Advice on full decat

[Ricco_04]

Hi All,

When I had my last MOT I found out that I still qualify for the non-cat test    I am about to fit my decat downpipe and get her re-mapped but as I have the more lax requirements (3.5% & 1200) can I get away with full decat?

I have gone through some posts and found some people do pass and others don\'t? - I have read some people have had 7% Co!  :eek

If it depends on mods then all I will have is twin Apexi filters, 3" downpipe, scilenced mid pipe, Apexi GT Cat back & Apexi PFC

Thanking you in advance

[GeckoGareth]

Hi Ricco.

have you any information regading our UK cars not needing a CAT as I\'m probably this afternoon going to remove mine and go with a silenced midpipe and different rear silence. It needed the new exhaust for the MOT but the one I got has a midpipe included and I was a little worried about emissions.

Mines a 92 or 93. No mods, has a K&N in the std airbox but that\'s it.

If I can get the pre-cat binned and a downpipe in place it\'d be good to know that I\'m not going to fail MOT\'s as a result.

Also does anyone know what to do with the air pipe that runs into the CAT? I\'ve also heard some people on about a heat sensor there as well.

Cheers

G

[Ricco_04]

All I know is that if your car is UK and pre June 1995 then there is an option to have the non cat test of 3.5%co and 1200ppm which is also just taken at idle and not the 3,000rpm fast idle test.

I have been told that the following should pass this :

Standard UK car (ie 2 cats)
Uk car with precat removed
Uk car with precat removed and main cat replaced with a hi-flow sports cat (provided all is running correctly ie not rich)

but unsure as if the full de-cat will pass?  With full decat and a remap it is effectively the same as the decat jap spec\'s with a remapped PFC so wondering on other people\'s readings?

[GeckoGareth]

All I know is that if your car is UK and pre June 1995 then there is an option to have the non cat test of 3.5%co and 1200ppm which is also just taken at idle and not the 3,000rpm fast idle test.

I have been told that the following should pass this :

Standard UK car (ie 2 cats)
Uk car with precat removed
Uk car with precat removed and main cat replaced with a hi-flow sports cat (provided all is running correctly ie not rich)

but unsure as if the full de-cat will pass?  With full decat and a remap it is effectively the same as the decat jap spec\'s with a remapped PFC so wondering on other people\'s readings?

Ah so looks like I might have issues with the pre-cat in place and the main CAT removed? bugger

Hopefully will be able to sweet talk them. They pass a lot of Ferraris which apparently are a nightmare on emissions.

Guess I\'ll be needing a PFC to adjust stuff if I got te pre-cat removed also.

cheers

G

[probedb]

I think you can adjust the PFC to give it better readings and pass, I\'d speak to one of the tuners for some advice.

[Ricco_04]

Ah so looks like I might have issues with the pre-cat in place and the main CAT removed? bugger

Hopefully will be able to sweet talk them. They pass a lot of Ferraris which apparently are a nightmare on emissions.

Guess I\'ll be needing a PFC to adjust stuff if I got te pre-cat removed also.

cheers

G

You still might be able to pass with just the pre-cat, not sure if anyone has ever expiremented with to find out?

Personally I would always remove the precat instead of the main cat (if you had to leave one in)  You are removing a lot of hot metal away from the engine bay too.

Im after the emissions readings from people with full decat to see what differences there are - like I say, some people pass ok, some are boarder line and some are way off the mark.  I just want to make sure because if it is boarderline then I will just leave the main cat in and have no troubles (hopefully!   )

[GeckoGareth]

Will keep you posted on how I go then Ricco. I\'ll be the test subject.

G

[Adie Moore]

I\'m also thinking of this mod myself, but am more concerned with the loss of back pressure = boost creep and/or spikes. i have a HKS down pipe and HKS super dragger back box, apexi filters and pfc on a \'97. i\'ve read that its the waste gate that can\'t flow enugh to keep the boost pressure down, when this is done, but only read of this once. if this is the case can the pfc keep things in line or just supply more fuel so as at least prevent the mix from going a bit lean.

[Ricco_04]

The problem you have with the standard wastegate is that it is only really big enough to cover light mods - regardless of the controller you use for it.  Backpressure isin\'t an issue on turboed cars - the better flow the better IIRC?

GeckoGareth : didn\'t mean to make you the test subject but oooooh go on then

seriously, if anyone has there emissions results to hand then I would really appreciate them  

[Ricco_04]

I don\'t suppose anyone could have a look at their last emissions and post up could they?

[G@NDY]

I have both CATs removed and mine never went near the emissions tester at the last mot, guess its just a question of where you take it  :bandit

[GeckoGareth]

Hey Ricco,

Well the cat was removed and off to the MOT test with just the pre-cat.

They put in your number plate and print off a checksheet. This said that I should have a CAT

Thought oh dear this is a no go but kept chatting to the guy about cars and RX\'s in general. When it came to the emissions test he went through the yes/no answers on the emissions computer including stuff about was car used before a certain date. Eventually the machine kicked into a non-cat test.

My car passed easily. I\'m in Bolton and the print out is back home but I think it was something like 1.25% CO and the other thing they test HC\'s? was about a 1/4 - 1/3 of the allowed limit. So it pretty much walked it. I\'m thinking that it might even pass with a straight through downpipe in place given the current readings. If you want exact figures I could find out by giving me house mate a shout. Let me know.

This was done without the AC on as well so would imagine even lower figures with that turned on to drop the idle speed a bit. De-cat all the way I reckon. Best get saving for my pipe and a Power-FC.

cheers

G

[Ricco_04]

Many thanks for getting back to me with that  :cheers

I have decided to go the full de-cat route  :InLove  and as I have a PFC it should be fine (I have the 3.5%co and 1,200 HC limits too  :Thumbsup! )

Thanks again for the help guys  :chat

[dr3]

Just to add to your peace of mind, you will be fine as long as you have the air pump running. The extra oxygen forced into the exhaust manifold helps burn off the HC\'s as the  gas is so hot there, it also must dilute it to a certain extent to bring the ppm down.

I put an analyser on my car with a full de-cat system and ran it with and then without it on and it brought the emissions down a lot, I can\'t remember exact figures, but it brought it well within limits. Just remember blank off the pipe that goes to the centre section cat.

[vxer]

I put an analyser on my car with a full de-cat system and ran it with and then without it on and it brought the emissions down a lot, I can\'t remember exact figures, but it brought it well within limits. Just remember blank off the pipe that goes to the centre section cat.

Ah, i think that clears up my confusion! So the airpump goes to both exhaust manifold *and* cat?

Cheers, Paul.