I need boost info for 83-86 TC and Cougars

Originally posted by Walsted:
How does the BCS know what gear I am in? The EVTM shows the BCS connected to the EEC,

but doesn't show how the EEC knows what gear the car is in, unless it figures by doing a calculation using input speed and engine rpm.

I don't see where the EEC sees the boost pressure; does this mean the BCS has two positions, a low position (open to the WG, normally set at about 10psi, circuit not energized,) and a high position (closed to the WG until 15psi, circuit energized)? When I ground the connection for the black/pink wire off of the BCS, I hear it click.

I plan on grounding the black/pink wire and seeing if I can get 15 in all five gears without going over. If so, a length of wire might be a real cheap substitute for a 15psi boost control valve. Otherwise, I will be able to tell you if the turbo light and alarm work.

The EEC uses the VSS or Vehical Speed Sensor on the tranny.

The EEC knows how much boost you have by using a Hobbs switch.

You are right about the operation of the BCS. Now just add that a Hobbs switch tells the computer what the boost is at and then the computer controls the BCS. If you look at the early cars with out the BCS they only have one Hobbs switch while the later ones have two. Loction of them is behind the passenger side strut tower.

You can either grond the BCS for 15PSI in all gears or just remove the hoses for it from the turbo and bypass it with one piece of hose. The BCS does not "limit" or control the boost, it just opens. The "limiting" factor is controled by the size of the hole in the little "T" that the hose for the BCS comes from. So if you wanted 18 PSI in all gears you could open the hole in the "T" a little more. (that is a trial and error why to do it, but it works.)

Originally posted by GT350R:

The EEC uses the VSS or Vehical Speed Sensor on the tranny.

So if I have this straight, the boost isn't specifically limited to a certain gear, just a specific vehicle speed/engine load combination that coincidently only occurs in a certain gear, right?

The EEC knows how much boost you have by using a Hobbs switch.

That is where I get a bit confused. I can't figure out where the Hobbs input connects to the EEC, as in, what pin? I checked this excellent reference and couldn't see a pin for it, and I couldn't find it in the EVTM, either. Of course, it could be that I don't look hard enough or in the right place.

On another note, when I changed the EGR solenoid, I just swapped the whole bracket with an '88 auto, and the boost was still at 86 levels instead of 88 levels. I gather that the Hobbs switches are not year or pressure setting specific?

Thanks for explaining this all to me in simple terms over a couple of threads.

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Mike Walsted - Nato member
1986 5-speed TurboCoupe .

Look at the bottom right on this one, http://www.angelfire.com/pa3/turbocoupe/diagram.htm

Could use the nuetral drive input to "know" what gear it is in also , but I am not sure.

No the hobbs switch just tells the results. The computer than decides what to do with the results.

the more I thing about it, the more I think that it is a variable switch that tells teh computer what the boost is at. I guess that would depnd on if a Hobbs switch is NEVER a variable switch and is only an on/off switch.Either way it works the same, just the wrong name (mabey) for the sensor.