Quote:
Originally Posted by CrazyHorst
I'm not sure what this test will prove other than that the vacuum gauge is working correctly.
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Actually it does more than that and you answered your own question. Plus it doesn't cost much for us poor DIY types that are more practical than theoretical in addressing tech issues. A very cost effective test regardless.
It will detect any gross exhaust back pressure issue or restriction whether it is a clogged CAT converter or even a banana stuck in the exhaust.
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Here is some anecdotal proof:
Click here<---Be sure to read it in its entirety
Post #23
Quote:
Originally Posted by cool02grandprix
ok I went and got a vacuum tester like you have.....
at idle I get 13-14 in hg
rev to 2000 to 3000 and it drops to basically to about 0 (zero) and then at idle back to 13-14 in hg
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Obviously not a reliable scientific method to fine tune your exhaust system or if you are looking for horsepower. Here is a good link from Thrasher Engineering on some more practical DIY testing:
Click here
Quote:
Exhaust Backpressure Study
Replacing the stock production exhaust system with a low-restriction, free-flow one is usually one of the first modifications made to any vehicle in the name of performance. We all know they're louder, but how much performance do they really add? We've all seen supposed dyno tests, usually run by the exhaust manufacturer's themselves on their own dyno, indicating vast power gains, and psychologically, we always equate a healthy exhaust rumble with increased power in the seat of the pants, but how much power are we really gaining? To find out, we're running a simple backpressure study, and our results will be posted here as they come. Admittedly this study is not totally scientific as there are many uncontrolled variables, but it should be sufficient to provide a rough estimate.
It is generally accepted by automotive engineers that for every inch of Hg of backpressure (that's Mercury - inches of Hg is a unit for measuring pressure) approximately 1-2 HP is lost depending on the displacement and efficiency of the engine, the combustion chamber design, etc. Our sources indicated that in the case of the L67 3800SC, 1HP per inch of Hg is reasonable.
1 inch Hg backpressure = 1 HP lost
For reference, we have the following conversions factors:
1 ATM = 14.7 PSI = 76 cm of Hg = 29.921 inches of Hg = 1.013 bar
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