Air Fuel Ratio

[BlaineP]

Does anyone know the ideal range for our AFR?

 

[Zissou]

14.7:1 is the stoichiometric air to fuel ratio.

 

[codestp202]

What kind of info are you looking for? AFR's while in boost?

 

[BlaineP]

Yes, pretty much. Right now I'm running Cobb stage 1 tune. I have everything to go stage 3. Just waiting on the 2jr intake to ship. So I'm trying to get a good handle on the numbers and temps I need to be aiming for. I under there's a lot of variables that go into this. This is my 1st turbo car and I'm not trying to screw it up.

 

[Butterybunz]

When you are wide open throttle, you want to see a number less than 12. It's best to leave it to the experts and get a pro-tuner to review your datalogs and adjust your tune to your specific mods.

 

[Fiester]

At a stoich afr of 14.7, you are most efficient. So at most normal driving operations, you want to target a lambda of 1, aka afr of 14.7. During WOT maneuvers or heavy tip-ins, you enrich to reach peak power as well as cool the cylinders, as running rich provides a cooling effect. Like the post above me, you want to see afr below 12 during WOTs. With a turbo, staying at stoich during a WOT would likely result in you sprinkling metal bits all over your engine bay.

 

[codestp202]

Yeah, I run about 11.8 while at WOT on my e30 stratified tune

 

[BlaineP]

Thanks. Looks like I'll do a couple WOT pulls after work and see where it's at.

 

[codestp202]

Thanks. Looks like I'll do a couple WOT pulls after work and see where it's at.

Just checked my logs again, while boost is building I'm in the very low 12's, 12.1,12.2. When I'm at peak boost going towards redline my afrs are 11.8 going down to 11.4. This might change a bit as I'm on my first revision of their new tune I'm trying out.

 

[BlaineP]

I didn't get to run it hard this evening. But I'm running 14.55-14.70 at idle and normal driving. What times I did get to mash on the gas it would drop to the 12's. So this seems safe by what has been said. Thanks for the insight. Any other gauges y'all like to monitor?

 

[Tatedup33]

14.7:1 is the stoichiometric air to fuel ratio.

Hey a bit off topic but i just i stalled my cobb ap today and the afr guage doesnt fkuctuate or move techincally ita like its not working it jist reqds 14.70 on wot or even off ? Any ideas?

 

[Zissou]

Hey a bit off topic but i just i stalled my cobb ap today and the afr guage doesnt fkuctuate or move techincally ita like its not working it jist reqds 14.70 on wot or even off ? Any ideas?

You stalled and it's reading 14.7? I would think it go to 0 or null if you stall the engine, but I haven't done it.

 

[Tatedup33]

You stalled and it's reading 14.7? I would think it go to 0 or null if you stall the engine, but I haven't done it.

My bad i meant installed i mean it dosent move the afr gauge im going to disc9nnect battery and reconnect see whats up

 

[Bucarock]

Hi guys
I just put dizzy tune stage 2 like 2 days ago and my AFR goes to 15.30 and my OAR goes to -0.96
should I e worried about it??

 

[LiLfieSTa]

Was just wondering about this today since i dont have much knowledge on this topic.
Currently running Dizzys e30 tune with colder plugs.

Lately on a cold start, i notice my AFR will idle and fluctuate around the -15.8 to -14.55 range and continue to do so even when the car is warmed. But once i give it a little rev, then it returns to the -14.55 to -14.77 range and then stays flickering between those 2 numbers.
This is normal correct?

Also AFR is in the -11.38 on WOT

 

[pwnall1337]

Factory tune targets 12.7 AFR until higher RPM (5900~) where the turbo shaft speed is very high and the increased fueling is to provide cooling to the pistons from the hotter air entering the cylinders.

The fiesta st is an open deck motor and because of the improved cooling, it can run much leaner.

Below are factory values.