Discussion
the car is running high on the hydrocarbons and running bad at tickover, when removing one of the lambar sensors it runs better, if i remove the second sensor the car stops ! thincking about removing the cat do i have to remap the ECU and what about the lambar sensors. The car is a 1994 and running on a close loop back to the ECU from the sensors?
pink-fever said:
1994 and 40,000 on the clock. the engine does not sound tappy ?
Just cos it does not sound Tappy does not mean that it is not worn.
The engine may not sound ticky with a worne cam as the hydraulic lifters take up most of the wear until the cam is very bad.
My Griff 500 had 42k on the clock and was a little tapy but nothing obvious or out of the ordinary.
but when it went in for a possible head gasket failure the cam was found to be total cream crackered.. some lobes were worn by 3mm or so. Once the case hardening goes the cam will get worse VERY quickly..
I had my cam replaced with a V8 MC2 cam (Hydraulic again) and stage 3 heads (both heads were cracked too)
This is what nacnuds SEAC cam looked like when it was changed (and his Hydrocarbons were very high
) 
you can read more here
www.tvrcc-bristol.co.uk/reports/03/0302Peninsula/main.htm
>> Edited by pebbledash on Monday 19th July 16:51
jamesuk28 said:
Hi i just started a similair topic in TVR general,
My mechanic recokns I can decat (1993 Chim) and I don't need the cats for my mot???
I was under the impression all cars made in or after 1993 required a cat. Who is right?
the cut off point is somewhere in 1993 but it seems the precise date is a bit of a nightmare to establish (if there is one) you may find you need them
jamesuk28 said:
Yes i think it was 1st August 1993, Ill have to get him to look at the stamp in the engine, it gives the date my car was born, just like a budweiser.
The legal position with Cats is a little bit of a grey area, it is not iligal to remove them (as far as i can determin) but the car has to be fitted with them as new, also they are not required to be fitted to pass the MOT, But the CAR if manufactured after 1/8/93 and is not exempt for any reason MUST PASS the required Advanced emissions test(wrongly called the CAT test).
If the car can pass without the cats then, it would get its MOT. There is a source on the internet, and the gov stuff (very heavy reading) which details this.
here
www.bobmckay.co.uk/cattest.html
Quote:-
"CAT test is an unfortunate term which leads many to think that the MOT is testing the Catalytic converter fitted to later vehicles but this is not so.
The MOT is testing emissions, so if the emissions from the tailpipe meet the requirements the vehicle passes. Whether a CAT is fitted is irrelevant. The deciding factor is the vehicles date of first registration. A "Cat" may be fitted to a vehicle which only needs to meet the two gas test and if the emissions are satisfactory, it passes. A "Cat" may have been removed and the vehicle is required to meet the "Cat" test standard by virtue of its first registration date. If the emissions meet the standard then it passes."
Another point is that the TVR Griff and Chims had 3 cats originaly 2 Pre Cats and one main cat, the pre cats were there so that after x seconds of start up the car would pass a seperate emmisions test, this test is not part of the MOT but the car when delivered by the manufacture Must pass the test.
>> Edited by pebbledash on Monday 19th July 17:51
Very interesting Mr Bond, Thankyou.
My car is a "L" reg sso am I right in thinking it was registered on or after 1 aug 1993?
I thought the main cat sat in the "bucket" after the "Y" piece, but my mechanic says they sit before the "y" piece. Its all very confusing. I would love to decat, but don't want to fail the MOT and then have to pay to have them re-fitted.
My car is a "L" reg sso am I right in thinking it was registered on or after 1 aug 1993?
I thought the main cat sat in the "bucket" after the "Y" piece, but my mechanic says they sit before the "y" piece. Its all very confusing. I would love to decat, but don't want to fail the MOT and then have to pay to have them re-fitted.
jamesuk28 said:
Very interesting Mr Bond, Thankyou.
My car is a "L" reg sso am I right in thinking it was registered on or after 1 aug 1993?
I thought the main cat sat in the "bucket" after the "Y" piece, but my mechanic says they sit before the "y" piece. Its all very confusing. I would love to decat, but don't want to fail the MOT and then have to pay to have them re-fitted.
There are three cats on a standard (if its safe to use in a sentance with TVR in it) Grif/Chim system.
there is one in each of the Manifolds, in the big bit just as the 4 pipes merge, and before the bend and the Probe !!
Then there is the Biggy, the Main Cat this is in the Dustbin sized portion of the downpipe (the joint in the y peice)
The pre-cats (the ones in each manifold) can be removed without entering the Grey area of the Law as they are only required to meet the x second start up, emmision test.
The main cat is the one that does the bulk of the work.
again it is all down to the test that the car has to pass.. this is where the 1st August 1993 bit comes in so basicaly if its post the date its IIRC CO<=3.5% and HC<=1200ppm, after this date, its an "Advanced Emmisions Test" which is CO<=0.3% and HC<=200ppm.
Hope that Helps..
Mark With a griff 500 With No Precats..
>> Edited by pebbledash on Monday 19th July 19:54
If theres nothing actually wrong with your cat then I'd leave it in, removing it will give you about 0.05bhp extra, the only benefit is a bit more noise and it gives you a few MOT issues, but nothing that can't be 'bypassed' 
The only reason mines completly cat less, is it was either that or buy new cats as they had died
The only reason mines completly cat less, is it was either that or buy new cats as they had died
deeen said:
... so if u take out the precats u will be fine, cos the mot does not test emissions from cold, but to be sure of passing the mot test, its safest to leave the main cat in.
It should do, mine does.
If it doesent I would guess you have other issues.
raceboy said:
If theres nothing actually wrong with your cat then I'd leave it in, removing it will give you about 0.05bhp extra, the only benefit is a bit more noise and it gives you a few MOT issues, but nothing that can't be 'bypassed'
The only reason mines completly cat less, is it was either that or buy new cats as they had died
Ditto...
My precats came out, as one was a bit fubar'd
replaced the precats with none return cones, main cat still where TVR intended it to be.. >> Edited by pebbledash on Wednesday 21st July 08:32
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