I went with an H pipe, had the car retuned by Lund, and felt that it lost some low end torque when not in boost. I took the car back in, they added some timing and made some cam adjustments and the car made more power. However, the car still feels like it does not want to rev as easily as it did before the cats were removed. The car haul ass at WOT, but It is slow as hell when just rowing through the gears. Just wondering if anyone else out there felt a loss of low end get up when the cats were removed? Thanks!
H pipe = Loss Of Low End Get Up
- Thread starter Flcracker
- Start date
You can check out a dyno comparison that I posted back in December: http://www.svtperformance.com/forums/showthread.php?1095793-My-O-R-H-Pipe-Dyno-Run
Between the two graphs, the same dyno was used, just the second graph was about a calendar year after the first graph. The first graph is x-pipe with cats, second graph is offroad h-pipe (no cats.)
You will notice that while the top end power is more without cats, take a look at torque around 2500 rpm on both graphs. With cats, about 350 rwtq. Without cats, somewhere around 310 rwtq. So, we can see about 40 torque being lost to the wheels at 2500 rpm removing the cats.
Between the two graphs, the same dyno was used, just the second graph was about a calendar year after the first graph. The first graph is x-pipe with cats, second graph is offroad h-pipe (no cats.)
You will notice that while the top end power is more without cats, take a look at torque around 2500 rpm on both graphs. With cats, about 350 rwtq. Without cats, somewhere around 310 rwtq. So, we can see about 40 torque being lost to the wheels at 2500 rpm removing the cats.
Thank you very much for providing me with the data to support my suspicion. I'm wondering if a catted x pipe would solve the problem, or do I need to have the cats reinstalled? I can't stand how slow it is when just rowing though the gears. Thanks again.
Looking through your mod list, I see that you have a PD blower with stock headers. Personally, I think it would be better for you to get some long-tube headers. Not only will this allow for some more low-end torque, you will pick up torque throughout the entire powerband. Plus, you will get the added sound quality bonus (in my opinion) of having an h-pipe and no cats.
I have no data to back this up just seat of the pants feel. I just swapped out my catless X pipe for a catless H, it feels slightly more responsive in the low end. I really can't feel a difference at the top end other than a noticeable change in exhaust tone. The H sounds deeper, louder, lower in it's note. Overall I'm liking the H pipe better thus far.
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I have never ever heard of losing torque from getting rid of cats...
It seems to me that headers would actually make the loss of low end torque greater because you are increasing air flow which is what the 3 in. H pipe is doing. Do you have some data to support headers increasing low end torque? Thanks
Headers will not cause loss of torque (except maybe if you do something ridiculous like get 2" primaries). In fact, in an N/A application you can use the 1-3/4" headers and gain quite a bit of low end torque.
I'm afraid so, especially under boost.
Ok, can someone please clarify because what I was thinking seems to be totally wrong now based on this.
I was considering an aftermarket Hpipe (maintaining factory cats) with a used Gt500 over axle exhaust to my GT500 mufflers. Is this even worth it? I surely don't want to lose torque or is that only if you go "catless?"
I can tell you from first-hand experience that my car felt better when just casually driving with the cats than the h pipe. I get what you're saying about the power band shifting. I'd rather have more tq down low where I use it every day.
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