just had a thought on big header tubes.....


lets pretend i have a engine with a soild cam and alot of overlap... really, its a high RPM bad as i dare to be motor on the street..


now lets say i put extremely large longtubes on it...

now at low RPMs i should have little scavenging effect from low volicity.... right?


wouldnt i want that at idle anyway? because at the low RPM, a good scavenging exhaust would suck my fuel right back out and make my eyes water even more?



just trying to get a idea if it would idle/low speed better with bigger tubes then small ones... this is a just for thoughts...... i already know im using the big longtubes for their high RPM flow... but just wondering about the low RPMs where my motor isnt that efficent...

 

What size are the tubes?

 

i donno, just talking theory.... how big do you want them to be?

 

Well, as far as manufactured longtubes go, the largest size you can get for thirdgen's is 1 3/4" supercomps from Hooker. Anything bigger would be custom, but uneeded unless you were running a really boosted big inch motor. 1 3/4" isn't all that big on a small block, especially if it's turning some high rpm's. However, in theory, is you got a set of 2" custom headers on a sbc (N/A or low boost) then the exhaust velocity would be very lower, so yes you would have very little scavenging affects. At low rpm, there is very little scavenging affect on any motor, so it wouldn't try to pull out the unburnt fuel mixture.

I haven't taken any physics or thermodynamics classes so I can't give you any scientific theories, but that is how's it's been explained to me. Maybe we can get some smart physics people in here to comment. Aperion (sp?) could probably help out as well as a few other people....