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View Full Version : just installed boost gauge and low boost???



94jedi
09-11-2005, 06:17 PM
Hey all, I just put in my boost gauge and I'm not making any boost. I'm at 10 in Hg at idle and during normal driving. Is that normal? Then when I floor the gas pedal, boost peaks at like 7 or 8 psi and trails down to 4psi or so near. The thing is the car feels fairly strong. I'm recently GIAC'd which is my only performance mod. My car probably still has the original DV but I have a 710N I'll be putting in it's place shortly. Sounds like a boost leak right? could a bad DV also cause this?

Any ideas?

01'A41.8T
09-11-2005, 06:31 PM
Your vac is off. Mine sits at 20 at idle. Could be a leak or a pinch in the hose.

94jedi
09-11-2005, 06:58 PM
hmmmm...I'll check for kinks.

also, not sure f it makes a differnece, but I tapped off the front hose, not the back FPR hose.

alen
09-11-2005, 07:02 PM
how many miles on the chip? it must be your DV. change it and tell us if there's a difference. your numbers (vac and boost) are definitely off which means there is leak.

01'A41.8T
09-11-2005, 07:23 PM
Front hose is the better of the 2 so no worries there.

A4quattro1.8T
09-11-2005, 10:00 PM
Yeah, you have a vacuum leak. My vac sits between 20-22 at idle.

OutkastSL
09-11-2005, 10:21 PM
definately a vacuum leak. check all your vacuum lines, dv, and where you tap'd the vacuum line for the boost guage. i'm at about 20-22 at idle too.

94jedi
09-12-2005, 05:48 AM
Originally posted by OutkastSL
definately a vacuum leak. check all your vacuum lines, dv, and where you tap'd the vacuum line for the boost guage. i'm at about 20-22 at idle too.

Ok so I checked the line at the point where I tap'd it and I went to 12 in Hg at idle and I boost to 8 or 9 psi now, which tells me that was leaking a bit. I'm thinking maybe when I tightened the compression fitting on the back of the gauge the hose might have slipped out slightly, causing a less than perfect seal. Should I have used teflon tape on the threads of the fittings? I'll re-do that connection tonight and see if it improves. I haven't checked for kinks in the hose under the knee bolster though. I will do so tonight as well.

Could a bad DV valve cause that much boost loss? The strange thing is that the car feels fairly strong.

offroader1006
09-12-2005, 06:20 AM
i had mine tapped off the front line going to the DV when i bought it.

it had a boost leak and only spiked at 15(it hits 22 now)

it made the car run like shit when in boost, so you would def know it it was bad.

and then it started affecting the DV. if it makes a fluttering sound when you let off the gas instead of the crisp pshhh, the DV isnt working right.

bitterchild
09-12-2005, 07:18 AM
you should definetely be pulling at least 18 at idle.

mike-2ptzero
09-12-2005, 09:44 AM
Originally posted by 94jedi
Ok so I checked the line at the point where I tap'd it and I went to 12 in Hg at idle and I boost to 8 or 9 psi now, which tells me that was leaking a bit. I'm thinking maybe when I tightened the compression fitting on the back of the gauge the hose might have slipped out slightly, causing a less than perfect seal. Should I have used teflon tape on the threads of the fittings? I'll re-do that connection tonight and see if it improves. I haven't checked for kinks in the hose under the knee bolster though. I will do so tonight as well.

Could a bad DV valve cause that much boost loss? The strange thing is that the car feels fairly strong.


What gauge did you use and are you using rubber hose or the nylon line? Best way to install a gauge is just to use rubber hose with a plastic T to tap into the front vac line, then slip the rubber hose over the fitting on the back of the gauge and put a wire tie on it to hold it in place.

94jedi
09-12-2005, 10:26 AM
I used the VDO hose kit that comes with all the little AN fittings. It's a hard thin silicone hose, not the soft aquarium tank type hose. I've heard those kink/colapse easily. I will take pics tonight of everything.

goldenchild
09-12-2005, 10:38 AM
that would be the nylon line which mike is sayin do away with and replace it with a rubber hose used for pressured lines. i used the nylon line with no prob and i sit @ 20-22 vac

94jedi
09-12-2005, 11:28 AM
Guys, should I use teflon tape on the threads of the fittings?

goldenchild
09-12-2005, 11:39 AM
yes

alen
09-12-2005, 02:34 PM
Originally posted by 94jedi
Guys, should I use teflon tape on the threads of the fittings?

won't hurt.



Originally posted by offroader1006
and then it started affecting the DV. if it makes a fluttering sound when you let off the gas instead of the crisp pshhh, the DV isnt working right.

I know what you're talking about because I broke a porsche 110 valve (almost same as the 710N) and know what the sound (and power :D) difference is between a working and non-working one. however, at heavy load and low rpms when i slowly let off the gas i get a fluttering noise which is pretty noticeable (although nothing near a honking noise when i ruptured the 110) and this is with a 710N and a forge 007 + cone air filter. were you talking about the honking noise? i'm sure fluttering is 'normal'.

mike-2ptzero
09-12-2005, 02:42 PM
Most of the time a fluttering sound is compressor surge.

alen
09-12-2005, 02:51 PM
to save on the parts and especially the compressor and shaft, i should stop doing that?