Boost Gauge Readings (Somethings got to be wrong)

[kmoore]

I just installed my boost gauge today which is a 30 vac- 30 psi gauge. When i first start the car it is on 20 vac. When i rev it in neutral it shows about 10 vac. Is that right? Then, when i put it into first and take off slowly, it will show about 10 vac also. When i am still in first, and i really punch it, it will go to the 0 mark I can't get any boost on the psi side to show, in first gear. No madder how hard i punch it. Then, when i am in second, and i punch it, it will then boost to about 10 on the psi side of the gauge. Hooray i am getting boost finally. In third it is the same thing. But, when i am just cruising in second, third, or fourth at about 2000-2500 rpm it will show about 15 vac. When i just touch the pedal just a little bit it will go to about 10 vac. Shouldn't when ever i touch the pedal it should show 0 (for just a little gas) or some amount of boost (giving it a little more gas) on the psi side of the gauge? I really need some info. Thanks (can you tell i'm confused)

By the way when i am cruising and i let off the gas it will show 25 vac., which i'm pretty sure is normal. Any way just let me know if this is normal and why i can't get boost in first gear. Thanks

 

[cecil722]

Where did you tap into for boost pressure and also check and see if there are kinks, pinches, or hard bends in the tubing running to the gauge. This can cause inaccurate readings.

 

[TSIMonsteR]

what brand gauge is it out of curiosity?

 

[Tevenor]

First gear is so short, it's lucky we see any boost at all.

ANd no, just touching the gas pedal will not produce boost if you are below the boost threshold of the turbo. If you are on the stock T25 than that period of time is pretty low in the RPM range.

Showing vaccum at cruise is normal. The turbo is not forcing any more air than the engine can take and hence a vac occurs.

 

[kmoore]

The gauge is an autometer ultra-lite (Manual). I tapped in to the right boost source (The thing on the top right-hand corner of firewall and the line going to the middle of the IM). I know for a fact that there is no kinks or bends in the hose because i triple checked the entire line. On the back of the gauge there is a brass looking nut and gromet thing that goes into the back of the gauge. When i screwed that on all i did was hand tighten it. I did not use any sealing of any kind either. Should i have done that? Should i take the gauge back out and put some sealing on the threads and tighten it down on the gauge really tight? Do you think that would fix it?

 

[daren_p]

Everything you have described sounds normal to me.

 

[JayRolla]

Everything seems right except the 1st gear. I see 11psi in first. I never heard of not seeing it because the gear is to short. The gauge should still show boost from my experience. Thats wierd man.

 

[BeerBaron]

Everything seems right except the 1st gear. I see 11psi in first. I never heard of not seeing it because the gear is to short. The gauge should still show boost from my experience. Thats wierd man.

Ditto, I'd do a boost leak test for the hell of it because you should def see some boost in 1st if you are punching it.

 

[daren_p]

1st gear won't load the motor like the higher gears so you won't see what your boost is set to in first, but ya you usually do see some boost. Don't think you have any issue with the gauge they either work, don't work or are off zero. They don't work properly in some gears while not work properly in others. Everything you described sounds pretty much normal, except not seeing any boost at all in first when you got WOT. A boost leak test is always a good idea.

 

[hidingfrogleap]

I have an autometer mechanical 30vac 20boost gauge and mine's been sticking recently and so watch it while getting on it in gear (probably in 2nd since you said that was going ok for you). Everyone is right though, you should be able to see boost in first on the t25 even though you usually will shift out of this gear pretty quick. I would say something is wrong with the gauge itself, rather than a leak since a leak, if I'm not mistaken, should affect the pressure regardless of the gear you're in.

 

[MyBeatGSX]

Also check for pre-turbo exhaust leaks. This sounds like what mine did when the turbo to manifold gasket was completely blown out.

 

[kmoore]

Ok, cool. I just took off the gromet thing on the back of the gauge off and i put some sealant on the threads. Maybe that was it? Hey, by the way what does "WOT" stand for? Just curious. Thanks for the help

 

[winterftbl]

WOT Wide Open Throttle

 

[VETDRMS]

I'm sorry, but hand-tight is not going to be enough for a proper seal. Get a 3/8" wrench (whatever the size is) and snug it down, that fitting is a compression fitting and needs some compression to seal. Do not go too much or the brass insert will turn and cut your line.

-Travis