Switched to 3 bar GM MAP sensor and knock greatly reduced! Any idea why??

[Rice Over Wheat]

I installed my MAP sensor yesterday and dsmlink shows it's functioning perfectly. I tapped into the stock MDP .5v wire for power and replaced the MDP pin 73 with the MAP output wire.

I did a couple test runs with no change to my tune and registered a drastic reduction in knock...only a single .4 count! This is compared to about 6 counts around 5k before. Does anyone have any idea why this would be? I thought the MDP/MAP signal to pin 73 only was for logging purposes. Does the ecu use this in any timing/airflow/fuel calculations? Because the MAP reads about 20% more accurate than even my Dakota Digital boost gauge with electronic sender. I'm wondering if the increased accuracy from boost/vac readings in the ecu improved things.

 

[GVR4592]

Unless you made changes in dsmlink to use the map sensor, then it's just for datalogging.

Were you getting 6 degrees of knock retard or 6 counts of knock?

 

[Rice Over Wheat]

Oops, I meant about 6 deg of knock regularly in the 5k range before MAP, then a single .4 deg afterwards. Very strange.

I have noticed that my CEL flickers now and then at very low throttle randomly and very rarely. Perhaps I had phantom knock this whole time and the sensor needs to be changed out. My A/F at WOT is about 10.5 and I have water/meth injection.

 

[2gAWDTalon]

The ecu does not use the MDP sensor or your new MAP sensor for any calculations. Your car having less knock after installing the GM 5 bar makes no sence... be hey take what you can get! Congrats on finally getting rid of that ridiculous knock!

 

[daren_p]

Maybe you were seeing phantom knock previously? Or did you always see it at the exact same spot?

As for the random CEL flash at low throttle conditions, have you ever noticed if it usually happens when the car's first warming up? I had my CEL set much lower but would to see a random flash at low throttle conditions but only during the first 10-20 mins while the car was warming up. I noticed that I was starting to be able to hear my lifters on start up so I cleaned them all when I did my cams & no more random knock while the cars warming up.

 

[Rice Over Wheat]

^^^

Yeah I think you are right about the flickering knock while warming up...with my new cooling system I take a good 5 to 10 minutes to fully warm up and this does happen after the engine is cold I think.

I might change my knock sensor next...it's just weird my knock issues disappeared like that. I felt the sensor and nothing was oozing out of it.

 

[daren_p]

^^^

Yeah I think you are right about the flickering knock while warming up...with my new cooling system I take a good 5 to 10 minutes to fully warm up and this does happen after the engine is cold I think.

I might change my knock sensor next...it's just weird my knock issues disappeared like that. I felt the sensor and nothing was oozing out of it.

I believe the oozing issue is only a 1g knock sensor issue.