Playing with an emission tester during the last MOT test, I noticed the right two pipes gave 1.9 CO / 400 HC. Left two pipes 1.2 CO/200 HC. Above is at idle. The silencer is original. Would it be normal to get different readings like these from right and left hand side exhaust pipes? I've been taking this car for its annual test since 2005 and this seems to be the first time both sets of pipes were measured simultaneously. I have noticed, that ever since I've owned the car, more vapour comes out of the right hand pipes during a warm up phase in cold weather. Thanks in advance for any comments.
The euro 328 silencer (like most F silencers) is not internally symmetric: Image Unavailable, Please Login Image Unavailable, Please Login so this accounts for the flow difference and could affect the emission measurements (and the headers and upstream pipes aren't identical either, and the mixing inside the silencer may not be perfect so slight differences in cam timing for each bank, slight differences in the injector fuel delivery, etc.), but the real test would be to have the MOT station swap the measurement probes and see if the difference stays exactly the same -- my guess would be that some of the difference is in the MOT equipment.
Absolutely normal; like said by Steve, the fact that you have two exhaust pipes each side (well...actually, one pipe, but with an "Y" final outlet) does not mean that the two cylinder banks' exhausts are individual, which would mean one bank of the engine discharging into one outlet on one side, an the other bank through the other outlet on the other side. Both exhausts from each bank discharge into the exhaust box, where the gases are mixed together; as the "innards" of the exhaust box are not symmetrical, it means that, at the rear of the car, one side always discharges more gases than the other... Rgds
Thanks guys for your reply.Very helpful. So, not that I intend to, but if I did, which side would I chose to use as a reference for CO adjustment? Or take an aggregate of the two? This would equal 1.5 on mine, which I think is ok?
An average of the two would be fine (and using the same instrument to measure both tips would eliminate any equipment differences, but that doesn't prove your single instrument is accurate ). Your present numbers are A-OK.
I'd take the highest reading. The higher reading is what's coming out your engine, the weaker side reading is being diluted. Sent from my SM-A505FN using Tapatalk
I'd also say that at 1.5 it's a little bit high but if in doubt look at the colour of your spark plugs, they dont lie. Sent from my SM-A505FN using Tapatalk
