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What does your Boost/Vac read at Idle?

Im just trying to figure out this Greddy EBC and see how the vac is now. I had 2 vacuum leaks and the thing was going nuts (fixed). It reads around -89 at idle now (psi pressure unit setting not kPa setting)

If you're saying your unit is reading negative 89psi at idle, something's not right.

Typically vacuum is read in units of inches of mercury. Even at that, you can only obtain about negative 14psi at sea level in a perfect vacuum.

Perhaps I mis-read?

Well the manual doesnt say anything about inches of mercury. Its mostly all in kPa like the diagrams. But the EBC is set at psi now and at idle the screen shows -89 would that be -8.9? Because at positive pressure it will read 70 which means 7.0psi

This EBC is confusing me

If i change it to kPa it reads around -.60 X100 kPa at idle

I'm afraid I'm not much help on setting up your EBC.


However, -8.9psi sounds a bit more reasonable. It still seems a tad on the low side at a stand still, warm, idle. I typically see around 20inHg to 24inHg or -10psi to -12psi.

Well I just used google to convert the kPa unit into psi just so I could make sure the -89 really means -8.9.

and -.60 kPa x100 is what it shows on the EBC so that would be -60kpa and in psi thats roughly -8.7 at cold idle.

Does that make sense? So I gues -8.7psi at cold idle

It's inacurate to take measurements of anything when the engine is cold unless you're tuning cold start in a stand alone. So that includes vacuum, boost, af/r's, fluid levels etc unless otherwise noted. Give us readings through a gauge that isn't t-ed into anything at normal operating temp. My gauge reads 20 in/mg at operating temp idle.

That vacuum reading is almost spot on. -8.7 PSI is equal to about 18 inches of mercury. That's almost exactly where you want your idle vacuum level to be. Once the car warms up it should drop even lower. The "perfect" idle is at 19 inches of mercury.

Alright sweet thats what I wanted to know. Thanks!

Idle and out of gear its ~20inHg. Coasting down a hill in gear, it can get as low as 25inHg. With boost, the skys the limit

BSOD2600 wrote:Idle and out of gear its ~20inHg. Coasting down a hill in gear, it can get as low as 25inHg. With boost, the skys the limit

I am pretty close to the same. About 18-19 at idle.

Alright sweet, so my vacuum is fine now. Its about -9.9psi when its warm at idle. Im also going to be getting a Boost/vac gauge asap just so I have 2 different references and so I dont have to keep converting. Plus the gauge looks cool haha