I've seen that there are some users on this board who have an S4 with an SAFC, but are using the S5 TPS connected to the gas pedal to feed the SAFC a throttle% signal.

My question is this (and I can't get my search to work, so sorry if it's been posted before):

If you go that route, is there any way you can get cruise control to work? If you were to turn on CC, the SAFC would always be seeing 0 throttle, even if the car was building boost to climb a little hill or something.


Comments?

 

It's late right now, and I might be missing something. But the last time I looked at a cruise control schematic.............it didn't have squat to do with an aftermarket SAFC. It's based on rpms (the cruise control) not tps. Cruise control has zipity doh dah to do with the tps. I posted a jpg of the cruise schematic recently, on this site.

 

Actually it's based on road speed, not rpm.

I don't see what the problem is. The cruise control has nothing to do with what you're doing.

 

Road speed (measuresd at the speedometer), brake switch, & clutch switch is all you need.

 

I don't see why it would be reading 0% if it hadn't been before. cruise will still move the throttle, am i missing something?

 

The cruise control has no clue about the TPS.

Its logic is simple:
If the speed is slower then the setting, pull on the throttle cable.
If the speed is too fast, let off the throttle cable.

 

I realize the cruise control will still work, that wasn't my question (sorry if it wasn't clear).

The problem is the SAFC will be seeing 0 throttle from the S5 TPS since the gas pedal will not be moving. So, the SAFC will be setting the fuel map to the low throttle setting, possibly leaning out the car if you're going up a hill and under boost.

Does that make more sense?

 

*****Actually it's based on road speed, not rpm. **** Ok. Speed sensor in the combination meter, not rpm. I sat in the corner for thirty minutes with the dunce cap on. Punishment enough I figure.

I've never seen the tps setup for the SAFC that you speak of but read of it on this forum. But, does not the accelerator pedal move when the cruise actuator pulls/lets off the throttle linkage???? Seems it does if memory serves.

Using the pressure sensor instead of the tps, seems to work just fine though. Some of us set the HIGH setting to correspond to the point that the boost gauge starts to read pressure. Anything below is set for low. Well actually about 23percent to 53percent as read on the SAFC. I shouldn't mention numbers because they don't make sense unless you've rigged the SAFC using the pressure sensor.

 

I'd actually rather have the SAFC use the pressure sensor, but I'm not sure how to do it. The guy I bought the car from wired it in, but he did say he wired in the pressure sensor, I just don't know how to switch to use that instead of the throttle to determine hi/lo settings.

 

Well now that I've done penance and sat in the corner with the dunce cap on for thirty minutes, maybe one of you fellows who put your foot in YOUR mouths will explain the attached schematic. It goes like this: See the Speed Sensor??? See the Tachometer? See the red line I drew under the feed signal for the Speed Sensor?????? See the red line go from the Tachometer TO the Speed Sensor?? See Jane run, run Jane run.

So maybe you can explain *Based on road speed* and what seems to be a contradiction by the attached schematic????? Humbly yours, Hailers (put smiley face HERE).

 

OOOps, Gotta go back and sit in the corner. My last post was errrrr....b.s. Gotta get some glasses. That's a ground that runs b/t the speed sensor and tach and other items. Not a signal from the tach to the speed sensor.

 

I'm still a little confused about what your asking but I would like to make one comment:

When you use the S5 TPS on an S4 car, You wire the Wide Range of the TPS to the S-AFC and the Narrow Range of the TPS to the stock ECU. So in a nutt shell, the stock ECU sees the same signal that it always did and the S-AFC is happy with the full range TPS...

Oh, FYI: When the cruise control is on and the cruise actuator applies throttle to maintain speed, your TPS will not read zero. It would read the same amount of throttle as having your foot on the gas pedal. If you don't see what I mean, Go under the hood and pull on the cruise control actuator cable and watch what happens to the TPS...it moves...

 

...

 

I know that part.

What I mean is there are people on the board who have hooked the S5 TPS behind their gas pedal in the passenger cabin (leaving the original S4 TPS where it's supposed to be to give the ECU it's signal), so that when they push on the gas it activates the S5 TPS that's behind the pedal and sends the throttle signal to the SAFC. What I'm saying is that I didn't think the gas pedal moved when you had CC on, meaning that the S5 TPS that was placed behind the gas pedal would be sending a 0% throttle signal, therefor the SAFC would be running in the low throttle fuel map.

 

Then you answered your own question. The Cruise Control would keep the S-AFC on the low map, however I don’t think this would be a problem since the CC would never go that deep into the throttle… that would be one hell of a hill if you’re doing 55-65 MPH and you need more than ~30% throttle to maintain that speed.

 

Well, on a road trip this last weekend there were a couple spots where the car was under boost while using CC, that was my biggest concern. Cruise was set around 75-80.