Removed 2nd cat only. Restrictor Ring needed?

Hi

Quick question, if I only remove the 2nd cat will I need to put a restrictor ring in?

Renamed the thread to something meaningful. Please use descriptive thread titles.

cheers

do you still have the first cat in? What exhaust? What decat pipes?

I think it's conventionally a bit frowned upon to only remove the second Cat' HOWEVER... I've been running BPU+ for 3 years with that spec (1st Cat' in; 2nd Decat') and had absolutely no problems. No restrictor ring, as the cat' provides the additional restriction that the stock wastegate can't cope with at increased boost.

do you still have the first cat in? What exhaust? What decat pipes?

Yeah it has the first cat still in. I put a 2.5 inch second decat, and a Mines exhaust

2.5inch decat will be fine. First cat will be enough of a restriction to avoid overboosting.

2.5inch decat will be fine. First cat will be enough of a restriction to avoid overboosting.

Is there much of a benefit just taking the second cat out John? What kind of HP increase would you envisage?

My VVTi Tip is completely stock with the exception of an RS-R from the second cat back. Just wondered if fitting one decat would make much of a difference to the power output.

Cheers

Havard, you would be better off taking out the 1st decat and leaving in the 2nd. The 2nd one is far less restrictive yet it still allows an MOT pass on emissions. It's win win really.

You would probably still require a restrictor ring though.

Taking off the 2nd decat would probably net you around 0.1bar of boost. Will be the equivilant of around 15-20hp. No restrictor ring required in this setup.

H - get a 2.5" CW decat (which I have for sale). And you'll gain spool and midrange.

Oooh, im interedted in getting this 2.5" 2nd de-cat now i know no faffing around reqd.... so people are saying 1.1bar is safe with second de-cat only, and 1.2bar with both de-cats and restrictor ring (on a jap spec)?

D

With both cats out, you'll need a 1.2bar RR. Speak to Chris Wilson for one. My car came alive with a double decat.

You still need a new pump and a fcd and plugs if your going to hit 1,2 bar

My Plan is to get and fit the 2nd de-cat, then buy a 1st de-cat, pump and plugs when funds come in, I have an HKS F-Con that im told can be mapped to act as a FCD, but how will i know if it is already mapped to enable this or not?? Or is it a fact of waiting to double decat and trying it??

Cheers

You will know when you hit 1 bar if you have fc.

I thought that might be the case lol..

Cheers

H - get a 2.5" CW decat (which I have for sale). And you'll gain spool and midrange.

Is this for the first cat or the second Johnny?

Also, how much do you want for it.

H.