decat removal and replacement

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I've been browsing a few forums today - some topics referring to decatting the exhaust pipe.

Back in my toe'rag days, a friend of mine used cut down scaffold pole to replace the pipe where the cat would have been. Is it possible to do a DIY job like that on the MR2, or is it not advised?

Is it actually worth while removing the Cat converter to let the engine breath freely & possibly prolong its life??

[Liz]

If you mean about running a decat pipe, there are quite a few of us with one of these.  I would not recommend a scaffold pole!!

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Where can you get decat pipes from? I'm looking at cutting cost and doing a DIY jobby as I'll be shortly (hopefully) splurging every last penny into buying a mk3

I had a look on ebay, but unfortunately it just returned pipes for a mk2 MR2

[Anonymous]

If you decat an N/A engine you'll kill the mid-range torque and the car will feel gutless as hell.

[markiii]

on an N/a car with no ECU tuning a decat is pointless, you will lose Torque and fail an MOT really poinltess

on teh Mk3 what will both help engine longevity and likely make your engien more responsie/increase power is removing teh PRE-cats

theres a huge sticky at the top this section detailing why/where and how

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Really? Is that due to back pressure loss?

So its not a good idea?

[markiii]

Really? Is that due to back pressure loss?

So its not a good idea?

not a good idea without  ECU tuning

it's not back pressure persee but right idea

when toyota mapped the ECU they will have based it on a certain exhaust flow model, on an n/a engine just having a bigger pipe slows down gas flow which affect the tune and puts a massive hole in the torque curve

on teh roadster I've tried it in much teh way you suggest, and all it did was ake teh engine more rev happy but murder teh midrange, suffice to say it went back on.

that said if you buy something like teh PPE 4-1 manifold and decat pipe that is designed to work together you can gain up to 11bhp and not put a hole in teh torque curve, that though is going to cost more like £300

[Kool PT]

Remember that PPE also do a high-flow cat which will not only let you up the power without failing your MOT, you won't kill the torque either.

Precats should be out to help airflow & also help to prevent that rather irritating engine failure thing.

I was thinking about looking into a PPE group buy of some sort soon...high flow cat & exhaust

Web site quotes +8bhp from cat when used with their manifold, and one forum user got about +12bhp from the pair combined.

[markiii]

Remember that PPE also do a high-flow cat which will not only let you up the power without failing your MOT, you won't kill the torque either.

Precats should be out to help airflow & also help to prevent that rather irritating engine failure thing.

I was thinking about looking into a PPE group buy of some sort soon...high flow cat & exhaust

Web site quotes +8bhp from cat when used with their manifold, and one forum user got about +12bhp from the pair combined.

good idea I'm sure Matt at PPE will look after you if you mention ROC

[ChrisGB]

PPE reckon around +8bhp from the manifold and cat. They now also offer a metal matrix cat which should flow more gas and last longer. This costs an additional $50 US and worth the difference IMO.

Using the manifold and cat into a free flowing exhaust improves things further still. I got +19bhp by fitting a combination of PPE manifold and cat + Che single exit exhaust. It is hard to tell for sure, but the car feels quicker now I have the Blueflame exhaust in place of the Che. I cannot get to a dyno until late September.

PPE reckon that the decat pipe is worth 2bhp over a catalysed one, but that into the stock exhaust. The decat pipe may be worth a little more with a free flow exhaust. You still need a cat of some sort for the MOT. The PPE setup is designed to work with the decat pipe, so you will not lose midrange torque, so they tell me.

On the stock manifold, the setup is designed to work into a cat. Although I have not tried it, there are reports of the midrange going limp if engine setup is not altered to accommodate the decat. I would think that to make best use of the decat pipe on a stock setup, you would need to be able to alter valve timing / overlap, so Apexi PFC or PE Camcon, with rolling road mapping sessions.

I cannot see a bit of scaffold pole doing much for the running of the car, though I would like to see the fab / bending required to replace the stock cat with one. Silverstone Performance, Greestreak, Che and some others do off the shelf decat pipes, or your local exhaust fabricator could probably cobble something together. You will need an O2 sensor conditioner to lift the post cat oxygen sensor out of the exhaust gas stream a little or your check engine light will come on all the time.

Chris