I tried searching the site for past info.but couldn't find anything. Does putting on a 3" downpipe with the cat back make a noticeable difference with HP and does it void the factory warranty or cause problems. I do have the performance upgrade. I've read that without the down pipe the cat back alone doesn't make an appreciable difference. I would like to hear from those who have done this or something very similar. Thanks!!

 

I had the Hahn catted DP and catback installed in 1 shot. I've had it since the car had 2200 miles on it (19K now) and have never had any problems with it. When I had it initially dynoed it pulled 260hp, 250lb/tq. Typically the general consensus around here is that the DP is the biggest restriction point w/ the twin cats in place. I'd start there if you want to get some gains. Hope that helps.

Later
Allex

 

Whats the noise level like? I had a 2007 mustang gt and that thing was obnoxious without the cats.

 

Its not too bad without cats because the turbo muffles it. Its still loud when you stomp on it but sounds great

 

Does hahn or anybody still make downpipes for the hhr. I just bought one and told myself that I would not get the mod bug but I got bitten. This little thing has some potential that I wasnt aware of when I got it. It is probably a little faster than my mazdaspeed6 that I had. I cant find a place that makes a dp for this thing.

 

Cobalt DP is the same as HHR DP on MT.
HHR automatic DP is 1" longer, you may need to adjust CB to fit, in some cases.

 

First I have heard about manual and automatic DP not being the same length. What is the best method to modify a cat back to adjust for this?

 

I did a Hahn catless DP/exhaust not to long ago. got it from a member here. definite HP gains. never tried it with just the catback though.

runs great
no issues at the dealer

It was really loud at first.
my dealer notice it was hitting against the gas tank area
after they repositioned it, it became a lot quieter. (imagine that)
most noticeable at warm up, downshift and of course WOT.
IMO during normal driving it is not that much louder then stock

like BartSS said it sounds great

 

I agree wit Peevlos. The Hahn exhaust isn't obnoxiously loud unless you're at WOT and it still has a really nice deep raspy note.