Emissions problem
Discussion
I'm hoping someone on here can give me some advise.
I've built an engine, based on an MPi unit, for a kit car. The engine is 1342cc, fitted with an SW5i cam, ported head (larger inlet valves) and fitted with 1.5 roller rockers. I've also fitted a Specialist Components injection kit.
I've had the engine on the rolling road (89bhp), but I think (judging on the soot on the exhaust tip) that the emissions might be too high for IVA. I should add that there were a couple of things that were picked up during the rolling road session (including the need to replace the lambda sensor) that were to be addressed.
Looking back at my notes when I built the engine (a few years ago now), that fitting 1.5 roller rockers along with a cam can lead to the emissions being high.
So my question is - can I swap out the rockers for standard ones - or 1.3 roller rockers if I can afford them (I believe standard ratio is about 1.27), without needing to change the head gasket? Or would it be best to change the head gasket anyway?
Hopefully 2023 is the year to get the car on the road (after 12 years!).
Thanks all.
I've built an engine, based on an MPi unit, for a kit car. The engine is 1342cc, fitted with an SW5i cam, ported head (larger inlet valves) and fitted with 1.5 roller rockers. I've also fitted a Specialist Components injection kit.
I've had the engine on the rolling road (89bhp), but I think (judging on the soot on the exhaust tip) that the emissions might be too high for IVA. I should add that there were a couple of things that were picked up during the rolling road session (including the need to replace the lambda sensor) that were to be addressed.
Looking back at my notes when I built the engine (a few years ago now), that fitting 1.5 roller rockers along with a cam can lead to the emissions being high.
So my question is - can I swap out the rockers for standard ones - or 1.3 roller rockers if I can afford them (I believe standard ratio is about 1.27), without needing to change the head gasket? Or would it be best to change the head gasket anyway?
Hopefully 2023 is the year to get the car on the road (after 12 years!).
Thanks all.
Hi Stevie,
I don't have the emission figure to hand (I'm not at home), but remember they managed to get it around the requirement for an MPi mini. But this wasn't consistent because of the lambda problem. It's the soot on the exhaust tip that leads me to think I could still be heading for an emissions failure.
For the IVA, the car needs to be meet the 1200ppm limit for hydrocarbons at a fast idle (again from memory) - if it's a pre-96 A Series the limit is 1400ppm I think.
I thought it was quite well established that combining the rockers along with a cam could lead to emissions being high for the Siamese port A Series engine - I did build an MPi engine for my mini (1330cc, SW5i, 1.3 roller rockers, MEMS) which passed the MoT emissions each year which leads me to think retro fitting the standard rockers will help.
I should add I'm intending to put the car in for the IVA as is - if the car passes emissions all well and good. But I'm expecting the car to fail (most do) and I will then have a complete list of things to rectify - emissions possibly being one of these.
Perhaps I should've simply asked if it's possible to switch out the rockers without needing to change the head gasket. This would apply to anyone wanting to do this. My worry would be releasing some of the tension could affect the integrity of the gasket.
Any thoughts on this?
I don't have the emission figure to hand (I'm not at home), but remember they managed to get it around the requirement for an MPi mini. But this wasn't consistent because of the lambda problem. It's the soot on the exhaust tip that leads me to think I could still be heading for an emissions failure.
For the IVA, the car needs to be meet the 1200ppm limit for hydrocarbons at a fast idle (again from memory) - if it's a pre-96 A Series the limit is 1400ppm I think.
I thought it was quite well established that combining the rockers along with a cam could lead to emissions being high for the Siamese port A Series engine - I did build an MPi engine for my mini (1330cc, SW5i, 1.3 roller rockers, MEMS) which passed the MoT emissions each year which leads me to think retro fitting the standard rockers will help.
I should add I'm intending to put the car in for the IVA as is - if the car passes emissions all well and good. But I'm expecting the car to fail (most do) and I will then have a complete list of things to rectify - emissions possibly being one of these.
Perhaps I should've simply asked if it's possible to switch out the rockers without needing to change the head gasket. This would apply to anyone wanting to do this. My worry would be releasing some of the tension could affect the integrity of the gasket.
Any thoughts on this?
Cooper1999 said:
Hi Stevie,
I don't have the emission figure to hand (I'm not at home), but remember they managed to get it around the requirement for an MPi mini. But this wasn't consistent because of the lambda problem. It's the soot on the exhaust tip that leads me to think I could still be heading for an emissions failure.
