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      11-06-2008, 05:34 AM   #86
exdos
Second Lieutenant
England
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Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

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Quote:
Originally Posted by lucid View Post
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.