... and my 997.1 S "feels" slower! It just doesn't seem to pull in the mid range like it used to. There does seem to be a slight increase in how fast I get to redline in each gear, which logically would mean it is faster. Nevertheless, it does indeed feel slower than stock.

The guys that installed it were great and have a strong reputation on the forums (GMG) so I don't think it has anything to do with the installation.

Has anyone else had a similar experience, or am I just nuts?

 

What happens is the top end is better so the midrange doesn't feel so strong. The fact it feels like the car is getting to redline faster (time in gear gear is shorter) means the car is making more hp. I have to say when I did my setup the cars midrange in fact got so much stronger. The dyno's I have seen seem to support that. It could be the GIAC software doesn't mesh well with your setup. I would have done the exhaust with stock software then go aftermarket if I felt I had to.

Dave

 

Ok, that makes sense. Perhaps I'll have them flash the ECU back to stock and see how that affects things. What's odd is you have a similar setup and noticed a stronger midrange.

 

Usually a lot of the people on the forum suggest disconnecting the battery for a couple of minutes after installing ECU.

Try disconnecting the battery for 15-20 minutes and then take it for a long drive It should help!

 

My mid range is much stronger than stock.

I have an AWE header, and cats with a Remus muffler. I tried the AWE mufflers, Performance wise they were great, just too loud for me.

The Remus Muffler may actually add some back pressure so that may be why mid range is great. Several people who have drove mine say it feels torquey like a V8. Plenty of top end though, ijusdon't get to use it much on the street.

The APR software seemed to make adiffernce too.

I have the answer, I have an IPR plenum, do you?

 

Thanks all for the recommendations and your experiences!

 

PM sent. I need some more information.

 

I just realized the PM I sent you back didn't go through because I didn't have enough posts.

To answer your questions from the PM: no, and no.

 

Header design could be a big factor here. I don't know what the GMG headers look like, but if the primary tubes are long then that will provide more high-end power but reduce low-end torque which may be what you're experiencing.

Also, flashing the ECU has the same effect as disconnecting the battery. But if you added the parts after the flash then you'd want to 'reset' by disconnecting the battery.

 

I added the Cats after having done the flash. I'll reset the battery tomorrow and see if that changes things. If it is the headers causing the problem, does it makes sense that the Cats would exacerbate the torque loss?

I could sense the loss of midrange torque when I just did just the chip and headers. When I added the cats, the midrange loss seemed even more profound.

 

In any exhaust design there are compromises. Sounds like you've designed yours for maximum power. Adding the cats increases the rate of escape of your exhaust gases and increases power and yes all these things together can move the torque band. Header design will have the biggest impact on torque shift. In a nutshell in the mid-range you are making less torque but you're applying it faster (more power).

Disconnecting the battery probably won't help you much in this scenario but it can't hurt to do it. This way the car will properly learn your completed setup. I would work with GIAC (great guys) to make sure your tune accounts for your headers and cats. Then drive it a bit and see if it grows on you. If not, consider exchanging the headers.

 

No disrespect this is just not correct. The car is designed for maximum horsepower at 6900rpm, the cars OEM exhaust is already quite free flowing and adding cats will not drop midrange torque or even low end torque. In fact the opposite will happen. I have yet to see a dyno in which there was a horsepower or torque loss anywhere in the rpm range with the addition of the sport cats. The sport cats are a win/win situation in the fact they improve horsepower throughout the rpm range.

Here's a graph from AWE..






The sport cats are what added the horsepower and torque here, the mufflers accorging to AWE only added 4hp and 4 ft/lbs of torque.

Dave

 

Well the gains are actually 5 crank HP and 5 crank Torque

Actually if you look really close the Torque is still lower than stock between 2800 to 3500 RPM (unfortunately ). But once the headers are added the torque is higher than stock all through the RPM range!

 

Here is another graph ...also keep in mind the dip at 2800rpm could be an issue when the dyno operator applied WOT. Also, for the sake of debate and give you the fact that the car lost 3-5ft./lbs of torque at such a low rpm:

1. Look at the midrange gain with the cats.
2. How often are you at 2800rpm during spirited driving??
3. The car gained over 35ft/lbs of torque at 4500rpm..this is what I mean you can really feel this mod, especially in the midrange.



I have the cats and I can tell you right now that was the one mod I did that you actually say..."damn, I actually feel that".

I'm seeing well over 27rwhp peak over stock with cats and mufflers according to AWE. You mean the mufflers are 5chp..right?

Also, max torque came in 250rpm sooner.

Dave

 

Dave, I know what you are saying and agree with you. I was just referring to the fact that playing with the exhaust decreases back pressure and might cause a little low-end torque drop...

I can't drive my car like I want when I'm driving in traffic... That is why I mentioned it in the first place. I was trying to say maybe that is why he feels the car doesn't feel like it used to.

BTW I am getting AWE cats and mufflers soon so I will be able to comment better on the issue in about a week or two