North American Turbocoupe Organization

anasazi4st Offline
Senior Member
I am about to start the DIY IVR project, as it’s probably physically impossible for my TC to have as much fuel in the tank as the gauge shows—and the Temp and Oil Pressure gauges are also unrealistically high.

After getting the OEM DIY apart I was surprised to see an adjustment is possible—rudimentary as it is. While I am 99% certain that the DIY one—as documented by vegas_ss and based on the one developed by Jeff Korn and Gary’s Garage Mahal, I am curious if anyone has ever tried to adjust this using the screw shown in these pictures here:

[Image: IVR-PHOTO-1.jpg?rlkey=iguty7f1lss29ab2hn0uf5w3p&dl=0]
[Image: IVR-PHOTO-2.jpg?rlkey=0fssch6xuc33hfovmm2zp02r4&dl=0]

Admittedly unless you have a lot of patience, this adjustment is probably something you would not want to attempt. I wonder—out of curiosity, again—if there would be a way to test this out of the vehicle?

Such an adjustment might be helpful if you don’t want to attempt the DIY fix.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 3 T5OD full rebuilds, 6 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....

vegas_ss Offline
Senior Member
You would need to apply power to the IVR input and ground, then measure the IVR output. Problem with that approach is trying to determine the actual input voltage the IVR will see. When I tried using a lighter adapter with a voltage readout, it was quite a bit lower than the voltage at the battery with the car running (~12.5 vs 13.7), not sure where the drop occurred but the lighter was rewired to a fuse panel switched circuit so I could leave the adapter plugged in.
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS, DCM, Borla Cat Back, too much other stuff!!! (SOLD)
2009 Pontiac G8 GXP 6M, 6.2l LS3, Kooks Long Tube, Hi Flo Cats, Mild Cam

Jeff K Offline
The ancient technology mechanical IVRs are known to have the contacts momentarily stick together causing the gauges to pin to the max value for several seconds and then return to normal operation after the contacts unstick. Seen this many times on many of the old (60s and 70s) Fords I used to own. The mechanical / thermal IVRs are basically a primitive mechanical PWM (Pulse Width Modulation) voltage regulator. Solid state is the way to go IMHO.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized

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