivers are sealed and they lead to a lake...they don't "t-off" with one another which would have a scavenging/venturi effect...I understand your point I just don't think that exact situation is happening in the box.
Take another look at Part 4 in the diagram of your air intake, the arrows certainly suggest that all the inlets from Parts 1,2 and 3 are directed towards the engine. To me that suggests that they "T-into" a single confluence, and NOT "t-off" each other, if you see the difference in my semantics. To me, "t-ing into" suggests coming together, whereas t-ing off" suggests splitting apart. Likewise the confluence of the ducts from Parts 1,2 and 3 do not meet in a "lake" (i.e. still water/air): when your engine is turning, air inside Part 4 will always be moving. When the throttle is at minimal opening and when there is positive ram pressure in the air intake system, this will be like sluice gates being rapidly shut to the flow of air towards the engine, which will result in a "damming" of the flow causing the air to overflow out of the system when the pressure at any of the three sources is exceeded.

If I owned you car, I would have had that intake in pieces by now, so that I knew for sure exactly how it functions. Can I suggest that you draw a little schematic diagram of the function of Parts 1-4 so that you can work out exactly how they all integrated into one single air-intake system in ALL scenarios.

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If the pressure zone at that point is less than what is present inside the airbox(the pressure fed from the front two inlets), then air will come out of that vent.

That's not correct. If the engine is operating at less than 100% VE under WOT, then it will take air from whatever source it can get it, including the hood vent. Likewise, you will find that under WOT the pressure of the air inside the air-intake system will always be at a pressure which is below the pressure at the mouths of all three intakes, with or without ram pressure, because, after all, the engine is an air pump. May I suggest that you experiment with a domestic vacuum cleaner and a Magnehlic pressure gauge placed around and inside the tip of the hose to form a mental picture of the differences in air pressure that occur when air is being sucked into a pipe by an air pump i.e vacuum cleaner/M3 engine.


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Originally Posted by ace996 View Post
I do not think that zone/vent is allowing any positive pressure to be added to the airbox, on the contrary, I think it acts as a true vent...allowing pressure to be released out the box. Why else would rain fly out of the box or leaves poke out through the mest on the vent when driving?

On my vacuum cleaner, there is a little sliding vent on the solid connector to which the flexible pipe and the solid pipe for the end fittings attach, which can be opened to reduce the suction from the end of the pipe; I have yet to see anything blow out of this vent when opened, because the flow of air through the solid pipe from the suction tip towards the vacuum cleaner produces a "venturi effect" which always sucks air into the vacuum cleaner. I bet you NEVER see rain or leaves fly out of the hood vent under WOT.
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      11-05-2008, 04:15 PM   #76
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Originally Posted by swamp2 View Post

I think this may have answered a big question many of us have had and still seems to be overlooked (in that no one replied to this yet)
. The intake on the front bumper cover being at positive pressure is obvious. The fact that the pressure changes signs ALONG the hood going from - to + is the big surprise I think none of us realized. From my perspective I always guessed the hood intake was at a negative pressure from a simplisitic Bernouillis equation argument (high speed = low pressure). I would be very curious to know if this is a function of speed (perhaps + at some speeds and - at others).
You will find that the pressure differentials along the length of the hood will always be relatively the same: i.e -ve pressure at the front and slightly +ve towards the windshield. As the speed increases, the pressure at the front of the hood will become more -ve and the pressure towards the windshield will become more +ve. Motor manufacturers have known this for ages and that's the reason why the air-intakes for the cabin venting are located at the end of the bonnet/base of windshield.

