Intake manifold pressure questions...(not boost, but vacuum!)

[Drewcool2]

At idle on my 420a, using a pocketlogger I get a reading of 13.3-14.2 in. Hg. Then at 3500rpm I get a reading of 8.3-8.9. I hear people say that 17 in. Hg is normal at idle. My compression is 175psi accross the cylinders, but should that really bring my vacuum down that much? I cannot find any leaks around the intake manifold or throttle body. (spraying non-flamable brake cleaner in different places)

Where am I loosing all my pressure, and would this be hurting performance at all? Or can this low vacuum be the reason my engine revs down slower than most cars?

 

[ltvarney]

I have 150 across the board and vacuum is between 17-19 at idle depending on weather conditions and running time. Chances are there's a small slit in a vacuum line somewhere. Might be a good time to replace all vacuum lines as a general maintenance procedure as well as sprucing up the engine bay and tracking down the problem with a shotgun approach

 

[Drewcool2]

So I'm going to need a vacuum hose kit to replace all the hoses. Where can I get one of these online?

Thanks

 

[Drewcool2]

I've been trying to find any sort of leaks either at a gasket or on a hose, and I havn't come across 1 leak yet. If I get like 13in Hg, and it's supposed to be 17, there are some major leaks right? When I disconnect a large hose the intake manifold, the pressure hardly changes. It goes from the 13in. Hg to like 12in. Hg. Is there a chance maybe my MAP sensor is bad, reporting the wrong pressure?

 

[TalonRacer18]

I dont know what the vacuum should be at on a N/T. the 17-18 is for turbo cars. the nt's will probably be lower

 

[Drewcool2]

Ok, well I just hooked up an old-fashioned vaccum gauge to my intake manifold just to figure out that my vaccume is 16-17 in. Hg. So it looks like my sensor is bad. Here's the interesting part...
When I rev it to 3500RPMs, my MAP sensor reads 8-9 in. Hg. But my manual gauge drops vaccum for a split second, then is steady around 19in. Hg. I think the manual guage is right, it's supposed to drop, then get more vacuum than it was at idle.
Should I go buy a new MAP sensor? Where can I get one?

 

[Drewcool2]

^Bump^

 

[Drewcool2]

I bought a new (used) MAP sensor, and my pocketlogger still says my intake manifold pressure is 13.3-14.2 in. Hg. (exact same numbers my other sensor reported)
When I hook up my manual vacuum guage to the intake manifold, it still says 16-17 in. Hg at idle. Why does the pocket logger show the incorrect manifold vacuum? I don't have a SAFC...