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I also had a nice option which were the JCR hi-flo cats , these were 200 cell and changed only the cat section of the exhaust and made the exhaust louder with the valves closed and open . It retains the valves -& made the exhaust maybe 30% louder in both poistions . Was also a cool option and very high quality but i wanted more .
i have mine for sale , if interested pls pm me . Tks
Thanks for all the information, not easy to get GT2 mod info as there are so few around. The JCR HF Cats sound like a nice option but as an Engineer I just can't keep the cats once I do an exhaust, along with a nice weight savings, they are a significant bottleneck on the high HP turbo cars, plus I have never had a smell issue with the three decatted vehicles I have owned and even decatted a turbo car still isn't particularly loud (to my ears anyway...I grew up racing/riding unsilenced 2 stroke bikes and nothing is louder than a 750 two stroke with full open expansion chambers, so anything quieter than that passes my ear street test ). I also live in Florida which has state statutes saying vehicles must be equipped with federally mandated smog equipment but it is ignored by the authorities so just another reason to go catless. I would however like to insure the CEL light does not come on, which I believe can still be accomplished with an O2 sensor bypass valve in place in conjunction with the tune. Also thanks re: M-Engineering concurrence quality. I have heard/experienced the same going back several years when "M" was the chief software Engineer at Cobb. Take care and nice chatting.
The powertrain components are identical between our cars; I’d expect similar sound effects if you have a product with similar physics.
That is badass as hell...i don't want to mod my exhaust exit points though so that is out of the question for my GT2 but Wow, what a sound. Can I ask, is that the OEM CS exhaust? Beautiful steering wheel and instrumented display btw.
100 cell, per published specs. I am rather sensitive to nitrous oxides and don't sense much of it despite the low cell count.
The CS idea is basically two cats flowing into one big mixing chamber and straight out to the atmosphere. The big pops on throttle lift probably has to do with there being such a large void for vacuums to form and reverberate. Should be less of a problem if you have a commercial product with side exhausts. Would definitely recommend the 100-cell HJS cats in any case.
Do 100cell cats do much?
I've never removed them but cracked a few and too loud without turbos, but also never knew what the other advantage was in keeping them, back pressure?
Flow > backpressure. Don't believe the myths. There's no performance benefit to having cats, it's all about EPA, state, and federal regulations.
Not entirely true.
Here is a dyno graph of the same car/same tune with Cat Bypass Vs. HFCs.
They are virtually the same. IMO 200cel cats are the best choice so that you avoid the CEL and do not have to worry about emissions while having 95% the flow of a catless set up.
Here is a dyno graph of the same car/same tune with Cat Bypass Vs. HFCs.
They are virtually the same. IMO 200cel cats are the best choice so that you avoid the CEL and do not have to worry about emissions while having 95% the flow of a catless set up.
Exactly, but I think you are misrepresenting the causal outcomes. With a tune optimized for cats it should/could out perform a catless car, but for a tune optimized for more flow (read decatted) it should certainly out perform a catted car, especially in a turbo environment. If it doesn't we need to revisit the laws of thermodynamics.
Exactly, but I think you are misrepresenting the causal outcomes. With a tune optimized for cats it should/could out perform a catless car, but for a tune optimized for more flow (read decatted) it should certainly out perform a catted car, especially in a turbo environment. If it doesn't we need to revisit the laws of thermodynamics.
Precisely. There is no argument; catalytic converters reduce flow and backpressure does not equal torque/power. All that matters is exhaust speed and scavenging with the correct exhaust pipe diameter.
That's why we see ALL race cars with cats, right? Right???
Precisely. There is no argument; catalytic converters reduce flow and backpressure does not equal torque/power. All that matters is exhaust speed and scavenging with the correct exhaust pipe diameter.
That's why we see ALL race cars with cats, right? Right???
Nobody is arguing that bypass pipes are not optimal on a track car. Simply pointed out that your statement was not exactly correct, and gave a comparison backed up by data. (Same car, same tune parameters, all within the same day)
If you are running track only, go bypass pipes. If you are going to be primarily on the street, the cons far outweigh the pros.
08-30-2021 | 06:21 AM
