RomRaider

Thanks for the info Jon. Apparently older Subarus polled the MAP sensor which is what I read in the tech tips bulletins. Maybe I should add the atmospheric pressure multiplier/offset to the defs so that if it fails, you don't have to replace the ecu.

Yuck. So you'd start your car at sea level and take a trip into the mountains with 7K+ feet of elevation and it still thinks you're at sea level?
The 92-95 civics had a baro sensor in the ECU like the new scoobs have.

So will this be available in the next release? I would like to be able to run ~25 psi without having to use an MBC, etc. Will a different MAP sensor be pretty much plug and play (are they a standard size and connector arrangement)?

Thanks,

Mike

MAP sensor scaling will be added to the next ecu definitions release for 32bit ecus.

Can't wait...

My motor should be in next week!

hijack: What you get???

Maybe some of you can help me with some math, because for some reason I am stumped. Trying to install and calibrate the TurboXS MAP sensor. They give you a card with some numbers and I am trying to figure out the multiplier and offset to use for the stock Ecu.

#s Are:
2.082 Volts = 6.11 psia
3.225 Volts = 19.69 psia

hmm, actually I think this sensor might read 3 bar from 1-5v given those numbers.

ok. Someone correct me if I am way off. But I calculated this out
Offset = -6.11 psia
Multiplier = 8.85psia/v

Sorry Freon, I edited your response instead of quoting it ending up deleting your thread. My bad.

I was going to say that the units would depend on whether he is using the standard (imperial) or metric defs, both of which are available in each ecu def update.

Oh man that was a long post and I already closed the little excel file...

Quick version:

(delta psi) / (delta voltage) = slope
(19.69 - 6.11) / (3.225 - 2.082) = 11.88psi per volt

I.e. every +1 volt = +11.88psi

To double check,
(3.225 - 2.082)*11.88
should equal
19.69 - 6.11
... which it does

To get the offset, you just work back from either of the points you know.

So 0 volts must be 2.082 volts worth of psi less than 6.11psi or
0 volts must be 3.225 volts worth of psi less than 19.69
Since we now know the slope, we know what "2.082 volts worth of psi" means.

I.e.
6.11 - (2.082 * 11.88) = -18.63
19.69 - (3.225 * 11.88) = -18.63
Obviously these should match.


slope/gradient
psi 11.88101487
mmHG 614.5352521
bar 0.819380336


x-intercept/offset
psi -18.62627297
mmHG -963.427912
bar -1.284570549

As merch said I guess it depends on what defs you are using. I use metric and it uses bar (1bar ~=750mmHG ~= 14.5psi)

This is a bit odd because this means 5 volts = 40.78 psiA = ~26psiG = only 2.8bar, not 3 bar. I guess it is not-quite-3bar MAP sensor then. Doh?

Yeah, it was. Sorry again.

Yeah, we tried and it didn't end up being the same. So instead we took our own voltage measurements and figured it out. Now it reads within .25 psi so it needs a slight tweak. The card comes with 2 calibrations, one for PSI and one for BAR and they are way different. Anyway, we measured.


1.73v @ 14.655 psi
0.95v @ 6.68 psi

I don't remember what values I came up with that calculation...
But our final values were
Multiplier = 12.35 psia/v
Offset = -5.22 psia

It reads .25 psi high at high vacuum and high boost, but dead on at 14.655 atmospheric with the engine off.


I guess the next question is...Has anyone been able to log more than 37psi absolute (22.3 psi boost). Having the bigger sensor in there is cool and all but if the ecu won't read above that I am out of luck for my boost control. I think someone mentioned that it does, you just can't log it. If that is so, its fine with me. We only hit 23.2 psi maximum so I'll have to lower fuel cut slightly to check if the ecu is in fact reading above 37 psia.

You just can't log above 37 psia. I'll go ahead and add the ability to log boost directly to the next logger definition update and this will in effect eliminate any boost ceiling when logging.

Send me a PM with your rom id if you would like me to add it to your current defs.

Did anyone else try disconecting their MAP sensor[s] and notice that the car will still log manifold and relative pressures? I am installing a GM 3 bar on an STi and with both sensors disconnected, it still logs correctly, although it does throw a CEL.

I'm confused....is there another MAP sensor in the car aside from the one on the throttle body?

Upon that kind of fault, it will calculate manifold pressure based on load.

Can you determine the failsafe equation to calculate boost? That might be useful.

I've derived my own from my logs but it would be useful to see what the ecu thinks it is.