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Old 11-19-2012, 07:14 AM   #61
PEI330Ci
58mm of Bliss
 
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Join Date: Jul 2003
Location: PEI,Canada
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My Ride: 330i, 330Ci
Quote:
Originally Posted by Sound Performance View Post
We have done some of that. Jason reported that taking off the HPF intake and replacing it with a 4" setup netted him over 50 hp!
Would that have more to do with exceeding 125m/sec with a 3" inlet pipe, than the manifold/plenum itself?

Obviously running large pre-manifold pipe will affect transient response...so it's a trade off with response versus peak power.


Quote:
Originally Posted by Sound Performance View Post
We have both measured ex back pressure at the turbo. It is not all that ridiculously high actually but that does not tell us the entire story in a log manifold as because the turbo sits near the rear and the first 5 runners all merge together, there may be high BP at the front cylinders.
Really good point, and pretty hard to measure without high speed sensors that would catch the dynamic response. I've looked into this from a response perspective, and the only sensors fast enough to measure this cost $1100-$1300 each depending on the range. Then you have to be able sample higher than Nyquist frequency...which is well above what most motorsport data loggers are capable off. Basically...you're into lab-grade equipment to watch this properly in real-time.....

Total cost including the logger, analysis software, and sensors would be about $11-12k. Pretty hard to build that cost into a manifold design unless you are selling a lot of them. (Or it's for a Motorsport project) Maybe FSR could comment on this?
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