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      11-06-2008, 08:34 AM   #89
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Drives: E30 M3; Expedition
Join Date: Apr 2007
Location: USA

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Originally Posted by exdos View Post
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.
I wasn't criticizing your or anyone else's interest in understanding how their car works and tweaking things here and there for performance gains. I have the same interest. I am simply saying that if one ends up tweaking the car in a way that increases performance, one has simply undone a trade-off that has been done by M engineers. Noise, efficiency, durability, cost, drivability are all constraints the designers need to deal with. I am speaking about a highly optimized design like the E9X M3. I don't know how well optimized your M is. Some people on this forum think that they can actually find ways to increase performance that the M engineers were not aware of, and don't really understand how complex products are developed by world-class product development teams, and that there is a reason why most things are the way they are in stock form. Others just make false claims.

The most entertaining one was by the scoop manufacturer, when they claimed that the car has a poor cooling system because coolant temp went up in dyno runs. Pure BS (not the temp going up part). As if M engineers are simply incapable of measuring and tracking a vital performance parameter, and this scoop manufacturer all of a sudden discovered a significant flaw in the design when they stuck the car on their dynojet. As if the car was designed to sit on a dyno and deliver 414hp. Of course, there is nothing wrong with the cooling system of the car. I've driven it pretty hard for 45 minutes non-stop on the track 3 times in one day, and for 30 minutes non-stop several times on really hot summer days, and there were no signs of overheating. Others have reported similar experiences. Regardless, it is a street car, not a race car, and if someone wanted to do more with it, it might need an extra oil cooler, but that is beside the point.