Post H-pipe removal

Removing cats is good for ~4 rwhp so a lot of it's probably be a little of both.

Depends on what changes were made in the tune too. Removing the cats is supposed to be worth a few HP, but you should also gain a few torque down low.
Dan

I agree with the others, cats will account for some HP loss. I was thinking that the HP could be more if the cats were bad or going bad. This may sound crazy but let me explain.

(with cats, factory h-pipe)
Before I put the car away for the winter I kept thinking the car seemed less powerfull than when I first got my tuner/tunes installed, poorer throttle response than before, and I always had a rotten-egg exhaust smell. That smell can indicate a cat problem and perhaps create a flow restriction or computer de-rating.

(without cats, O/R H-Pipe)
I now have the O/R H-pipe installed but haven't driven the car yet (still winter in Iowa and the roads are salty), so power difference can't be quanified. First impressions are the throttle response is way better then before. Perhaps this is my perception since it's a new part and you always hope that a new part is going to make a huge difference.

What I'm saying is if your cats were bad or going bad, the HP loss could be more than what was stated. I guess I always thought removing the cats was good for about 8 - 10 hp? Which can be a noticable difference.

COBESGT said:

(without cats, O/R H-Pipe)
I now have the O/R H-pipe installed but haven't driven the car yet (still winter in Iowa and the roads are salty), so power difference can't be quanified. First impressions are the throttle response is way better then before. Perhaps this is my perception since it's a new part and you always hope that a new part is going to make a huge difference.

Click to expand...

Did you reload a tune or reset the battery?

NastyStang113 said:

Did you reload a tune or reset the battery?

Click to expand...

Battery was disconnected and removed from the car when I had to plug-in the highest O2 Sensor on the passenger side. As far as the tune goes, I shouldn't have to reload the tune since the tune doesn't have to be changed to shutoff the rear O2 sensors (Brenspeed Tunes already have them turned off).

Were you thinking something was wrong or just a general question?

If the battery is disconnected or the PCM is reflashed it'll clear all of the "KAM" data and this information is stored for the computer to process it's "adaptive learning". The P1000 code is just saying you need to complete a drive cycle to get all of it's data. It's normal and happens. Once you complete a driving cycle it'll go away.

I gained 8 rwhp and 10 rwtrq with the installation of the off-road pipe. So take that away, along with the feel / sound of having no cats.. yeah, I could see how the car could seem slower.