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Boosting properly?


Old 06-14-18, 04:33 PM
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Smile Boosting properly?

Hey Everyone,

I just want to say thanks to anyone in advance that takes the time to respond to me here. I know I can find what I am looking for but I would like to get this figured out sooner than later. I just posted in the new members section as I am just returning after being gone for like almost 10 years. I am looking at a low mileage Silver FD touring 93 model that looks impeccable. I took a brief ride with the owner last Saturday before he had to leave town. The car sounded and felt great, idled great, hardly any smoke after sitting for a couple of weeks on a trickle charger and without any metering all would seem well. Towards the end after several attempts to push the turbos I noticed the aftermarket boost gauge was reading only about 5 psi consistently through gears even mashing it on the highway, and at idle I believe it was sitting in the negative (cant recall if this is normal or it should be at 0).

1) Could there be a vacuum hose leak causing the boost to be weak? I seem to remember this being a possible problem with my turbos in my 93 touring back in the day and it was the first thing I totally replaced on the car.
2) I forget what connections are made for the boost gauge, could it be improperly connected and showing less boost than there is?
3) What is the easiest way for me to verify the boost pressure? I do not have any of my old parts like Greddy boost controller or Apexi Power FC or anything.
4) Anyone in Colorado reading this want to check her out with me? =D
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Old 06-18-18, 12:11 AM
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A vacuum leak going to any of the boost/wastegate control solenoids or reservoirs could cause a loss of boost. My vacuum chamber behind my alternator was cracked for the longest time and I was down on boost, couldn't figure out why until I swapped out my PS pump.

At idle, your gauge should be reading vacuum (so, negative). Mine runs about -0.65kPa, so, whatever that is (I think like 11 mmHg or something?). The boost gauge is typically plumbed to one of the two nipples on the UIM next to the brake booster vacuum line. Check for any nicks or bends in that line. If its a mechanical gauge running all the way to the cabin, be mindful of pinches to the line as well.
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