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Originally Posted by swamp2 View Post
The next question is not just the absolute pressure on the hood, but the pressure differential between hood locations and the inside of the airbox. This is what really governs flow into or flow out of the box. If the M3s hood intake is indeed always under positive relative pressure this answers many questions. Unfortunately, some who have observed the situation report that there is an outward flow from this location (don't recall which speeds, but I think many). They noticed this from either debris or using a thread. This seems to be contradictory.
As I've described in my posting to Ace996 above, I bet this doesn't happen under WOT at any speed.
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      11-05-2008, 05:10 PM   #77
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Originally Posted by ace996 View Post
So you plugged a leak in your intake system and made your ram-effect more efficient...that's what I would like to do. Increasing the amount of air that is forced into the box is not going to make as much of a difference if there is a hole in it. It's like filling that tub with two drains(air manifold and the hood vent)...block one and the water will fill up faster, just like it did when you blocked the brake-duct exit.
No, you're wrong. The MC's OEM air intake doesn't have the leak you are suggesting. The OEM brake duct on my MC is NOT actually a scoop for the air intake system, it merely acts as a source of cold air into which the snorkel from the air-filter box is attached. However, I have converted it into a scoop for the air-intake system by almost completely blocking it off, this has increased the pressure inside the "scoop" over what it was when it was a "brake duct". The second air intake is behind the headlamp and this is VERY leaky and is not sealed at all. If you block the mouth of this second air intake, then the MC loses power BIG TIME at WOT.

The photo below shows what I have done.



It appears to me that you have the idea that some of the air entering your intake system through the air scoop, Part 3, when the engine is working at WOT will exit out through the air intake/vent Part 1. This just won't happen. Even if the engine is operating at a VE of, say, 110%, the pressure inside the air intake system just in front of the throttle isn't going to be at a static pressure of much above ambient air pressure, but for your engine to be operating at a VE of more than 100%, then that will only occur due to ram effect as a consequence of your car moving at sufficient forwards velocity to produce a sufficiently high positive dynamic pressure at the openings of Parts 1,2 and 3. Your engine, being an air pump, will always be at the lowest pressure point relative to the pressures at the openings of Parts 1,2 and 3 when the engine is working at WOT. Yes, the air pressure above Part 1 will be lower than Parts 2 and 3, but at WOT it will always be above the pressure immediately in front of the throttles. Remember your engine is a normally aspirating (= sucking) air pump and this creates relative negative pressure to draw air inside it.

Think about this: if your bath taps had hose pipes connected to them so that the water leaving the hose pipes was below the level of the overflow drain in the bath, do you think that the water would stop flowing out of the pipes as soon as the water level covered the ends of the hose pipes and that this would stop the bath from filling further? If not, why does this arrangement not stop the taps from running, even if the hot tap was only flowing at half the rate as the cold tap?
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      11-05-2008, 05:26 PM   #78
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Originally Posted by exdos View Post
On my vacuum cleaner, there is a little sliding vent on the solid connector to which the flexible pipe and the solid pipe for the end fittings attach, which can be opened to reduce the suction from the end of the pipe; I have yet to see anything blow out of this vent when opened, because the flow of air through the solid pipe from the suction tip towards the vacuum cleaner produces a "venturi effect" which always sucks air into the vacuum cleaner. I bet you NEVER see rain or leaves fly out of the hood vent under WOT.
That's what's undetermined. Actually, one poster said that with strings he saw the hood vent reverse flow at WOT...I believe this was on a track...so, yes, our (the forum members) experiences seem to lead to that fact.

To addressyour vacuum cleaner example, you would never get debris/dust to fly out of that vent because you have nothing forcing the air "in" the tube. It is being sucked. Now, an extreme example, if you took a leaf-blower and put it in front of your vacuum's hose...you may just see debris fly out of tht vent.

My question, which hasn't really been answered ...other than someone's string...is "do the intakes in front push enough air into the airbox, at WOT, to still allow a positive, ram-air effect with the hood-vent closed"?
I need to place a pressure sensor inside that tube and go WOT at various speeds and see if there is significant drop-off of pressure.

