[Mk2] [Turbo] Decat...help pls

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nickg07
Posts: 729
Joined: Mon May 30, 2011 2:50 pm

[Mk2] [Turbo] Decat...help pls

Post by nickg07 »

Hi im looking at a decat for my Mr2 turbo now, what i dont understand is this:

Most decats ive seen on ebay are 3" bore...but the stock exhaust system is less than a 3" bore is that correct? The applications says its bolt on..but how can this work if the stock exhaust system is only 2.75"?

Note my exhaust system is an apexi hayabusa but im guessing that it connects to a standard downpipe/cat so it must be 2.75" at the cat end...so if i wanted a 3" downpipe decat what happens here? ?!

help a noob please guys!
Slarty
Posts: 4224
Joined: Thu Oct 26, 2006 3:52 pm
Location: Barking, Essex

Re: [Mk2] [Turbo] Decat...help pls

Post by Slarty »

Although they're a 3 inch bore, they might step down to 2.75 inch at the flange. Even if they don't, 0.25 inch on diameter is only 0.125 inch on radius so you'd only be 0.125 inch bigger each side/all round. 0.125 inch is only 3 mm. hardly worth worrying about.
nickg07
Posts: 729
Joined: Mon May 30, 2011 2:50 pm

Re: [Mk2] [Turbo] Decat...help pls

Post by nickg07 »

I phoned gtschris he measured through bore of a stock turbo cat at 65mm and the Berk is 75 mm. i know my apexi has 76mm piping but it does, annoyingly i guess step down at the downpipe join flange.

Thing is im having my flexi replaced but want a decat at through same time but my mot is up in the next few months and i can't put it through now cos the flexi needs to do first. and tsar a n reg car so has to take the stricter test.
toyokid
Posts: 251
Joined: Thu Dec 16, 2004 6:46 pm
Location: North Yorkshire
Contact:

KO'd?

Post by toyokid »

I am de-catting with a 2.5" pipe
made by KO Racing
Have used it on my rev 2 for 6 or 7 years
and am now moving it to my rev 3.

The exit from a CT turbo is less than 3"?
a smaller diameter keeps the gas speed up?

Subject to passing the MOT, which mine has
you have extra free performance?

Stephen
Shmed
Posts: 3568
Joined: Wed Dec 15, 2004 2:38 pm
Location: Worcestershire

Re: [Mk2] [Turbo] Decat...help pls

Post by Shmed »

I have a Hyper 2.5" decat if you need one. Selling it for £50.
January 2014
..the only thing I can promise for sure is slow progress.

May 2015
just have this niggling thought that if I rip out the wiring, then the car will never get out of the garage again.

Still in the garage...
craig_mr2_mk1
Posts: 464
Joined: Thu Dec 08, 2005 8:41 pm
Location: kidderminster
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Re: [Mk2] [Turbo] Decat...help pls

Post by craig_mr2_mk1 »

Turbo's don't need to have a Cat anyway, As all tubby's are imports there's no emmisions data recorded so should be put through on a pre 92 test.
toyokid
Posts: 251
Joined: Thu Dec 16, 2004 6:46 pm
Location: North Yorkshire
Contact:

KO Racing 2.5" downpipe

Post by toyokid »

Due to a change of circumstance
I am now selling my 2.5" KO Racing downpipe
which I have lagged today with 1000 degree wrap,
there is an extra bung for a wideband sensor.

Stephen
Marf
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Joined: Tue Jan 17, 2006 4:56 pm
Location: West Sussex

Re: [Mk2] [Turbo] Decat...help pls

Post by Marf »

craig_mr2_mk1 wrote:Turbo's don't need to have a Cat anyway, As all tubby's are imports there's no emmisions data recorded so should be put through on a pre 92 test.


not true, any import car that does not appear on the testers database that was manufactured after august 1995 should be put through the cat test with the stricter limits.

Image

So any N reg or newer Turbo should be tested under the stricter limits. Doesnt always happen, depends how savvy or friendly the test station is :wink:

Also worth noting that a cat does not need to be fitted by law[1], you just need to be able to hit the emissions targets for your car.

[1] this is apparently changing next year.
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