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11-05-2008, 03:53 AM | #67 | |
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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. |
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11-05-2008, 04:35 AM | #68 | ||
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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. 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, 05:20 AM | #69 | ||
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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, 05:32 AM | #70 | |
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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, 06:43 AM | #71 | |
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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, 10:57 AM | #72 | |
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11-05-2008, 11:07 AM | #73 | |
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11-05-2008, 12:23 PM | #74 | |
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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, 03:01 PM | #75 | |||
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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. Quote:
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. Quote:
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, 03:15 PM | #76 | ||
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11-05-2008, 04:10 PM | #77 | |
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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, 04:26 PM | #78 | ||
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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. Quote:
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, 05:04 PM | #79 | |
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11-05-2008, 09:20 PM | #80 | |
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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, 10:10 PM | #81 | |
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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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11-05-2008, 11:23 PM | #82 |
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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, 03:42 AM | #83 | |
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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, 03:48 AM | #84 | |
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2009 E92 M3 | Alpine White | Black Extended | Advan RS | Turner Test Pipes | Dinan Axle-Back | OETuning | Eibach Springs | UUC SSK | VRS Front Lip | VRS Type I Diffuser | Matte Black | RPi Scoops | MS Filter | Yokohama AD08 | F1 Pinnacle Special Thanks: Gintani | OETuning | eAs |
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11-06-2008, 03:56 AM | #85 | ||
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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:
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11-06-2008, 04:34 AM | #86 | |
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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, 04:44 AM | #87 | |
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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, 04:54 AM | #88 | |
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I wish my MC had been fitted with one like it as standard. |
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