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Originally Posted by swamp2 View Post

I think this may have answered a big question many of us have had and still seems to be overlooked (in that no one replied to this yet)
. The intake on the front bumper cover being at positive pressure is obvious. The fact that the pressure changes signs ALONG the hood going from - to + is the big surprise I think none of us realized. From my perspective I always guessed the hood intake was at a negative pressure from a simplisitic Bernouillis equation argument (high speed = low pressure). I would be very curious to know if this is a function of speed (perhaps + at some speeds and - at others). The next question is not just the absolute pressure on the hood, but the pressure differential between hood locations and the inside of the airbox. This is what really governs flow into or flow out of the box. If the M3s hood intake is indeed always under positive relative pressure this answers many questions. Unfortunately, some who have observed the situation report that there is an outward flow from this location (don't recall which speeds, but I think many). They noticed this from either debris or using a thread. This seems to be contradictory.
Without testingequipment, I can only surmise that the pressure gradient is not enough at our vents to cause meaningful positive pressure. Back at the windshield...yes, that's why "cowl-induction" was so popular with the muscle-cars of past...but I believe, and the flying rain drops agree, that we do not have sufficient pressure on the outside of our hoodto allow any meaningful amount of ram-pressure to be contained in the airbox.
But, as we have all been saying, we don't have the proper data to support either position.
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      11-05-2008, 06:04 PM   #79
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Originally Posted by exdos View Post
No, you're wrong. I have a knack for that but not exactly...I agree with you, I just didn't phrase it well enough.The MC's OEM air intake doesn't have the leak you are suggesting. right, you in effect "added" a higher-pressure source of air for the intake, by blocking off the "brake-duct" portion of the "brake-duct". Yes...I'm with you.The OEM brake duct on my MC is NOT actually a scoop for the air intake system, it merely acts as a source of cold air into which the snorkel from the air-filter box is attached. However, I have converted it into a scoop for the air-intake system by almost completely blocking it off, this has increased the pressure inside the "scoop" over what it was when it was a "brake duct". The second air intake is behind the headlamp and this is VERY leaky and is not sealed at all. If you block the mouth of this second air intake, then the MC loses power BIG TIME at WOT.

The photo below shows what I have done.-that's cool man, good job.

It appears to me that you have the idea that some of the air entering your intake system through the air scoop, Part 3, when the engine is working at WOT will exit out through the air intake/vent Part 1.That is exactly what happens at anyhing under WOT...at WOT, I don't know without taking pressure readings. Again, if the air being forced in from locations 2 and 3 isgreater than the engine's draw, there will be spillage out of #1.
Do those two inlets provide 16.8 cubic meters per minute or more??? I don't know. I'd bet it's not, but I don't know.


Think about this: if your bath taps had hose pipes connected to them so that the water leaving the hose pipes was below the level of the overflow drain in the bath, do you think that the water would stop flowing out of the pipes as soon as the water level covered the ends of the hose pipes and that this would stop the bath from filling further? If not, why does this arrangement not stop the taps from running, even if the hot tap was only flowing at half the rate as the cold tap?
If you sealed that tub, and the pressure in the tub, with a small drain, was greater than the outlet pressure of the hot tap, then yes it would stop the water flow. IMHO, that's my impression of the airbox.
Without the pressure sensor, I can't say anthing with certainty...it's all theory now.
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      11-05-2008, 10:20 PM   #80
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Quote:
Originally Posted by ace996 View Post
So I took apart the airbox looking for some 'free' ways to increase flow. While the top of the box was off, I really considered the design and have some doubts about the efficiency of the 'ram' effect with the stock box and with the aftermarket scoops. I love the lower scoop (fog-light location) and the intake at the kidney grills, surely they will allow some 'ram' effect but the top opening...the driver's side nostril, I believe, is the problem.

My thought is that the driver's side hood nostril will let any additional ram air pressure out of the box. I don't see that opening creating any positive pressure for the intake, just another place for air to be ingested at high rpm. I really wonder if the hood nostril inlet was closed-off that airbox pressure would be higher at higher speeds.

Your thoughts?
Hi ACE,

Sincere apologies if i sound a lil stupid and have not much knowlege on the subject of RAM intakes. Using basic common sense and logic to piece my arguement together.

I reckon a RAM air system would not be a waste and i suppose its benefits would be subject to which part of the world you live.

