Saturday, April 09, 2005

Intake restrictions measurements

So the other day I came across an interesting post on about MAP not holding steady as the rpms increase. Apparently that's an indicator that you have a bottleneck/restriction in the intake system. After talking to some people, it seems to be a rather reliable source of information about how well your intake is flowing.
So I dove into some logs of mine, to see how mine fairs, and heres few figures:

96-97kPa at 4500rpm-6100rpm and 80%+ throttle
98-99kPa at 2700-4300rpm and 75%+ throttle

So while it is not a huge drop, of course it would be better to not have any at all, especially that I'm mostly interested in the higher-rpm operation. I'm not sure what I can improve, as I have just about all the intake-side mods: SLP lid, Granatelli MAF, LS6 intake, K&N filter (probably dirty after winter, might be the culprit). Another thing to do would be to start porting and polishing everything in the path of air, namely MAF and Throttle Body.

A sidenote: why won't someone test all the various lids with this method? it's a quick bolton, and all you need to do is few 'in gear' runs from 2-6krpm and see how MAP behaves throughout the rev-range.

So I wanted to compare my 'drop' to someone else's 'drop' to see if mine's bad or just minor.
The past few days I've been helping this kid with a typical 'got new cam, I get mad knock now' story, so I looked at his logs how his car compares. This is a 2002 Camaro with SLP lid, Fram Filter, FTRA

He has a bigger intake restriction:
1800-3200rpm can get 98kPa in MAP, while
4600-6200rpm gets 92-96 (with 92 on the high rpm side and 96 on the lower).

I will post pictures demonstrating the dropoff later. If anyone has any good logs/screenshots of really bad (or not at all) dropoffs, please send it to me, I'd love to see more extreme cases and see the effects of them.


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