Lets talk big injectors

[DAVe3283]

I am running 75% overs in my LB7, so probably close to 100% over in a LLY. They are harder to clean up than my 60% overs, but a lot of that is my big single (71mm) and stupid cam that won't do jack until 2500+ RPM. I have a tune that runs pretty clean on the street, but it lags out the ass. Play with the MAF limits and it gets quick(er), but starts to smoke pretty easy when getting on the throttle.

I get a tiny bit of haze at idle. Can only see it at night in headlights or at the right angle in the right light during the day. That might have more to do with my low compression (350 PSI due to static CR and cam overlap) than the injectors, though.

And no problems with MPG on the bigger injectors. I run the rail pressure a bit aggressive once I get off idle to help smoke, and that seems to help MPG a bit too. Idles 40 MPa (5.8k PSI), cruise in the 120-140 MPa (17k-20k) range. I could/should probably back that down a bit, it doesn't take that much to clean up. And for reference, it does 660 HP with 1750 uS, 25° @ 3600 RPM.

From what you've said, I think you will be happiest with 100% overs, if they will hit your HP target. The bigger you go, the more lag you have to deal with if you want it to spool clean, or the more smoke to spool if you want the same lag as before.

 

[Big Chris]

Thanks for starting this thread James. It made me take advantage of a free weekend and finally install the 60 overs in my LLY that I've had on the shelf for months.

 

[Chevy1925]

From what you've said, I think you will be happiest with 100% overs, if they will hit your HP target. The bigger you go, the more lag you have to deal with if you want it to spool clean, or the more smoke to spool if you want the same lag as before.

Why is it exactly that it seems to take more fuel (increase in smoke) to get comparable spool up to smaller injectors? That seems to be a common theme in the thread but also seems to go against how to quicken spool up on a truck. To me, doesn't quite make sense but I may be missing something to the puzzle

 

[catman3126]

Running 400 over lbz's modded bodies in my built motor at 1100 us on the big tune and she rips. Dirty yes but very smooth. I need some time to mess with it at idle but I believe the pilot shot is so big it ramps up the idle and causes it to chop fuel and hunt at idle. I have gotten as low as 65-70 miles on one tank testing and tuning. But doesn't do bad on the freeway at 70 seems to be 15 or so.

 

[catman3126]

Thanks for starting this thread James. It made me take advantage of a free weekend and finally install the 60 overs in my LLY that I've had on the shelf for months.

Finally getting those things put in? Right on

 

[catman3126]

Ive ran 60s and 150s in my Lb7 and surprised at how clean the 150%s are with the stealth 64.5 and the 91mm setup.

Have 60% in the boyfriends LBZ not yet fine tuned still clean, little more haze than I would like but we're still breaking it in.

I'm happy with my 150s! Plenty enough fuel, not sure what power in my lower tunes, I know bob drove the truck from their shop to SDX last year and averaged 18mpg on my biggest tune.


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This is what I've been kicking around. I believe my 471 is just not moving enough air during around town even though I have a .90 ar ans it makes no boost until in the mid 2k range in rpm.

 

[Cknight199]

I've got 250%'s with Motorsport nozzles and modded bodies. (I think they flow more than that with the Motorsport nozzles). They haze pretty bad but I haven't even messed with tuning at idle yet to dial that in. 1000us cleans up with the s476, the next tune (1200us) is a bit smokey when WOT. Anything more and it just smokes more. I need more air currently...

1600us was a bit smokey on the dyno... Lol


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[Lb7_Katie]

This is what I've been kicking around. I believe my 471 is just not moving enough air during around town even though I have a .90 ar ans it makes no boost until in the mid 2k range in rpm.

I hated my 60s with a 366 well I hated the 366 hahaha I like the 60s with the fleece charger in the LBZ. But man is the Lb7 smooth with the setup it has now, you get a light haze but it's soooo clean! I'm super impressed!


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[Yngdmax92]

What's the largest nozzels you guys have just swapped on to stock bodies and had good luck with? Probably not good practice but I'm saying, with out sending them to exergy or s&s

 

[Cknight199]

What's the largest nozzels you guys have just swapped on to stock bodies and had good luck with? Probably not good practice but I'm saying, with out sending them to exergy or s&s

I had 40's. I wouldn't go larger than 60% if your just swapping nozzles and not having them flow balanced.


