Engine Vacuum Voltage Test
#8
Banned
iTrader: (3)
Well, that chart needs to be extrapolated down (that is the response for the actual BARO sensor, same as the stock one, that is used for the test).
I think its pretty safe to say that the "fail" point would be about the same as the "fail" point indicated in the FSM, which is around 8 PSI net.
In other words, measured engine vacuum of less than 56 kPa or negative 6 PSI or so. I think that's about -12 inHg.
That said, I've had brand new motors read low for one reason or another, even when the compression was on-spec or better.
At my altitude, -7.5 PSI would be considered a "bad" motor, but its what mine reads with 130 PSI of compression.
It has something to do with the turbo system, no doubt.
Something in the air path alters the manifold vacuum. Probably some slight forward pressure from the turbo at idle.
I think its pretty safe to say that the "fail" point would be about the same as the "fail" point indicated in the FSM, which is around 8 PSI net.
In other words, measured engine vacuum of less than 56 kPa or negative 6 PSI or so. I think that's about -12 inHg.
That said, I've had brand new motors read low for one reason or another, even when the compression was on-spec or better.
At my altitude, -7.5 PSI would be considered a "bad" motor, but its what mine reads with 130 PSI of compression.
It has something to do with the turbo system, no doubt.
Something in the air path alters the manifold vacuum. Probably some slight forward pressure from the turbo at idle.
Last edited by MazdaManiac; 05-09-2009 at 05:57 PM.
#12
Test Performed
Mileage 77,017
BARO Voltage 4.026
BARO Voltage @ Idle 1.828
So, I assume I take the differential of these two which would equate to 2.198 V. If that is true, my PSI at hot idle is 8.1
Correct me if I'm wrong about the differential, but it makes sense since the engine is an air pump.
BARO Voltage 4.026
BARO Voltage @ Idle 1.828
So, I assume I take the differential of these two which would equate to 2.198 V. If that is true, my PSI at hot idle is 8.1
Correct me if I'm wrong about the differential, but it makes sense since the engine is an air pump.
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