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Old 08-27-2012, 10:42 AM
BogiesAnnex1 BogiesAnnex1 is offline
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Originally Posted by Cridder View Post
The headers for my 88 S-10 are 1 5/8" shorty's with a collector thats like 2 inch's long, i was thinking of extending the collectors out to 18" , i was thinking this mite act like an expansion chamber, maybe create a quazi long tube header effect and broaden the power range a little more off the bottom hopefully without hurtin the low end to much. any ideas? experience.
You are on the right track, the issue in this case is how to create and manage a returning negative pressure wave. Now be aware that no matter what you do you cannot duplicate the effect of full length tubes empting into a suitable collector; but by adding enough collector length to shorties so that the total length of the shorty and the attached collector is about the same as a set of long tubes with their collector. However in the case of the shorties with long collector the collector needs to either end into the atmosphere or into a large resonator box, so as to trip the return signal. However, given the signals will be diluted there will not be the hard pull from the exhaust on each cylinder at certain RPMs because that level of harmonic tune just won't be there. Keep in mind that long tubes do not continuously optimize this, the harmonic tune frequencies come and go with RPMs and they can be as much a negative element on making power at one RPM as they are a positive one at other RPMs. This is very apparent on raw dyno readings where the power is rising and falling within a band of general rising. Most of the dyno data you see published is smoothed; the real world is seldom like that. On a positive note, diluting out the signal peaks will tend to remove these up and down power excursions. For a street driven engine that sees most of its time in a moderate RPM range this stability can be a good thing for operating efficiencies at cruise rather than tuning to a peak power output at a high RPM that is seldom seen in normal use. The late model Ford Mustang gets by very well with shorty headers, thank you very much.
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