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The mkiv Supra Owners Club

Brand new 1ST 3" decat pipe


johnd-mkiv

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These pipes have been jigged up an tested on a two supras with no problems, made from 316 stainless and mild steel 10mm lazer cut flanges that have been tig welded into place. also includes a 1.2bar restrictor ring made from stainless steel

 

£100

 

image

 

comparrison to a genuine apexi decat

 

image

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Depends if its a NA or Turbo

 

If its a NA then no you dont need to do anything but get the second decat to fully unrestrict the exhaust..

 

If its a Turbo then decatting will increase the boost and i 'think' you need a boost controller as the boost goes over 1.2 bar, and you turbos will go 'BANG'

 

I have a NA so if the turbo bit isnt quite right, Sorry im learnin :)

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Just found this

 

Name:

Decat

 

Also known as:

Double Decat

CAT removal

Straight through exhaust pipe

 

What is it?

The stock Supra has two catalytic converters. These do all manner of wonderful things for the emissions of the engine, but to do so they get in the way of the exhaust stream, and this reduces the flow and increases backpressure. In a turbo car, backpressure is an evil, and once you are past the turbos you need a little as possible. The restriction also increases the heat in the engine bay because one CAT is on the downpipe.

 

Decatting simply replaces the exhaust pipes with the CATs in for exhaust pipes without CATs in. The diameter and quality of material etc. varies but they all do this one simple function. The bonus factor is that freer-flowing exhaust means a small increase in the volumetric efficiency of the engine. That means more power. Double bonus is the the turbos can flow more air so they produce more boost. That means *lots* more power. People who get decats done regularly report of the car feeling like a new one afterwards, the difference is that big.

 

However, the increased boost is a double-edged sword, you have to watch out for boost creep, running lean on fuelling, and fuel cut kicking in. Running lean after a decat is a very real phenomena, the J-spec fuel pump isn't up to the job most of the time, and the ECU can't fuel for more than 1 bar of boost anyway, especially once the fuel cut is removed.

 

Pros:

Increases the volumetric efficiency of the engine, thus giving you more power

Increases the boost of the turbos, giving you more power

Removes heat from the engine bay

 

Cons:

Apart from some success with the first (1993.5) MkIV Supras, you will need to swap one CAT pipe (usually the centre section one as it's easiest) back in order to pass an MOT

Boost creep may occur

Fuel Cut may occur

Your fuelling may not be adequate for the extra boost

Stock j-spec ceramic turbos appear to go pop faster under the higher boost levels

You will need a colder grade of spark plug with a 0.8mm gap (instead of stock 1.1mm) as the higher boost will cause a Misfire

 

Thanks to Ian R for this..

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Yea i have a TT and also have a blitz boost controller which is set to 1bar. That should be ok???

 

 

Well look at you Surj, going all BPU.

DON'T DO IT!!!!!

 

You'll make me do it, and I really haven't got the cash flow for it at the moment.

 

don't listen to me matey, I'm only jealous. When you get it done you'll have to take me for a spin in it.

 

Oh, and just a little advice, get a walbro fuel pump upgrade, you really don't want these engines running lean, the results tend to be pretty terminal.

 

Seeya soon dude.

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Haha how you doing Dan? Hey should have my new wheels delivered tommorrow. Hope they all fit ok over my brakes. Getting my sounds done on thursday. All i got to sort out is my exhaust. Got an apexi exhaust at the mo but want a nice rubble from it so rather than change it i might as well decat it. Looks like its gonna cost me more though! haha!!! We'll see what happens mate.

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I will take one mate....im in essex too so will come and collect, have you fitted any yet....are they a direct fit?....it wont be for a while though as the car is off the road waiting for some much needed cooling mods ;)

 

 

no worries mate give me a shout when your ready, direct fit no cutting or messing around un bolt, bolt in jobby ;)

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You going to do the 2nd as well John?

 

 

going to look into whats involved when i make mine and ill see from there. I'll keep you updated;) was thinking along the lines of making one pipe that does both first and second in one

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going to look into whats involved when i make mine and ill see from there. I'll keep you updated;) was thinking along the lines of making one pipe that does both first and second in one

 

seems a sound idea to me. Although tricky when MOT time comes knocking, would mean replacing both cats

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