Catalytic Converter/AJ6 Eng. TT exhaust 6.0 V12

[Jaguar5993]

Hello,
On my 1995 6.0 V12 Coupe I fitted the AJ6 Engineering Torque Plus Kit with good results(although I do not know the power output details yet).
However, I thought it would be a good idea to add the TT exhaust system to gain the full performance from the kit.
This of course, meant doing away with the cats. and as my left-hand cat.was already shot ,due to a problem a few years ago(now fixed)so, I went ahead.
I must say to AJ6 Eng. credit, the car went and sounded great with this kit. I did keep my standard middle boxes on, with some fabrication, so I had the best of both worlds in my opinion.

The first problem with the TT downpipes and cats. removed, was that these pipes hung too low. It was only 3 1/2in from the ground! Combine this with low profile(225/55 ,20 spoke)tyres and older springs the problem of grounding was a nightmare!

The second problem was the car failed the MOT with emissions(I know, I should of got the emissions checked before the MOT!!).

I had taken the AJ6 Eng. advise on their Exhaust Emissions section.I quote,"Contrary to widespread belief the UK MOT does not require a catalyst to be present,".
Basically,most cars in good tune and depending on the year, should pass without cats. My car is a late 1995 one.
Would that make the difference??

With the disapointment,I did not get the read-out of the CO % figures.
The car was in top tune,ie;new plugs,filters,new OEM lambda sensors and all jets sonic cleaned etc.
I am going to refit the old cats back,but need a left-hand replacement.

Option 1.Cut out the old cat and replace it with a new cat.(OE Jag £99).
Option 2. Replace to a new complete,down single cat system(£300 eBay).
Option 3. If anyone has a good second- hand one(part No NHC6701AA LH).
With recession hit wife, I can't stretch to a Jaguar £600+ new one!!
Any ideas anyone?
Many Thanks.
Nick 6.0 V12 Coupe(1995)

[almcl]

Nick

It didn't fail on CO2. Carbon Monoxide, possibly, (CO) if so, then a high CO reading could be a faulty lambda sensor, leaky injector(s), faulty temp sensor or something else. In any event, fixing the problem would be better than disguising it by refitting the catalysts.

The reason for the MOT failure is available to you on-line. Go to http://www.motinfo.gov.uk/ and input the info on the fail certificate (you did get that?) or the reference number of the V5.

Not sure if this will give you the readings, possibly not under the latest regime, but if it doesn't you ought to be able to request them from the garage that did the test. Try and get at least the HC and CO.

[masterb]

Nick,
Have you got an adjustable ECU? with your TT system?
I Have an AJ6 engineering ecu on my car and it was adjusted to the lower/leaner end of its adjustment, just before going for mot.
It's reading's were so low/clean that the garage told me to make the car more rich using the adjustment on the ecu.
He then re run the test so i could get the setting richer, but still within limits.

If you have an adjustable ecu , you should see a shaft coming out of the ecu, if i remember rightly you turn it anti clockwise to make the car run leaner, and obviously vice versa.
PaulB.

[Jaguar5993]

Hi,
Thanks for the advice.
On the failed MOT certificate it said;"Exhaust emissions carbon monoxide content after 2nd fast idle excessive."

Still looking into it. AJ6 engineering have said that an engine in sound condition with an operative Lambda feedback system should have no trouble passing an emission test without needing catalysts.

My sensors are new,correct types and having owned the car for 8 years and kept it in top form with its 61.000 mile engine ,I am a bit surprised why it failed. I might have to get it plugged-in and see what comes up.

Unfortunately,I do not have an adjustable ECU. AJ6 Eng.supplied their special EPROM chip for my PCM(ecu), to use with the TT exhaust set-up.

Thanks again,

Nick
6.0 Coupe(1995)

[kevinhafner]

Hi Nick,

A bit late in the day I know but I went through exactly the same as you did about 4 years ago.
The conversion was done in 2002 and I wanted to upgrade with the TT. I spent about £500 cleaning injectors, renewing everything there was to renew and she still failed on the CO reading on the MOT. I sent my readouts to AJ6 but they still insisted it should pass without the cats.
I reverted back to the old cats, saved by my clever mechanic!
In the intervening years I have replaced a coil and an amplifier on one bank which was trashing the cat, maybe the original problem for the CO level not being correct?
At the same time I asked the guy doing the MOT for the readings on each bank. One passed and the other only just failed and for that reason he failed the whole car. I pressed him even more and it was only at this stage did he admit that if the combined average for the two exhausts are below the limit they should pass the car!
If you try Graham at Grulogger I found him extremely helpful and was able to provide me with not just one but two second hand cats. He advertises in the magazine.
Regards, Kevin. P.S I still have the TT exhaust sitting in my workshop with about 1000 miles on them which is what I did before the MOT came up! Mine is a '93

[Jaguar5993]

Hi Kevin,

Thanks for responding.I thought I might be the only 6 litre owner to do this AJ6 Eng. upgrade and I had thought that all the problems were due to me being too greedy for power!!

I am pleased to say, that still with the AJ6 Eng. Plus Torque kit on(minus TT exhaust),my car is running the best it ever has.
My left-hand cat. was shot to pieces and as a d.i.y dabbler, I only found out how bad it was when I had it in my hands and all the melted moon rock came out.
You are right,I would highly recommend Graham at Grublogger. I managed to get a good s/h cat. from him,although not as cheap as they used to be,but better than £700 from Jaguar for a new one!!
So now I have a sorted engine with two good cats.on,with the bonus of more performance, but minus any exhaust drumming(thats another story!)

I am guessing that at some stage, that I accidentally repaired the original fault that caused the melt-down(as previously stated in earlier posts),because just before the re-MOT I got the car tested at a Jag specialist friend near me for the CO content and was pleased at a read-out of 0.1% of which he said"Thats better than some modern cars".The MOT guy said "How the **** did you do that?"
Aj6 Engineering to their credit did try and advise me and said that as these cars are getting older ,there only has to be something out/worn to tip the CO into tilt,so the cats.are really needed.They said that they tried to design some cats.that went after the TT exhaust down pipes, but they said there wasn't the room and the cats. would of been too low to the ground.

All the despair of the last few months has just melted away,well,untill the next problem that is!!It is an ageing XJS!!
Thanks again
Nick

[kevinhafner]

Hi Nick,

By the sounds of it you had your plus torque kit done fairly recently. Would you mind telling me how much it cost as I'm thinking of doing it to my convertible.
I can't believe the difference in the performance between the two as they should be identical engines, both 6ltr but the converted coupe is so much faster on acceleration. And the convertible only has 41000 on the clock while the coupe is more than double that!
I did notice the difference in performance when the TT exhausts were on, even if for only 9 months but I did keep grounding out, the same as you!

Regards, Kevin.

[Jaguar5993]

Hi Kevin,

Sorry I cant help you.I got my Plus Torque Kit in 2002 and I cannot remember how much it was.

I guess you have checked their website out ? I have seen that it is coming in at £1200E exc.VAT??

I have realised that I had been running with the kit on with a duff L/H cat.for some time.So I thought putting the TT exhaust would be the cure to all things!!I am now in a good place with the car .

Good luck!

Regards