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Question about cat bypass and pre muffler


Jack.16

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So, l'm going to be purchasing a cat bypass for my 1985 carrera (don't have cats), however I have a 86 motor in the car (which comes with a cat). Would l loose power if l go with a cat bypass? Should l go for the pre-muffler? Noise/pollution doesn't matter, just don't know which one l should go for. Thanks

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I have just ordered a m&k cat bypass to replace my pre muffler in my 86 (NZ car no cat) because the pipes into it are a bit damaged, I don't expect any change in HP although I would if it was a cat I was replacing but I am no expert . I think you would need to re chip to get max benefit. I am also going to a 1 in 2 out m&k muffler.

My car without cat is rated at 231 hp and I think the cat versions are 207 hp also with lower compression

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I have just ordered a m&k cat bypass to replace my pre muffler in my 86 (NZ car no cat) because the pipes into it are a bit damaged, I don't expect any change in HP although I would if it was a cat I was replacing but I am no expert . I think you would need to re chip to get max benefit. I am also going to a 1 in 2 out m&k muffler.

My car without cat is rated at 231 hp and I think the cat versions are 207 hp also with lower compression

Paul, I'd love a report on this once installed. I've been umming and ahhing about the M&K 1/2 system for a while but can't bring myself to commit. Ideally I'd love to hear it, other than idling but people on YouTube only seem to film the car idling.

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  • 2 weeks later...

I'm interested in what the difference in sound level and tone is with cat bypass or pre-muffler compared to the stock cat?  Was/is there any droning introduced by replacing the cat with either?  Looking at (hypothetically) replacing my cat with a bypass.  I have a (Fabspeed? I think) 1 in 2 out SS muffler with stock SC heat exchangers. 

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Stew, I replaced my cat (87 Carrera) with a bursch cat by pass pipe (essentially a straight through pipe) and the difference in noise is neglible...can really not tell the difference..

Also replaced my O2 sensor at the same time as the old one looked pretty shabby..

Seat of the pants car feels like it revs a little harder but not sure if it's the car by pass or the new O2 sensor helping its cause...

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I'm interested in what the difference in sound level and tone is with cat bypass or pre-muffler compared to the stock cat? Was/is there any droning introduced by replacing the cat with either? Looking at (hypothetically) replacing my cat with a bypass. I have a (Fabspeed? I think) 1 in 2 out SS muffler with stock SC heat exchangers.

Just installed a m&k cat bypass on mine and made quite a difference in noise and performance, shoot us a pm, may have a vid of it
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