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11-04-2008, 07:09 AM | #45 | ||
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Swamp2,
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The spikes that I'm referring to are these. Take a look at the very first graph I posted, entitled: "Volumetric Efficiency of M Coupe with EXDOS Ramcharger during acceleration in 1-2-3 gears", and in the plot of "Volumetric Efficiency in percentage" (the yellow line) you will see at the start of each acceleration in all three gears, that the VE produces an upward "spike" at the start of each acceleration phase, where the VE recorded is higher than the subsequent recording whilst under acceleration. I attribute the spikes in 2nd and 3rd gear, when the car is moving, down to the fact that there is a build up of static pressure within the air intake system, due to the ram effect, from lifting off the throttle whilst changing gear. In the case of the first gear acceleration from vehicle standstill, the drop in VE after the initial start is due to there being no ram effect at the outset and the NA engine is actually creating negative pressure within the air intake system, but once the vehicle gets to around 20mph, the ram effect really starts to contribute to filling the cylinders, as shown by an increase in volumetric efficiency. In the case of my car, the VE now gets to 100% at around 60mph with my latest mod, whereas before, the car needed to be at 80mph to achieve 100%VE, and before that previous mod it was 90mph. I have done an awful lot of study and experimentation on air-intakes over the past three years with the goal of attempting to make ram-effect a useful source of free energy at ordinary road speeds. I think I'm slowly getting there. Quote:
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11-04-2008, 10:40 AM | #46 | |
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What a pleasure it is to discuss this with you. Great post, I'll explain in RED...
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Be good, TomK
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11-04-2008, 12:29 PM | #47 | |
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Like you, I also enjoy a good discussion where we can all learn form each other It's my pleasure to discuss this subject with people who appreciate that ram-effect can be harnessed at speeds much less than Mach2. I think there are essentially two main differences between a ram air-intake for a sports bike and that for a sports/performance car. To generalise: 1. most sports bikes will be driven in dry conditions, only, so the risk of ingress of water into the engine in a completely sealed air intake system is much reduced than a car which will probably be driven in all weathers, and 2. the stagnation point on the front of a car is at bumper level, whereas on a bike it is at fairing level, which is much higher, therefore the chance of picking up water by going through puddles and standing water is again much reduced in a ram air-intake on a bike. Therefore, any car which has a duct into the ram air-intake system must also have the facility of venting to allow any accidental water ingress to escape. In the case of my MC this vent is behind the headlamp and at a level lower than the air filter box, whereas in the diagram of your car the vent is in the hood. If a ram air-intake didn't have a vent before the engine then it would act like a vacuum cleaner and suck anything which could pass through the filter into the cylinders. Therefore, if you had a flap fitted to the bonnet vent then how would it allow water to escape? Looking at the diagram of your air intake, I'm sure that if you were to look inside your air intake system at Part 4, which appears to be the confluence of all the inlet pipes, you will see that the direction of all the inlets is towards the engine, so that when the throttle is open the engine is sucking air from all three inlets, irrespective of the actual pressure differences that exist at the mouths of the three different inlets. This means that the air entering Part 4 in the pipe at the highest pressure (the duct in the bumper) will cause a "Venturi effect" and pull air through the other two air intake pipes, which have their mouths in zones at lesser pressure (albeit in zones of positive pressure). Under these circumstances, the air entering the intake system at the highest pressure will have "prority of entry" into the system and it seems most unlikely that the air from the bumper will "reverse flow" to exit out of the other two air intakes. However, if the engine speed requires less than all the air that is available, i.e at part throttle and when the ram effect creates an excess (like when the bath taps are filling a bath at a great rate than the plug-hole is draining it) then the air being forced into the air intake system under dynamic ram pressure, the excess will "bleed" from the system through the inlet which is at the lowest pressure relative