# turbo vacume



## retardeds13 (Jan 6, 2005)

i just hooked up my boost gauge and the vacume shows up to 20-25psi when ideling. Is this normal. it is T'd off between the blowoff valve and throttle body. 
I had it T'd off between the wastgate and hotpipe and it showed less than 5pounds vacume. can anyone give me some info. plus it reads boost correctly.


----------



## asleepz (Feb 24, 2004)

Well it would help if we knew what engine we were dealing with.


----------



## James (Apr 29, 2002)

you're reading mmHG when in vacum on most boost gauges. at idle you should be reading negative also. 

the reading sounds very normal... though you should tap the gauge somewhere in the intake manifold itself.


----------



## retardeds13 (Jan 6, 2005)

I didnt know that the vacume was reading at mmHG (What does that stand for anyways?) By the way my engine is a s13 red top. Thanks for the help james


----------



## James (Apr 29, 2002)

millimeters of Mercury.


----------



## Joel (Jun 11, 2003)

most people use the FPR signal line


----------



## retardeds13 (Jan 6, 2005)

what would that have anything to do with boost pressure?


----------



## lshadoff (Nov 26, 2002)

What is important is the pressure the engine is experiencing. The closer to the intake you can measure it, the better.

Lew


----------



## James (Apr 29, 2002)

the FPR does read boost pressure from the manifold, you wouldn't want it reading from anywhere else.


----------



## retardeds13 (Jan 6, 2005)

ive never heard or seen anyone use that metheod....Or maby i just wasent looking hard enough


----------



## Joel (Jun 11, 2003)

its very common. A lot of boost gauges tell you to put it there in the instructions.


----------



## asleepz (Feb 24, 2004)

retardeds13 said:


> ive never heard or seen anyone use that metheod....Or maby i just wasent looking hard enough


Happens a lot but I had a nipple right off my intake manifold that was free (don't ask me why but it was) and I used that.


----------

