Backpressure question

Stella94GT · Mar 4, 2008

it is my understanding that a mild car actualy needs backpressure for the best performance is that correct? My exhaust combo is long tubes, o/r x, and straight pipes so basicaly no restiction. im woundering if it will net me any hp to weld in some mufflers?

ryclef331 · Mar 6, 2008

Stella94GT said:
it is my understanding that a mild car actualy needs backpressure for the best performance is that correct? My exhaust combo is long tubes, o/r x, and straight pipes so basicaly no restiction. im woundering if it will net me any hp to weld in some mufflers?

It may net you a couple of ponies across the board but nothing to write home about. Its all preference. There is a restriction just having an exhaust on the car. Mufflers are up to you...you won't notice or feel any difference I'd bet

Trickflow.GT · Mar 6, 2008

plus your car wont sound very good without mufflers

topless95 · Mar 6, 2008

too little restriction/ no restriction will diminish/eliminate the positive effects of exhaust scavenging

golden5.0 · Mar 6, 2008

back pressure usually helps the car make more torque down low and in the middlerpms. Less restriction frees up horsepower in the higher rpms. I would put some mufflers on you will feel the difference I had the car without mufflers for around two weeks once and felt the difference when i slapped some on.

ryclef331 · Mar 7, 2008

golden5.0 said:
back pressure usually helps the car make more torque down low and in the middlerpms. Less restriction frees up horsepower in the higher rpms. I would put some mufflers on you will feel the difference I had the car without mufflers for around two weeks once and felt the difference when i slapped some on.

There is a difference between running open headers and a full exhaust with no mufflers though. If he is running the exhaust all the way out the back with no mufflers, slapping a set on is going to have minimal gains...less than 8hp and 10lbft of tq difference. I'd bet money on it. Anything pretty much under 20hp...your "a$$" dyno isn't going to feel it. You dyno and ET numbers can improve yes...but your calibrated butt isn't that accurate. I don't care who you are.

Mr. OAM · Mar 7, 2008

Wait a minute! People here and at other message boards feel the 5 - 15 HP gain they get from their underdrive pullies all the time!! :hammer: And that is considered money well spent.

Steve

ryclef331 · Mar 8, 2008

Mr. OAM said:
Wait a minute! People here and at other message boards feel the 5 - 15 HP gain they get from their underdrive pullies all the time!! :hammer: And that is considered money well spent.

Steve

I hate when people tell me that. I want to do back to back tests...5 passes...no times displayed on the same car, same driver. I will randomly install and uninstall a set of underdrives and the driver has to make 5 passes and guess which passes are with or without pullies. I'd bet MONEY on it he doesn't get all of them right.

golden5.0 · Mar 8, 2008

well before My underdrive crank on my Auto vert my previous best was a 14.8 @ 94.5mph and since its auto I hit those times over and over on cool nights. After the underdrive I have a best of 14.6 @ 95.98 and again hit those times all the time on cool nights.

Stella94GT · Mar 8, 2008

thanks for the opinions guys, i actualy emailed summit in their tech section and asked the same thing but they still havnt gotten back to me. i actualy love how the car sounds. my mind set for the car is that every little bit help so when i finish up my exhaust this spring i might just get a pair of mufflers welded on.

i know it is basicaly all sound preference but is there a muffler that out performs the rest?

ryclef331 · Mar 8, 2008

golden5.0 said:
well before My underdrive crank on my Auto vert my previous best was a 14.8 @ 94.5mph and since its auto I hit those times over and over on cool nights. After the underdrive I have a best of 14.6 @ 95.98 and again hit those times all the time on cool nights.

I'm not disputing that fact. In BLACK AND WHITE (i.e timeslips and dyno charts) hell yeah there is a difference. I'm just saying that a person's "seat of the pants feeling" isn't going to notice a difference in hp of 10-20hp. Thats all. YES there IS more power there but the differences aren't that noticible. Hell, the first time I sprayed nitrous, a 50shot, EVER, I braced myself for dear life expecting my seat back to break the hell off but I hit it and said...wait....something is wrong. It is just not accurate to say "oh man...It feels like I picked up probably 12 more horse."

Mr. OAM · Mar 9, 2008

I'd love to see the guy that can say at the end of the run "Hey, that felt .2 of a second faster." :coolsmiley:

There's also the "placebo effect".

Steve

golden5.0 · Mar 11, 2008

Mr. OAM said:
I'd love to see the guy that can say at the end of the run "Hey, that felt .2 of a second faster." :coolsmiley:

There's also the "placebo effect".

Steve

youre right I didnt feel a big difference in the underdrive. But with the mufflers wow it was huge maybe because its an automatic but it was horrible down low and when I put my flows back on I felt a huge difference.