autometer pro-comp vs sport-comp accurracy

[sherfield2002]

ok when i bought my 91 tsi about 2 weeks ago from a friend it had an autometer pro-comp ultralite boost gauge. he told me i could borrow it until i bought my own. i bought a sport comp gauge and it is reading an 3-4 psi less than the pro comp. all i did was unhook the fitting from the old gauge, put some teflon tape on it and connected it to the new gauge. it reads about 17-20 on the vacuum side at idle which is what most people say theirs runs. the old gauge didn't read quite that much vacuum but its not as big of a difference as the boost reading. the old gauge showed me runnin right at 15psi now it shows i'm runnin 11-12psi.. and yes the fitting is tight as i could possible get it. any help would be appreciated

 

[Defiant]

If you want to go to the bother, take it back and swap it out with another.... which may read 3 psi "off" in the other direction.

Boost gauges at the consumer level aren't particularly accurate when measured one-against-another, but so long as it stays in one narrow area while you're using it, that's what really matters most.

This one may settle down to a better accuracy with some months of use.

 

[sherfield2002]

so do u think i am actually runnin 15psi like the old gauge said or am i runnin about 12 like the new one said?

 

[Defiant]

Well, that's the thorny question. Is the new one accurate, the old one, or are they both off by half? Easiest check would be to get a Mityvac with a gauge on it, figure it's accurate, hook it up to the line to the boost gauge and work it. Or, a vacuum/fuel pump pressure tester.

 

[sherfield2002]

whats a Mityvac

 

[Blu Divil]

Originally posted by sherfield2002
whats a Mityvac

Its a vaccuum pump with gauge - acurate and tested.
Good for various vaccuum relaided problems..