For the IVA, the car needs to be meet the 1200ppm limit for hydrocarbons at a fast idle (again from memory) - if it's a pre-96 A Series the limit is 1400ppm I think.
I thought it was quite well established that combining the rockers along with a cam could lead to emissions being high for the Siamese port A Series engine - I did build an MPi engine for my mini (1330cc, SW5i, 1.3 roller rockers, MEMS) which passed the MoT emissions each year which leads me to think retro fitting the standard rockers will help.
I should add I'm intending to put the car in for the IVA as is - if the car passes emissions all well and good. But I'm expecting the car to fail (most do) and I will then have a complete list of things to rectify - emissions possibly being one of these.
Perhaps I should've simply asked if it's possible to switch out the rockers without needing to change the head gasket. This would apply to anyone wanting to do this. My worry would be releasing some of the tension could affect the integrity of the gasket.
Any thoughts on this?
Without information, it is impossible to even offer a route to "fix"...the actual test results are vital.I don't have the emission figure to hand (I'm not at home), but remember they managed to get it around the requirement for an MPi mini. But this wasn't consistent because of the lambda problem. It's the soot on the exhaust tip that leads me to think I could still be heading for an emissions failure.
For the IVA, the car needs to be meet the 1200ppm limit for hydrocarbons at a fast idle (again from memory) - if it's a pre-96 A Series the limit is 1400ppm I think.
I thought it was quite well established that combining the rockers along with a cam could lead to emissions being high for the Siamese port A Series engine - I did build an MPi engine for my mini (1330cc, SW5i, 1.3 roller rockers, MEMS) which passed the MoT emissions each year which leads me to think retro fitting the standard rockers will help.
I should add I'm intending to put the car in for the IVA as is - if the car passes emissions all well and good. But I'm expecting the car to fail (most do) and I will then have a complete list of things to rectify - emissions possibly being one of these.
Perhaps I should've simply asked if it's possible to switch out the rockers without needing to change the head gasket. This would apply to anyone wanting to do this. My worry would be releasing some of the tension could affect the integrity of the gasket.
Any thoughts on this?
Even my old turbocharged carb'd Mini could pass MOT without too much difficulty and the latter version of it used the SW5 too, and that was in the late 90's
A fuel injected car should be even easier
High hydrocarbons generally is poor combustion, could be a problem, misfires, far too much overlap ( Not an SW5 problem ) etc.
If you really thought a milder cam would help, you could open up the rocker arm clearances for the purposes of the test as this would in turn reduce any overlap.
But carrying out changes with no means to test emissions....will be pointless.
But you need to know the actual problem, full emissions report before doing anything really.
Stevie, what you say makes sense. I won't be presenting the car for IVA for a couple of months so am only trying to preempt possible problems.
It is possible the car has a misfire, but I know the car has sparks over all four cylinders and the engine runs so I know the fuels getting through. And ignition timing is controlled by the ECU so shouldn't (hopefully) be a problem.
I need to get back to the car and have a better look at it.
It is possible the car has a misfire, but I know the car has sparks over all four cylinders and the engine runs so I know the fuels getting through. And ignition timing is controlled by the ECU so shouldn't (hopefully) be a problem.
I need to get back to the car and have a better look at it.
Just because the ecu controls timing, does not mean the timing has been set "optimally" for emissions.
Just because it controls other things, does not mean likewise.
Cam timing, camshaft itself, fuel distribution/injection timing will all play a role too. ( and general engine health )
Has the setup ever been tuned correctly by a competent person ? Inn this instance concentrating on idle/emissions for the test ? If not, then it will need done with them monitoring emissions.
But as said, one way to easily reduce overlap, make a cam seem smaller, is simply increase tappet/rocker clearances for the test.
But I would seek advice from the supplier/tuner of the ecu/injection setup as well before buying or changing any parts
Does the IVA force you to run a cat too ? Are these results with/without ?
Just because it controls other things, does not mean likewise.
Cam timing, camshaft itself, fuel distribution/injection timing will all play a role too. ( and general engine health )
Has the setup ever been tuned correctly by a competent person ? Inn this instance concentrating on idle/emissions for the test ? If not, then it will need done with them monitoring emissions.
But as said, one way to easily reduce overlap, make a cam seem smaller, is simply increase tappet/rocker clearances for the test.
But I would seek advice from the supplier/tuner of the ecu/injection setup as well before buying or changing any parts
Does the IVA force you to run a cat too ? Are these results with/without ?
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