Turbo Timmy

Ok I got my S-AFC hooked up today and all of the sensors seem to be functioning. The only strange thing is in monitor mode, the throttle % goes to 100% when you push the throttle about half way down. (where the secondaries come in?) The voltage is right on (0 - 5 v). We took off the IC to look at the TPS and couldn't see any way to adjust this. Is this normal???

RXTASY1

Yeah..... unfortunately on our cars it is. I have my SAFC set to LOW=80%, HIGH=99%

Scott 89t2

the 87-88 cars only have a narrow range TPS. so at 30% throttle the tps goes to 100%.

I think some poeple have rigged up the dual 89-91 sensors and just used the 2nd full range one for the tps.

the other way to to hook the tps sensor wire into one of the boost sensor wires since they have the same voltage (0-5v) so instead of it being throttle denpendant tuning. it's boost dependant.

Chris Ng

https://www.rx7club.com/vforums/show...=&threadid=7459

Scott 89t2

opps, I ment the 2nd full range one for the S-AFC,

Chris your link doesn't work

Turbo Timmy

I see what you are saying. I was driving around tonight just fooling around with it and my car runs perfect from 0-100% in the throttle sensor range. Too bad I'm barely pushing the pedal!

At around 50% true throttle (100% to the tps) I'm seeing .95v from the 02 sensor. At WOT it's over 1.0 volts. If I lean it out at WOT won't it make it too lean for the lower range?

Turbo Timmy

What exactly is the Throttle Point setting for? I put the low to 80% and high to 99% but what does that mean?

Chris Ng

https://www.rx7club.com/vforums/show...&threadid=7459

Hmm that link should work.. it's jsut a link to an old post I made concerning the s-afc..

Donny: You basically have 3 "fuel maps" with the s-afc.. 2 of them are adjustable.. Low/mid/high maps.. If you set the LO throttle setting to 80% and the high throttle setting to 99% it basically means that anytime you are below 80% throttle sensor reading, you will be running off the LO fuel map.. anytime you are above 99% throttle reading , the s-afc switches over to the High throttle map... if you are between 80 and 90 % the s-afc will give you an interpolated correction (mid point between the lo and high throttle correction values at the given rpm)
okay.. so this basically works great on 89+ cars that have TPS's that measure the full range of throttle application.. unfortunately as you have found out, on the earlier cars your TPS is more like an on and off switch..converting over to the later model TPS is a pain in the ***.. you can't just use the later model TPS, you must also use the later model throttle body, since the linkages are diffrent.. if you go ahead and switch throttle bodies, you're gonna have to start running premix.. since the later units do not have the linkages to operate the mechanical oil metering unit...
It is entirely possible to tune the car using the narrow range TPS.. alot of people have done it.. just be prepared for alot of tuning pains..
Tuning the s-afc using the boost sensor output makes life a bit easier.. however there is also a learning curb in getting it tuned properly...
Be aware that if you run an FCD, the boost sensor output will max out at 100% when you hit the point where the FCD clamps it's voltage that it sends the ecu.. in most cases this will be at about 8 psi..

hope this helps

Turbo Timmy

Thanks for the info... I have no OMP and am already running premix, and have a Superchip which disables fuel cut. So basically here are my options:

1. get an 89 throttle body so i can use the full range tps (bolt on?)
2. rewire it to use boost sensor
3. try to tune it as is - pain in the ***
4. sell and get 3rd gen (ok not really)

amused

Hey, it was suggested to me that instead of hooking the TPS wire to the Ecu, you can get a more accurate reading by hooking it to the map sensor.

this true? and where would i want to tap into?

Blowtus

Just use the map sensor Timmy. Should only involve moving one wire... can't be that hard