i've been tryin to learn how to tune w/ the s-afc, but i can't figure out about the Lo/Hi Throttle points...how do u know what percent to set?...and what do they mean?...how much throttle is how much percent??...

 

How much throttle is how much percent??? If you push the throttle halfway, that's 50%. All the way is 100%. 1/4 of the way is 25%.

Anyway, this is simple, and you'll understand it after this short explanation. The S-AFC has 2 separate fuel settings for Low and High throttle. What these do is they determine the AFRs when you're at Low and High throttle. The Lo/High throttle percentages determine when each of those fuel maps is used. So, let's say you go out and set your Low throttle to 25% and your High throttle to 65%, this means your SAFC will choose the Low throttle fuel settings when your accelerator is pressed down 25% OR LESS. Conversely, when the accelerator is pressed down 65% OR MORE, the SAFC will choose the High throttle fuel settings. When the throttle is between 25-65%, the SAFC will average out the fuel settings of both Low and High.

Does that make sense?

S-AFC/S-AFCII tuning guide.

 

i understand that part...but when its 25% Lo throttle is that at each gear??...Lo settings apply to 25% throttle at 1st, then 2nd, 3rd and so forth?...why couldn't the setting jus be at 50%/50% instead??...and now that i read the info from the link, is it saying that the baseline corrections for fuel is minus whatever percent from zero since initial settings are at zero??...

 

also, is 25% throttle around 1750rpm???....(here's my educated guess....25% of 7000rpm = 1750rpm)

 

Wow, this guy is confused. The throttle (gas pedal) controls many things, but it primarily determines how much the throttle body (a valve where the air intake meets the intake manifold that determines how much air is let into the cylinders). When the gas pedal is pressed down half way, the throttle body valve is 50% open. The % of throttle has no direct correlation to RPMs. You could be at any rpm with any given throttle % (generally speaking)

Getting back to the throttle discussion. The more air allowed in the cylinders (by the open throttle body valve), the more gas must be added to attain the ECU's (computer that controls your car) desired air fuel ratio. The SAFC II differentiates hi/lo throttle settings because Evos (and alot of other turbo cars) have a very rich air to fuel ratio under hi throttle situations at high rpms for safety reasons. However, this robs the engine of power (combustion with a rich air fuel ratio is less powerful) so the SAFC II is a module that allows the user (in an indirect way by tricking the MAF sensor to read less air is actually coming in through the air filter and air intake) to modify the air fuel ratio.

I think this is pretty accurate, but correct me if I'm wrong.

 

Good gracious, man, put down the crackpipe. Throttle has very little to do with RPM. As I said before, it's HOW FAR DOWN YOU PRESS THE ACCELERATOR. You know, that pedal you press with your foot? It opens the throttle plate. The further you press your foot down on the pedal, the more the throttle opens. You can go much higher than 1750rpm without going beyond 25% throttle. YOu probably do it everyday when driving in traffic. In fact, I don't know if I EVER go as low as 1750 rpm...that's crazy low. This would be easy to see if you put the SAFC in monitor mode and chose TPS as one of the parameters. You could then sit there with the engine turned off, but with the key in the "ON" position, then press the accelerator. You'll see the TPS numbers go up and down along with the pressure of your foot. _THAT_ is throttle %.

Also, yes of course, the settings are for every gear, you nut. It's just a way to determine which fuel settings are applied when you're romping on the gas, and when you're just cruising or slowly accelerating. You want the aggressive fuel settings when boosting and in open loop...you want the low settings when going slow and in closed loop.

 

he's right.

 

damn....i see...so the percentage is throttle position...i was way off...in the link that warrtalon put it says for baseline for 660's = -15% across, highs and low that means that throughout the rev range its -15% from 0% right? (leaning out)....coo...i think i got it...so when u tune for Lo throttle it should somewhat be at 14.7, and for Hi throttle a little rich since its under load right?...

 

Do you have 660 injectors? I highly doubt you do if you're just beginning to mod. You should have your entire low-throttle map set to 0% across the board. You then just go do 3rd gear pulls and tune for a good AFR and good timing at WOT all through 3rd gear (4000-7500rpm).

 

naw...don't have 660's...jus askin if that's what it meant...so basically when u tune (w/ recommended datalogger, EGT, and AFR meter) u jus try to have 14.1 AFR thorugh each gear right?....but for Hi throttle u need to set it a little rich yeah?...sorry if i'm askin stupid shiet but i really wanna know how to tune...need to go to the next step instead of jus fixin up cars from top to bottom y'know?....

 

14.7:1 at cruise, but it will cycle.

WOT you should tune for about 11.1/11.2 on 91, 93 can give you a bit more room. This is all baseline numbers though, every car is different.

 

cycle?

 

The ecu is constantly aiming for stoic (14.7:1) while cruising, since loads and throttle inputs are ever changing, the ecu cycles up and down from 14.7:1 to keep everything happy.

Check out the 02 Voltage on this log before I go WOT. See it cycling?

 

yeah i see...cuz the afr is never constant, always fluctuatin...damn, so it gets more complicated now that u gotta adjust ignition timing too eh?...why is it that when u tune for Hi throttle its gotta be on 3rd goin WOT and not other gears?...thanks for the help man...hopefully i can try to mess around w/ the s-afc (or any other fuel controller) w/o blowin my shiet up...what datalogger is that?...

 

taking into consideration that ever car is different.... what would be a safe setting to see some improvement....? opinions?

based on this first setting, you can twink it, as you upgrade.

- Eddy