I'm reading .01 with my 4 bar sensor. Just curious what you other guys are seeing?

 

Your talking about what the PFC outputs for boost? I have the stock pressure sensor and adjusted my PIM scale and offset in the Datalogit to make the PFC boost readings correct so my boost reads 0 with motor off. Most people with default PFC data will have their boost read negative a fair amount. The actual value varies with altitude and fluctuating "barometric" air pressure. You can change your PIM offset so that your boost reads 0. It will change the PFC boost and vacuum readings a very small amount and shouldn't be a problem but it's always good to watch A/F ratios after any changes. .01 kg/cm^2 = .14 psi so your really not off by much and could easily be explained by changes in "barometric" air pressure. I'd recomend watching it for a couple of weeks and see if the PFC boost changes any before changing the PIM offset value if you change it at all.

 

I noticed that too, mine reads vacuum though. Last I checked...I think I read -35. So you think my reading may be off and I'm acutally boosting more than what the PFC is reporting?

 

35 mmHg = 1.38 inHg = .68 psi

Yes, The PFC reads lower boost than actual with the default PIM scale and offset. The amount of error is greater as boost goes up (1-2 psi low at 10 psi?). The PFC boost reading can be corrected with better scale and offset values but then the current tuning may need some changing. It is best to "calibrate" the boost before starting to tune and probably isn't worth changing if you already have a "good" tune. You need a Datalogit and a MityVac with boost and vacuum so not everyone has the tools and understanding to do it.

Here's a couple of related threads...

https://www.rx7club.com/showthread.p...oost+PIM+scale
https://www.rx7club.com/showthread.p...oost+PIM+scale

 

so, my .01 is pretty dead on correct?

 

Wow, thanks for the links. What I was understanding is that you have to change the offset and you have to change PIM values? Do you have to touch the PIM values? I don't have a datalogit, so can I just change the correction so it reads 0 with a commander? Or should I just leave it alone and just know that it's boosting more than what the PFC is telling me. If PFC is reading pressure incorrectly, wouldn't that throw off all the functions, as far as the ignition and fuel?

 

The PIM scale and offset values are not editable with the Commander and are not the same as changing the PIM values that relate to % of fuel in the Commander. Without changing these PIM scale and offset values there is no way I can think of to zero/correct your boost reading. This will not be a problem most of the time because the PFC reads absolute pressure/MAP pressure correctly and the fuel and ignition maps are tuned based on these. The boost settings are relative and one of the few cases that are affected. The default boost on the PFC goes to about 11psi instead of 10 psi beause the boost is lower than it should be.