How to follow fueling tables in LBZ/LMM files

[mecanicman]

I decided to make a little presentation on how fueling tables work on LBZ/LMM files. I will cover how all the main tables work, but will not cover how all the adders, mulitplyers, and restrictors work.

These engines use torque based fueling, meaning the computer finds the required torque to determine the required fuel. The first table the PCM referances is Driver Demand. This table finds required torque by looking at TPS vs. RPM.



Next the PCM looks at Base Quantity Torque Based fuel to give us a fuel volume in mm3. This is done by referancing the desired torque from the first table vs RPM.



Now the PCM looks at Base Pressure to calculater rail pressure based off of fuel volume vs. RPM.



Finally, the PCM calculates pulsewidth by looking at Injector PW table. This is done by using the calculated fuel volume vs. the rail pressure.



This is the path thru the tables to get to final fueling. Increasing any of these tables will increase the amount of fuel going into the engine.
The stock Driver Demand table peaks at a low RPM and tapers off at higher RPM's. To make more power, people copy the highest row to all cells(first picture below) This greatly reduces your use of the remainder of the fuel tables. This also commands almost the same amount of fuel at every rpm, possibly to much down low and maybe not enough up top. This can also adversly affect fuel economy by requesting more torque(and therefor fuel) in driving/cruise ranges.(as shown in below examples, the top 10 % of tps all uses the same single Base Quantity Torque Based column)





A better way to do this is to leave driving cruise ranges alone/stock, and progressivly increase the higher tps/rpm columns instead of the factory decrease. This will give you greater use of the other tables for better fuel control and maintain your economy in driving ranges. Some time spent changing these tables in the way I have described will lead to a smoother running engine, better economy, and better fuel control using larger portions of the available tables.

I tell people to modify the boost in the same area's you increase fuel. If you know the path thru the fuel, it is easy to see where you add the boost in the fuel volume vs. RPM boost tables.

[mecanicman]

Economy
I read on one of the diesel forums some time back that to get better fuel economy you should have a look at a Kodiak file. If you look at the driver demand table on the Kodiak, you will see that less torque is requested at lower tps values. Now obviously you cant take to much fueling out or you will not hold speed, but there is something to be learned here. I have attached a 2006 Kodiak file for comparison.

Power
This suggestion is NOT required for 95% of the vehicles out there, only for high horsepower extreme vehicles. The fuel tables axis only goes to 811 ft/lbs(1100 N/m). If you go thru and modify your Driver Demand table, you can accomplish a form of scaling by modifying the Injector PW table. Takes a lot of playing to make this work effectively, and like I said not required mostly, but a push in the right direction if that is what you are after.

[ajamesbond007]

Good write up! Before long, you will have a diesel tuning manual out there

[Pharcyde50]

Thanks for the write up

[ajamesbond007]

This should also be stickied...

[Bill@HPTuners]

I don't mind stickying it if you guys would prefer that. I've found that most people overlook the stickies all together and so the links would only be there to reference people in the future.

[ajamesbond007]

I don't mind stickying it if you guys would prefer that. I've found that most people overlook the stickies all together and so the links would only be there to reference people in the future.

Hey Bill, can you put this thread in the sticky you made for the diesel section:

http://www.hptuners.com/forum/showthread.php?t=38779

Figured it would be helpful as well as the other threads in that sticky.

Thanks!