MOT CO2 Emissions

[Cadami]

Engine in question:
Alfa 166 3.0 24V
Emerald ECU
GTA inlet cams and injectors
No CAT's or Lambda fitted.

Last year's MOT (January) results were:
Front bank - 2.339%
Rear bank - 3.448%

This year's MOT (March) results are:
Front bank - 0.290%
Rear bank - 1.099%

I assume the MOT kit is correctly calibrated and I'm sure I've not been playing with the ECU. Both cold times of the year and engine was up to temperature.

Any ideas why the reduction? Fuel? The front bank is seriously lean and I'm concerned for the valves :-)

[Sando]

Hi Al
Mine has been down to as low as 0.3 On low tickover at MOT with the old engine
Are you still running the air bypass valve? I don't use one, but what does quite often move is the throttle position sensor values. Resetting the throttle closed and wide open positions usually aligns things back up to match the map back to the actual throttle position But why bank to bank would be different not sure - from recent info check cams are still all lined up!

[Cadami]

Thanks Rob, I removed the valve last year as recommended by you. I'll get the laptop out and recalibrate the TPS just in case.
However, I've always thought this engine was a tad lumpy, which maybe a cam / timing issue. What's the simplest method of checking the cams apart from removing the cam covers and checking the cam timing marks?

[Sando]

It's either cam covers off, or if you marked the wheels up, or know the markings,check cam belt cover side if you can get in to see them behind covers/splash guards. At TDC I have cam wheels marked up so a straight edge lines up markings across each pair . But there were already marks on the wheels. It's only a guide to see if the belt has jumped. The cam locking tools are the proper accurate way to check, but probably way over the top for a weak mixture at tickover.
To be honest I'd reset the the TPS and tickover and just forget it and be glad it gets through MOT with ease.
its probably more to do with mapping at tickover than anything else, as without the ICV it's just butterfly position an map squirt and spark timing that does everything.

[Bernard]

Apologies if you already know this but the cams and drive belt wheels only location is the friction of the taper...there is NO key on the taper.....therefore if the bolt is not sufficiently tight the they could slip against each other...... If that makes sense.....