I have looked over the FAQ and a few other items, but have some custom PID creation questions.

I am looking to create a manifold vacuum chart to log vacuum on a long trip. The vehicle does not support BARO, but my phone does. The vehicle does have MAP.

I saw the address for the MAP and the phone barometer in a thread somewhere (can’t find it again at the moment).

What I don’t understand is the variable A, B, C, etc…

I see them in the math, but how do I know how or what gets assigned.

For example I believe my phone will return the barometric pressure in hPA instead of kPa, but the MAP will be in kPa.

So for vacuum in inches of Hg, I will need (MAP – (PhoneBaro/10) * kPa2inHg [where kPa2inHg is a conversion factor from kPa to Hg].

If there is a FAQ or post I missed that already discusses this I am sorry. If not a brief explanation of the variables would help.

Thanks.

Fizix

I will check it out, but I don’t think it is quite the information I am wanting.

I would still like to know generally how variables are assigned. (i.e. A, B, C, etc . . .)

Fizix

Thanks Capp777!

That was helpful, especially the first link. Now I think I am getting the hang of it.

It looks very similar to SPI interface protocols. The variables are the bytes of the data response, but unlike SPI it does not have a checksum at the end.

Fizix

Just curious if your boost reading was near
zero with KOEO and if you live at sea level?

Val{Intake Manifold Pressure}-Baro()

You may have to convert kPaA to PsiA
for this to work properly…

(Val{Intake Manifold Pressure}*0.1450377)-Baro()

I believe Baro() uses [33], your phone baro
reading or 14.6 depending on whats available.