In theory, I reckon M3s that reside in hot and humid countries along the equator line, (i.e. South East Asia, India, Africa) would benefit little from a RAM intake system during the day because of the hot air that may not aid efficient combustion, however with a RAM system would make significant differences when temperatures drop in the evening.

Based on the assumption that you live in the states, the RAM would do you some justice thoughout the seasons of the years especially during Autumn, Winter and Spring when the air masses are likely to be denser and cooler. Times like these i wish i was back living in Aus with my M. lol

Apologies if my logic makes no sense but i figured i'd give it a shot.

Hope my arguement is pretty good cos i just coughed up some money for the GRUPPE M RAM intake system for my E92 M3. Then again my car comes out mostly in the evenings and weekends.

http://gruppem.co.jp/matching/produc..._result_en.php
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      11-05-2008, 11:10 PM   #81
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If your car is parked outside in a thunderstorm, where does the rain water go that falls into the hood vent?
It drains from the same "gill-like" opening between 1 and 4.

Also, about the dyno charts. In the case of the M3, I suspect that the baseline dyno charts are being obtained with the stock intake with no flow directed at the car. If that is indeed the case, directing flow at the car with a modified intake would be misleading. The car already has a front facing intake. Whatever gains observed between the two dyno runs could simply be attributed to the functionality of the front facing intake rather than the modification (in the recent case under discussion, scoops). And, of course, as many people, including you, have been saying, it is meaningless to claim that the fan simulates any kind of meaningful real-life airflow to begin with. Airflow increases with rpms and velocity, and there must be dynamic effects in how the engine responds to that. The car/engine will NEVER experience static airflow over its rpm range in operation. The dynos prove absolutely nothing. That cannnot be how BMW has experimented with and tested its intake designs. They must have instrumented the car and driven it around in various conditions. That is the only way to understand what is going on. The rest is false science/rubbish.

At the end of the day, BMW engineers have been thinking about all this much more than any one of us have been, and they are more qualified--meaning they have fluid dynamics experts working on the problem. I have an understanding of fluid dynamics, but I am not an expert. I doubt that any of the posters on these threads are either. The point is, on a recent M car like the E9X, the only way one will achieve gains over the stock setup if one manages to identify and undo a trade-off that has been done by BMW engineers such as noise reduction. That is actually pretty much the basis of almost all engine modification for this car; to identify and undo the design trade-offs that have been made in the stock setup.
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      11-06-2008, 12:23 AM   #82
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At the end of the day, BMW engineers have been thinking about all this much more than any one of us have been, and they are more qualified--meaning they have fluid dynamics experts working on the problem.
Yup. And nowadays it is almost all done with a computer using CFD (computational fluid dynamics), which of course is its own area requiring significant subject expertise to insure you don't have garbage in, garbage out.
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      11-06-2008, 04:42 AM   #83
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Originally Posted by ace996 View Post
To addressyour vacuum cleaner example, you would never get debris/dust to fly out of that vent because you have nothing forcing the air "in" the tube. It is being sucked. Now, an extreme example, if you took a leaf-blower and put it in front of your vacuum's hose...you may just see debris fly out of tht vent.

My question, which hasn't really been answered ...other than someone's string...is "do the intakes in front push enough air into the airbox, at WOT, to still allow a positive, ram-air effect with the hood-vent closed"?
I need to place a pressure sensor inside that tube and go WOT at various speeds and see if there is significant drop-off of pressure.

I've previously referred to an article here: http://www.autospeed.com/cms/A_2162/article.html where the photograph below is found. In this photograph it shows the pressures on the bonnet of that vehicle recorded at 50mph (80km/hr).



As the photograph suggests, the hood vent on your M3 will be positioned in a region which might experience a +ve pressure at 50mph of around +0.4 to +0.5 inches of water.

I've previously posted the graph below showing the increase in pressure versus forwards velocity, and it's below.



As you can see the theoretical maximum attainable ram pressure at 50mph would be around +1.3 inches of water, therefore, it can be deduced that the pressure on the hood in the position of your vent Part 1, is at approximately 1 inch of water less pressure than the theoretical maximum ram pressure, BUT it is still at a pressure greater than ambient pressure.

