Anybody have AEM calibration for a Gen3 map sensor? I have the equation....

Justin311 · 05-27-2007, 01:14 AM

...but don't know what AEM has going on behind the scenes. Here is what AEM suggests for the Gen2 map sensor cal:

And from here: http://gtfour.supras.org.nz/mapsensor.htm

Quote:

ST185: V = 0.1319*psi + 2.7000 up to a maximum of 5V

ST205: V = 0.1025*psi + 2.3293 up to a maximum of 5V

It seems the scalar should be 2.70. However AEM has 2.04 in there.

So moving on to the Gen3, I'm trying to figure out how this equation:

V = 0.1025*psi + 2.3293

Can be uploaded into the AEM. So far nobody seems to have been able to do it. Its easy math...if I only knew how AEM was using each input and putting it in an equation form

Here is some of the thinking I've been doing:

P = 0 psi; V = 2.3293V (this gives me the "scalar" in AEM)
P = -22.7 psi; V = 0V (looks like this is the "offset" in AEM ~22.41)
P = -12 psi; V = 1.09V (this is the min voltage AEM suggests, gives a min pressure of -12 psi. Seems reasonable).

Any input??

MikeV · 05-31-2007, 09:10 AM

Deja vu.

Seriously, I think the Toyota sensor in AEM's wizard has absolutely no relationship with the GenIII MAP sensor (as, I guess, you're proving).
Ignore the equation, look at the graph - that should be everything you need. While AEM seems to publish nothing useful about what their offset & scale parameters really mean, there are some hidden ckues:
1) MAP sensors normally have a linear response, from (min volts) at <= min pressure to (max volts) at >= max pressure. If it's linear, all you (should) need are those two end points, and you have described the entire curve.
2) The other clue - take a look at how AEM models some 'known' MAP sensors (specifically, the AEM and GM sensors) in the wizard. "Load Scalar" seems to be the actual bandwidth of the sensor (nominally 3 for a 3 Bar sensor), Load Offset is normally zero. I can only guesstimate that the load offset is the difference (in some unknown units) from -1 Bar at (min_volts). in other words, if the sensor reads -1 bar at it's lowest setting (most do), the offset should be zero.
3) So... go back to the graph (not the equation), you can pretty much read off the end points... I'd go with an offset of zero to start.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

05-31-2007, 09:10 AM	#2 (permalink)
MikeV mr2partz.com Join Date: Apr 2007 Location: Joisey Posts: 46 Thanks: 0 Thanked 1 Time in 1 Post iTrader Rating: (1/100% )	Deja vu. Seriously, I think the Toyota sensor in AEM's wizard has absolutely no relationship with the GenIII MAP sensor (as, I guess, you're proving). Ignore the equation, look at the graph - that should be everything you need. While AEM seems to publish nothing useful about what their offset & scale parameters really mean, there are some hidden ckues: 1) MAP sensors normally have a linear response, from (min volts) at <= min pressure to (max volts) at >= max pressure. If it's linear, all you (should) need are those two end points, and you have described the entire curve. 2) The other clue - take a look at how AEM models some 'known' MAP sensors (specifically, the AEM and GM sensors) in the wizard. "Load Scalar" seems to be the actual bandwidth of the sensor (nominally 3 for a 3 Bar sensor), Load Offset is normally zero. I can only guesstimate that the load offset is the difference (in some unknown units) from -1 Bar at (min_volts). in other words, if the sensor reads -1 bar at it's lowest setting (most do), the offset should be zero. 3) So... go back to the graph (not the equation), you can pretty much read off the end points... I'd go with an offset of zero to start.