Digital Dash boost problem

[DOUGGN]

I am a new 87 GN owner. I just got the car - it has a digital dash. I have a few questions about how it should be as I don't have anything to compare it to. The car is stock with 77,000 miles - never been apart. It does have a three inch down pipe and a full dual exhaust system after the cat. It has a random tech. aftermarket cat and the pipes are 2 3/4 diameter.

1. My amber boost light comes on but it takes a while. The red never lights. I can hear/feel the turbo coming on but don't know if it is operating as it should. If I go by the lights its not even making 9 lbs at wot.

2. The car seems to shift from first to second very quickly. It doesn't even chirp the tires on the upshift.

3. Does anyone have advice on other things that I should check to make sure everything is operating properly?

Thanks,

DougGN

 

[87gninpa]

I wouldnt put much stock in the factory boost gauge, especially on the digital dash. Amber is supposed to light up @ 5 lb and red @ 10 lb (I think). Either way, you should just put an aftermarket boost gauge in the car so you can see how much boost you are really putting out.

As far as the trans shifting early, you need to adjust the TV cable. Follow the procedure here:

TV Cable System

 

[Victory]

I had a similar problem with my boost readings when I first brought my car. Yes, you should install a boost gauge for accurate readings, but if you also want the digital gauge to function you probably need a new pressure switch. That fixed my problem.

You can get one here --> Pressure Switch - Boost Gauge

They are adjustable to a degree (when the yellow comes on and when it switches to red), but if the red never comes on the switch is probably busted. It's located on the passenger side of the engine compartment on the fender.

Good luck!

 

[DOUGGN]

Thanks for the help so far! Should I just assume that because my lights are not lighting properly it is because of the switch or is there some other way to check that the turbo is really putting out what it should?

 

[87gninpa]

It is most likely the switch, but the only way to check your boost for sure is to hook up a real boost gauge. Good thing to have on the car anyway.

 

[Turbojohnny]

i HAVE A DIGITAL DASH ALSO
MY AMBER AND RED LIGHT GO ON.
I JUST BOUGHT A BOOST GAUGE AND IT IS DIGITAL TO MATCH THE DASH.
I WAS WONDERING IF THE GAUGE SHOULD READ MINUS NUMBERS AT IDLE -3 -4 THEN WHEN I KICK IN THE BOOST I GIT 7-9 JUST TOOK MY FIRST RIDE WITH THE GAUGE

 

[salvageV6]

The readings depend upon the type of gauge, ie. whether or not it reads vacuum or not.

The only way to calibrate the factory dual boost switch is to get a setup with regulated shop air into the fitting and use an ohmeter to measure each switch terminal to the case which is grounded to the car in normal use.

Each switch closes to ground at the aforementioned boost levels, or whatever you set them to if they work, and the ground lights up the dash indicators which have power on one side of the bulb when the key is ON.

Usually they get a bit corroded as well internally, electronics cleaner can help that issue.

The adjusting screws are under rubber caps. if I remember correctly.

It took me a good two hours to clean and get mine to function decently to light up properly.

You need to get them set right with as little hysteresis as possible and also make sure they repeat at the same point each time.

A new switch might be easier to work with, but unless you verify the settings with a real boost gauge you still don't know exactly what they mean or when they turn on even if it's a new switch.

Best bet is a nice vacuum to boost gauge which can go to 30 psi.

 

[DOUGGN]

I tested my lights in the dash by the procedure on the forum. My lights both work. I adjusted the transmission shift cable as well. I still only get the first light to come on when I accelerate. If I'm moving about 20 mph and take off the first light will come on. It doesn't shift out of first so fast anymore. It does not chirp the tires on the upshift and you have to listen carefully to hear the turbo spool - is this normal?

If the wastegate has an adjustable shaft - how do you know it is set correctly?

If I pop off the e-clip and pull the rod off the shaft, the shaft moves in to the diaphragm unit about 3/8 of an inch. I can grab the rod by hand and pull it back out and clip it back on.

Anyone have a recommendation on a nice digital guage for boost? Most pods I've seen have at least 2 holes - what other guage is helpful - exhaust gas temperature????

 

[krom]

I tested my lights in the dash by the procedure on the forum. My lights both work. I adjusted the transmission shift cable as well. I still only get the first light to come on when I accelerate. If I'm moving about 20 mph and take off the first light will come on. It doesn't shift out of first so fast anymore. It does not chirp the tires on the upshift and you have to listen carefully to hear the turbo spool - is this normal?

If the wastegate has an adjustable shaft - how do you know it is set correctly?

If I pop off the e-clip and pull the rod off the shaft, the shaft moves in to the diaphragm unit about 3/8 of an inch. I can grab the rod by hand and pull it back out and clip it back on.

Anyone have a recommendation on a nice digital guage for boost? Most pods I've seen have at least 2 holes - what other guage is helpful - exhaust gas temperature????

Oil pressure or water temp.

 

[DOUGGN]

Turbojohnny - what kind of gauges did you buy that match the digital dash?

DOUGGN

 

[DOUGGN]

Anyone know where to get a nice 2 pod a pillar gauge holder? I've seen some on ebay but I would like to get one that is the full a pillar and is matched to the color of the GN interior.

DOUGGN