EXHAUST PIPE SIZE?

[oxbrain]

That is the torque loss. The larger pipe requires more flow(higher rpm) to get the same velocity and scavenging effect. The pistons work harder to push the exhaust out, resulting in a loss of torque.

[funky technician]

scavange happens pritty much strictly in the header and down pipe of an engine, after the cat,a minute increase or decrease in exhaust diameter is only going to have a minute efect on your scavangeing, considering that the exhaust is cooling and turbulating by the time it goes threw the cat and into the exhaust, so any changes of flow that far back is going to have very little effect on the heads port scavenge ability (to a point), proper porting and matched headers that are tuned to the valve overlap give you scavenge, not catback exhausts.

[jpriest26]

holy crap now im really confused. im just replacing the pipe from the cat back and wanted to know what size was ok to go up to. i have a 1.3 fuel injected engine. just want to help it breathe better and give it a better tone

edited for language, admin

[jpriest26]

the muffler is coming off since its about shot so im just puttin a straight pipe with duall resonators on it for sound

[funky technician]

ya, this kinda turned into a thread jack, sorry, a little bigger than stock is probibly all a b3 really needs anyhow, stock is like a straw

[jpriest26]

thanks. dang i felt like i was in physics again and just as confused lol

[Safety Guy]

If I could take a "practical physics" class where we'd use Festivas, guns and a few other interesting items, I'd take it and learn a whole lot more than doing theoretical math problems on some chalkboard!

I'd love to learn more practical uses of the following:

polar moment of inertia
Bernoulli's principle
Cx
center of gravity
center of pressure
sectional density
laminar flow
and more stuff I can't think of right now...

Karl

[jlord16]

I tired analysing exhaust flow once and its complicated as to do mathematically

bernoulli's and laminar flow eeekkk, gets so complicated after that

[Deathshead]

if your running a b3 or b6 you might want to check with the factory walker replacment's alot of times they are larger diamter then stock..

Im not sure that brand came on my car when i got it but its huge compared to a stock 1.3 size pipe. works perfect with my b6.. looks like a pre-bent off the shelf exhuast too.

[jpriest26]

well so much for the exhaust question it backfired really hard the other day and blew a 3" long 1" tall gash in the pipe where it turns to go over the read axel. so i just cut it off right there, put a resonator on it and now it has no muffler and rolls out the side just behind the pass door. since the catalytic converter is more or less hollow from me knockin all the broken packing out of it i now have a straight pipe with an echo chamber and a resonator. its loud as hell but it actually runs a lil better and smoother. better pickup, better top end, and doesnt rap out nearly as quick as before when the exhaust was intact

[funky technician]

LOL it must sound like a time machine! whatever works :wink:

[jpriest26]

well actually it doesnt sound all that bad. at lower rpms it has a low throaty tone while at 3000rpm or higher it has a snappy ricer sound. when u let off the gas to slow down or between shifts it even cackles some. now i just have to get a long straight piece of pipe and ill be able to run my exhaust how i wanted it with dual resonators

[jpriest26]

if i can figure out how to link a video on here ill make one of how it sounds now