Cat removal?

FabiaTDi · Dec 24, 2003

Has anyone here removed the cat from their TDi?

Is it worthwhile just removing/replacing the cat or is it better to replace the whole system?

How restrictive is the cat and what sort of gains can you expect?

Lots of questions I know!

Merry Christmas all!

driveforward · Dec 24, 2003

Rage removed the cat from his Ibiza TDI and actually found his stats DECREASE... which may be worth noting...

FabiaTDi · Dec 24, 2003

Seems strange!
Any reasons why this would happen?
Its a possible mod that has been mentioned by a tuning company.

Cheers.

m0rk · Dec 24, 2003

tdi's have low down torque which may require back pressure.

resistance isn't always a problem.

Neo_VR · Dec 24, 2003

What were/are Rage's final performance stats?.. did he break the magic 200bhp?

DP1 · Dec 25, 2003

Maybe a sports cat would be the best replacement?
You get some back pressure, keep it legal and gain power.

driveforward · Dec 25, 2003

Originally posted by Neo_VR
What were/are Rage's final performance stats?.. did he break the magic 200bhp?

.....no

DP1 · Dec 25, 2003

Well at the time Ians TDi had 150 Bhp and could keep up with Simon on the 0 - 60 sprint. I took the pictures myself to prove it. Just ask Ian. :devil:

FabiaTDi · Dec 25, 2003

Did Rage get his car RR'd after the new exhaust was fitted?

driveforward · Dec 25, 2003

Originally posted by FabiaTDi
Did Rage get his car RR'd after the new exhaust was fitted?

Yes he did, results are confidential... see my earlier post

FabiaTDi · Dec 26, 2003

Originally posted by driveforward
Yes he did, results are confidential... see my earlier post

So not as good as the results in his sig then?

Personally I was just thinking of a decat (probably from Powerflow) rather than a whole new exhaust. This should help free up the back box a little as I have heard the cat can be restrictive.

m0rk · Dec 26, 2003

the point being - is back pressure a good thing or a bad thing?

Neo_VR · Dec 26, 2003

Originally posted by FabiaTDi
So not as good as the results in his sig then?

Personally I was just thinking of a decat (probably from Powerflow) rather than a whole new exhaust. This should help free up the back box a little as I have heard the cat can be restrictive.

Just speak to Ross and get your name put down for a Milltek

DP1 · Dec 26, 2003

Originally posted by m0rk
the point being - is back pressure a good thing or a bad thing?

I was under the impression that some back pressure is needed. After having a de-cat exhaust and free flow back box Rage's BHP went down.

Its like a trade off, which would you rather do? De-cat it and have a faster turbo spool up time. As theres very little back pressure.
Or get a sports cat and exhaust system? so you have lowered back pressure and gain BHP.

FabiaTDi · Dec 26, 2003

So how does a sports cat differ from a standard cat? Does this retain some back pressure?

So if some back pressure is required on a diesel - anyone know why?

Thanks for all the great responses! :cheers:

DP1 · Dec 26, 2003

A catalyst has as such 'elements'. On a sports cat there are more of them and there larger. This allows higher rates of air flow.
As actually proven by Simon, the power went down when he eliminated back pressure.

Shock_Xe · Dec 26, 2003

my race cat is 100 cell i think where as normal cats are 400-500

DP1 · Dec 26, 2003

Sorry, I'm confused over which has more cells.
Last nights pop is finally wearing off now.

Regular cat on the left, with many small cells. Sports on the right with less, but bigger cells. Borrowed from Milltek.

FabiaTDi · Dec 26, 2003

The Milltek sports cat still looks like it would be fairly restrictive in the picture though to me.

techie · Dec 26, 2003

Im not 100% sure if a Sports CAT would be applicable for a diesel.

Petrol CAT's are a three way convertor whereas a diesel one is two way. Their chemical make up is different.

Personally i'd just de-cat it. We do this on our PD's alot. Milltek make a large bore downpipe without a CAT and we fit that to a larger bore system with twin round tail pipes. We add a rear valance from a four motion Golf which has the cut out for the silencer so it looks smart. (for the 130 and 150 PD Golf).

Power is usually up a few bhp on a normal remap on the PD and turbo seems to spin up faster.

Cat removal?

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