I have previously posted the graph below, which shows the change in volumetric efficiency of my car that occurs related to vehicle speed.



This graph shows that with all my air-intake mods, my car now achieves 100% VE at WOT at around a speed of 60mph, when the theoretical maximum ram pressure will be at +2 inches of water pressure. Therefore, using all the above information and my deductions, it suggests to me, at least, that on my car, when the air intake system can provide a constant supply of air at +2 inches of ram pressure, then the pressure of air inside the air intake system, at the position of the throttle, will be at ambient pressure. As such, at WOT, the pressure inside my air intake system will ALWAYS be at a lower pressure than the ram pressure at the source of a front scoop (Part 3) which will be at around +2 inches of water pressure and ALWAYS be at a lower pressure than the pressure above the hood vent (Part 1) which will be at a pressure of more than + 0.5 inches of water. As such, assuming your M3 can achieve the same VE figures as my MC does, as I see it, your M3 air intake system is completely self-regulating: Part 1 acts as an air-intake under WOT and a vent at lower throttle openings, and therefore it doesn't need a flap at all to operate. The M3's air intake design is ELEGANT.
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      11-06-2008, 04:48 AM   #84
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At the end of the day, BMW engineers have been thinking about all this much more than any one of us have been, and they are more qualified--meaning they have fluid dynamics experts working on the problem. I have an understanding of fluid dynamics, but I am not an expert. I doubt that any of the posters on these threads are either. The point is, on a recent M car like the E9X, the only way one will achieve gains over the stock setup if one manages to identify and undo a trade-off that has been done by BMW engineers such as noise reduction. That is actually pretty much the basis of almost all engine modification for this car; to identify and undo the design trade-offs that have been made in the stock setup.
+1. It's hard sometimes to figure what the BMW engineers did sacrifice considering this is an M3 and not the standard 3 series.
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      11-06-2008, 04:56 AM   #85
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Originally Posted by Mischievous M View Post
In theory, I reckon M3s that reside in hot and humid countries along the equator line, (i.e. South East Asia, India, Africa) would benefit little from a RAM intake system during the day because of the hot air that may not aid efficient combustion, however with a RAM system would make significant differences when temperatures drop in the evening.

Apologies if my logic makes no sense but i figured i'd give it a shot.
Now how does that work?????????

Your car has to function in whatever environment in which it finds itself. If it happens to be in a hot and humid country, where the ambient temperature is, say, 35 degrees C and at 100% humidity, then that IS the coldest and dryest air the car can intake without any elaborate air conditioning. FACT.

Sure, a car engine in such an environment will perform better at night when the air temperature drops, but that's down to the environment change and not the car.

Quote:
Originally Posted by Mischievous M View Post
Hope my arguement is pretty good cos i just coughed up some money for the GRUPPE M RAM intake system for my E92 M3. Then again my car comes out mostly in the evenings and weekends.

http://gruppem.co.jp/matching/produc..._result_en.php
I hate to tell you that you have just wasted your money by ditching a wonderful OEM air-intake system for something that will rob you of even more power in a hot climate. You've obviously not been keeping up with this thread.
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      11-06-2008, 05:34 AM   #86
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It drains from the same "gill-like" opening between 1 and 4.

Also, about the dyno charts. In the case of the M3, I suspect that the baseline dyno charts are being obtained with the stock intake with no flow directed at the car. If that is indeed the case, directing flow at the car with a modified intake would be misleading. The car already has a front facing intake. Whatever gains observed between the two dyno runs could simply be attributed to the functionality of the front facing intake rather than the modification (in the recent case under discussion, scoops). And, of course, as many people, including you, have been saying, it is meaningless to claim that the fan simulates any kind of meaningful real-life airflow to begin with. Airflow increases with rpms and velocity, and there must be dynamic effects in how the engine responds to that. The car/engine will NEVER experience static airflow over its rpm range in operation. The dynos prove absolutely nothing. That cannnot be how BMW has experimented with and tested its intake designs. They must have instrumented the car and driven it around in various conditions. That is the only way to understand what is going on. The rest is false science/rubbish.

