How do you calculate offset and scalar for a 3 bar map?

[SlvrSky07]

Hello. I was wondering the formula or how to find the correct values for a Bosch 3 bar map 0281002845. Also I read the GM part # is 55206797. The one I went with is a 3 Bar TMap Map Sensor with IAT from here:
http://www.bmotorsports.com/shop/pro...oducts_id/1721


I seen on a few other websites people that used this sensor had 322.5806 (linear) and -8.05 (offset) for a 2007 colbalt and someone used 305 (linear) and 10.33 (offset) on an LS1. I would like to be able to see what one is correct.

Right now I have a 2 bar map sensor but running near 1 bar of boost causes the map sensor to max out if there is any boost fluctuation.

Any help would be greatly appreciated!

[Iam Broke]

I'd just grab a GMS1 Bosch sensor & use the values that have been posted many times for it in your tune. Perhaps that is the same part number, I don't have the data here.

[SlvrSky07]

I guess Im confused on it since Ive seen posts calling the kit with that part number GM stage 2 and GM stage one. Can anyone tell me what one is correct?

[SlvrSky07]

I am assuming this is the post you are referring to?


from this thread

The numbers seem off a bit since with a 1 bar sensor the values are : 94.43 (linear) 10.43 (offset) and for a 2 bar 200 (linear) and 8.15 (offset). I would think it would be somewhere about 300ish for linear and under 8 for offset, or am I wrong?

[Gremlin85]

I believe what you see is what is pulled from GM's reflash if you bought the kit and had it installed and flashed at the dealer. If GM puts it in there, I'd just go by that.

[|V3nom|]

thats also for the lnf and not the le5 so i dont know if that makes a difference or not.

[Iam Broke]

Someone with the LNF 3 bar GMPP kit should post the Bosch P/N for you off of the sensor. Then after it's verified the same, use the GM data posted above.

[SlvrSky07]

From what I have read they are the same sensor but I'm not 100% sure. I have heard from multiple people just to use those settings and they will work fine. It just seems like the wrong numbers to me but I'm not an expert.

[SlvrSky07]

I just got my car out of storage and installed that 3 bar MAP sensor. I flashed the ECU with those values from the GM stage 2 kit. I couldn't get the car to start with those values. I changed it to my estimated values of 300 linear and 7.5 offset and it started right up. I'm guessing the LE5 ecu doesn't work with those numbers. Does anyone have the correct linear and offset for a 3 bar map?

[SlvrSky07]

Is there anyway to figure that out mathematically if you have the sensor specs?

[DSteck]

I guess nobody knows how to read a data sheet.

http://www.bosch.com.au/content/lang...cification.pdf

Scroll to page 3. It's the same as part 0 281 002 437... A 20-300kPa sensor that uses Characteristic Curve 1.

0.4v is 20kPa
4.65v is 300kPa

Work the mx+b and you'll find a MAP Sensor Linear of 329.41kPa and a MAP Sensor Offset of -6.35kPa.

That screen shot is showing the linear per volt. You need linear per five.



329.411764705882 and -6.35294117647061 if you really want to push the digits out.

[SlvrSky07]

Thank you DSteck! I'll give that a try tomorrow. That sounds more like the number I was looking for.

[SlvrSky07]

Thanks! It works correctly now. Can you explain to me how you calculated that number?

[DSteck]

http://lmgtfy.com/?q=Bosch+map+sensor

First result. Click it... On the right there are technical specifications for sensors. Page three shows absolute pressure sensors. Part 0 281 002 437 is a three bar sensor. Manufacturers use the same core in different bodies so this will be the same for the one you have. The characteristic curve is 1. Scroll down.

P1 (20kPa) occurs at 0.4v and P2 (300kPa) at 4.65v. The slope is (300-20)/(4.65-0.4) which is 65.88. Multiply by five to get the linear value (which is how much range the sensor has over 5v). That's 329.41.

4.65v would be 306.35kPa of range (329.41*(4.65/5)). Subtract that from 300kPa at 4.65 and you get the -6.35kPa offset.

[SlvrSky07]

Thank you for taking the time to explain that. I'm sure it will help many people. I appreciate the help.

[pblawler]

I know this is old but it is a great help and explanation of linear and offset