Map sensor jumping erratically

[CranknChrome]

i always get the good ones. One of these new lt1 to ls1 conversion kits came into my shop for tuning. It also has a vortech supercharger on it. so its a 2bar map sensor. the kit came with a ecm setup for n/a with the lt1 firing order and other parameters. before i changed it to 2bar sd enhanced the map sensor sat a 105kpa. it ran enough to get it to move. Now that i have changed it to the 2bar, the map sensor bounces 0-105kpa koeo. Upon trying to start it. The map sensor jumps to 105-200kpa. replaced map sensor. pulled harness apart and checked wires. also tried making wires straight from ecm to the map sensor. got a picture a log and the tune file attached.actualwhenrecording.pngmap bouncing.hpl2barsetup.hpt


also after trying to start map 2bar shows 29.1 psi.

[kevin87turbot]

Just remove the 1 bar MAP sensor from your scanner and leave the 2 bar MAP sensor there. That'll fix the reading on your scanner.

You should also add an IAT sensor to the engine. That's important for proper SD calculations.

[CranknChrome]

I removed the 1 bar and it straightened out. Still shows 209 as soon as i turn the key to start it. got a new 2 bar sensor but the connector is different so now i a m waiting on the connector.

I had the maf and iat sensor disconnected trying to see if i messed something up while i was removing a maf sensor. When they put this together they put 2 maf sensors on it. they were using one for the iat and one for the original maf. I moved and rewired the 5pin maf to pull all of it. I know i will have to fail the maf to stay in sd mode but at least there isnt 2 on it any more.

I tested the map sensor per the shop manual and it shows "normal". On the scanner the voltage never moves off of 4.8 and the psi goes from 0.0 to 29.3. I would think that something else would have to change for it to read that. when i changed the tune file to 2bar enhanced it changed the map characteristics to 200.0 and 10.33. as far as i can tell from other threads it might need to be 8 but it should still be close.

[blindsquirrel]

A PSI reading in the scanner is just doing a voltage conversion. If you give it the wrong settings the conversion will be wrong. Are you absolutely positive the sensor is what you think it is?

What I mean is, 4 volts is 4 volts. You can make a 1-bar sensor display any PSI you want by inputting the wrong linear/offset numbers (or accidentally, if the actual values do not match up with what you think they should be).

[kevin87turbot]

A PSI reading in the scanner is just doing a voltage conversion. If you give it the wrong settings the conversion will be wrong. Are you absolutely positive the sensor is what you think it is?

What I mean is, 4 volts is 4 volts. You can make a 1-bar sensor display any PSI you want by inputting the wrong linear/offset numbers (or accidentally, if the actual values do not match up with what you think they should be).

That's exactly right. I'd bet that it's a 1 bar MAP sensor on it now.

[CranknChrome]

The new connector should be here in the morning. In the meantime I?ll be changing plugs and oil. Fouled out and full of fuel.
Thank you

[CranknChrome]

It was a 1 bar. This customer put all this money into this supercharged lt1 because it wasn?t running right and it?s been the map sensor the whole time. It?s up and running. Got some exhaust leaks to fix in front of the o2?s and then maybe it?ll get some more consistent readings.

Thank you for the help