I hooked my boost gauge up this weekend, and I'm not getting the readings i expect. At idle, the gauge reads 20 on the vacuum side. It doesn't 0 out until about 2700 rpm, and maxes out around 4lb's of boost in the high 4xxx's. It seems low to me, and i don't know why i read so much vacuum. The gauge 0's out when the car is shut off.

What could be causing this? vac leak somewhere? My vacuum lines are all different sizes. I t'ed the factory line twice, and there's a small vac line going to the gauge, a slightly bigger line to the BTM box, and the factory rubber line is even bigger. Can this be messing up my readings??? Or is it just a leak issue?

 

You should read 0 the second you hit WOT, even at 1000 rpms. Does the gauge read zero if you just disconnect the vacuum line from it? FWIW, I have about 20-22 inches of mercury at idle on a fairly stock L98.

Andris, with a few mods

 

yes it reads 0 when disconnected or if the car is off

 

High teens-low 20's sounds about right for an almost stock L98. Maybe you need a smaller pulley

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try another gauge hooked in a different location, then compare the two.

 

He just needs to be careful to not overrev that Paxton SC.. they aren't really known for living a long life when spun at high rpms..

 

Wraith,

20" of vacuum is great, you do not have a vacuum leak, as far as the boost, if you have a ported plenum,mini-ram, good flowing heads,etc... all this will lower your boost because the engine can breathe better.

later

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that's the thing....the engine is bone stock....stock tpi, stock heads, stock cam, at least as far as i know. It was no record setter before. I ran some 14.6's and 14.7's with it pre-paxton, which is about right.

I should be pushing more boost. I'll move the gauge other places and see what happens.




[This message has been edited by TheWraith (edited March 16, 2001).]