Tuning larger injectors for mileage

[IdahoRob]

Remember Tom the truck will use what ever mm3 is needed to achieve desired mph at that time. You can lower the pulse at certain mm3 but if you log, you'll see the ecm using a higher mm3 than before to achieve the desired mph per load.

Timing is where you'll see gains. Also remember, larger injectors flow different % rates at different pressures. Pressure helps a bit also.

 

[TheBac]

Thanks Rob. That helps me understand it.

I lowered all the three Base Timing tables and the four Timing after Pilot tables 5% from 0-55mm3, and blended the 55-65mm3 lines to smooth.

I do have a question, though. Is it "Base Timing + Timing after Pilot = Total Timing" or "Base Timing - Timing after Pilot = Total Timing"?

I havent figured out what to do in the Fuel Pressure table yet. Im working on it. I probably have to log FPR and timing and see where it is at part throttle and freeway.

 

[chevyburnout1]

IIRC shouldn't you raise timing for better mileage?

 

[S Phinney]

If you raise pressures a little quicker then you could help your fuel mileage.

 

[Dozerboy]

Ya you should be raising the timing. Raise it until it starts to rattle then back it off a little. I have gone as high as 12 but hear the LB7s won't go that high before rattling. I would do it with the engine warm reset the ECT timing adjustments. Sweet posted a spread sheet a while back for this. Then try it with the engine cold to and you may have to back it off a little more. When looking for rattle make sure you mix up your driving habits a little to make sure it isn't rattling at different RPMs and MM3s then you normal drive at.

On the LBZ I had to drop the PW after raising the fuel pressure.

 

[chevyburnout1]

I do have a question, though. Is it "Base Timing + Timing after Pilot = Total Timing" or "Base Timing - Timing after Pilot = Total Timing"?

I found this about figuring pilot timing if that helps. I'm still fuzzy :spit:

Pilot timing(PIINJTIM)= inj timing C + after inj timing D +(pilot pulse*rpm*3/500000)

 

[DAVe3283]

I agree that changing pulsewidth won't really affect mileage much (because you'll just use more or less throttle to go the same speed). The reason for modifying the pulsewidth, IMO, is to help the engine idle right and transition off-idle. Well, altered pulsewidths do change the shift points slightly (because the truck thinks it is working harder/easier than it is), which CAN affect mileage. I found altering the TBIQ and shift points at light throttle gained me ~0.5 MPG, but changing the pulsewidth did little to nothing.

I think your biggest gains are going to be in timing and rail pressure. You might need to alter your timing across the board to compensate for the larger injectors opening faster (or slower??). Outside that, I'd spend most of my time on rail pressure, and see what happens.

But I think you are on the right track: change ONE thing at once. That way you know what works, and what doesn't. Keep us posted for sure!

Oh, and chevyburnout1: The horsepower draw from the CP3 is inconsequential compared to the horsepower draw to move the truck down the road, so I can't imagine it dropping your mileage when raising rail pressure. It is more of a NVH thing. Have you ever noticed how a stock tune will use a ~500uS pulse across a wide throttle range? Best I can tell is this produces the least noise from the engine. But I could be wrong.

 

[TheBac]

Well, the lower timing didnt hurt anything. Mileage didnt suffer, at least in my anecdotal instance.

I took my stock tune and raised all the timing tables 5%, and lowered fuel pressure base 5%. Truck is slightly louder (pretty much like my race tune) and a bit laggy from a start, but seems to run fine otherwise.

On a side note, my FASS pump keeps blowing off my FPR, causing a nasty surge. So I unplugged the pump and replumbed my stock fuel lines. No more surge.

 

[DAVe3283]

I had to alter the first few cells in B1010 to get my truck to stop surging at idle after installing my lift pump. It would also throw a CEL from overpressure when coasting down hills. Changing the table fixed it.

If you hook the pump back in, you might try playing with that table. IIRC I added ~100 mA to a few cells before it ran right.

Edit: sounds like your truck is like mine: it won't run right anymore with a true stock tune. I have a file called stock_fixed that is stock with a few changes to make it run the way it should (altered B1010, some codes off, fuel gauge recalibrated, EGR off, etc.).

 

[TheBac]

Dave, I know B1010 very very well. Its a first-thing-to-change-in-every-tune kinda thing with me. Ive been having problems with it ever since I installed the modded regulator, and found the surge stopped/lessened considerably when the fuel pump was off. But the FASS isnt a flow-thru, so I had to disconnect it.
I think the FPR could also have been contributing to the mileage issues, but do not know for sure.

 

[chevyburnout1]

I know I'm almost perfect with my B1010 tuning. I took your advice and used most of the LBZ units minus a few and seems to work pretty well. Have no surge or lope anymore but occasionally when I go to start it it fires, then almost dies, then fires and idles smooth. I need to log some more but its close.

