SAFC Part Throttle Correction Question

[Chezedik]

I made a half assed attempt at searching, but before I get flamed, you go click on the little blinking red search button, and type in SAFC and search (or any combination of post body search and SAFC+whatever). Alright, now that I took care of the flamers (ha, ha.... flamers..):

I was thinking about something before I went to bed last night. I am planning on controlling my fuel with the SAFC, but I was thinking, is there a way to control part throttle AFRs with it, because I have read a number of times of the engine leaning out in part throttle and pinging, KA-t go boom. Any takers?

[KATwo40]

The SAFC2 has a hi and lo throttle adjustment, and uses sliding increments between the two.

For example, you could set low throttle to be any throttle inputs up to 15% throttle opening.

Then, set high throttle to be any throttle inputs of 60% throttle opening or higher.

You can also change the actual MAF correction adjustment (resulting in fuel injector pulsewidth change) for both settings. You could have high throttle on -29% and low throttle on -32%. Of course, it would take a wideband to determine the corrections that are appropriate to your application.

The SAFC2 will graduate between those two points.

That answer your question?

[Chezedik]

Yes, thank you.

[Chezedik]

Any chance of it being done using a dyno sniffer?

[DRIFTEADOR]

I am planning on controlling my fuel with the SAFC, but I was thinking, is there a way to control part throttle AFRs with it, because I have read a number of times of the engine leaning out in part throttle and pinging, KA-t go boom. Any takers?

yeah, set your low throttle enrichment on the high side, but that will hurt part throttle performance and gas mileage a little too. unfortuantely safc doesnt tune based on load, it's based on throttle position which means it doesn't correct for weather or basically any conditions where there is a higher load even at the same throttle position adn rpm (like going uphill, hauling, etc)

[fabio420]

my personal experience with my car is this. The first time I had high throttle at 60% and low at 30% and I blew my engine by high boost in part throttle (14psi at about 29% throttle in the highway) Now I have it set at 15% low and 30% high and I've been beating on it no problem. Even being an automatic (so it downshifts when it wants to) hasn't given me a problem. So if it does cost me more on gas or whatevr, I'm just sayning what has worked for my car for the past month (~1000 miles) at 10psi.

[KATwo40]

Any chance of it being done using a dyno sniffer?

Only on a steady state dyno (like a Mustang dyno, which can hold different loads/rpms). Stay away from inertia dynos for anything more than WOT pulls.

Also, remember, if you have a catalytic converter the readings after the converter will show leaner than they actually are. So, you could tune to 12.5:1 and really be more like 12-12.2:1, which is perfectly safe, when setup correctly. But that's another discussion altogether.

[KATwo40]

unfortuantely safc doesnt tune based on load, it's based on throttle position which means it doesn't correct for weather or basically any conditions where there is a higher load even at the same throttle position adn rpm (like going uphill, hauling, etc)

This is not entirely true.

The ECU used RPM, Throttle position, engine temp, and air mass (from the MAF) to determine load. Using the SAFC only alters the signal from the MAF, thus reducing the airflow seen by the ECU. This does result in the ECU thinking the load is less than it actually is.

However, this doesn't mean that load isn't calculated at all when the SAFC is used. The ECU still calculates load and changes timing. Granted, the timing map is still too aggressive for boost applications above 6-7psi, unless proper fuel tuning, intercooling, fuel and some base timing retard are present.

Furthermore, the MAF corrects for changes in weather, because it meters the mass of the air, which is directly impacted by temperature, humidity, altitude, etc.

[DRIFTEADOR]

thats assuming fuel vs load is linear, but its not. especially for boost. hence the different low and high throttle maps. otherwise it'd just be one correction through the entire rpm range.

say on a really cold day the turbo spools sooner/more than normal, while still in the low throttle map. the maf will recognize the small increase in airflow, and add some fuel but the safc's enrichment multiplier on the low throttle map may not be enough to keep the motor happy in boost.

[KATwo40]

thats assuming fuel vs load is linear, but its not. especially for boost. hence the different low and high throttle maps. otherwise it'd just be one correction through the entire rpm range.

say on a really cold day the turbo spools sooner/more than normal, while still in the low throttle map. the maf will recognize the small increase in airflow, and add some fuel but the safc's enrichment multiplier on the low throttle map may not be enough to keep the motor happy in boost.

This makes sense. I guess I just didn't read this far into the first post. Thanks!