Griffith CAT's, how many and passing emissions test without?

[black_potato]

Hi,

I will be a few months away from from an MOT when I pickup the Griff and my biggest concern is emissions..
The current owner of my intended car purchase claims the car passes MOT's as is but I'm not convinced.

Question 1....
My assumption is there are normally 3 CAT's, 1 in each 4-1 Manifold (The pre CAT's) and 1 in the Y piece
(https://tvr-parts.com/tvr-parts/part-details/tvr-s0160/exhaust-y-piece)
Are there any more ?

Question 2....
Which ones do you normally need to pass MOT, maybe the Y Piece is enough in most cases ?

Question 3.....
Can you realistically meet emissions requirement without a CAT. In my case I will have an Emerald ECU so will have a lot more tune-ability than most so if anybody has specific experience of passing with an Emerald and what is required that would be great. If the answer is no.. You have tried and failed that is also very useful.

And.. Question 4 if I maybe greedy.
How robust are the Y Piece CAT’s. I have been offered a 2nd hand one but I’m a little wary that it will be effective.

TIA

Richard

[TV8]

Mots are not always a problem and with a working main cat would pass easy.
Why not ask for the car to be MOT’d pre sale with you present?

You get a good look under the car and maybe have something you we’re not aware of highlighted and resolved at time of purchase?

[mk1fan]

If I recall correctly, if all is well with the car (factory spec wise) then the car should pass with just the CAT in the Y piece.

Depends how 'friendly' your MOT place is for 'de-CAT'.

I think ACT do a 'sports CAT Y piece' if you want to gain some performance but keep 'legal'.

[phazed]

Your car is guaranteed to fail without the main cat.

I used to run Megasquirt, it always fails but then miraculously passes and I am slightly poorer.

[TV8]

phazed said:

Your car is guaranteed to fail without the main cat..

Hi Peter,
happy new year to you - how are you doing? Still thinking Pork?

My blue car always passed the MOT without the main cat but the pre-cats were both in place. The current one typically needs a re-test...

[markcoopers]

I assume you are looking at a post 1993 car?

The Emerald vs any other aftermarket ECU will only be as good as the mapping. However most emerald ECU's for a while now had a switchable map facility so you could map for different fuel grades or states of tune. You may be able to tune one of these maps without the cats and still pass an MOT if running for a short period of time....ie idling during MOT test. We used this facility years ago to get a number of Westfield sevens through MOT and even IVA tests.

[phazed]

TV8 said:

Hi Peter,
happy new year to you - how are you doing? Still thinking Pork?

My blue car always passed the MOT without the main cat but the pre-cats were both in place. The current one typically needs a re-test...

Hi Graham. HNY to you too.

The P word is on hold at the moment. Concentrating on upgrading loads on the chim at the moment.

[QBee]

OP, deducing from your post that your car has a Clive Y or similar, there are a couple of choices, but the main one is to swap in a standard Y for the test, with the main cat in it.
I have one in the shed that you can borrow or buy (your choice), and I regularly work just north of Saffron Walden if that helps you to meet up.

[black_potato]

Thanks QB. At the moment I belive it has a ACT decat setup. Manifolds and single piece Y section.

I have a couple of months to get it worked out. MOT is end March I believe.

[SMB]

black_potato said:

Thanks QB. At the moment I belive it has a ACT decat setup. Manifolds and single piece Y section.

I have a couple of months to get it worked out. MOT is end March I believe.

Remember what I said on your other thread though, any y piece you get will need to be modified to take the single lambda probe solution that's been installed on the car you are buying. Any standard y will not have the probe mounting. So that means you can't borrow.

[QBee]

SMB said:

black_potato said:

Thanks QB. At the moment I belive it has a ACT decat setup. Manifolds and single piece Y section.

I have a couple of months to get it worked out. MOT is end March I believe.

Remember what I said on your other thread though, any y piece you get will need to be modified to take the single lambda probe solution that's been installed on the car you are buying. Any standard y will not have the probe mounting. So that means you can't borrow.

......unless you weld in a lambda boss. Put it also probably means a remap too.

I think Jools does a low emission map for the Emerald. It takes one of the three map positions. You may already have a low emission map. Worth checking if Jools did the mapping?

[RobXjcoupe]

My Griff has the act manifolds with decat pipes and original ecu. It won’t pass an emissions test until the straight through pipes have been swapped with the cats.
I can’t be arsed with bolting and unbolting anymore. So the cats will be permanently fitted soon. Doesn’t make any difference powerwise just less noise with the cats bolted on and no headaches when driving with the roof down.

[spitfire4v8]

strictly speaking any car that was originally fitted with a cat should have one for mot pass whether it meets the emissions standard or not. no cat = fail.
irrespective of that you wont get a decatted rv8 tvr to pass the emissions test anyway legitimately, theyre just too dirty.
The good news is the main cat is all you need to get to the emissions limit and because it is a large area it means only cars over say 300hp are losing out significantly in bhp terms by keeping it.