Tom whats your timing at when your just cruising? My stock tune ran about 2º and commanded about 29mm3 doing 65 on the interstate. I now have the timing up to about 8-9º and noticed now I only need to command about 18-20mm3 at the same speed. Even the idiot gauge went up 0.5mpg. Lowered pilot pulse a bit but I'm still running stock pulse and pressure tables. I'm probably gonna raise it up a bit more here if work slows down and see what it'll do. Any timing I add I always subtract from the coolant multiplier table so the truck is still as stock as it can be when its first started in the freezing morning. Once I find a good medium for timing I'm gonna play with pressure some more.

Now if only I could keep my foot out of it


And thanks Dave and everyone else informing me on the cp3. Good info to know.

 

[Mike_S]

The pump is always making 20,000+ psi even at idle.

No its not. It only creates that kind of pressure when its commanded to do so. The regulator type on this pump regulates the inlet flow to consequently regulate the outlet flow and pressure. It is not a return-type regulator in this instance.

 

[DIESELMAFIAPER.LB7]

That damn b1010 table I dunno timing an higher rail pressure work really well for mileage

 

[sweetdiesel]

That damn b1010 table I dunno timing an higher rail pressure work really well for mileage

Near imposible to gain milage from b1010 it's to hard to use as mid range

use this table for idle and wot only or you will chase tails and waste time. Jmho

idle set up is real easy just look a mv as for wot drop down the last 2 numbers works well if you feel the need to adjust more then you need to understand what your doing because this can be adjusted in a more consistant way jmo

 

[sweetdiesel]

No its not. It only creates that kind of pressure when its commanded to do so. The regulator type on this pump regulates the inlet flow to consequently regulate the outlet flow and pressure. It is not a return-type regulator in this instance.

Exactly

 

[JoshH]

Tom, why did you drop rail pressure? Generally speaking, dropping rail pressure will hurt mileage.

 

[DAVe3283]

I know I'm almost perfect with my B1010 tuning. I took your advice and used most of the LBZ units minus a few and seems to work pretty well. Have no surge or lope anymore but occasionally when I go to start it it fires, then almost dies, then fires and idles smooth. I need to log some more but its close.

Tom whats your timing at when your just cruising? My stock tune ran about 2º and commanded about 29mm3 doing 65 on the interstate. I now have the timing up to about 8-9º and noticed now I only need to command about 18-20mm3 at the same speed. Even the idiot gauge went up 0.5mpg. Lowered pilot pulse a bit but I'm still running stock pulse and pressure tables. I'm probably gonna raise it up a bit more here if work slows down and see what it'll do. Any timing I add I always subtract from the coolant multiplier table so the truck is still as stock as it can be when its first started in the freezing morning. Once I find a good medium for timing I'm gonna play with pressure some more.

Now if only I could keep my foot out of it


And thanks Dave and everyone else informing me on the cp3. Good info to know.

I do the same thing. I even made a spreadsheet for it. Saves me a bunch of time. One day, when I finish my normal tune, I'll play with the cold engine tune. IMO it leaves a lot to be desired. Until then, my engine is stock when I first crank it up.

That damn b1010 table I dunno timing an higher rail pressure work really well for mileage

Near imposible to gain milage from b1010 it's to hard to use as mid range

use this table for idle and wot only or you will chase tails and waste time. Jmho

I think he was putting two thoughts into the same line, separated by a "". I agree, B1010 shouldn't get you any mileage, just make the commanded and actual pressures line up closer (well, unless your CP3 can't keep pace).

 

[TheBac]

Tom, why did you drop rail pressure? Generally speaking, dropping rail pressure will hurt mileage.

Because I really dont know what Im doing. It would be really nice if someone would outline just WHEN the ECm uses the different timng tables. EFI gives no explanation, and Ive yet to find one from anyone here. 3 base, 4 after, >10 multipliers...sheesh.

Timing up, pressure down sure turns a nice truck into a dog. Lets see what happens when I change pressure back....

 

[[email protected]]

I would think pressure down and timing up should work, but I know what your saying when you drop pressure the truck looses a lot. What about more overall boost with lower pressures and more advanced timing?

 

[JoshH]

Because I really dont know what Im doing. It would be really nice if someone would outline just WHEN the ECm uses the different timng tables. EFI gives no explanation, and Ive yet to find one from anyone here. 3 base, 4 after, >10 multipliers...sheesh.

Timing up, pressure down sure turns a nice truck into a dog. Lets see what happens when I change pressure back....

Are you talking about A, B, C base timing tables? I'm pretty sure they change with altitude. I think there is another table where you can define what altitude (actually barometric pressure) it changes to each table.