I really dont to all that much about turbo stuff and this is just something thats been bothering me.. I noticed this the first time I got my car out of the shop..the vaccume read like 35 and I beleive the SES light was on..and then a few days later the vaccume went down between 15-20 and the ses light was off. I first thought I just had a kink somewhere infront of the gauge or that the gauge was sticking. I normally take it easy on the car and occasionally getting on it and hitting my full 5 psi of boost. Recently I did a little testing and I think that on the days I get on it a lot my vac goes back up to 35.. Does any of this make since? And what does your vaccume mean? I take it good to have a lot of vac. pressure. Also every time I get the car back shop it seems like the SES lights on ... what causes it to come on. Ney of this wouldnt be the cars ECU trying to change towards the stock settings ( I know nothing about the ecu stuff) I have greddy e-manage blue. Any help would be awsome thanks..

 

what codes are you getting?

 

A normally aspirated engine is always in vacuum (meaning that the engine is always sucking air through the plenum, so the pressure is "negative" in the plenum at all times). Your car can only go to positive manifold pressure (i.e. boost) because of your F/I kit. At idle, your gauge should be reading right between 20 and 22 in/hg of vacuum. The only time it should read more vaccuum than that is if you're engine braking. I've never seen 35 though, so that to me would indicate a gauge problem, not a kink in a hose because a kink would make the value closer to zero, not farther from it.

And yeah, can't help you with the SES until we know what the codes are.

 

+1

 

Gauge Prob

 

i have a small questions, what would a boost gauge read if it were hooked up to a NA car ? would it basically go up to 0 under WOT and stop there ? just always wondered what would the gauge would read out, if it would even go to 1 or so.

 

Yes it would...

 

I think it depends on whether the gauge is relative or absolute as to whether it would read 0 or 1. It is impossible for a plenum on an N/A car to see anything above 14.7 PSI (1 atmosphere) at sea-level, which would be 0 or 1 depending on the gauge because anything greater would be "positive pressure" and that would imply that something is pressurizing the chamber. from the front side.

 

Guys thank you so much for your input..And sorry I thought about it last night and the vac's not reading 35 but about 25...Sorry About the SES light I took the car to pepboys, advanced autoparts and some other shop trying to get a reading and they couldnt do it..What would cause my vac press. to drop down to 15? and whats "engine braking"?

 

If your gauge is reading 15 in/hg of vacuum at idle (and assuming that the gauge itself is operating correctly), you have a leak somewhere. Has the plenum been off the car lately? What other intake work has been done (that means from the filter all the way to the engine)?