Looking at the pics your griff has a wideband, so assuming you have the output correctly scaled, and the lambda trimming enabled, you can have a lambda=1 part trottle and idle map in one of your three map slots and just use that in conjunction with a main cat for mot time, swapping back to decatted and richer mixes if you desire the rest of the time.

I'm unsure of the legalities of running decatted on the road (outside of mot time) which is why i used to advertise my decats as off road use only, then it was up to the customer if they wanted to run that on the road ...

[citizen smith]

black_potato said:

Hi,

I will be a few months away from from an MOT when I pickup the Griff and my biggest concern is emissions..
The current owner of my intended car purchase claims the car passes MOT's as is but I'm not convinced.

Question 1....
My assumption is there are normally 3 CAT's, 1 in each 4-1 Manifold (The pre CAT's) and 1 in the Y piece
(https://tvr-parts.com/tvr-parts/part-details/tvr-s0160/exhaust-y-piece)
Are there any more ?

Question 2....
Which ones do you normally need to pass MOT, maybe the Y Piece is enough in most cases ?

Question 3.....
Can you realistically meet emissions requirement without a CAT. In my case I will have an Emerald ECU so will have a lot more tune-ability than most so if anybody has specific experience of passing with an Emerald and what is required that would be great. If the answer is no.. You have tried and failed that is also very useful.

And.. Question 4 if I maybe greedy.
How robust are the Y Piece CAT’s. I have been offered a 2nd hand one but I’m a little wary that it will be effective.

TIA

Richard

If you have not handed over any cash yet, then ask the seller to put 12 months MOT on it. If the seller is convinced that the MOT has never been a problem, then there should be no issues with putting 12 months MOT on it.

I always stipulate what I want 12 months MOT, prior to any car purchase of any value!

[QBee]

So my old catted TVR Y piece, with a wideband boss welded in, should enable any Emerald-fitted car to pass the MOT legitimately? Subject to having the right map in the relevant slot.

I have half a mind (goes with TVR ownership, I hear you say) to get a wideband boss welded into my old Y piece, with a screw-in plug available so it can still be used by 14CUX cars. Then it can be passed around the Chim/Griff/V8S community for MOTs. Once each person has the right map in the memory, or saved on their computer, all it will cost them is two couriers a year.

What do you think, J?

[Sardonicus]

spitfire4v8 said:

strictly speaking any car that was originally fitted with a cat should have one for mot pass whether it meets the emissions standard or not. no cat = fail.
irrespective of that you wont get a decatted rv8 tvr to pass the emissions test anyway legitimately, theyre just too dirty.
The good news is the main cat is all you need to get to the emissions limit and because it is a large area it means only cars over say 300hp are losing out significantly in bhp terms by keeping it.

Looking at the pics your griff has a wideband, so assuming you have the output correctly scaled, and the lambda trimming enabled, you can have a lambda=1 part trottle and idle map in one of your three map slots and just use that in conjunction with a main cat for mot time, swapping back to decatted and richer mixes if you desire the rest of the time.

I'm unsure of the legalities of running decatted on the road (outside of mot time) which is why i used to advertise my decats as off road use only, then it was up to the customer if they wanted to run that on the road ...

This ^ is my view too , and anyone that says they can get through a legit cat test and meet the defined limits is talking bks although the tester is under no obligation to fail a car with no cat its emission requirements he is interested in although clearly the two go hand in hand anyway

[SMB]

Sardonicus said:

although the tester is under no obligation to fail a car with no cat its emission requirements he is interested in

the MOT guidelines actually say, if the original cat is obviously removed it's a fail. So most take that to mean fails emissions, but as with most MOT items there is a degree of tester interpretation, so a car obviously missing a CAT by visual inspection could be a failure.

official wording
A catalytic converter or particulate filter missing where one was fitted as standard.

using a car without a CAT on the road between MOT's then comes down to being stopped, which is most likely if you have given them any other reason to stop you, that may be driving style, noise ( often associated with de CAT), or other obvious vehicle flaw. Actually determining a de CAT car can be quickly done based on exhaust smell as mentioned above.

[Englishman]

With my car enthusiast hat on, I can see the rationale to removing CAT’s to maximise power output.

But as the previous owner of a 450SE wedge, where the garage used for my annual MOT said it was most polluting engine they had ever measured, I have now decided CAT’s are a good thing for the planet, my children and grand children's future, so where fitted originally, they stay on my TVR’s.

I’m sure a few will say, 'but there are only a few thousand TVR’s so what harm will it really do' (true), but when someone in the White House says basically the same thing….. We all have responsibilities to future generations, leave those CAT's in place please.

[WinstonWolf]

I never thought I'd read such a thing on PH

[RichB]

black_potato said:

Hi, Question 1....
My assumption is there are normally 3 CAT's, 1 in each 4-1 Manifold (The pre CAT's) and 1 in the Y piece...

Correct.

If it's any help, I run my Griff 500 without the pre-cats but with the main cat and it passes with no problems.

As I understand it the pre-cats are there because in order to get type approval the engine needs to run clean after a short period of time e.g. 5 mins and that's why the pre-cat are high up the manifolds. Once up to temp then the main cat copes easily. When you take your car for an MOT it is, of course, warmed through.