What Decat

[madmunky]

I resently got my supra and want to get it fully decated, I know it has a Chris Wilson De-Cat but what do i need to remove the second cat, that car is a j spec tt rz.

 

Thanks for any advice

 

(also will decatting cause flames out the exhaust, are they legal?)

[Chris Wilson]

I make my pipes as two seperate items, a first de cat pipe to remove the cat nearest the engine, and a second de cat pipe to remove the second cat. Depending which cat is already out you need the other de cat pipe. You need colder plugs and a restrictor ring, also a means of defeating the stock fuel cut when the ecu sees more than 1 bar boost, unless it has some fancy ecu fitted already that takes care of this internally (unlikely). I have everything in stock ready to ship. It shouldn't flame, no.

[madmunky]

Ok thanks will have to look into it, the car has a uprated ecu and a boost controller, I expect the one i need it the one nearest the engine and the restrictor ring, how much are they? and how easy/hard to fit?

[merckx]

how much are they? and how easy/hard to fit?

I paid about £150 for each one.

 

It's a little awkward getting to one of the 3 nuts that hold the 1st cat to the turbo elbow, it helps to have a long extension and a universal joint for the socket set.

 

It's best soak to them with penetrating fluid for a while too, you don't want to snap the studs!

[madmunky]

Thanks, is there anywhere which explains why you have to have the restrictor ring?

[merckx]

Quoting Homer

 

To raise boost beyond the stock level the restrictive catalytic converters are removed, thus allowing the turbos to spin faster and produce more boost pressure.

 

There is a down side to this. With both cats removed the turbos will in fact over speed far past their safe limit and reach over 1.6bar (23.2psi). This is due to the small size of the jspec wastegate which cannot cope with the increase in exhaust gasses.

At these pressures the ceramic blades in the turbo can become detached from the shaft and therefore cause catastrophic failure of the turbo.

 

In order to add some restriction back in to the exhaust a restrictor ring is added to the exhaust system. A restrictor ring is simply a metal plate that fits normally between either between the 1st and 2nd decat pipes, or the 2nd decat and cat-back. The centre of the restrictor is drilled out to a smaller diameter than the exhaust itself (normally around 2inches). A properly sized restrictor should bring the maximum boost pressure down to 1.2 bar or less.

 

A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases causes the turbine to lose speed, which in turn reduces the rotating speed of the compressor. The primary function of the wastegate is to stabilize boost pressure in turbocharger systems, to protect the engine and the turbocharger. The wastegate is controlled by a wastegate actuator.