retro

It's been a while since I have done any tuning and I can't find a conversion table that translates the voltage output for both the GM 2 bar and Greddy Sensor. There was an old thread that had it here but it appears to be gone.

I have the pressure-to-voltage for my GM 2 bar MAP sensor (source robbietherobot.com). I need the same for the Greddy sensor, so that I can convert the PSI that the EMU is logging into volts then back to the correct PSI.

I know that you can tune the maps in volts, but the data logger will only show PSI.

I am using Emanage Ultimate v 2.13. I also noticed that there are several versions of "Factory Pressure Sensors" available. Anyone find an option that matches the 2 bar map sensor?

Joe Perez

iTrader: (8)

My first instinct was to be a wiseass and tell you to search, but you already covered that. Looks like the conversion document was lost in the Great Purge.

I've re-attached it to an existing sticky thread. Last message here: https://www.miataturbo.net/showthrea...818#post155818

retro

Thanks for adding to the sticky. That's the exact file I remember.

-Keith

RSNick

Link not working, I need this! Can anybody help?

Thanks

Nick

msydnor

iTrader: (3)

On a similar note, I am about to install an EMU on my mazdaspeed miata. Should the EMU pick up a signal through my factory ECU from the factory map sensor?

olderguy

iTrader: (19)

Does this help?

RSNick

Thanks buddy, I can't get to it here at work but I'll try later at home on a pc

Joe Perez

iTrader: (8)

I guess you could try it, though I have no idea what the conversion would be for that sensor. As a baseline you could try measuring the voltage at atmospheric (engine off) and that would put us in the ballpark.

msydnor

iTrader: (3)

Thanks, I'll give it a shot

RSNick

Ok, got it. Interesting and helpful chart.

So even though I have a 2-bar sensor it will max out at 14.5psi?

Joe Perez

iTrader: (8)

A 2 bar (absolute) sensor will max out at 14.5 PSI relative.

People get hung up on the idea of relative pressure vs. absolute pressure.

When we speak of boost, we are usually speaking of relative pressure, that is, pressure in addition to ambient atmospheric pressure. On earth, at sea level, ambient pressure is appx. 14.5 PSI. That is by way of comparison to a total vacuum. We call that amount of pressure 1 bar.

So if you are running 10 PSI of boost, that's 14.5 PSI + 10 PSI, or a total of 24.5 PSI absolute.

A MAP sensor, by its very name, measures absolute pressure. It can measure not only boost above atmospheric, but also vacuum below atmospheric. A 2 bar sensor can thus measure 14.5 PSI below atmo, and 14.5 PSI above atmo.

RSNick

Thanks Joe, that is a good clear explanation; I am approaching all this from a position of absolute ignorance.

Nick