Vcoat

I also felt a power lossafter installing the pypes violators along with my dynatech headers and high flow cats. I went back to the stock mufflers and the torque returned...I dunno.. must be that resonance thing Al is talking about..

Lees07GT

Al is right. With all due respect, the truth is in the dyno or at the track, not in what people "feel". As Al said, backpressure is ALWAYS bad. It makes the engine work harder to push out the exhaust gases. This represents a loss in power at the driveshaft. On the other hand, if an exhaust system ismade too large (where this sizeis depends on the application), it can actually be detrimental to power out. This is because the hot exhaust gases are not moving fast enough and they are having time to cooldown excessively in the pipe. The larger the pipe, the slower the flow. This cooling of the exhaust causes the gas to become more dense. The colder and denser gas is more resistant to flow thanhot gases, hence,backpressure increases. So you want a system that is large enough to reduce backpressure and parasitic loss, but is not solargethatthe slower flow rates allow the hot gases to cool too much while still in the pipes, thereby increasing backpressure.

By the way, these are not my original thoughts. I'm not that smart. This theory on exhaust size/performance effects is takenfrom ahot rod mag I read a few years ago, forget which.

swooshpimp

I feel that I lost some low end power when I put on my cat back exhaust system from Pypes - I dont like that I all. I will be replacing these mufflers with the stock to see how that differs now. I bought a Mustang formuscle power not top endamongst other reasons.

Arwing

I also think one of the reasons it feels like the loss in low end torque is maybe because my SLP's sound like a RACE CAR, like it sounds faster than im really going?

i dont know just a thought :\

Lees07GT

I think you have a good point. After changing exhausts on a bunch of cars over the years, I've wondered about this too. Maybe after driving a car for a while, the brain begins to relatethe feeling of acceleration with the sound level of the exhaust. The subconsious expects a given noise level to equal a certain level of acceleration. So when the exhaust levels are substantially increased, maybe the brain is disappointed that the acceleration hasn't increased at the same rate. I just put some Flowmasters on my old Chevy pickup, and it sounds great, just like a muscle car. I'm sure the Flows have not hurt the trucks performance. If anything, they may have had a very small positive effect. But the truckSEEMS slower, somehow. I get all this great deep throbbing sound, but it doesn't actually go any faster than it did before. So maybe my brain just has to get reprogrammed for the much louder exhaust note and how it associates sound levels to the feeling of acceleration.

Stkjock

Al,

HP gain from axleback... LivernoisMotorsport..did a dyno test of the Corsa set up on a GT500.. test +14HP w/ Corsa...

pause play @ 5 seconds for numbers...

http://youtube.com/watch?v=faWG_ADExao

Now the 4.6L I'd guess doesnt get as much of a boost... but 5-10hp?????

CrazyAl

I belive that on a GT500 for sure. The bigger engine and the supercharger demands a lot more exhaust flow than a naturally aspirated stock GT.

Stkjock

Al,

do you think a supercharged 4.6L (Vortech) would p/u HP from such a set up as well?

Dave

CrazyAl

Of course, the exact performance would vary depending on how much HP you were pushing out of the blower, but I wouldguess about 5-10 HP or so could be gained above the stock exhaust with a good set of mufflers (axlebacks)....not that the Corsa is anything special, but any of the straight-through types such as the Loudmouths or the Borla Stingers, etc, should do this as well.

Stkjock

Al,
Thanks.... kinda what I figured... the Corsa is a straight thru design if I remember correctly... BTW 435RWHP is what I had with a magnapack... before I swapped it out for the Corsa's... did not like the drone.....

Dave