why do my numbers always change?

derK

New Member
Mar 31, 2005
146
0
0
39
CANADA
one day i set my Fuel pressure and my S-AFC pretty good where i was getting consistent 10.5-11.5 A/f ratio numbers. But today with the exact same values plugged in i was running LEAN...like 12.5-13.5

Why does it ALWAYS do this to me?? i used the same gear to test it out, it is about 10 degrees warmer today then the other day when i tested out my car but still that shouldn't matter that much. What is wrong with my car?? why doesn't it learn my values?? am i doing something wrong??

It's pretty annoying before every ride you take that you have to re-tune the car.
 

sethron71

Authorized Vendor
Jul 19, 2005
871
0
16
40
Las Vegas, NV
www.SethIngham.com
Make sure you have the constant hooked up to the S-AFC and do not do the initialize(I believe it is called) because it resets the settings. But it should remember your settings everytime and you should not have to retune it.

Also watch fuel pressure as mentioned above. You can also check/replace:
-AFM electronics (not likely when then fail it won't run)
-O2 Sensor failing or extremely corroded

HTH,
Seth
 

starscream5000

Senior VIP Member
Aug 23, 2006
6,359
0
36
Hot and Humid, KY
sethron71;993054 said:
Also watch fuel pressure as mentioned above. You can also check/replace:
-AFM electronics (not likely when then fail it won't run)

The car will run, it just won't rev high (only about 1500 RPM) and you'll only be able to creep into a mechanics lot, or your home ;).
 

bountykilla0118

In Pursuit of 500rwhp
Jul 16, 2005
1,088
0
36
39
Atlanta GA
Sounds like you aren’t satisfying the TCCS with the VF signals its looking for during idle, cruise and part throttle which is 14.7 read below and focus on the red words :)

I have a SAFC II and I dont have to retune are you tuning below 70% throttle?

UNKNOWN;975510 said:
Set the Low Throttle point to 69%, and the High Throttle at 70%.

Zero out everything on the Low throttle map.

Tune ONLY on WOT. The TCCS will compensate whenever it is in closed loop. Also known as part throttle, since the ECU goes into enrichment mode (a form of open loop) under WOT. When you lean out the mix, the ECU senses it and makes changes to get it back to normal. Then your WOT mixture is also affected.

http://i80.photobucket.com/albums/j187/isnms/Supra/vffueltrim.gif

I have been running mine like this for several months now, and it held the first tune i did on it. One trick that helps is to use the blue wire (normally for MAF Voltage input) and hook it up to the Vf output pin on the ECU. That way, you can see if the ECU is happy or not just by going into The ETC... Sensor Check option on the SAFC.

Vf:
0 volts: full rich
1 volt: rich
2-3 volts: OK
4 volts: lean
5 volts: full lean

When driving around, this number should stay at 2-3 volts. If not, the ECU IS making changes by itself! The idea is to work with the ECU, still trick it some, but also cooperate at the same time.

Very quick run down:

At WOT, I would say generally 10.5 is where the stock ECU likes to be. 11.5 is a safe tune. 12.0 is a good performance tune. 12.5 is where things getting quite risky. 13.0 isn’t good. At WOT, the ECU ignores sensor inputs (open loop), so it isn't compensating. That's why you can tune with the S-AFC. At idle you should see ~14.7, cruising will vary across the board because of ECU control, throttle position and other variables. The stock ECU retards timing sharply at ~5,600RPM so SAFC tuning anything above 5,600RPM is relatively pointless.

SAFC advances timing as it pulls fuel due to the nature of dinking with the AFM frequency to trick the ECU into thinking that it's flowing less air, so it puts in less fuel, and puts in more timing advance. Basic SAFC 101. This is a good thing, and a bad thing. More timing + less fuel = more power BUT too much timing and not enough fuel are very bad. You probably have no way of knowing what your timing is once you're running, so set your base timing at 8-10 (for safety) and try not to advance the S-AFC farther than -20%. What you are doing is adjusting fuel while reducing the risk of over advancing timing (which can cause detonation). If you must go farther than -20%, then set all back to 0% and reduce fuel pressure to lean your motor.

You can go lower than -20%, but *I* prefer to try to keep the S-AFC as close to 0% as possible while maintaining proper AFR. You can always add timing later by increasing your base timing. While good in principal, I usually end up in the -18% range at the upper RPM.

The S-AFC is a TRIMMING TOOL, intended to FINE TUNE the fuel curve. It's not intended to be tweaked out -40%... Once you get your fuel dialed in, you can advance your timing a bit. Detonation is not your friend.

Disclaimer - All this assumes reasonable engine condition - boost levels - fuel and supporting mods... It's best to do this on a dyno, and with a professional overseeing your work. If you blow up your engine after reading this, it still 100% your fault.

- Assume you are tuned for a 11.5:1 AFR on your wideband

My suggestion:
SAFC average = -15% | base fp = 23psi | timing = 12
Your base settings are close to neutral, with a bit more timing. The advanced timing gives more power and helps the turbo spool. Having a higher advanced base timing = more power across the whole RPM range.

Speaking generally, again. Some of the above would be skewed by other factors but I'm discussing within the circle of what you have control over. Set up your car to run well with the SAFC set to 0% across the board. Adjust your fuel pressure to get a reasonable idle and AFR. Set your timing a bit retarded to give a margin of error. Tune your fuel w/ SAFC. Then advance your timing SLOWLY. If you don't have an AFPR, then look at buying one because it should come before the SAFC.
 

Nick M

Black Rifles Matter
Sep 9, 2005
8,894
38
48
U.S.
www.ebay.com
somebody that needs to read a book said:
At WOT, the ECU ignores sensor inputs (open loop), so it isn't compensating.

No. He has it backwards. At WOT, the ECU looks at all the sensors except the oxygen and adjusts injection duration off of that. Yes that is open loop. In closed loop, the ECU uses the oxygen sensor to adjust injection duration.
 

derK

New Member
Mar 31, 2005
146
0
0
39
CANADA
i have my throttle points at 69% and 70%. I did do the Vf test before, but only at idle. I did not drive around town with my volt meter attached.

So basically, i should jump the VF1 and E1 ports and drive around town keeping my throttle under 69% to see what my ECU is doing?? if i'm seeing 5v i need to add fuel to my BASE fuel pressure. If i'm seeing 0v i have to lower my fuel pressure??

so once i have that set where the ECU likes it to be, i can go ahead and tune my High throttle settings?? BUT i DO NOT mess with my Fuel pressure at this point right??