Max overlap for MOT pass
Discussion
I got my car MOTd a while back and it failed emissions. Which was fine I thought, I will get some CATs fitted and job done.
Unfortunately it has been brought to my attention that my cam may have too much overlap (4 degrees).
My tune is a bit ropey at the moment and needs sorting out, but before I take it to get tuned I need to make a judgment on wether or not to replace the cam with one that has less overlap or take the risk and hope it will pass after CATs and a tune. Otherwise I will end up paying for a tune (and transportation to the tuners) twice.
So, what is the max overlap anyone has got an MOT pass on. I am talking true, legal pass here not "friendly MOT centre" pass
Here's my engine spec:
227/234 .614"/.576" 113+2
Thanks
Unfortunately it has been brought to my attention that my cam may have too much overlap (4 degrees).
My tune is a bit ropey at the moment and needs sorting out, but before I take it to get tuned I need to make a judgment on wether or not to replace the cam with one that has less overlap or take the risk and hope it will pass after CATs and a tune. Otherwise I will end up paying for a tune (and transportation to the tuners) twice.
So, what is the max overlap anyone has got an MOT pass on. I am talking true, legal pass here not "friendly MOT centre" pass
Here's my engine spec:
227/234 .614"/.576" 113+2
Thanks
Edited by Gunnytron on Monday 14th August 19:26
It's a how long is a piece of string question.
But a ropey tune sure as hell wont help.
And no cats fitted for an MOT test that requires cants to be fitted...also sure as hell wont help.
And OEM cats usually be more efficient than any aftermarket cats.
There are just too many variables here to give you the answer you want to hear.
But a ropey tune sure as hell wont help.
And no cats fitted for an MOT test that requires cants to be fitted...also sure as hell wont help.
And OEM cats usually be more efficient than any aftermarket cats.
There are just too many variables here to give you the answer you want to hear.
If i remember correctly emmisions are based on the age of the engine not the car, Hot Rodders do not like to fit new crate motors to their early iron because with it comes modern emmision regualtions, they prefer to build engines with early serial number blocks to avoid this scenario
Ian.
Ian.
Gunnytron said:
It's a 94 RX7 (I should have mentioned that) so technically doesn't need CATs.
Well if you just have to bass a basic MOT...ie sub 3.5% CO and 1200ppm HCC, then that should be a piece of piss.But technically a 1994 car should require catalytic converters. Almost every car post August 1992 should, with only a handful of exceptions.
How does yours fall into the exceptions ? Or is it a rotary thing ?
stevieturbo said:
Well if you just have to bass a basic MOT...ie sub 3.5% CO and 1200ppm HCC, then that should be a piece of piss.
But technically a 1994 car should require catalytic converters. Almost every car post August 1992 should, with only a handful of exceptions.
How does yours fall into the exceptions ? Or is it a rotary thing ?
As it's a pre-95 import there isn't a legal requirement for it to have CATs fitted. Obviously it still needs to pass emissions though.But technically a 1994 car should require catalytic converters. Almost every car post August 1992 should, with only a handful of exceptions.
How does yours fall into the exceptions ? Or is it a rotary thing ?
MyM8V8 said:
You have an emissions problem for a start.
I'd begin by wanting to know the state of the tune. If that's guaranteed optimum, I'd be looking at a set of cats. If that doesn't sort it you have a cam problem,
That is a logical way of looking at it. This may lead to having to get it tuned twice, but the auto-tune of the ECU I have (Holley) may be good enough to compensate for a different cam.I'd begin by wanting to know the state of the tune. If that's guaranteed optimum, I'd be looking at a set of cats. If that doesn't sort it you have a cam problem,
I guess I can also take it for another emissions test after it's tuned, then from those results, the tuner/exhaust place may be able to have a guess as wether or not the CATs will allow it to pass.
Gunnytron said:
As it's a pre-95 import there isn't a legal requirement for it to have CATs fitted. Obviously it still needs to pass emissions though.
And as I said, if does not have to pass a cat based test, and only the basic, then that should be a piece of piss, unless your car is f
ked.stevieturbo said:
And as I said, if does not have to pass a cat based test, and only the basic, then that should be a piece of piss, unless your car is fked.
hmm, you do raise an interesting point. I know it was tested as a 94, I assume they tap the number into the database and it tells them what to test it as?ked.Might make some enquiries about that as the reason I got a 94 was so that I didn't have to run CATs
Gunnytron said:
hmm, you do raise an interesting point. I know it was tested as a 94, I assume they tap the number into the database and it tells them what to test it as?
Might make some enquiries about that as the reason I got a 94 was so that I didn't have to run CATs
Again there are a few exceptions up to around 94...but they really are very few.Might make some enquiries about that as the reason I got a 94 was so that I didn't have to run CATs
But possibly if the car was an import ? maybe there is some leeway there, or again maybe it's a rotary thing, as dont think they were ever particularly clean engines ?
But normally the legal age for a car to require cats, is August 92.
Definitely find out exactly what emissions levels you need to meet.
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