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      11-05-2008, 06:20 AM   #69
Second Lieutenant
Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

Posts: 221
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Originally Posted by Sticky View Post
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.

Originally Posted by Sticky View Post
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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