Boost readings?

What does the boost gauge read at idle when installed on these cars? Also what is the gauge read when cruising?

this car has no lag, what good is a boost gauge?

Boost gauges are good as a monitoring tool. Not much use when standard besides knowing how much boost your car is actually running but it gives u a good indication when your car experiences any vaccuum leaks etc.

It is also good so you stay out of boost until the car warms up.

I installed a boost/vacuum gauge this past weekend, it's liquid filled to reduce flutter in the needle and all. I cut into the same area (tube coming out of the intake manifold) that the Newsouth DIY on this forum said to, but my gauge isn't Newsouth. I had to compensate by buying an extra type of T-fitting that would reduce from 1/2" tubing to 1/8". Anyway, when I go out to my car in the morning, the gauge reads "0". I start up and I get between 20-22 in.Hg vacuum at idle. I drive about 70 miles to work every day, and when the car has just warmed up, it will read (only under load around 3000-4000 rpms) a boost of about 11 psi. But most of the time I drive it reads about 10 in.Hg vacuum. About 1/4 of the way to work, the vacuum starts reading around 20 in.Hg at about 65 mph at 2500 rpms. Then when I get to work and I let the turbo cool down for about a minute or two, the vacuum reads almost 30 in.Hg at idle. What's going on here? I can't understand why, as the car warms up, the gauge is reading higher vacuum and less boost. I have run through a lot of possibilities in my head, and I can't put my finger on it. If I had a leak, there would be less vacuum and less boost showing on the gauge. Has anyone had this happen to them? If so, how did you fix it? Please help me out.

Except for the 30 in, it sounds about right. Not sure that type of number is possible with our engines.

20-22 is about right. Under light pedal driving I bounce around between 22 and 10 in HG.

Stock engine will spike (under WOT) around 14psi and hold at 9?psi (under WOT). You will only see readings on the "psi" side under acceleration.

nightfishing said:

Except for the 30 in, it sounds about right. Not sure that type of number is possible with our engines.

20-22 is about right. Under light pedal driving I bounce around between 22 and 10 in HG.

Stock engine will spike (under WOT) around 14psi and hold at 9?psi (under WOT). You will only see readings on the "psi" side under acceleration.

Click to expand...

That's all about right. The 30Hg is way off. You should read 20-25(max) at idle. Check your line and filter/t-connector for leaks/kinks. It may be due to your specific gauge also, not sure...

Thanks guys, I have a feeling it might be my specific gauge though because I have to vent it during these cold months due to Virginia's massive temp. changes (it changes readings slightly when the temp. or altitude changes). If there were any kind of leak, my gauge wouldn't read MORE vacuum, it would read less. When the car warms up for over 30 minutes of driving, not only is it showing more vacuum, it shows less boost too (it will only spike to 6 or 7 psi). But if the car is only running for 10 minutes and it is warmed up, that gauge will show exacty what you guys are saying, about 9-11 psi boost, and 20-22 in.Hg vacuum at idle. Anyway, thanks again, I will just have to think on it some more. But again, if anyone has had this problem, or even has a liquid filled boost gauge, please let me know. Thank you !!

ecoterragaia said:

Thanks guys, I have a feeling it might be my specific gauge though because I have to vent it during these cold months due to Virginia's massive temp. changes (it changes readings slightly when the temp. or altitude changes). If there were any kind of leak, my gauge wouldn't read MORE vacuum, it would read less. When the car warms up for over 30 minutes of driving, not only is it showing more vacuum, it shows less boost too (it will only spike to 6 or 7 psi). But if the car is only running for 10 minutes and it is warmed up, that gauge will show exacty what you guys are saying, about 9-11 psi boost, and 20-22 in.Hg vacuum at idle. Anyway, thanks again, I will just have to think on it some more. But again, if anyone has had this problem, or even has a liquid filled boost gauge, please let me know. Thank you !!

Click to expand...

Curently now my vacuum is reading less than normal, and i am only boosting 14psi (spike) which i should be around 21psi (I'm chipped). My boost gauge is a electronic type (not mechanical). I know its not my boost gauge cause i disconnect it and tried it on my brother's car and it reads normal.

I have changed the Diverter valve to "C" and still the same. I believe its the PCV value, so i ordered the new "G" revision PCV valve with the updated breather hose. People who have replaced this have had great success. WIll be doing this job Friday morning. Will update on the outcome of this.

FYI, Took it to dealer and they said everythings looks ok cause no CEL was thrown plus they have not heard of this new Updated "G" revisions.

I figured it out. Yesterday the sun came out for the first time since I installed the gauge. It warmed up the gauge considerably, and the needle was at about 8 in.Hg vacuum without starting it up. I vented the gauge to get it back to zero, and it ended up giving me normal readings the entire way home from work (a little over an hour drive), spiking at around 12-14 psi a couple of times when I gave the car a hard acceleration from a roll in 2nd gear all the way through 5th gear (I try not to do that too often, though it's so much fun). Again, thanks for the advice.

I also have to say that this forum is much better than the other GTI forums I belong to. People here are more tech oriented, and I appreciate that. In other forums they seem to only want to talk about how the car looks (which I do understand because it's an awesome-looking car) and what you can do to make it's appearance nicer, rather than how to improve performance without killing your engine. People here are more cautious and seem to be more aware of how the car works. Thanks for that.