Tuning larger injectors for mileage

[TheBac]

Just curious how a person would go about getting better mileage in everyday use when running larger injectors?

Is it simply a matter of taking the stock tune and lowering pulse in both -no pilot and -with pilot a percentage (Im thinking 10-20%) below 10mm3?

-or-

should any reduction be distributed between the main injection and pilot injection tables? For example, if I use a 15% reduction, then split it, say, 5% pilot, the rest in main?

Just curious where I should start, or if Im barking up the wrong tree again...

 

[DAVe3283]

Logically, you'd take a percentage off both to compensate for the larger injectors.

However, what I'd personally do is:
1) Lower pilot injection pulse table by a percentage, i.e. 15%
2) Raise rail pressure to help fuel atomize better (this will make the engine louder though, so find a good balance... 80 MPa at idle saves a noticeable amount of fuel, but sounds like a Cummins, lol)
3) Lower main injection pulse in the 0-10 mm3 range by percentage, enough to get the truck to idle smoothly and not "jump" when barely touching the throttle. Basically, scale it back until it seems to run like stock.

In theory (or in my head) that would work great, and you'd pick up some mileage at the expense of a slightly (to moderately) louder engine.

BUT... take this with a grain of salt since I've never tuned large injectors before.

 

[TheBac]

Thanks Dave.

I based that thought on the idea that the pilot injection # is added to the main injection # to give total fuel amount. Guess I was right?
Reducing main but leaving pilot alone would really screw up fueling, wouldnt it?

 

[chevyburnout1]

I'm glad you brought this up. I've been looking for some updated info on this also. Even though I only have 50hp nozzles. I'm still very fuzzy on messing with the pilot injection.

 

[TheBac]

I did the things Dave suggested and it seems to be ok.
Took 5% off the pilot table 0-10mm3, and 10% off main and main/no pilot from 0-10mm3.
Engine doesnt seem any louder, but mine is one of those "noisy and loud" LB7s. Throttle response doesnt seem any different, and not doggy by any means.
I will have to fill up and see what mileage I get under my normal driving conditions.

 

[Dozerboy]

Thats what I would do maybe even keep dropping it slowly from here. Give it a week or so to see if it shifts funny or there are any other signs its short on fuel or power. I've started playing with injection some for mileage too. My LBZs a bit different though.

 

[chevyburnout1]

I'll have to try that this weekend. Unfortunantly I'm also trying to tune out my LBZ FPR so I need a good weekend.

 

[TheBac]

Yeah, its all "playing" with it. Im pretty sure it wont hurt anything. The pain is the loading the tune, then driving around, then changing the tune, then repeat.....

For the LBZ FPR, look at a stock LBZ tune's B1010 first. Thats what I did. Im pretty sure there's one in the "library" that comes with the EFI software...at least there was one in mine. That'll give you an idea where to start.

 

[chevyburnout1]

Thats basically what I've been doing. Just about got it but here and there RP will still get a bit rough. Doesn't help I get home at 9:30. Just gives me time to modify, program, then hope it runs correctly on the way to work in the morning lol.

Back to the injectors, I have already bumped up the fuel pressure a bit just in the cruising ranges. Can definitely hear a difference in engine noise, especially next to a wall or bus. I was curious about pilot timing though. Would it benefit being tinkered with? My daily driver tune runs stock pulse and a smoothed and tinkered main timing table.

 

[sweetdiesel]

Tom when your driving around how ofton are you in the 10mm3 area?

Or are you just trying to increase fuel milage when sitting at stop lights?

I'm willing to bet you will see more bennifit from timing than you do from fuel tables

 

[DIESELMAFIAPER.LB7]

I agree timing should help more I pulled fuel outta the pilot so it was stock fuel took 45% out man did it knock an run like shit bleeding white smoke put it back truck ran way better knocked less but I had to kick the rail pressure up to bout 7200-7400psi at idle think that's like 45mpa? Can't remember currently tearing my truck down lost an injector or two think they also may have been my culprit to my low rail pressure

 

[chevyburnout1]

What kind of timing changes would you make to the Injection timing After Pilot Base table?

 

[chevyburnout1]

2) Raise rail pressure to help fuel atomize better (this will make the engine louder though, so find a good balance... 80 MPa at idle saves a noticeable amount of fuel, but sounds like a Cummins, lol)
.

Gotta remember too, the engine is driving the injection pump. Raising the pressure means the pump is working harder and in turn sucking more power from the engine, and more fuel.

 

[DIESELMAFIAPER.LB7]

You wont notice anything like that from a cp3 so no worries there

 

[chevyburnout1]

Its what I've heard, but if not, sweet

 

[TheBac]

Well, its either quantity or time. Who knows which?

I can always start over with some timing changes after I see happens with what Ive already done.

 

[gmduramax]

Gotta remember too, the engine is driving the injection pump. Raising the pressure means the pump is working harder and in turn sucking more power from the engine, and more fuel.

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

 

[chevyburnout1]

I'm just repeating what I read over on the EFI Live forums. Guess I'll have to tear apart a CP3 when I get the chance to better understand its operation with the FPR.

Back to TheBac's original question I'm still wondering if messing with pilot timing will help with mileage. I'm pretty comfortable with the main injection timing and pulse but I still have a lot to learn with the 'pilot' timing.

 

[TheBac]

Well, I dont think the pulse idea works. Mileage isnt any better based on the limited driving ive done (~150 miles).

I will try the timing idea next. Same general idea on split as the pulse.

 

[sweetdiesel]

Your still going to want the truck to not belch smoke .... So adjust fuel for that

most fuel changes are needed in the 50 to 80 mm3
add timing will probably work best pending how much u cut fuel

pilot timing has not helped or hurt me in mileage or power
I do shut it off after 2000 and 30 mm3