New Perrin exhaust - lost torque
 

I just installed a Perrin 2.5" resonated cat back. I've been driving it around a week or so and I've noticed my low end torque is gone. It doesn't zip off the line anymore. It smooths out the power band nicely and sounds a bit better, but there is definitely a loss of low end torque.

I see I have two choices: 1) rinstall the OEM pipes. 2) add another upgrade to gain it back.

If I go number 2, which power mod will be the most economical to get the job done. I just want to keep the higher rpm gains and just give. Ack the low end torque I lost.

You could get your butt dyno calibrated

Or a header and a tune for some real gains...oh and E85.

I've been honing this butt dyno for 46 years - it's a finely tuned machine!

A header and tune would do it. It I feel the cost is too sever.

sell the exhaust and get flex fuel adapter thingy.

I'd prefer not to do a tune. Only because we have a-holes for a dealer here and they would just love to void my whole engine warranty.

How do you lose power from a simple catback exhaust, wouldn't you gain even the slightest HP, not lose? Does this apply to all aftermarket exhausts?

In my experience on a NA engine when you typically gain on the top end you sacrafice on the low end and vice versa. This isn't iron clad of course there are exceptions. I thought this might be one when I looked at the dyno on perrins website. It showed no loss of torque at low rpm, but to me the loss is evident.

As far as how you loose low end power, if you just bolt on a more free flowing exhaust you will gain top end, but the reduction in back pressure will typically loose you low end torque. A tune would most like help with reducing the loss I imagine.

HP is meaningless for the most part. For a street car it's all about torque.

My Perrin catback 2.5 arrives in a few days, I'll keep an eye out for any loss of low end torque and report back if I see the same result.

Thanks. I would be very interested.

This is interesting because i believe the 2.5" Perrin is the same as Stock (correct me if i'm wrong). I noticed the same thing but i have a 3" exhaust installed because i was boosted for a bit. I was thinking about either going back to stock to be a bit more sleeper (i have UEL headers) or going with a 2.5" exhaust for better back preassure

I think it is the same 2.5" diameter pipe, however I'm not sure if the internal structure of the mufflers are the same. If they were there would be no power increase, so this leads me to think they are internally different.

I'm going to bet if you went back from 3 inch to 2 1/2 inch you would feel an increase of torque just because of that alone.

I wouldn't believe it without actual dyno numbers. A change in sound can do a lot of weird things to how you perceive a car's performance. Sometimes it "feels" faster when it really isn't. Yours probably sounds like it should come off the line faster than your visual cues tell you.