Ignition map for better emissions

[Jeff Ninebar]

My car was well over on the CO emissions for the MOT today, 5.75 % max is 3.5%

basically its running rich at low revs, is there anything I can do with the ignition timing to make it burn more fuel from 1000-2500 rpm? it sits at idle fine on the afr gauge at around 14.5 and on boost is ok, don't really want to adjust the mixture too much as it ticks over and runs ok as it is...

this is the map that is in there at the moment. I have not had it mapped on a rolling road yet this is just a 21psi map that was on the Nodiz forum for the 5GTT

[Matt Cole]

It might be worth having a word with Chris at eff parts. Maybe email him that map and hopefully he can offer a little advice.

[Ian S]

Generally, if you turn up the Lambda the CO goes down.

Just a tweak of the idle mixture screw might achieve this.

If you still have the original carb, at least.

Mine one time had a CO of 0. He increased that by turning the mixture screw.

IF the CO is high, does that mean it lean? Maybe slightly less advance would change that?

[Fordy]

if using a ford coil pack, check it for strength on both sides of the coil 2-3 and 1-4

check base timing matchs the flywheel with a timing gun, if your retarded alot that'll not help emissions

then i'd be checking mixture screw for breakage

[Jeff Ninebar]

Generally, if you turn up the Lambda the CO goes down.

Just a tweak of the idle mixture screw might achieve this.

If you still have the original carb, at least.

Mine one time had a CO of 0. He increased that by turning the mixture screw.

IF the CO is high, does that mean it lean? Maybe slightly less advance would change that?

high CO is rich. I get a lot of soot on the exhaust pipe, so i guess i'm getting incomplete combustion due to rich mixture or too much advance

[Ian S]

I presume that the earlier the combustion starts, the more happens before it's sent out of the exhaust.

If it starts too early, power might be less as the cylinder pressure needs to peak at some number of °ATDC, I've forgotten what but seem to recall it's not all that many, say 10 to 20.

Completeness of combustion might be another thing, or partly related if the burn is faster with higher cylinder pressure.

Either way, I expect there is a limit for richness and how much advance can utilise it, after which the emissions become higher.