Dmacnz

Does anyone have handy the Sensor gradient and offset for a GM 3 bar map sensor for ESL?
I have ran some numbers but come up with something which doesn't seem correct!

Thanks

FlipC

Well I think I got this sorted.
Waiting to hear back from Andy but here it is in case anyone else needs this type of info.

Using the formula in the ESL manual I would get a gradient in the 300's but an offset of like 10. Which is per norm entry #'s for a MAP. But ESL's was different. Finally found formula to get those #'s.

So here is the formula:
1. Find the minimum and maximum voltage and absolute pressures.
2. Convert the pressures to mbar.
3. Subtract the minimum and maximum voltages to find the range, then do the same for the pressures.
4. Divide the pressure range by the voltage range to calculate the scalar.
5. Multiply the minimum voltage by the scalar to calculate the offset. Note that a positive voltage gives a negative offset.

For the GM 3 Bar MAP
501 - .761 volts (.631 average) @ 40 kpa
4.784 - 5.044 volts (4.914 average) @ 304 kpa

.631 volts @ 40 kpa x10 400 mbar
4.784 volts @ 304 kpa x10 3040 mbar
4.153 voltage range 2640 pressure range

2640-4.153 = 635.685 (Scalar/Gradient)

635.685 x .631 (min volt) x -1 (.999) = 400.716 (offset)
x .8 (ESL Manual) = 320.893

Round these up for 636 Gradient and 321 Offset.

As of now I haven't found out where the -1 and or .8 are derived from.
So I am using the ESL manual .8 as the offset outcome seems to be more inline with the stock MAP data.

Also I am going to use a pressure tester along with a voltage meter
to physically test my MAP because as you can see, there can be deviations.

Hope this helps someone

ossett2k2

iTrader: (9)

Excellent info. Thanks
As the manual says to contact ESL if wanting to set boost above 1.7bar which is pretty much the stock map sensor limit,would I be right in thinking this 3bar sensor and your calculations for scale&offset would allow upto 2bar of boost?

FlipC

Technically - yes.
As manual states the 92-96 MAP good to 1.26 bar (18.27 Psi)
and the 97/98 MAP is for 1.86 bar (26.97 Psi)
But the software clips this to 1.7 bar (24.65 Psi) I think that is the Boost Ceiling settings (1.72 bar - 24.94 Psi) which is technically the limit on a top mount inter-cooler (as far as I have seen) and stock MAF scale (I believe)

The GM 3 bar map allows up to 44.1psi, which translates to 29.7psi boost.
So for a MAP sensor you need what ever Psi you want to run PLUS 1 bar.

1 Bar = reads 1 bar/14.7 psi - used on NA cars.
2 Bar = reads 1bar PLUS up to 1 Bar of boost for a total of 29.4 psi
3 Bar = reads 1 bar PLUS up to 2 bar of boost for a totla of 44.1 psi

And so forth.

duster

Stock maf scale and topmount ic will end way before 1,7 bar of boost, my maf ended near 1 bar with big turbo and inlet temps were in the space already...Its very dependent from turbo's capability's, how good your engine breathes and many different things.

ossett2k2

iTrader: (9)

I'm mafless and fmic so should have no problems,also running a bigger twin scroll turbo.
It's good info to know that I can run 1.7bar+ in the future using ESL
It is a shame that ESL can't run AVCS heads so I might move to a different engine management in the future.

The Rig

iTrader: (13)

1.7 bar + sheesh I can smell metal lol

I'd be pooping it running say 1.8 bar even on a rebuilt forged engine

My 115k original block can stick to 1.4 and like it ha

ossett2k2

iTrader: (9)

I'm back down @1.35 for now until I can get a stronger bottom end.
I might go EJ207 or forged and see how far I can push it,but I hear what you're saying,1.7bar is plenty enough,especially on a daily road car

Bob Rawle

The gradient and offset for the GM 3 bar that you have posted are completely wrong so be wary of using them.

You also need to recalculate the barometric figures as well.

The MY97-00 map sensor has a read limit of 1.68 bar (its a 2.68 bar map sensor)

cheers

FlipC

Are you saying the formula is wrong or the #s I used as inputs?

And I can not find any info on calculating any of the barometric fields. - Please tell?

FlipC

I just realized I should have translated that into 3 bar instead of single bar...