At the end of the day, BMW engineers have been thinking about all this much more than any one of us have been, and they are more qualified--meaning they have fluid dynamics experts working on the problem. I have an understanding of fluid dynamics, but I am not an expert. I doubt that any of the posters on these threads are either. The point is, on a recent M car like the E9X, the only way one will achieve gains over the stock setup if one manages to identify and undo a trade-off that has been done by BMW engineers such as noise reduction. That is actually pretty much the basis of almost all engine modification for this car; to identify and undo the design trade-offs that have been made in the stock setup.
I don't claim to be a professional engineer or have any specialist qualifications in this field. However, I have a specialist science-based degree and am able to teach myself about scientific principles which interest me. If you haven't already deduced from my postings, I am probably the Number 1 fan of the BMW air-intakes and from my data-logging and graph preparations, I am able to get my head around how these air-intakes work, because nobody at BMW will ever tell us.

I find it totally bizarre that people like Mishchievous M (and there are plenty like him) choose to ditch their OEM air-intakes for something like his new GruppeM "thing" . I notice from visiting his link to their website, that GruppeM are now describing their product as a "Ram Air System" when they do NOT utilise ram -effect at all: as I described in an earlier posting, these "things" are normally called CAIs. Obviously, a little bit of "rebranding" helps to sell them!

I have spent no more than a total of $50 (UK equivalent) on modding my air-intake/exhaust system. All my mods are essentially "tweaks" to the OEM system. You've seen the photo of my "brake duct" blocker, which converts the part into an air scoop - this cost me nothing, but permanently increases ram-pressure within the air intake system at all speeds and at all times. If I didn't understand what was going on in the sytem, then I wouldn't have worked this out.

My exhaust mod, again, cost me nothing. I was given a pair of OEM silencers by someone who was ditching them to buy an aftermarket set for $1600 (UK equivalent). I saw, not one, but two different purposes in modding a pair of rear silencers. I stripped them out and made them free-flowing, but I also resculpted them and converted them into part of a rear diffuser design that I've made, as per the photo below. I know that this diffuser works because I've measured the air pressures around the car in "real world" driving conditions and obtained dyno figures from my DashDynoSPD. I also obtained a free pair of catalytic converters for my MC which I partially stripped out, but when I looked at the data I obtained when driving the car, I actually lost performance so I had to remove them, even though a lot of work went into that project. I only keep the mods that provably work.





Likewise, fitting a pair of front flippers to my car has not only increased front downforce, but it also increases the air pressure above which directly feeds into my front brake duct/air scoop. So I've obtained more ram pressure and consequently more engine power.

I don't claim any expertise in this field, but by properly measuring, monitoring and logging, I know what works and what doesn't because I've got the figures to prove it to myself.
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      11-06-2008, 05:44 AM   #87
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Now how does that work?????????

Your car has to function in whatever environment in which it finds itself. If it happens to be in a hot and humid country, where the ambient temperature is, say, 35 degrees C and at 100% humidity, then that IS the coldest and dryest air the car can intake without any elaborate air conditioning. FACT.

Sure, a car engine in such an environment will perform better at night when the air temperature drops, but that's down to the environment change and not the car.



I hate to tell you that you have just wasted your money by ditching a wonderful OEM air-intake system for something that will rob you of even more power in a hot climate. You've obviously not been keeping up with this thread.
Mate,

Thanks for the clarification on the facts so I guess i need to jump across to Plan B which is to sell off the RAM intake system to my mate in Melb who is keen of the fitment to his M3 if i am not up too installing mine.

So you suppose a drop in filter would be much better choice yea?

Like i said i am pretty new to this whole concept of tuning physics and I am very happy with the opinions shared.
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      11-06-2008, 05:54 AM   #88
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So you suppose a drop in filter would be much better choice yea?
Your M3's OEM air-intake is such a wonderful design. All you need is to keep your filter clean to allow your engine to preform at its best, whereever in the world you are

I wish my MC had been fitted with one like it as standard.
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