turbo question

[1987gnwanted]

Sooo.

I m looking into buying my first GN,This will be my first encounter with a turbo charger... I found one at a used car lot.Which is cool I can make payments.

I went an started it up and looked at it..let it idle a bit
liked it**

Question..

This car idled at 5lbs of boost..1000 rpm

when I see photos online of people selling their Gns in the photos of their gauge cluster i see the rpm at about 1000rpms but the boost is at 0..

why does the car i found idle at 5 lbs??

i doubt it's a problem but if so i would like some insight ... i really wanna know what im buying...

 

[turbojd]

It's probably not a big deal, my GN's tach and factory boost guage is all out of wack to. All GN's will do this as they are now dealing with 20+ yr. old circuit boards which oxidize and cause the crazy readings. Caspers electronics can fix this if it bothers you that much. I would take somebody that knows these cars with you to look it over though.

 

[SuperCPA]

It's probably not a big deal, my GN's tach and factory boost guage is all out of wack to. All GN's will do this as they are now dealing with 20+ yr. old circuit boards which oxidize and cause the crazy readings. Caspers electronics can fix this if it bothers you that much. I would take somebody that knows these cars with you to look it over though.

X2 - That is some very good advice.

 

["Turbo-T"]

I have found personally that if you remove the rubber hose off of the MAP sensor the boost gauge will read a little bit, even if you are not making boost.

I think the MAP relies on vacuum to keep it at zero, then when you start getting into the boost for a second there's no vacuum or pressure at the hose, then eventually some pressure will come out to tell the MAP to send out a stronger signal.

It is likely your hose is not connected or the plastic line is brittle and has broken somewhere. However it is also likely to be a common innacurate tach/boost gauge LED set up. I'd check first to see that the MAP is getting vacuum to it. Very easy to do.

I am surprised you found a true GN on a used car lot in todays day and age that allows you to make payments. Any car lot I ever found a GN on wanted all the money up front, by either cash or certified cashers check.

 

[nuclearxp]

Couldn't you just pull one of the vac lines off the TB and check if there's either vac or no vac (equilibrium) at idle. If the thing really has 5psi of pressure at idle you'd feel noticeble air coming out.

 

[413turbo]

I have found personally that if you remove the rubber hose off of the MAP sensor the boost gauge will read a little bit, even if you are not making boost.

I think the MAP relies on vacuum to keep it at zero, then when you start getting into the boost for a second there's no vacuum or pressure at the hose, then eventually some pressure will come out to tell the MAP to send out a stronger signal.

It is likely your hose is not connected or the plastic line is brittle and has broken somewhere. However it is also likely to be a common innacurate tach/boost gauge LED set up. I'd check first to see that the MAP is getting vacuum to it. Very easy to do.

I am surprised you found a true GN on a used car lot in todays day and age that allows you to make payments. Any car lot I ever found a GN on wanted all the money up front, by either cash or certified cashers check.

well said, more than likely bad hose to to map sensor. it's located on the front passenger fender. i'd check that hose first. i've had this problem before.

 

[bmackinnon]

well said, more than likely bad hose to to map sensor. it's located on the front passenger fender. i'd check that hose first. i've had this problem before.

I would say no, more likely (almost certainly) turbojd's answer... old, out of cal. factory boost gage/lites (and tach). They are all out of whack after 20 years.... and no, it can't be idling at 5 psi boost.... Even if the map hose was bad, if the dash gage were in cal it would read zero (atmospheric), not boost... Mine reads zero while idling under vacuum and about 5-6 psi when my VDO 0-30 psi boost gage just lifts off the peg.... so do ALOT of other's.... many off worse than mine....

And YES.... follow jd's advice and find someone who KNOWS these cars to give it a look-see before you buy... post your location up on another thread asking for a helper.... bet you find one near you.....
HTH...

 

["Turbo-T"]

Yeah but mine reads 5 PSI at idle with the vacuum hose off. Put it back on it reads 0 PSI until you start getting into it.

 

[bmackinnon]

Yeah but mine reads 5 PSI at idle with the vacuum hose off. Put it back on it reads 0 PSI until you start getting into it.

Vacuum hose off = 0 vacuum, 0 boost = atmospheric pressure = point at which the boost gage needle would read actual zero, just before starting to lift off the peg when driving = the exact same factory gage calibration error as mine (5 psi).... :wink: Anything less than 0 psi boost = vacuum = factory gage (should be) reading zero... Some factory gages are off enough by now that even under an idling vacuum condition, they will show some boost on the lites. If I pull my hose off the map, my factory gage will read 5 psi also, running or not. Copy? Over?

 

["Turbo-T"]

Vacuum hose off = 0 vacuum, 0 boost = atmospheric pressure = point at which the boost gage needle would read actual zero, just before starting to lift off the peg when driving = the exact same factory gage calibration error as mine (5 psi).... :wink: Anything less than 0 psi boost = vacuum = factory gage (should be) reading zero... Some factory gages are off enough by now that even under an idling vacuum condition, they will show some boost on the lites. If I pull my hose off the map, my factory gage will read 5 psi also, running or not. Copy? Over?

No sh!t sherlock. I was simply stating my boost lights read something when no signal was applied to the map sensor. I never said that's the way it was supposed to be. I know what the difference is between boost and vacuum and when either is present.

 

[QwuickTurbo6]

Like stated earlier, it's probably just the LED's being over 20 years old. As they age, they begin functioning at a wider frequency range, so when the first light comes on, the second one follows suit when it really shouldn't.

 

[1987gnwanted]

thanks for the advise...I had a friend whos had a GN come look at it and he said it wasnt worth what they were asking..and he said it was just an electronic malfunction in the cluster..dont know how he knew but he was sure..thanks for the advice everyone I'll keep it all in mind since im still somewhat in the market for a GN..but looks like I'll have to come up with 10 to 15k all at once..my dreams of easy payments have gone out the window..

 

[Phoneguy]

If your credit is good you could try CapitalOne, I have seen several people mention them on the board. You get pre-qualified for a certain amount and they send you a check.

Bryan