Speed Six. Failed MOT on emissions, (again).
Discussion
Got new Lambda sensors (from Powers, the expensive ones.
New CATs (£400 each).
New exhaust.
Injectors cleaned and flow tested, all perfect.
New air filter.
Throttles balanced.
New plugs & leads, (old plugs looked a perfect colour when they came out).
Not faults on ECU, reset adaptives.
CO reading well in limit.
HC reading well in limit.
Lambda reading 1.079, limit is 1.03
Tried everything, revving it, fast idle, rag up muffler.
Could not get the Lambda to come down.
Always had this issue since I bought the car, don't reckon it has ever passed from new. Used to go to friendly MOT man but he's retired and now can't do that.
Does anyone know how to adjust the mixture to lean it out so the Lambda comes down ?
Well miffed
Have you got the software? If so whats your AFR on 123 and 456. anything +10 -10 is pretty good. If your in alarm then you may be lean or rich depending. That is usually sorted by flow rate balancing for each cylinder. If you have good flow rates ( all abound 7 ish) then i would say timing or tappets.
That Lambda reading is already lean so you need to richen it up.
Have other sensors been checked like the throttle position to ensure it is set correctly? If it can be moved going towards a slightly higher number at closed throttle might do it.
If not do these have an adjustable fuel pressure regulator or anyway of increasing the fuel pressure? That would be the easiest way to richen it up and if you are well in within other measurements might have the room to do it.
Have other sensors been checked like the throttle position to ensure it is set correctly? If it can be moved going towards a slightly higher number at closed throttle might do it.
If not do these have an adjustable fuel pressure regulator or anyway of increasing the fuel pressure? That would be the easiest way to richen it up and if you are well in within other measurements might have the room to do it.
After a bit of research this is a fairly common issue.
There is a clause in the DVSA Exhaust Emissions Standard 19th edition that specifically cites the Tuscan Speed 6 on page 176.
My Tuscan falls in that VIN code and therefore the applied emissions limit should have been 0.9 - 1.2 and I would have passed.
I pointed this out to the MOT station and showed them a copy of the 19th edition. Unfortunately they can only enter the year of manufacture into the testing machine and this automatically picks the (wrong) limits.
Finally got to the bottom of this. The car is fine the tester is wrong. The machine is only recognising the car year of manufacture and does not take into account make and model. Looking at the DVSA standard for emissions edition 19 (current), page 176. Lambda limits for TVR Speed 6 are, max 1.2 and not 1.03 therefore my car is within the limits. I pointed this out to the MOT guy and he has rung me back this morning to tell me that he has got the machine manufacturer to update the software so that it recognises it is a TVR and the limits are different. Emissions retest booked for 4.00pm today, lets see what happens this time.
There is a clause in the DVSA Exhaust Emissions Standard 19th edition that specifically cites the Tuscan Speed 6 on page 176.
My Tuscan falls in that VIN code and therefore the applied emissions limit should have been 0.9 - 1.2 and I would have passed.
I pointed this out to the MOT station and showed them a copy of the 19th edition. Unfortunately they can only enter the year of manufacture into the testing machine and this automatically picks the (wrong) limits.
Finally got to the bottom of this. The car is fine the tester is wrong. The machine is only recognising the car year of manufacture and does not take into account make and model. Looking at the DVSA standard for emissions edition 19 (current), page 176. Lambda limits for TVR Speed 6 are, max 1.2 and not 1.03 therefore my car is within the limits. I pointed this out to the MOT guy and he has rung me back this morning to tell me that he has got the machine manufacturer to update the software so that it recognises it is a TVR and the limits are different. Emissions retest booked for 4.00pm today, lets see what happens this time.
Edited by quint22cp on Thursday 10th September 11:09
Interesting, I was chatting to a guy from X-Works at the Oulton Park Gold Cup over the bank hol weekend about my AFR issue on my late 2000 Tuscan and he said early Tuscans would always run slightly lean and his needed the latest ECU chip from Powers to fix it, it's basically the latest Speed Six software with improved map. Might be worth a chat with Powers.
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