beroznikmal

Can anyone tell me what the pressure reading from the VAFC indicates? I had adjusted my valve clearence and noticed a change in the pressure reading at idle....
Thanks
Beroz

beroznikmal

Anyone?

Gernby

The pressure reading is from the MAP sensor. The signal from the MAP sensor is what the V-AFC modifies to trick the ECU into changing the air / fuel ratio. I don't know why a valve clearance adjustment would have any effect on this at idle. Were the valves way out of spec? How does the car run?

Wesmaster

I would say the weather is more likely to be the cause for the change. This reading will probably not be perfectly consistent day to day.

tenblade2001

Does anyone know the "normal value" mine is high -400s to -500 depending on the temp.

beroznikmal

mine was - 600 and now it is - 500 mm.Hg.... idle with 3 bars.......

RT

You young whipper snappers don't know about all the things people used to diagnois using vacuum reading ....... "you boys ain't from around here is ya?"
In the high 400 to low 500 range is pretty normal but 600 is a little on the high side ...... either your idle was high (a/c on maybe) or you had too little intake valve clearance (tight but more than zero) or ........ Were your intake valves on the tight side before you adjusted them?

beroznikmal

yes finally a wise one between us .... this is exactly what I was thinking......My clearance for both my intake and exhaust were on the tight side the reading reduced after I adjusted the clearance as mentioned above.....

beroznikmal

From my research, the manifold pressure will give a good indication to waht is going on...... an increase or decrease in the pressure may infer more or less overlap in valves.... I know that Z car tuners also use this to approximate their A/F ratio......

Beroz

silvermonster

so a tight valve clearance will cause a high value MAP reading and a loose valve clearance will have a low value MAP reading?