Aftermarket Boost Gauge Reading

[habitatguy187]

Ok, first off I searched the threads for about 30 mins and didn't find any help, so here I am. I have a 92 tsi fwd that runs great. All I've done to it is hack the aircan and take out the silencer. I bought a used aftermarket boost gauge off ebay (i know, i know) and hooked it up yesterday. Well, first off it came with about 6in of nylon hose, so I went to napa and bought 6 ft. of vacuum hose that fits REAL snug. So i hooked up the vac. hose and ran it through the firewall (couldn't find any threads on that one either) and hooked it up with a T-fitting. Before starting my car it sits on 0, after starting my car it hits -19-20. Now when boosting it won't go past 9psi. I know I don't have any boost leaks, (fixed one a month ago and did a test about 2 weeks ago) and my factory boost gauge reads right at or around 11psi when WOT. So I'm wondering if it's because of the vac. hose ran all the way instead of nylon? Or if it's because I didn't seal the T-fitting (fits REAL tight) Or is it the gauge? Or just a kink? I don't think I have any kinks. And if I do need to seal the fittings, what should I use? Thanks

 

[PIMking]

could be that your only boosting at 9psi. Im running wastegate pressure and im only at 9 psi. your stock boost gauge is just a guess Its tech called a boost estimator (sp)

 

[habitatguy187]

I was out in my car again after I posted this and I was watching my gauge again and it's actually 7psi instead of 9. Each mark is 2psi in the negative but only 1psi in the pos. So i thought it was 9 when really it shows 7. But anyway I have a feeling that it's the vac. hose getting pinched by the grommet in the firewall. Has anyone else ever ran a vac. hose through the firewall?

 

[Hotmodder]

I ran my boost gauge through the firewall, mine was made out of hard plastic hose, i ran it to a T fitting and split it into the vacuum hose from the front of the intake, (next to the coils). Its right on for me, at first the aftermarket boost gauge would be a little shaky due to not a tight fitting at the T, but i hot glued around all connections and it works fine. Just follow it and look for kinks, and it might also be because you hooked it up to the wrong vacuum hose.

 

[habitatguy187]

So I checked my CEL codes last night with a voltmeter and ran a code 31 (knock sensor) from my limited understanding the knock sensor basically slows the car down so you don't blow stuff up. Would this also lesson the boost pressure? Because I ran new nylon line and glued all the fittings and still no pressure.

 

[Tim Melton]

I dont think you have any problems you said it reads max 7 psi and -19 to-20 when at idle that sounds right for a car with stock boost.Im assuming you dont have the boost turned up unless you need to update your profile.That and forget about the stock boost gauge its uselless and inacurate.

 

[habitatguy187]

After searching around a bit it looks like stock boost for a 1g is 11psi. Soooooo, idk. I tried to change the knock sensor today but no luck. Thing is stuck on there pretty good.

 

[r1991_4g63t]

is your stock BCS hooked up or do you have a MBC? when i was running wastegate pressure i was sitting exactly where you are. 20in of vacuum and 7psi boost

 

[habitatguy187]

is your stock BCS hooked up or do you have a MBC? when i was running wastegate pressure i was sitting exactly where you are. 20in of vacuum and 7psi boost

Yes my stock bcs is hooked up and I haven't touched it, and I haven't installed my mbc yet because I thought my boost gauge was messed up, but maybe it isn't.

 

[r1991_4g63t]

see if the line coming out going to the air can is blocked, or the BCS itself. that woulkd cause you to run wastegate pressure. or if the BCS is bad altogether and not opening

 

[habitatguy187]

Ok, changed the knock sensor and it's all ok now. (thing was TIGHT TIGHT TIGHT!!) Have some boost sputter but it's probably my plugs, anyway my gauge reads correctly. And stock boost IS 11.3psi.