A/R at certain point

[dhay14]

what A/R should a f7r turbo be running on 10 PSI at WOT in 3th gear? and at Idle?

Dhayrone.

[volymmannen]

what A/R should a f7r turbo be running on 10 PSI at WOT in 3th gear? and at Idle?

Dhayrone.

Lambda 1 represents the \'stoichiometric\' air:fuel ratio of 14.7:1 where there is enough air present in the mixture to burn all the fuel with no excess of either but leaving just enough to set in motion the catalytic process inside a \'three-way\' catalytic converter. In effect, the cat depends on \'finishing off\' any combustion which did not take place within the engine, forcing the emerging gases to react with each other and convert to a mixture of steam (H2O) and Carbon Dioxide (CO2). Where a conventional engine runs too lean, the Lambda reading will be more than 1 and the \'in service\' emissions test assumes that this will mean the car is emitting too much Nitrous Oxide (NOx).

so in a turbo car at boost you should have 0,85-1.0 at idle alwas 1

[Laine_16v]

You should see see 12.7:1 at WOT.

And 14.7:1 at idle, although i think you richen the idle slightly though to help acceleration fuel enrichment.

[Chris H]

Stoich/Lambda 1 is the chemically correct ratio for complete combustion but a few issues,

you never get complete combustion
Its not best for economy or power

Stoich is what manufacturers aim for when mapping. Emissions compliance is a higher priority that either power or economy.

If you got complete combustion you would only emit CO2 and H2O no IC either CI or SI can achieve this.

14.7:1 at idle, low load and medium load is what you want for emissions compliance but as I said its not good for power or economy.

Saying 12.7:1 is really not much use, its a good starting point but you may find peak power and safe temps may be at 13.5:1

Fuel dumping is a poor way to map a turbo

[dhay14]

thanks boys

when cold my car idles at awounr 11something:1 si i guesss thats too rich
in 3rd WOT i can remember it runs 12 something at 10 PSI

is this good? it should be tuned but is it safe now to boost it 10psi or better to go easy on it untill propperly mapped?

chears

dhayrone

[Chris H]

cold idle will be rich but 11:1 is pushing it!

tbh if its 12:1 at 10psi in 3rd, I'd probably bump the boost up to lean it off slightly. Should pick up power and economy

[kj16v]

For idle and cruising manufactures tune for 14.7. It's a medium between power, economy, and emmisions. It doesn't optimise any of them but balances all of them.

For off-boost cruising you should find best torque around 13:1, but poor fuel economy. Whereas you'll get best fuel economy around 15:1, but emmisions will be higher (who cares. Not like anyone can check while you're moving!)

There isn't an exact point where an engine makes best torque. Best torque will be a plateau, either side of which torque will drop off.
For on-boost acceleration You'll likely find best torque between 11.7 and 12.5.
For a turbo engine I definitely would not go leaner. Not without having it on a dyno along with monitoring egt and detonation. You might find more power by going leaner than 12 but, without monitoring all of the above, you most likely also find melted pistons!

If I was road mapping your car (not using a dyno) I'd aim for: 14.7 @ idle, 15.0 @ cruise, 11.5 @ Full load.

BTW: Winding up the boost may not neccesarily lean the fuel mixture. Mapping doesn't work like that. What gear ithe car is in doesn't make a difference to the target AFR

[Chris H]

you'll finding upping the boost will lean it out, as its not a inear relationship with fueling and boost pressure. Theres so many variables in the process, like wheres the MAP sensor taken from? Wheres the wastegate feed taken from? and blah blah.

10PSI might only be 4psi manifold pressure, upping it to 12 PSI might make manifold just under 5 psi, there won't be a substantial change in fueling so it will lean out slightly.

Most mapping is a lot simpler than folk think, most think every rpm is mapped, the truth is only substantial changes every 1k or 500rpms, the rest is left to adapt on the interims, the joys of closed loop feedback etc. When open loops used most just fuel dump which is what a mix of 11:1 is doing, thats just plain shit mapping IMO.

As for the gear thing, yes mapping can be terrible and damaging but be fine in 1st and 2nd as it rattles through the revs with no issues, 3rd is where most people hold it to the limiter most of the time, not 4th or 5th. In the higher gears MAX boost will be established and held for much longer and mapping should be suitable for that, but third is the best for on road mapping.

Can do it in 4th or 5th but you better have it right so you can outrun anyone that decides to chase you, leave the numberplates at home as well.

[stan]

Fuelling at idle will depend on cam spec, eslecially so on NA engines.

I find most well tuned engines like an idle AFR of around 12.5/13:1, it just keeps them a bit more stable when there is alot of scavenging and reversal going on, nothing to do with accln enrichment.

Dont just concentrate on getting AFR "correct", what are you doing about ign timing??

[Chris H]

dizzy out a metro