rkbycrof

Thinking of taking my Blobeye STi to the next stage and taking the downpipe cat out, it already has the centre section cat removed.

Does anybody know if I'll get the CEL light coming on after the downpipe cat is removed?

Or should I wait until I plan to get it remapped sometime next year?

Cheers for any advice.

Rich

Midlife......

iTrader: (2)

You will almost certainly get CEL P0420 (cat below efficiency)

Shaun

rkbycrof

Does that actually mean anything to the car? ie is it safe?

I don't plan to have the car remapped until probably 6-9 months time.

Thanks for your quick reply!

Henrik

iTrader: (5)

My check engine light came on after about 50 miles IIRC.

It wont pass an MOT with just one cat, of course, but also if some other sensor (etc) failed you wouldn't know about it as the check engine light would already be on

rkbycrof

Will it not pass with one cat? I thought there was a reasonable chance that come MOT time if I put the centre cat back in it would pass!

What did you do about your light? I guess the chances of something going wrong in the 6-9 month period I'll be running before it goes for its remap are slim.

johnnyroper

your best bet is to decat it just before you get the remap and not leave 6-9 months,you could end up damaging the engine due to increased flow and higher boost.
and then when mapped i think the mapper can overcome the cel light caused by lack of cat

johnnyroper

why wont it pass mot with just 1 cat?
i think a prodrived sti only has 1 cat as do most 4 cylinder cars

fonzy

I'm sure most decat downpipes, do away with both cats, i.e. decat downpipe, centre section backbox as opposed to the standard 4 sections. So you'd have to fit both cats for the MOT.

Midlife......

iTrader: (2)

As Johhnyroper mentioned Newage STi's can throw boost spikes when fully decatted and not re-mapped. You could try and change the restrictor but it would be best to de-cat just befor the remap

Then find a de-cat friendly MOT station...it should be able to pass emissions tests with only 1 cat but only if fully warmed up

Shaun

555-Scooby

in most cases i think it will pass the MOT with just the downpipe cat fitted...dont think it will pass with just the centre one fitted.

easyscoob

dont u get sum ecu fix for that??

Henrik

iTrader: (5)

Sorry, I had a brain fart... I meant to say without a cat

finchyboy

Must admit i've heard the same they will pass with the downpipe cat in place and the centre cat removed.

rkbycrof

OK, I'm seriously confused now I had an understanding that if I decatted my blobeye STi I would probably be OK come MOT to just refit the centre section cat, although it would have to be warm to pass. Is it the case that I would have to fit both cats back to pass?

Also original question on CEL, do the fixes you can buy work or waste of money? I want to remap first half of next year so should i just wait?

Henrik

iTrader: (5)

Scoobynet lore seems to suggest that you *may* pass with just a centre cat. Some do and some don't AFAIK.

As for the CEL's: I'm not sure if the STI has an up-pipe cat, but if it does then the fix for the decat up-pipe CEL is a 2.2kOhm resistor from maplins (9p) plugged into the original contact.

The rear oxygen sensor is still needed, but apparently the thresholds are changed when mapping so that it doesn't throw a CEL (without the sensor, it will throw a CEL). AFAIK there are no other fixes to this.

GazTheHat

I got it within a couple of miles of the decat system being fitted. It didn't matter much though as i kept it in negative boost until the following day when it was remapped.

I think the advice is to limp it until remap.

mgcvk

A mapper can reprogramme for the extra heat hitting the temp sensor once the cat is removed in the downpipe. Problem is that due to the higher temps the tip of the sensor often burns off so CEL will come on anyway. The 9pence - 12pence resistor should fix it. Don't buy expensive CEL fixes that require drilling holes in the pipework etc!!

Midlife......

iTrader: (2)

Sorry..........I have to beg to differ here mqcvk!!

If you are having the car fully de-catted and re-mapped then simply remove the rear 02 sensor and blank off with a bolt

Then the mapper simply "maps out" the P0420 CEL by telling the ECU that the sensor is still there and working

No sensor.....no P0420 CEL.....sorted LOL

Shaun

Henrik

iTrader: (5)

This is what I wanted to do, but apparently it was not possible with my Ecutek3 remap (unless I understood it incorrectly). My mapper said that the sensor had to be present, but that the threshold values would be adjusted so that it wouldn't throw a CEL.

Henrik

iTrader: (5)

The oxygen sensor is a problem as well, though, not just the cat on fire sensor There's no simple fix for the rear oxygen sensor CEL, afaik

rkbycrof

This all seems to be a bit of a nightmare. A new question then, is decatting the downpipe worth all of the hassle?

GazTheHat

Not unless you're planning on a remap. Then yes it is.

Midlife......

iTrader: (2)

OK

I have a newage MY02 Bugeye WRX with a full de-cat with no rear 02 sensor, just a bolt.....Bob Rawle used EcuTeK to Map out the CEL P0420 (cat below efficiency)....

There is no "cat on fire" dashboard light for the newage

As Gaz says..... don't fully de-cat without a re-map..especially the STi's

Shaun

Henrik

iTrader: (5)

Bob mapped mine as well and he said I had to keep mine in

Maybe i misunderstood him.

rkbycrof

OK, thanks for the advice, I've been itching to decat it for a while now but guess I'll just have to wait until I can do the remap at the same time. Message seems pretty clear, don't take a chance with an STi!

Midlife......

iTrader: (2)

Henrik

You can keep the OEM rear 02 sensor for a de-cat newage......Bob Rawle just tells the ECU that all the cats are in place LOL

While I think about it......I still have my OEM rear 02 sensor in place and it's the EGT sensor that's not there

rkbycroft....

I messed about for a while removing various cats from my car (with increasing noise) but it wasn't until I had the car re-mapped that I noticed any improvement in actual performance !!

HTH

Shaun

Mackers

So can you fit a full decat system and headers without any sensors refitted if getting a Ecutek remap on an 04Sti or not?

Also wheres the ideal section to place a Defi EGT sensor?

Dave.

AndyLyman

iTrader: (1)

I got an adaptor £22 from Ebay USA to fix my p0420 on my 02 STI...

just screws in the exhaust and the lambda sensor screws into the adaptor - job done....

do a search on ebay for CEL FIX, the adaptors are there as from 27/8/07

Andy

rkbycrof

How long have you had yours fitted, does it actually work?