[Justin]

question about AFR:

idealy is it supposed to be at a single number the entire time the ECU is in open loop mode?

Drove around a bit today ( first time after install ) and i saw numbers from 11.x -- 15.x and when coasting/idling i got upto 20.x

should, when the ecu is in open loop, the number be at a constant <insert number here>?

 

[Ckanderson]

No... it will vary.

 

[Justin]

by how much is it supposed to vary? should it stay on the same number at least, just change tenths of a digit?



:freak:

 

[Ckanderson]

no... it will vary alot.... it is based on RPM and throttle position and boost... among other things...

 

[Justin]

i've got a lot to learn...

 

[Justin]

see, i'm not understanding afr anymore... i thought i was. i thoguht that it was supposed to stay at an ideal ratio the entire power band, regardless of what the boost, throttle position, rpm, or anything was. I thought you wnated to have an ideal AFR the entire time...


can someone try and explain, or link me to some good info, bout what the AFR is supposed to be when?

 

[Trent]

14.5-14.7 is usually what is considered to be "ideal" for idle and cruising. The ECU will do whatever it can to achieve this. This gives you optimal fuel consumption and optimal mileage.

The only thing you really tune for is WOT. On a car with forced induction (turbo, SC, etc) you do not want to exceed 12.0-12.2 at WOT. Most places tune at about 11.5 on the dyno because it will lean out a bit on the street. Dyno doesn't give exact load so most tuners keep it a little more rich on the dyno to compensate for the change the car will see on the street.

The A/F is changing constantly on the car. The only time you will see the number vary a tiny bit is on a car that is tuned properly. When it is tuned properly, and at WOT, the A/F will not move much at all, or shouldn't.

 

[Justin]

The only time you will see the number vary a tiny bit is on a car that is tuned properly. When it is tuned properly, and at WOT, the A/F will not move much at all, or shouldn't.

so on a proporly tuned car, at anything other than WOT the AFR will still jump around a bit? But when I'm at full throttle/max boost (I'm going to try and tune my emanage based on manifold pressure) then the AFR should remain fairly constant?