GM 3 Bar MAP Install

[kywhitelightning]

Under sensor scaling and pin 92 enter these values

Volts:
0
0.6274509803921569
1.137254901960784
1.607843137254902
3.882352941176471
4.921568627450981

PSI:
-14.7845
-9.02
-4.353499999999999
0.03850000000000264
20.07700000000001
29.41

In Evoscan I have this formula for MAP scaled
x*0.2745-19.1

Check the box in Evoscan then validate the readings with a pressure pump. If all the readings are off by say +1psi then consider changing the value in Evoscan. If the readings are all over the place both + and - then change the values in Ecuflash to match. As long as the actual pressure is the same as displayed pressure then you're good reguardless of how flaky the inputs look to both the logger and the tune.

Jeff

[Greg E]

Under sensor scaling and pin 92 enter these values

Volts:
0
0.6274509803921569
1.137254901960784
1.607843137254902
3.882352941176471
4.921568627450981

PSI:
-14.7845
-9.02
-4.353499999999999
0.03850000000000264
20.07700000000001
29.41

In Evoscan I have this formula for MAP scaled
x*0.2745-19.1

Check the box in Evoscan then validate the readings with a pressure pump. If all the readings are off by say +1psi then consider changing the value in Evoscan. If the readings are all over the place both + and - then change the values in Ecuflash to match. As long as the actual pressure is the same as displayed pressure then you're good reguardless of how flaky the inputs look to both the logger and the tune.

Jeff

Thank you Jeff!

To add to this, the reason there is a variance to the map sensor vs a real pressure gauge is due to 2 reasons:

*map sensors are absolute meaning they can't compensate for barometric pressure

*electrical varrances between different vehicle chassis.

I had actually started to collect data in order to come up with a calculation correction for Baro pressure but realized it was pointless because of the 2nd point.

[NOMIEZVR4]

Thank you sirs!

I'll test it today and post results.

[RealMcCoy]

Thank you Jeff!

*map sensors are absolute meaning they can't compensate for barometric pressure

I had actually started to collect data in order to come up with a calculation correction for Baro pressure but realized it was pointless because of the 2nd point.

I don't see the problem..? KOEO the MAP hands you a BARO reading. should be pretty easy to reference from there..?

[Greg E]

I don't see the problem..? KOEO the MAP hands you a BARO reading. should be pretty easy to reference from there..?

KOEO = Key on, Engine off??

I guess I could code a modifier which is updated when the engine rotation flag = 0 (engine not spinning). That would solve the eletrical and baro off set. Adds quite a bit of code though but it's not a bad idea. Especially for what I'm working on in the near future.

[99 vr4]

Thank you Jeff!

To add to this, the reason there is a variance to the map sensor vs a real pressure gauge is due to 2 reasons:

*map sensors are absolute meaning they can't compensate for barometric pressure

*electrical varrances between different vehicle chassis.

I had actually started to collect data in order to come up with a calculation correction for Baro pressure but realized it was pointless because of the 2nd point.

Point 2 is exactly why there is a sensor imposed voltage and sensor ground... The ecu tries to regulate this and take that variable away. Other wise none of the code would work between different cars...

Remember that all the important stuff, including the MAF, use the sensor ground reference. Now while the main signal is a frequency, there is a baro pressure and a temperature signal that are voltage based, and use the sensor voltage and sensor ground...

That being said, you should be able to code this, and AS LONG AS no one has used the sensor ground as chassis ground, things should be ok.

FYI, this is the reason I choose to have a sensor voltage and sensor ground pigtail on my harness with an extension harness with three wires to the MAP sensor... Less likely to hook up the map sensor wrong and less likely to be tempted to use the signal ground as a ground..

Brett

[Greg E]

Point 2 is exactly why there is a sensor imposed voltage and sensor ground... The ecu tries to regulate this and take that variable away. Other wise none of the code would work between different cars...

Remember that all the important stuff, including the MAF, use the sensor ground reference. Now while the main signal is a frequency, there is a baro pressure and a temperature signal that are voltage based, and use the sensor voltage and sensor ground...

That being said, you should be able to code this, and AS LONG AS no one has used the sensor ground as chassis ground, things should be ok.

FYI, this is the reason I choose to have a sensor voltage and sensor ground pigtail on my harness with an extension harness with three wires to the MAP sensor... Less likely to hook up the map sensor wrong and less likely to be tempted to use the signal ground as a ground..

Brett

We have had this conversation at least 6 times now.

So far my experience with running aftermarket sensors has been that some can offset all the other sensors. We already discussed this multiple times too. I haven't tried the GM MAP sensor to see if it does or not.

[99 vr4]

We have had this conversation at least 6 times now.

So far my experience with running aftermarket sensors has been that some can offset all the other sensors. We already discussed this multiple times too. I haven't tried the GM MAP sensor to see if it does or not.

Yes that was in regard to sending in a 0-5 v signal on an input expecting 0-1 v... causes unexpected offsets, mainly noticed on the O2 inputs.. Have you experienced this on the MAP sensor or Fuel Tank Pressure Differential sensor inputs? Probably not as they are designed for 0-5 v input....

AS LONG AS THE SENSOR DOES NOT EXCEED 5 volts, this should work.

[Greg E]

Yes that was in regard to sending in a 0-5 v signal on an input expecting 0-1 v... causes unexpected offsets, mainly noticed on the O2 inputs.. Have you experienced this on the MAP sensor or Fuel Tank Pressure Differential sensor inputs? Probably not as they are designed for 0-5 v input....

AS LONG AS THE SENSOR DOES NOT EXCEED 5 volts, this should work.

No I'm talking about other 5V inputs not the o2 inputs. Don't want to discuss it publicly because it'll cause hype but we have talked about it privately before. Remember out talk about how much power a sensor dumps onto ground?

[Chris@Rvengeperformance]

I used chassis ground for the gm map. Maybe it isn't the greatest thing to do, but at the end of the day I cared way more about my boost curve than the exact boost PSI I was running. It isn't like we are tuning SD with it.