What happens when using wrong MAP offset values?
Thread Starter
Teching In
Joined: Jun 2007
Posts: 48
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From: Irving, Texas
What happens when using wrong MAP offset values? I recently upgraded my turbo and found I also needed to adjust/increase my VE table values in the upper kpa cells. Well! In reviewing my tune I come across the MAP Sensor calibration and started to question the values.
I have been tuning a 2 bar OS for a while and using a GM#12580698 map sensor which I set the linear setting to 200 & offset value to 10.33 in the calibration settings. Don’t remember where I got these numbers.
So back to the search feature I go!!!
After substantial hunting and reading I found reports that the offset value should have been (8).
Today I changed the offset value to (8) and found my WB02 reflecting leaner A/F ratios at corresponding kpa values . I run up to approx. 150-160-kpa only. I did not push it further to the 206-208 kpa normal boost level.
Can someone please explain what function the offset table performs and how it affects the tune?
Further, can someone please verify the linear and offset values for the GM#12580698 sensor?
Will I be doing my tune an injustice by leaving the previous value as long as I acquire the proper A/F ratio and the WB02 and Commanded agree?
I have been tuning a 2 bar OS for a while and using a GM#12580698 map sensor which I set the linear setting to 200 & offset value to 10.33 in the calibration settings. Don’t remember where I got these numbers.
So back to the search feature I go!!!
After substantial hunting and reading I found reports that the offset value should have been (8).
Today I changed the offset value to (8) and found my WB02 reflecting leaner A/F ratios at corresponding kpa values . I run up to approx. 150-160-kpa only. I did not push it further to the 206-208 kpa normal boost level.
Can someone please explain what function the offset table performs and how it affects the tune?
Further, can someone please verify the linear and offset values for the GM#12580698 sensor?
Will I be doing my tune an injustice by leaving the previous value as long as I acquire the proper A/F ratio and the WB02 and Commanded agree?
The result of the incorrect settings means the sensor will not be properly calibrated and the sensor will read different that what is actually going on in the intake. When you go to a custom operating system the tune changes the number's in there for you.
If the car has the proper a/f ratio's and everything works fine then I dont see a problem.
If the car has the proper a/f ratio's and everything works fine then I dont see a problem.
Thread Starter
Teching In
Joined: Jun 2007
Posts: 48
Likes: 0
From: Irving, Texas
I have the custom 2bar OS but don't remember if I input the values or they were already when sent by HP Tuner. I know I had to switch to a 2bar MAP sensor.
Can you explain what affect or how the offset values factor in on the tune?
Can you explain what affect or how the offset values factor in on the tune?
Last edited by Warhorse; Oct 4, 2009 at 11:53 AM.
Those are the supplied numbers for HP's 2-bar os, and you can double check it to be correct in the scanner by hooking up a mechanical gauge as well as something that can supply boost and vaccum. Then you compare the mechanical gauge to the map sensor reading in the scanner. Make sure you have the MAF pid deleated or it will half the map values.
Last edited by black98ws6ta; Oct 4, 2009 at 02:33 PM.
Thread Starter
Teching In
Joined: Jun 2007
Posts: 48
Likes: 0
From: Irving, Texas
How do I find out what the correct offset for the map sensor should be?
I have used the search feature on this forum and also HP Tuners but have not found conclusive answer.
Can you or someone explain what will be affected in my tune when I re-enter the new value of (exmpl. 8) in liew of my previous value (10.33)?
How do I find out what the correct offset for the map sensor should be?
I have used the search feature on this forum and also HP Tuners but have not found conclusive answer.
How do I find out what the correct offset for the map sensor should be?
I have used the search feature on this forum and also HP Tuners but have not found conclusive answer.
Read the edited lower portion from my last post. The 10.33 and 200 numbers should be the correct numbers for that sensor. They will be very close anyways.
The affect of changing the 10.33 number in the tune will depend on the engine and tune. There is no reason for changing the number's other then fine tuning actual pressure at your altitude to match that of the scanner.
If you dont understand this simple process I am not sure you should be tuning. A small change in some of these tables could mean big problems.
Can you or someone explain what will be affected in my tune when I re-enter the new value of (exmpl. 8) in liew of my previous value (10.33)?
How do I find out what the correct offset for the map sensor should be?
I have used the search feature on this forum and also HP Tuners but have not found conclusive answer.
How do I find out what the correct offset for the map sensor should be?
I have used the search feature on this forum and also HP Tuners but have not found conclusive answer.
If your car was tuned around an offset of 10.33 and you enter 8, you will effectively 'shift' your VE table by 2.33 kPa. Imagine 'sliding' the whole VE map 'down' a shade.
A quick and non-technical method to get close to correct offset would be to either flash your setup back to 1bar and put a stock MAP on your car (or go to a buddies car who has a 1bar MAP and OS), turn the key to run (not start), start scanning, and record the MAP value. It will be be up around 100 (or slightly lower at higher altitudes). Now, re-install your 2/3 bar MAP sensor and OS. Turn key on and observe MAP. if it reads, for instance, 98 kPa but you saw 102 with the 1bar setup, then you need to add 4 (because it's in units of kPa) to your current offset value.