to the other two air intakes in the system. During "bleeding", dust, water and other detritus in the intake system can pass through the system to reduce the clogging of the filter. Whereas in a fully closed system, all solid detritus would be forced towards the filter under ram pressure. In all the different BMW air intakes that I've seen, none of them have the filter perpendicular to the ram pressure, which I assume is to help stop filter clogging and accidental water ingestion. Under WOT conditions, you will not see stuff coming out of the bonnet vent because as my Magnehelic pressure gauge has shown me, although the pressure in the system may be greater than ambient pressure, it will always be less than when the engine is not sucking air from the zones of high pressure where the mouths of the air inlet pipes are sited. It is only when you back-off the throttle that the pressure at the mouths of the air inlets returns to the full pressure values expected as per their theoretical ram pressure values at the speed of the vehicle. In my MC, under WOT in 3rd gear, the in the air intake is approximately at 2 inches of water pressure less than full ram pressure. I assiduously monitor fuel consumption in my MC as another indicator of performance benefit and since I've been modding my air-intake and exhaust systems I've seen an improvement in overall fuel economy of around 15% as well as obtaining a 15% improvement in power and torque. One of my air intake mods is to insulate the air intake system right up to the plenum (after the air-filter box and MAF) and I find that under spirited driving the air intake temperature is at around 5-7 degrees C above ambient as monitored by the DashDynoSPD. Not only does the ram air-intake providing cold air give the power increase, additionally, I find that my engine always runs cooler than other OEM MCs. Can you tell me if there is a hole in the back of the bumper "scoop" (Part 3 in the diagram) which can let stones and water pass through? |
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11-04-2008, 01:16 PM | #48 | |
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I don't see how the hood opening lets any collected water to escape. It's too high up and there would need to substantial flow to eject water out of the hood opening. However, it is possible for any water that enters the system to collect right below the filter, and drain out of the opening in the ducting between 1 and 4, which is visible in the illustration. That is the only opening apart from 1, 2, 3 that I could locate in the system, but someone who has taken the entire intake apart should verify that. There are examples of high pressure intakes with no outlet for water drainage. Clearly, excessive humidity in the combustion mixture would be undesirable, but I guess there is a trade-off being made there. The air filter would catch any debris, so that's not a significant issue.
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11-04-2008, 02:02 PM | #49 | |
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comments in red...
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Unless water is allowed to fully block and fill the airbox, air will always be ingested first..well, air and harmless water vapor. The fluid will surely find it's way to the lowest point...and I believe, after looking inside the airbox, that the lowest inlet would be the drain point. ---I'm not sure if the airbox has small holes...pencil sized...in the bottom of the airbox, as just about every one I've ever seen does employ for water evacuation. I'm not sure, but I've no concerns at all regarding 'water evacuation'. My goal, a pet project if I find the energy and time to do so, is to turn the M3 airbox into a true "ram-air" airbox. I believe that any application of "scoops" is a wasted effort until that is done. The big questions, at least to me, is how much air is required at high load/rpm to produce a ram-air effect in the airbox and how much is provided by the two frontal inlets...and at what speed. If we could determine that the engine is fed sufficient air at speeds over 50mph, even with the top vent taped-over or plugged, then that's what I'd do. I'll trade low speed performance for high speed ram-air anyday...that will benefit me more on the track than it would on the street (where I rarely whip it). We'll see... Be good, TomK
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11-04-2008, 02:06 PM | #50 | |
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11-04-2008, 02:14 PM | #51 | |
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This discussion is not for you, go away. And to answer your question...Eloy, the maker of the scoop said it didn't do anything...you calling him a liar, too? Your dyno examples are not relevant here and we're not outright discussing the scoops at this point. You poison enough threads with your juvenille drivel, please...the men are speaking...run along, you're not wanted here. Is that clear?
