Running lean?

[Andy Pandie]

Had the Tuscan on the rollers yesterday and it appears she is running lean. Probably wont be sorting it myself but more out of curiosity than anything else, what are the possible causes?

Also I know it's not good and will be sorted very soon, but what are the dangers?

Thanks in advance,

Andy 'P'

[nrick]

Depends on how lean, any recent mods?
If it is really lean it could cause damage through detonation to the head combustion chamber and piston crowns. Very serious, what makes you think it was running lean?

Can tell a lot from the plugs.

[Andy Pandie]

nrick said:

Depends on how lean, any recent mods?
If it is really lean it could cause damage through detonation to the head combustion chamber and piston crowns. Very serious, what makes you think it was running lean?

Can tell a lot from the plugs.

Thanks,

No mods, I repaired and reseated the air box properly over Christmas, but can't imagine that's made any difference. I'm only repeating what I was told, the AFR from the graph seems to be between 14.0 and 14.2, but I have no idea what it should be

I haven't done any investigation yet.

[nrick]

This might help
http://en.wikipedia.org/wiki/Air-fuel_ratio

[Andy Pandie]

nrick said:

This might help
http://en.wikipedia.org/wiki/Air-fuel_ratio

Thanks,

So 14.7 is the magic figure then, although it states anything less than that it's running rich? or have I just lost the plot? Need to do some more research I think.

[Alexdaredevilz]

Andy Pandie said:

Thanks,

No mods, I repaired and reseated the air box properly over Christmas, but can't imagine that's made any difference. I'm only repeating what I was told, the AFR from the graph seems to be between 14.0 and 14.2, but I have no idea what it should be

I haven't done any investigation yet.

Thats a great safe economy figure imo, noticed any decent mpg's recently?

But for power you need about 12.5-13 on a average

But also varys in every single engine, you just need to find the sweet spot for yours

Im sure some one will come along and tell me off for talking bks

Alex

[nrick]

No you're right best power is achieved close to the detonation point, however they don't do it for long. So everything is a compromise. The system on the Tuscan is closed loop so should adjust itself, but a look at the diagnostics should help with what is going on? IMHO

[dvs_dave]

I don't believe that it's closed loop at WOT? Additionally, according to Ryan from Syvecs the Speed 6 running the MBE ECU has a tendency to lean out at high revs due to the batch injection system causing the injectors to fire at a rate beyond their duty cycle.