De-cat Pipe On A Stock Fduk

[damehyndman]

Hi,

If you fit a de-cat pipe on a stock FD without fixing an apexi etc, is this bad news for the engine etc?

Dame

[Fish]

Dame it depends on the other modifications you have on the car.

If you\'re just replacing the mid-pipe with an otherwise \'STOCK\' system you should be ok.

Fish

[damehyndman]

Thanks to all who have posted. There seems to be a difference of opinion here. I have a Racing beat back box, but that is it, totally unmolested (apart from a steel AST:D) I have a spare mazda cat which I have had made free flowing, handy for MOT\'s, and a de-cat pipe, so obvious what the intent is.

Do you not think I\'ll run into boost problems Fish?

cheers,
Dame

[Timmy]

It can cause boost spikes. But is your car a uk spec? as the title of the thread suggests as they have 2 cats.

[damehyndman]

No like most it is an import.

[damehyndman]

So 2 cats and de-cat no boost problems, 1 cat boost problems?

[ro284]

I\'ve fitted a large bore unsilenced de-cat, but also have an Efiny Y pipe, Hard Pipes on standard IC, and aftermarket air filters(cold feed) Dolphin tail pipe, and yet to fit a large bore DP, at the mo i have an Apexi running on base map, running only under 4k, runs well but the heat light flashes at around 3k on acceleration, replaced knock sensor, no difference, but waiting to get full mapping done after fitting DP, My point is that when you remove the cat That seems to be when the engine is at some risk, which you may not see in the way of flashing heat light if you dont have Apexi! personally i would not rely on boost guage only,
Don\'t know if that helps at all, Blitzboy would advise better,
Bob

[Fish]

The rule of thumb is that on the earlier 8bit ECU\'s you can get away with 1 modification to the inlet/exhaust system. Anything more than that and you will have issues.

On the later 16bit ECU\'s you could get away with 2 changes.

Do a search this was covered to death years ago.

Fish

[dhracer]

It can cause boost spikes. But is your car a uk spec? as the title of the thread suggests as they have 2 cats.

So do the jap imports only have 1 (the main cat) then? If so then is there any point in replacing the downpipe on imports?

Sorry for being OT.  Personally I wouldn\'t bother risking it, save up a few changes and do it all at once with a new ECU, the difference in pace should make the car feel really quick again :3gears-rh

[damehyndman]

I did do a search Fish, obviously not very well. I shall err on the side of caution then and stick with the standard cat.

thanks,
Dame

[Timmy]

It is worth replacing the down pipe on imports but a stock import down pipe is an upgrade for a uk spec.
I\'m guessing a uk spec car u shudn\'t get boost spike from removing just one cat but i cud be wrong. Either way you shud definatly keep the cat on a stock ecu as the boost spike will cause you to loose a tip.