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11-04-2008, 02:16 PM | #52 | |
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11-04-2008, 02:21 PM | #53 | |
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11-04-2008, 02:35 PM | #54 | |
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The only thing you are clinging on to is a comment that the V2 scoops, NOT MADE FOR THE M3, did not produce the gains the V3 scoops do on the dyno. Conveniently ignoring that fact are we? Where is your data to support your argument the scoops don't make power? Where is it? |
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11-04-2008, 03:47 PM | #55 | |
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I've never had had any moisture in my air-filter box and I've driven in some horrendous wet weather too. However, if you were to drive into standing water then it is possible that a column of water could be forced up the intake and it only takes a bit of water (uncompressible) in a cylinder to blow an engine. Last year, here in the UK, we had lots of flooding and many BMW cars blew engines as a result of water ingestion. I'm sure that the owners completely forgot about the vulnerability of their air-intake systems when entering standing water (fording flooded roads) in order to attempt to get to the relative safety of their homes. |
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11-04-2008, 04:01 PM | #56 | ||
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I have found that the only reliable way of finding out what works and what doesn't is to use the datalogger and then calculate the Volumetric Efficiency as a continuing variable in the way that I have done to produce the graphs which show VE versus speed, rpm and air-flow etc. Any other assessment is not 100% reliable. Even the airflow versus rpm data doesn't actually show whether a modification is an improvement or not. Trust me on this. If I owned you car, I'd block your bonnet air vent and then datalog and calculate the VE and compare with OEM in order to see whether your idea works or not. The cost of a DashDynoSPD is a lot cheaper than most mods that you can buy. |
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11-04-2008, 04:04 PM | #57 | |
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For reasons that I've already given in an earlier posting in this thread, I would not put any faith in static dynos to show "real world" on-the-road gains from air-intake mods if the fan placed in front of the car on the dyno is not capable of replicating the air speed equivalent to the vehicle mph equivalent on a static dyno. |
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11-04-2008, 04:16 PM | #58 | |
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11-04-2008, 04:24 PM | #59 | |
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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 fan and dyno helps us get an idea of the added flow and how the car responds. I ordered a Vbox to give 60-130 numbers, and there are plenty available on M5board (for the M5/M6, the M3 obviously has not had scoops available as long and hasn't been available as long so it will be some time before we have as much data to reference). I will do what I can on my end to add to the community with my own data, dynos, etc. I'm sure others will be adding results as well over the next few months. |
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11-04-2008, 04:31 PM | #60 | |
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IIRC, There's a story of someone with a Winnebago RV putting his vehicle into Cruise control, thinking this was an "auto-pilot" and then leaving the driving seat and going to make a coffee in the back and the RV crashed. The owner then sued Winnebago for not making it clear in the manual that cruise control was not auto-pilot. As I understand, under your anti-trust laws in the US, if someone is daft enough to hit themselves over the head with a hammer, the "victim" can sue the manufacturer of the hammer for his self-inflicted injuries. Surely BMW need to consider that such an idiot might also drive one of its M3s/MCs? Likewise, it's possible that in "flash flooding" a completely sensible BMW owner could drive into standing water by simple accident, especially at night in the dark. |
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11-04-2008, 04:39 PM | #61 |
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But when you are actually measuring the ram effect, you MUST only measure real world conditions, because the ram effect is all about the change in air pressure with speed. If you can't replicate that on a dyno with suitable high-powered fans, then you may as well use your "butt dyno" to guess what is working and what isn't.
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11-04-2008, 04:42 PM | #62 | |
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Sure, in a flash flood you might accidently drive into deep standing water, but I don't know that you can win a case against BMW if BMW can demonstrate that is has done due diligence and considered the issue of driving in standing water in a "reasonable" way in its design process. Such extreme environmental conditions usually do not constitute basis for malpractice by the manufacturer. Otherwise, all cars would have snorkels coming out of the factory, which they don't.
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11-04-2008, 04:50 PM | #63 | |
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The thing is, if you can show gains at relatively low air speeds, the gains will only increase at speed and as speeds rise. The idea is to show the improved flow through the OEM setup, which multiple dynos in multiple conditions show. The delta increases. |
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11-04-2008, 05:29 PM | #64 | |
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...
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11-04-2008, 09:21 PM | #65 |
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exdos: Time to turn the hobby into a small business. Cooler running, more power, better mpg and do it yourself modifications? This is a winning combination.
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11-05-2008, 03:47 AM | #66 | |
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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? |
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