Scanmaster INT #'s @ 75 mph @ 75 degrees?

[Gary Wells]

Ok, coming home from a cruise last weekend I decided to leave the Scanmaster #'s for 20 or 30 seconds on each parameter while cruising at about 75 MPH with the ambient temperature at about 75 degrees or so. Everything seemed normal except the INT which would read maybe 125 or so, then jump up anywhere from 4 to 6 #'s, like to 131 or so, then back down to maybe 123 or so, then would jump up about 5 #'s or so. I am running a Tinman cold air with a large cone filter in front of the radiator support on the driver side over in the driver side fender compartment. Should it run about 125 or so under those conditions, & should it jump #'s like that?

 

[TurboDave]

There are two fuel trim items in the ECM... They are BLM which most are familiar with (long term fuel correction, aprox twice per second, that's long term in comuter speak). and then there are INT (short term fuel correction, aprox 20 times per second).

In layman's terms, think of the INT as the device that drives the BLM in the direction it needs to move. You should see the INT changing OFTEN, and and could move by huge amounts. If you had a Powerlogger hooked and were watching the two, you'd see how seemlessly that works.

Example: the INT might move all of a sudden up 10 numbers or more, and you'll then see the BLM start slowly creeping up, and as it's doing so, that jump the INT took starts reducing and at some point when the INT gets back down close to 128 the BLM will stop moving.

If the INT is only a few numbers off 128, the BLM may or may not move and fuel corrections will use INT. If there's a large correction needed fast, then the INT will move appropriately and the BLM will start heading that way.

Clear as mud? right?

There are still many things that can cause the INT to move around even on a seemingly flat cruise.

There's a huge write-up that I sent over to GNTTYPE.org explaining the operation of BLM and INT, and how they interact.

 

[Gary Wells]

Dave: Thanks for the quick response.