I've got the aftermarket boost gauge in place of the clock. It appears that the gauge gets it's info from the stock "charging pressure sensor". Is this correct? If so I need to incorporate this sensor into the new intercooler and into the new wiring harness.

For you EFI conversion guys: is it OK to leave the "charge pressure safety switch" open? In other words, can I leave this connection off my wiring harness?

 

Do you have a VDO unit? My Clock Boost gauge needs a physical boost line run from the back of the car of taken from the brake booster. It is your decision as to whether you want the overboost safety switch or not? Most likely your are having your ECU control your wastegate?

 

I installed a boost gage in the clock hole and it attached to the back of the brake booster in the front trunk. As for the overboost cutout switch, I would recommend leaving it connected. Always ask yourself the question, "Do you feel lucky Punk?" I'm sorry, I got the wrong quote. "What is the down side of doing something to my Pcar?" If you leave it connected what is the worst thing that can happen? If you disconnect it, what is the worst thing that can happen? If you apply that line to your question you will probablly leave the overboost switch connected.
Merry Christmas,
Rudy

 

Does it look like this? Wouldn't it T off the control line from the intercooler to the wastegate?

 

Mine is like yours but it fits into the brake booster. It should have a oneway check valve if you don't want a vacuum reading. There is no reason to go all the way back to the IC or any other part of the engine since the brake booster gets the same vacuum and boost as the other parts. The only reason to go back to the enging is if you want to control the boost. Then you have to have a connection to the wastegate.
Rudy

 

I have a gauge like the one above. I can't find a vacuum line coming thru the rear bulkhead and the PO had the brake booster disconnected so it's not getting vacuum there. I just hope the booster line wasn't disconnected due to a bad booster.

I'll control boost with the ECU, but of course I'd like the gauge to work.

 

I would try to find that line from the rear compartment to the brake booster - its a hard line so it will provide accurate readings given its length. And, take the readings from the manifold - who cares what's in the IC (even though the reading should be close) - you are interested in the pressure to the cylinders.

My ECU controls the overboost. Anything over 208kPa shuts the engine down, much like rev limiter. So no need for the CIS type overboost unit.

 

What was the factory boost gauge connected to? Will it work off the brake booster. Anything in particular needed to get it to work.
Harold
'79 930/DP935

 

Now I'm really confused. I pulled out the gauge and it does have a vacuum line connected to the brake booster line in the trunk. I'm 99% sure there was no vacuum line from the 1/2" hardline at the rear bulkhead to the intake, but the boost gauge was working!?!? BTW, the heavy brake pedal indicated to me that the booster line was disconnected from the start. I guess I'll just assume I've lost my mind, connect the brake booster line to the intake and hope all works again.

So that's another wire I can eliminate from my new engine wiring harness.

 

The factory gauge is electronic. It gets its signal from a sensor on the the intake.

 

If you contact North Hollywood Instruments and ask them to sell you the black plastic fitting that replaces the one at the back of the brake booster it will be real simple. It also has the oneway check valve in it. Then all you have to do is swap the OEM with the replacement and you are in business.
Rudy

 

Rudy, apparently I already have the fitting at the brake booster. I just can't figure out how it was getting a boost signal since the line at the rear bulkhead infront of the engine wasn't connected to anything (unless my memory is shot, which is not out of the question).

I'll be hooking up the intake manifold to the brake booster line so I'm moving on and not worrying about this anymore.

 

This is an electrical connection,--from the boost sensor mounted on any part of the pipe downstream from the turbocharger. That wire needs to run up to the back of the dashboard and then be plugged into the gauge.

Dan

 

Dan, does this mean it's getting two signals? One from the sensor and one from the brake booster line?