Anyone on here used a GM 3 bar map sensor to log boost through evoscan if so could you post up the formula you used in evoscan please.

 

Hi,

The formula given to me by tephra is:

0.17573*x-14.5

You then need to apply a correction for your altitude to give a baseline of 0psi

Eg: my actual formula in Evoscan reading request 38:

17573*x - 14.058

Cheers.

 

See this thread:

https://www.evolutionm.net/forums/ec...tructions.html

 

Cheers for the replies if i enter 0.17573*x-14.5 into evoscan and it does not read 0 is there any calculation to get it coreect or is it trial and error?

 

When would you want it to read 0? At idle, you're pulling vacuum, so you're going to see a negative number.

 

You would want it to read 0 with the ignition on and the engine off as surely this would show if the formula is correct for the altitude!! or am i missing something?

 

Correct, adjust the formula as needed so it reads zero with the engine off. I'm personally using 0.19347*x-14.317

 

That is the formula for the JDM map, the one I posted is for the GM map.

 

I'm trying to do the same on my viii , which pin on the ecu did you use and which MUT address do you log? I've got a 3 plug ecu from the JDM car.

Thanks

 

I have not done it yet as i wanted to make sure i had the correct info before starting but from what i,ve read i believe that pin 92 is correct for the signal and that is mut38 which is already set up in evoscan under JDMmap it just needs the new formula.

 

There is a more accurate formula now:

psig = x*0.17886 + 0.161 - 14.5
kpa = ((5.0*x/255) + 0.01765)/0.01591

with psig - yes adjust the 14.5 up OR down to get 0 on IGN-ON.

 

Dave, with the formula above for kpa, which is the local air pressure?

0.01765

or

0.01591

 

kpa is always absolute...

so at IGN=ON, engine=off the kPa should read 101ish.. at sealevel...

edit - if you want to remove atmo pressure then just subtract 101 (or whatever your atmo pressure is) from the end of the formula

 

so.. this is the formula for evoscan. what changes need to be made to my rom? i'm assuming i need to change some scaling to keep the car running right? i have a GM 3BAR and figure i may as well use it.

 

bump. anyone? i'm sitting at the shop, waiting to install. LOL