In reply to a message from Frank sent Sat 26 Mar 2016:
Okay Gentleman - I have the results of my back pressure test. I’m
assuming that the exhaust in a US spec Series 3 is pretty
restrictive with 2 Cats and 2 resonators… but the results seem to
show more restriction than I think there should be. Not terrible but
maybe getting toward clogged territory. What do you think?
Procedure - hooked my old-faithful vacuum/pressure gauge to the open
end of the AIR injection manifold. The only thing good about that
AIR injection system is that it makes it easy to get a back-pressure
reading. Car at operating temp. Gauge jumps around alot before about
2500 RPM so tough to get a good reading but it is low.
IDLE - 0 PSI
2000 RPM - approximately .25 (or less) PSI
3000 RPM - 1.25 PSI
3500 RPM - 1.5 PSI
3800 RPM - 2 PSI
Going back in the garage to look at the timing.
~Mike–
The original message included these comments:
Agree with Gregory, Mike - it ain’t ‘normal’; you may need to start start
digging…
However, while the two transmissions have virtually the same ratios; do the
two cars have the same rear axle ratio?
Engine power is all about rpms - and a fair test involves comparing rpms in
the situations described at the shift down point. And, of course; rpm
build-up is closely related to rear axle ratio - not omitting to mention
that the SI is some 500 pounds lighter…
Emission restrictions does interfere with engine power, as does the
mechanical fan - it all adds up, but still…
Frank
–
RustfreeMike
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