so i've got the Cobb stage 1 93 oct map loaded in my car for the past few weeks and i've only been hitting 17psi at peak as apossed to the 18.5psi the map notes say i should be hitting.

so i finally logged a few quick drives to compare the gauge vs the AP the results being...

at peak the difference between the gauge and the AP is about 2.5psi... gauge reads lower(ie 16psi on gauge vs 18.3psi on AP)

when cruising in vac the difference can be as much as 10psi... the gauge reading lower again (ie -0 to -10psi on the AP vs. -10 to -20psi on the gauge)


its a glowshift elite gauge, i tapped the vac line from the engine to the BOV, the line provided with the gauge is the clear plastic stuff.

so my question is whats up? is the gauge/electronic sending unit faulty? is just ****ty vac line that i should replace? or something else?

 

My guess is it has something to do with the gauge. I dont think its possible to have -20psi vacuum on our cars, at any point. I think -12 is probably the most vacuum you can get. There is a good chance that you have a little vacuum leak from installing the boost gauge, make sure that your lines are clipped and on there real tight. The AP is pretty accurate when it comes to readings because it draws it directly from the ECU. I am currently running the same map on my RA, I hit 18.5 consistently on the highway and under heavy acceleration. Otherwise, I hit about 11-15 with just normal driving.

 

mine sits at about -17psi but i peak at 21 o.0

 

Your vacuum is -17 at cruising speed?

 

ohh cruising? i meant idol ZZZzzzzZZZZzzzzz cruising sits at 0

 

huh, thats even weirder. Damn, I am just going to stick with Pipers response because its what I wanted to hear. Haha

 

After many hours of labor last night I installed my ProSport Digital Boost Gauge and tapped that little line coming off the BoV too. I clipped that on there nice and tight with several zip ties all around and read -8 to -9 at idle vaccuum. I have the GST basemap v2 and so far the highest i've seen is about 19psi at about 75% throttle. When I let off after that, it only hits about -12 on the vaccuum max...

I would say your readings must be faulty for sure. I'd say you have a leak Hopefully it's not the gauge! Glowshift I think is better or par with ProSport so...

 

yea think i'll try switching out the clear plastic vac line they supplied and try a normal black one, i zip tied all the connections so if this doesn't fix it maybe its just faulty and i'm pretty sure its still under warranty

 

first, i think the different in pressure is reasonable... correct me if im wrong, the ECU uses a sensor in another location to give boost reading, so its reasonable to see a different in PSI.

as for ur vacuum... maybe your gauge is reading in inHg? Thats wut Defi is giving me...
google: to convert inHG to PSI ... multiply by 0.4912

just guessing and trying to help here, no expect in anything

 

did the search for u..
http://www.glowshiftdirect.com/elite...uum-gauge.aspx

This model precisely reads boost levels up to 30 PSI, as well as the engine's vacuum and compression levels between -30 to 0 inHG.

 

well that never occured to me, as far as the vac goes but with boost its still off by 2.5ish psi

 

so i'm obviously taking the AP as gospel when it comes to data so, what should my boost gauge read at idle and at cruising speed (60kph and 2000ish rpm) just so i can have as much info to write glowshift with to hopefully get a new gauge or even a refund

 

I just made a thread about vacuum at idle. The general response was -8.5psi, well at least thats what Piper and I have at idle, no a/c, car warmed up. Cruising speed can very greatly so really the only thing that everyone would have in common is the vacuum/boost pressure on the AP at idle.

 

i get -16 inHg which is around -8 PSI too..

if u have the glowshift from the link i show u... ure reading in inHg... not PSI

 

thanks guys... why the hell did glow shift use inHG for vac and PSI for boost... might have been simpler to make it read all the same.... ah well i also shoud have read the full description