I have the mods listed in my sig. A buddy of mine thinks I may be losing back pressure with my exhaust setup! I have 3'' cat back and a Dynomax Bullet welded in right underneath my passenger seat with a turndown on the end of it. Could this be causing my car to run slower because of the loss of back pressure from the straight through muffler?

 

Although some will disagree with me, I don't think so. Less backpressure usually just moves your powerband higher in the rpm range which gives the false impression of a lack of low end torque.

 

In theory it is possible to lose a little low end do to reversion (when the exhaust flow reverses direction) taking place is you have a exhaust system with a large volume and it's turning low rpms and in turn a low velocity.

another phenomenon that contributes to the illusion of losing low end is when you run a wide open setup it is so loud. People associate loud with power and fast so if you nail it at 1500 and make a lot of noise your brain gets kind of confused.

If your running the stock manifolds your definitly not opened up too much. Also, even if you were running headers and lost a lil tq down low you'd be more than making up for it up top.

 

I think you are right, especially with the brain fooling you idea. I remember when I had my cutout on that thing was way loud but the car would be barely moving at low rpms but would pull like a mad man up top.

I was gonna change my exhaust just due to the fact that it is a good bit louder with my new cam. I still wanna stay with the bullet setup just not cut off underneath the car though.

Thanks guys.

 

If you make it exit either out the back or the side (not underneath the car) it will be quieter inside the car. Or if you angle the turndown 45 degrees so it's not pointed straight at the ground that will help a little bit.

 

We dont need no stinkin backpressure
http://web.camaross.com/forums/showt...threadid=42240


Let the guy go back to working on his 100hp/lit import

 

Actually backpressure can improve low rpm torque production. If you take a close look at the new Suzuki GSXR1000, you will see a variable back pressure valve in the exhaust for just this purpose.

Not a point meant to confuse the issue but there is some validity to having backpressure in some engine designs. For a small block chevy, less is better.

Mike

 

Agreed

 

I actually have the turndown pointing down and to the side. But the bullet is a straight through muffler and is alot louder with my cam. I may keep the bullet and just run 3'' pipe from the bullet and dump it over my rear axle and chop it off there. That should quieten it down some and it wont be as loud inside the cabin.

 

although i agre with all of the above-
i lost .4 sec by taking my muffler off in my long tube, 3'' y pipe and ! cat setup.

had i had a converter (or 6spd so i could launch harder) and been able to shift 200 rpm higher i'm confident i'd gain mph and et.
I did gain 2 mph and i was gaining like 26mph in the 2nd half on an exhuast/gears Lt1

 

Would you guys even consider a bullet a muffler though?

 

I have the same setup coming off my Longtubes. And i have no problem staying side by side or even edging out my friend in his (A4) C5 with Corsa catback. The turndown alone gives you some backpressure. My car runs faster with the setup now then with an open 3in catback. Most people lose et and not mph. THey lose ET cause you have to relearn your launching technique cause yo'll bogg easier off the line with an open exhaust. My first few runs were slower in ET until I revved up a little higher off the line than usual.

You might have seen the Vette im talkin about Ponykilla. Its yellow and has Z06 vents and wheels on it with 454hp stickers on the side. Lol, i know I know. Whats gotten in to him, I dont know. I should have looked at his stickers when we raced and said "Damn, I guess I have 454hp too"

 

Cant say Ive seen him before. What part of Gville you from? We should meet up sometime.

 

In the Berea area. Not far from downtown greenville. We have probably crossed paths before but you probably wouldnt remember unless you heard my exhaust cause im pretty much stock looking sinc i sold my wheels.

 

Hey man have you heard of www.scfyb.com? It is our state Camaro board, you should check it out.

I live in Simpsonville. Email me sometime and we can try to meet up.