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sbiggi
11-08-2005, 01:57 PM
What A/F curve do you tune for?

Do you tune most rich at peak torque?
Do you tune you air fuel based on air flow?
Do you make the whole curve flat under full boost?


Currently my fuel curve gets richer as airflow increases.

Example:
I hit peak torque at 4200 rpm, but I am flowing 35 lbs/min.
My airflow increases to 43 lbs/min and then planes off till 7k rpm or so.

My current A/F dips to 12.0 or so at 4200 and then gradually to 11.2 by 7k rpm. Timing rises from 11 degrees to 18 degrees by 7k. (Pump gas tune)


What is optimal? increase fuel with lbs/min? or a flat a/f under full load?

-Seth

sbiggi
11-09-2005, 12:06 PM
So... nobody knows? or dont want to tell?

I'm thinking it doesnt really make a difference if its not knocking.

buckley
11-14-2005, 10:43 AM
I really couldn't tell you man considering I have no way of controlling it at the moment. Maybe some of the other members would be able to help you out though.

-buckley

KeltonDSMer
11-14-2005, 12:57 PM
The closer you get to a mass ratio of 14.7:1 without knocking at any given timing advance, the more power you will make.

The thing that gets tricky is the fact that less airflow that the stock ECU sees=more timing, so it is a balancing act between finding a rich enough A/F ratio that won't knock, but at the same time won't pull all your timing or hit fuel cut from seeing a lot of airflow.

This is why people can't tune 800cc injectors with a piggyback, the ECU advances timing way too much to control knock.

sbiggi
11-14-2005, 03:56 PM
The closer you get to a mass ratio of 14.7:1 without knocking at any given timing advance, the more power you will make.

The thing that gets tricky is the fact that less airflow that the stock ECU sees=more timing, so it is a balancing act between finding a rich enough A/F ratio that won't knock, but at the same time won't pull all your timing or hit fuel cut from seeing a lot of airflow.

This is why people can't tune 800cc injectors with a piggyback, the ECU advances timing way too much to control knock.

I'm not running a piggyback. I can adjust timing a fuel to what ever I want, separately.

game-hunter
11-14-2005, 04:44 PM
The closer you get to a mass ratio of 14.7:1 without knocking at any given timing advance, the more power you will make.

The thing that gets tricky is the fact that less airflow that the stock ECU sees=more timing, so it is a balancing act between finding a rich enough A/F ratio that won't knock, but at the same time won't pull all your timing or hit fuel cut from seeing a lot of airflow.

This is why people can't tune 800cc injectors with a piggyback, the ECU advances timing way too much to control knock.

I thought the best power was had in the 12:1 range, best economy is in the 16:1 range and the best emissions are at 14.7:1. I don't recall the exact numbers besides the 14.7. Somebody correct me if I'm wrong.

-James

Hal
11-14-2005, 05:02 PM
14.7 is stoich, the target the ecu attempts to maintain during closed loop operation.

Under open loop (normally wide open throttle), the stock ecu will attempt to deliver an afr of about 10:1 based on air intake volume (and a few other details).

Tuning the afr for open loop will yield power increases, but the best power (on gasoline) is going to be had in the 11:1 range which is still rich enough to provide some cooling and thus allow more boost to be run.

You can make more power with boost, so it is often better to run the car a little richer and with less timing if your turbo system is capable of delivering the needed air flow.

If not, leaning the afr and adjusting timing *might* yield an increase in power when the turbo charger is maxed out.