Making SAFC's tps setting work properly on S4. I fix! Read how.
05-23-02, 12:37 PM
#1
Rotary Freak
Thread Starter
Making SAFC's tps setting work properly on S4. I fix! Read how.
It was actually pretty simple. I had a spare TPS which I pulled out of an rx7 from a junk yard. I have been pondering doing this for months and I actually did it all this morning.
First I took the TPS and cut half of the metal bracket off. If you look under the dash at the gas pedal you will see a black bracket that is about 1/2 inch wide. This bracket is part of the pivot point for the gas pedal. Basically all I did was bend the bracket of the TPS so that the "button" would touch the gas pedal, then I drilled a hole in the black bracket and used a small nut and bolt to hold the TPS in position.
Wiring... Looking straight into TPS harness, hold the harness so it looks kind of like this;
. ____
. || ||
. | | |
. ___
The bottom connector goes to the grey wire on the SAFC. No other wires should be connected to the gray wire (disconnect the grey from ECU harness). The "left" connector is ground (BrB) and can be grounded anywhere under the dashboard. The right connector is +5v from the ECU. You can get this off of just about any BrW wire on the car, make sure you check voltage first with a meter. I used the BrW wire right off my boost sensor because I had an extra wire there from when I rewired my fuel pump.
It takes a little bit of playing and bending of the TPS's bracket to get it to function properly. I also noticed that reseting the SAFC made things work better. I guess the SAFC programs itself for the stock TPS. In fact, you must reset it. (Go to ETC, initialize, select yes, turn key off then back on. Make sure you set your 4 cyl, TPS up, flapper 05 05, and corrections).
I will post pics if people care.
First I took the TPS and cut half of the metal bracket off. If you look under the dash at the gas pedal you will see a black bracket that is about 1/2 inch wide. This bracket is part of the pivot point for the gas pedal. Basically all I did was bend the bracket of the TPS so that the "button" would touch the gas pedal, then I drilled a hole in the black bracket and used a small nut and bolt to hold the TPS in position.
Wiring... Looking straight into TPS harness, hold the harness so it looks kind of like this;
. ____
. || ||
. | | |
. ___
The bottom connector goes to the grey wire on the SAFC. No other wires should be connected to the gray wire (disconnect the grey from ECU harness). The "left" connector is ground (BrB) and can be grounded anywhere under the dashboard. The right connector is +5v from the ECU. You can get this off of just about any BrW wire on the car, make sure you check voltage first with a meter. I used the BrW wire right off my boost sensor because I had an extra wire there from when I rewired my fuel pump.
It takes a little bit of playing and bending of the TPS's bracket to get it to function properly. I also noticed that reseting the SAFC made things work better. I guess the SAFC programs itself for the stock TPS. In fact, you must reset it. (Go to ETC, initialize, select yes, turn key off then back on. Make sure you set your 4 cyl, TPS up, flapper 05 05, and corrections).
I will post pics if people care.
Last edited by SaabGuy; 05-23-02 at 12:42 PM.
05-27-02, 07:51 AM
#7
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The TPS (POS!) on the S4's are only narrow range... they only provide and output for the first 15% or so of pedal travel... The ECU only uses it for on/off thottle transistion calculations... (for smoothness, but it still desn't work well!)
The S-AFC needs a full range signal to accurately re-map fuel... othrewise it's all the same after that first 15% of pedal play...
The S-AFC needs a full range signal to accurately re-map fuel... othrewise it's all the same after that first 15% of pedal play...
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05-27-02, 08:08 AM
#8
Senior Member
I'd be interested in knowing how this changes anything as well. I thought the general problem with the S4 TPS was that it has a very narrow range, which was much improved in 89+ (ahhh, thanks Bambam7)
So, did you leave the TPS under the hood, just feed the SAFC with a second TPS?
So, did you leave the TPS under the hood, just feed the SAFC with a second TPS?
05-27-02, 10:24 AM
#9
Rotary Freak
Thread Starter
I left the stock TPS where it was without modifying anything there. I mounted the new (junk yard) TPS under the dash right against the gas pedal. See the picture here;
05-27-02, 10:27 AM
#10
Rotary Freak
Thread Starter
Both the pictures are a side view of the new TPS under the dashboard. Read my starting post on how to wire it all up.
Doesnt anyone rate good posts anymore??? I think this one could be a nice one for the archive.
Doesnt anyone rate good posts anymore??? I think this one could be a nice one for the archive.
05-27-02, 11:05 AM
#11
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thats a cool idea
I had the idea of using a variable resistor in line to the SAFC to get the TPS reading in check
How did you guy get your S-AFC's to read the right RPM's? The closest I can get to actual is with it set to 4 cyl and its still off by ~200 Rpm's?
I had the idea of using a variable resistor in line to the SAFC to get the TPS reading in check
How did you guy get your S-AFC's to read the right RPM's? The closest I can get to actual is with it set to 4 cyl and its still off by ~200 Rpm's?
05-27-02, 01:58 PM
#14
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Sure, with a bit of drilling and such, the s5 TPS can fir- just a bit of work involved thats all....
One thing I would be worried about here.... Are you sure that that mecahnically, the measurment from that second TPS is linear???? looks to me like the geometery of relation between the pedal and the TPS isn't perpendicular, and while that's OK if it stays that way, it may change with arc... You might want to check that.
Good luck if it works well!!
Looks like a nice little boost for those s4 owners with S-AFC's!
Oh, and about the RPM's.. some people have this problem, other don't. Just make sure you have good grounds on the S-AFC and ECU... and it's actually more likely that the S-AFC is right, and your tach of a bit off...
Is it always 200 rpms off, or does it get more the higher the RPM's go?
Easy way to check is to just bring it to a shop, and tell them to hook a tach up to the car for a second.... then see which one is right!
One thing I would be worried about here.... Are you sure that that mecahnically, the measurment from that second TPS is linear???? looks to me like the geometery of relation between the pedal and the TPS isn't perpendicular, and while that's OK if it stays that way, it may change with arc... You might want to check that.
Good luck if it works well!!
Looks like a nice little boost for those s4 owners with S-AFC's!
Oh, and about the RPM's.. some people have this problem, other don't. Just make sure you have good grounds on the S-AFC and ECU... and it's actually more likely that the S-AFC is right, and your tach of a bit off...
Is it always 200 rpms off, or does it get more the higher the RPM's go?
Easy way to check is to just bring it to a shop, and tell them to hook a tach up to the car for a second.... then see which one is right!
Last edited by Bambam7; 05-27-02 at 02:33 PM.
05-27-02, 06:38 PM
#15
Rotary Freak
Thread Starter
Im sure theres an issue with how accurate the second tps is because of the angle which it touches the throttle, but hey its better than having it run at 100% all the time! And my method is probably a hell of a lot easier than incorporating the s5 tps, if you can find one in this world!
Yes my rpm is off by about 200 at 2500 rpms and about 400 at about 6000 rpms.
Yes my rpm is off by about 200 at 2500 rpms and about 400 at about 6000 rpms.
02-04-04, 08:25 PM
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Ok im alittle confused about how the SAFC works. You can set high and low throttle and change the percent of when it comes on. But since the TPS doesnt measure over 15% it is pretty much always reading 100% throttle. Doing this will allow the SAFC to adjust the fuel curve from 0-100% actual throttle?
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