Making JDM De-cats

106pete · Post by **106pete** » Thu May 31, 2012 12:09 pm

I'm looking into making some decats while I have some spare time in work but I'm not 100% sure on the cat I have to copy from, it was fitted to a car I've just stripped but it could be a uk one stuffed in there.

The cat also has a slightly angled flange at one end, does this need to be replicated or can it just be a straight pipe?

Does anyone have the uk and jdm measurements for me to go by and what size would be best, a 2.25' and 2.5' option I guess??

Thanks pete

Post by **Merlin** » Thu May 31, 2012 12:25 pm

We should see if we can get all of this info together and add it to the wiki. JDM CAT's have a rotated flange on them which is different to the UK CAT. I have been pulling info off PUK:

4th gen 2.2 VTEC
UKDM 34.5cm long
JDM 26.0 cm long

5th gen 2.2 VTEC
UKDM 97-98 34.5cm long
UKDM 99+ 39.5cm long
JDM 26.0 cm long (can anyone confirm?)
Type-S

Ted · Post by **Ted** » Thu May 31, 2012 12:32 pm

i've recently decatted the pickup but since sold it but from memory i would say it was a lot longer than 26cm and thats a jdm one.

Post by **Merlin** » Thu May 31, 2012 12:40 pm

I have a JDM decat from a 4th at my house so I'll measure it.

Post by **vanzep** » Thu May 31, 2012 12:46 pm

deffo 26cm for 4th gen JDM cat/decat

Dbo · Post by **Dbo** » Thu May 31, 2012 1:21 pm

also the JDM cat has the lambda sensor in it and a UKDM has no hole as lambda is in downpipe.
the JDM is 26cm long as had one made for mine and the flange from cat/decat to centre pipe is different from UKDM as has to cut mine off and weld it on

Post by **indigolemon** » Thu May 31, 2012 1:57 pm

Dbo wrote:also the JDM cat has the lambda sensor in it and a UKDM has no hole as lambda is in downpipe.

lambda is in downpipe for both, the JDM cats have an overheating sensor though.

Dbo · Post by **Dbo** » Thu May 31, 2012 2:21 pm

indigolemon wrote:
Dbo wrote:also the JDM cat has the lambda sensor in it and a UKDM has no hole as lambda is in downpipe.
lambda is in downpipe for both, the JDM cats have an overheating sensor though.

i have to disagree with you m8 sorry

i only had 1 lambda and it was in my cat and is still in it now in the garage(the bloody thing would not undo)
i have no lambda in my downpipe

so have been running without one!!!

Post by **indigolemon** » Thu May 31, 2012 2:30 pm

Dbo wrote:
indigolemon wrote:
Dbo wrote:also the JDM cat has the lambda sensor in it and a UKDM has no hole as lambda is in downpipe.
lambda is in downpipe for both, the JDM cats have an overheating sensor though.
i have to disagree with you m8 sorry
i only had 1 lambda and it was in my cat and is still in it now in the garage(the bloody thing would not undo)
i have no lambda in my downpipe so have been running without one!!!

Really? That's bizarre man. The lambda needs to be before the cat as the chemical reactions going on in the cat would likely screw with the readings. What's on the downpipe then? Is there a plugged hole?

Post by **Merlin** » Thu May 31, 2012 2:34 pm

Dbo wrote:
indigolemon wrote:
Dbo wrote:also the JDM cat has the lambda sensor in it and a UKDM has no hole as lambda is in downpipe.
lambda is in downpipe for both, the JDM cats have an overheating sensor though.
i have to disagree with you m8 sorry
i only had 1 lambda and it was in my cat and is still in it now in the garage(the bloody thing would not undo)
i have no lambda in my downpipe so have been running without one!!!

Sounds like your car doesnt have the correct configuration. Probably it won't make a huge difference where your lambda is if your running a Decat. Or have I miss read that and your running without a lambda sensor?

As IL said the JDM OEM way is Lambda in the downpipe and heat sensor in the CAT.