2G Intake Manifold Sensor?

Sniffbooger · Jun 26, 2020

Just wondering what is the purpose of the manifold differential pressure sensor on the intake? I know it's not the same as a MAP sensor, but what does it do? I've been told it's like a sending unit for the stock boost gauge? But my stock boost gauge stays pegged at the high boost mark when running, even at idle. Not sure if it's related to the sensor but I know it's not reading correctly. Thoughts are appreciated!

91talonts1 · Jun 26, 2020

https://www.dsmtuners.com/threads/map-mdp-sensor-whats-the-difference.484264/#:~:text=synthetek DSM Wiseman&text=The MDP sensor (Manifold Differential,the performance of the car.

The stock boost gauge is not much of a gauge at all. It doesn't have a sender, the ECU controls it, I'm assuming by calculating boost from airflow. It's not accurate or even useful really unless you're using it with link or something else that can change it to read out knock, with ECMlink there's several things you can set it to read. If yours is always pegged I would think you have an electrical issue like a short or something.

Sniffbooger · Jun 26, 2020

Hmmmm...it moves up and down when you turn the key to ON position, but stays at the top mark when running...I'll definitely have to check it out and change it to something else if I can. Is it possibly a defective MDP sensor?
My Autometer boost gauge is fine, mounted right below it in the bezel.

Thanks for the link!

1990TSIAWDTALON · Jun 26, 2020

I have an ECMLink ECU that does that too. I had the ECU as a spare until I bought my 90 GSX and I put it in so we can tune it. I wiggles wildly, then goes "full boost" even if I change the settings to knock or temp or something else. I am assuming it is in the ECU that is the issue. When ECMTuning gets up and going good again, I will send it in to have them look at it.

Sniffbooger · Jun 26, 2020

Ahhh...so that's one MORE reason to get my DSMlink installed ASAP....it's probably a flaw in my stock black box ecu....so when I install the Eprom ecu with DSMlink, I may not have this issue...

Zack Huffman · Jun 26, 2020

If your stock boost gauge is always pegged when running, you have an issue related to the airflow measurement the ECU is seeing/using. This can be caused by bad boost leaks, a really large set of cams, or most likely, from a miscalibrated or non-matching MAS.

The ECU uses only 2 things to calculate what position the stock boost gauge is to be in: the air mass flow measured by the MAS and the engine's rpm. The higher the airflow measured per rpm, the higher the stock gauge reads. Both ECMlink and Ceddymods will allow reassignment of the stock boost gauge's purpose.

As already stated, the MDP sensor is only good for triggering EGR codes.

Sniffbooger · Jun 26, 2020

delta448 said:
If your stock boost gauge is always pegged when running, you have an issue related to the airflow measurement the ECU is seeing/using. This can be caused by bad boost leaks, a really large set of cams, or most likely, from a miscalibrated or non-matching MAS.

The ECU uses only 2 things to calculate what position the stock boost gauge is to be in: the air mass flow measured by the MAS and the engine's rpm. The higher the airflow measured per rpm, the higher the stock gauge reads. Both ECMlink and Ceddymods will allow reassignment of the stock boost gauge's purpose.

As already stated, the MDP sensor is only good for triggering EGR codes.

This makes sense...I do have big 272 cams, and a good stock MAF sensor. And possible boost leaks LOL

...I lost my damn air pressure filler nozzle on my compressor so I haven't been able to test for leaks yet! Gotta get a new one. Gonna change my FMIC first, then BLT afterwards. Good info!

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