It is obvious from the way the are set up with RPM ranges that they are designed for lower RPMs. However has anyone fooled with a boundary change such as 1200/2000/3000?

I assume that they think if you are at high RPM you will be in WOT, therefore no need to have BLM's modified up at high RPM (thus why the stock boundaries are 900/1200/2000 for cruising).

But if the original mixture is not right at high RPM's, wont this cause improper fueling also? I cannot believe that the BLM block that good for 2100 RPM at 95 MAP is correct at 5500 RPM at 95 MAP. But according to the way GM set this up it is. But again, at WOT, BLM's revert to 128 and we adjust with the WOT tables to get correct fueling.

Anybody have an opinion before I blow up my engine?

Ben

 

I am currently running 1500/2000/2500 RPM and 50/60/70 KPa MAP boundaries, with no learning below 40 KPa.

The way I came to the decision to use these numbers was to log a bunch of regular part-throttle driving, then I graphed MAP vs. RPM. Based on how the data was distributed on the graph, I chose the boundaries that would give me activity roughly equally distributed across as many cells as possible (for better granularity in the learning). I say "roughly" because you will find that there is very little (if any) activity in some cells, such as 0, 1, and 4 due to their combination of vacuum and RPM.

I chose the 40 KPa "floor" based on the fact that with my combo it never gets below 40 KPa except under hard decel (pointless to do any learning there due to fuel cutoff).

BTW some things that will affect your boundaries are what cam you're running (vacuum), whether you have manual or auto, where your shift points are, etc. So each person's unique combo and driving style will necessitate different boundaries, if you want to get the most use out of the BLM cells.

 

RunRiot,

Thank you so much for the post!

How do you set up the 40 KPA "floor"? I am using TunerCat.

I assume when you talk about never getting under 40 KPA that you mean that at idle, it reverts to the "special" BLM's and so never uses 1-16?

What have you found performance wise?

Have you tried a different setup based upon "hot" driving - say like when you are going to race?

Ben

 

I don't have TunerCat, but in LT1-Edit it's called "minimum MAP for BLM update".
Idle uses cell 16, regardless of MAP. But I have a pretty "healthy" cam, my MAP at idle is around 70 KPa. Stock was somewhere around 30 KPa.
No, this stuff won't make a bit of difference for WOT performance... it is strictly for tuning part-throttle driveability. For example, if you have a big stall and modified shift points, you're probably not driving around under 2000 RPM... so the first 2-3 rows of cells become useless with the stock setup. Adjust the RPM boundaries so you're using all 4 rows, and the computer's ability to learn will be improved. Same thing with MAP boundaries.

 

Thanks RunRiot,

Please stick around the board and teach us all more of these gems!

Ben

 

Anyone know where this is in TunerCat?

 

The tables are refeered to as :

BLM Cell RPM Boundaries
BLM Cell MAP Boundaries

I changed my RPM boundaries to 1200/1900/2400 . I changed my map boundaries also .....I dont remember what I changed those to....I belive I upped each value by 5. Anyway the result was a wider range of cell usage which allows the pcm to be more efficent IMO. As was mentioned ,you really need to log runs to determine what changes to make.

 

Oh, I belive you can set the floor in the ECM constants with TC.

 

I still don't see it anywhere.
Not in DA3 or EE.

 

if you can send me a file with only the floor change i can add it to the definition file and send it back to you guys if you wish.