Co content ?

[keithTVR350i]

Can anyone tell me what the Co content should be for performance rather than economy (350 i)? or what the best compromise should be. Also just trying Bosch Platinum plugs (the four electrode ones) anyone else tried them and has any views ?
Thanks
Keith

[taz200i]

If you are talking about the CO measurement that is made as part of the MOT test, then that is set as an idle figure. The performance requirements are air/fuel ratios better than stochiometric 14:1. Modern economy engines run very lean, but that requires sophisticated combustion chamber design (a lean mixture is very difficult to ignite). Performance engines run rich, this is controlled by the ecu. You can fool the system to richen the settings, but this over the whole rev/throttle range. The idle setting will go rich and you could fail the MOT as well as any other areas affected by rich mixtures.

[350matt]

The exact setting for any engine will vary slightly however if you aim for 4.5% CO approx 12.5:1 / Air:fuel on full throttle, then that'll be about right if in doubt go richer rather than leaner, as this is somewhat safer.

Matt

>> Edited by 350matt on Thursday 9th January 12:15

[2 sheds]

At idle 4.5% would be quite rich on a 350i try 2.5% but you need to balance this against hydocarbons, if you go to low on the co the hydrocarbons will go up, i assume we're talking about a 350. if your setting the idle co it won't change the performance only idle & cruise. fuel pressure may give you a few bhp.
Tim