Talking with 2 GN shops in my area. One says change my cat and exhaust ( they aren't rotted out but are in his words a terrible system ), too restrictive. The other says I will get more improvement leaving the converter + muffler and changing to a 3 " downpipe. I can only do one right now. Thanks for the opinions in advance.
Do a cat back and replace the cat with a "test pipe" This will give you the most "bang for the buck"
My "cat back" is a 2.5" none mandrel bent duals that was $150 from a local muffler shop. I added a used pair of ultraflow straight though stainless mufflers and for my $250 total investment, I picked up 4 mph and .4 seconds in the 1/4 mile.
I've done back to back testing with a Terry Houston 3" downpipe and a stock replacement 2.5" downpipe and a ported stock elbow. The THDP was only worth .05 seconds/1.5 mph over the 2.5" DP on a high 11 second car (11.79 avg vs. 11.84 avg. ET)
Hope this helps,
http://perfauto.tripod.com
Thanks Chris. Basically the one shop was telling me that adding a TH 3" d.p. to my restrictive catalytic converter and mufflers would increase my performance more than using the stock d.p. and adding a high flow converter with the hooker mufflers. Is he right? Was your downpipe testing done with your testpipe and ultraflows already on the car? Also I live in Toronto and we have emmisions testing. Can I use a testpipe as my catalytic converter? As far as I know we require them on our vehicle for emmisions. If I can't any recommmendations on converter brands? Thanks!
My opinion ... biggest bang for the buck is the cat back system. Adding the 3" downpipe will help once the performance picks up a bit.
There are companies that make hi-perf. cat conv's
they flow better than stock.
Frank
With a stock downpipe do I get a 2 1/2" high flow cat or a 3". Just wondering about next spring when I get the 3" downpipe, I don't want to have to switch the converter again.
Also anyone know of any hooker exhaust distributers in Toronto or Ontario?
Random Technology is one source for high-perf cat's. Check with your favorite TR vendors.
It may be tough to get a cat that will mate with a stock DP now and a 3" DP later. Fit with these pieces is always tricky, as the 3" DP's tend to extend back further and require shorter catalytics or test pipes.
If it matters...
When I bought my 3" convertor and dual 2.5" cat back system from ATR 2 years ago, they said the system was worth 18-20 HP or so. They also said their DP was worth 40 HP or so.
Rick
My opinion ... biggest bang for the buck is; keep the stock cat back, replace the stock mufflers with straight pipes, install a three inch TH DP with a high flow three inch cat.
Hello-
I have a stock block and turbo, and a few bolt-ons. Bigger injectors, chip, SMC kit coming. I have a THDP, high flow cat, K&N 9" and 15 year old flowmasters. You can see my mods here:
http://personal.mia.bellsouth.net/mia/s/h/shawnco/gn.html
Well anyway, I REALLY like the sound of my flowmasters, but it is not quite loud enough for me. I want REALLY loud. Will replacing the flowmasters with a "hollowed out" muffler hurt performance? I figured the less back pressure the better, right? Also, the flowmasters must be a little clogged up after 15 years.
Car is daily driver with once a month track duty.
TIA
There are no "Mufflers". Stock is a single crossflow muffler and stock pipes are 2" ID. The stock "cat back" is crap. Throw it away and start over with a 2.5" dual system minimum.
Use a cat for emission testing purposes only. Don't weld it in place. Use a band clamp and have a test pipe that is the same size. I can swap my cat out in less than 15 minutes.
and flowmaster muff's can not get clogged they have no packing they are open chambers that deflect sound in 3 or 4 different areas to cancel out sound waves ...the turbo is killing alot of sound in your car.....besides quit is cool!
hehe gl