2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

S-AFC THR wire...pressure sensor or Throttle wire?

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Old 03-20-06 | 01:00 AM
  #26  
NZConvertible's Avatar
I'm a boost creep...
 
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From: Auckland, New Zealand
Originally Posted by X-JaVeN-X
He knows I have a turbo...his is turbo as well...he mentioned also, that about 40% was close to atmospheric...and 100% would be ~15psi, but he says to set the hi-throttle point to 99%...dunno if that was a typo or what...but I know most of what I've seen, everybody's hi-throttle is set from like 97% to 99%.
Those people are most likely either using the S4 TPS (1/4-throttle = 100% THR reading) or they have an NA (WOT = near 100% THR reading). I would definitely not use those settings on a Turbo.

How much boost are you running?
Old 03-20-06 | 09:41 AM
  #27  
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From: Washington, North Carolina
Originally Posted by NZConvertible
Those people are most likely either using the S4 TPS (1/4-throttle = 100% THR reading) or they have an NA (WOT = near 100% THR reading). I would definitely not use those settings on a Turbo.

How much boost are you running?
fair enough...i'm hitting right at 12lbs...
I've run into another problem I think....Before, my THR signal was hooked to the throttle signal at the ecu...and I got a response....now that I have the wire hooked to the pressure sensor wire at the sensor....I get no reading on the AFC.

when monitoring my afc, with the ignition on (car off)...my AFL~43%, THR=0$, PRS~-750, RPM=0 (of course)....so...am I not suppose to be getting a reading on THR with the ignition on (car off)?....Also, Should the AFL be reading 43% with just the ignition on?

I didn't wire up this afc btw...all I've done to it was change the one wire over, from throttle to pressure sensor
Old 03-20-06 | 10:04 AM
  #28  
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When I've done this in the past, I had poor luck with the stock boost/pressure sensor. It doesn't seem very linear. GM 2 or 3 bar sensors are available very cheaply (or free if the guy at the wrecking yard is in a good mood) and have a linear 0-5V output.
Old 03-20-06 | 10:19 AM
  #29  
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From: Washington, North Carolina
Alright...i just tested the pressure sensor with a DMM. I think this may be the problem.

Ok, all the below was done with the ignition on, and the car off)
Testing right off the sensor...there is an fcd plugged in. coming right out of the sensor, there are 3 wires...white, red, black. Tracing the wires back, the white wire matches to the brown w/red stripe on the factory harness, which is the pressure sensor output. This wire is only putting out .02 volts...it's the same right at the sensor, before the fcd, and after the fcd. The red wire, right at the sensor puts out 5volts...Now I'm assuming the black wire is suppose to be ground (please correct me if I'm wrong there). Testing this wire for continuity...I can't get a tone (my meter makes a buzzer sound when you get continuity). I had my meter ground on the battery...and I checked a couple other points under the bay and was getting good continuity. So, if that is a ground...where is the harness coming off the pressure sensor grounded? Where should I go from here?
Old 03-21-06 | 01:59 AM
  #30  
NZConvertible's Avatar
I'm a boost creep...
 
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From: Auckland, New Zealand
Originally Posted by Aaron Cake
When I've done this in the past, I had poor luck with the stock boost/pressure sensor. It doesn't seem very linear.
The data in the Paul Stokes DIY FCD article seemed very linear. Was that a Turbo or NA MAP sensor you were testing?

http://www.teamfc3s.org/info/articles/fcd/diy_fcd.htm

Originally Posted by X-JaVeN-X
Where should I go from here?
Eliminate the most obvious variable. Remove the FCD and plug the harness back into the MAP sensor.

Last edited by NZConvertible; 03-21-06 at 02:04 AM.
Old 03-22-06 | 03:07 PM
  #31  
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I was mainly playing with the NA sensor...The thing could have been broken though. I gave up a few minutes after I saw the weirdness and went straight to the GM sensor. The graph you linked to is far better then anything I saw.
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