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[DAVe3283]

Why is it exactly that it seems to take more fuel (increase in smoke) to get comparable spool up to smaller injectors? That seems to be a common theme in the thread but also seems to go against how to quicken spool up on a truck. To me, doesn't quite make sense but I may be missing something to the puzzle

I don't think it takes more fuel to spool, it is just that the same small amount of fuel when spooling seems to smoke more on big injectors.

If I were to guess, I think it would be due to the large nozzle holes leading to poorer fuel atomization. So instead of a fine mist burning clean, you get a bunch of big droplets that don't burn as clean to get the same quantity of fuel into the cylinder. You can help by increasing the pressure, but then it becomes harder to meter the fuel at low RPM/power demand due to how quickly they flow fuel.

On my setup, I haze more at 40% throttle than I do at 75% throttle. Once I get the pulsewidth and rail pressure up a bit, it burns really clean (no haze at all). But until I am on boost, I have to keep rail & pulse low, which means haze. I look at it as another excuse to merge on the freeway at 75% throttle

 

[catman3126]

I've got 250%'s with Motorsport nozzles and modded bodies. (I think they flow more than that with the Motorsport nozzles). They haze pretty bad but I haven't even messed with tuning at idle yet to dial that in. 1000us cleans up with the s476, the next tune (1200us) is a bit smokey when WOT. Anything more and it just smokes more. I need more air currently...

1600us was a bit smokey on the dyno... Lol


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Mines not even that smokey with 400's with 1100Us and a 471.

 

[Cknight199]

Mines not even that smokey with 400's with 1100Us and a 471.

What altitude?


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[Yellow Jacket]

What's the largest nozzels you guys have just swapped on to stock bodies and had good luck with? Probably not good practice but I'm saying, with out sending them to exergy or s&s

I ran DDP 36lpm nozzles on stock LLY bodies 2009-2010... and that was daily driven and street miles in nearly all of 09- spring of 2010....no issues, balance rates great. Tuned clean! Factory LLY nozzle is 16lpm, so a "200%" nozzle so to speak...I was told that would flow 70-85% over stock on a test bench like Exergy uses...

Then strictly pulling, I swapped a set of DDP 65lpm nozzles onto same stock bodies and ran them 2 seasons of pulling and they were flawless... I was told those would have been 160%-180% over on a test bench like Exergy runs...

 

[catman3126]

What altitude?


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whatever it is in Cd'a I think 2800-3K so yeah your higher I would guess where you are.

 

[Chevy1925]

I ran DDP 36lpm nozzles on stock LLY bodies 2009-2010... and that was daily driven and street miles in nearly all of 09- spring of 2010....no issues, balance rates great. Tuned clean! Factory LLY nozzle is 16lpm, so a "200%" nozzle so to speak...I was told that would flow 70-85% over stock on a test bench like Exergy uses...

Then strictly pulling, I swapped a set of DDP 65lpm nozzles onto same stock bodies and ran them 2 seasons of pulling and they were flawless... I was told those would have been 160%-180% over on a test bench like Exergy runs...

i think you mean a "100% nozzle so to speak" .

why the difference in what Exergy tests and DDP tests? different base pressures?

 

[catman3126]

I ran DDP 36lpm nozzles on stock LLY bodies 2009-2010... and that was daily driven and street miles in nearly all of 09- spring of 2010....no issues, balance rates great. Tuned clean! Factory LLY nozzle is 16lpm, so a "200%" nozzle so to speak...I was told that would flow 70-85% over stock on a test bench like Exergy uses...

Then strictly pulling, I swapped a set of DDP 65lpm nozzles onto same stock bodies and ran them 2 seasons of pulling and they were flawless... I was told those would have been 160%-180% over on a test bench like Exergy runs...

Wouldn't a 36Lpm be a little over a 100% over?

 

[DIESELMAFIAPER.LB7]

whatever it is in Cd'a I think 2800-3K so yeah your higher I would guess where you are.

Only about 1500 ft ish

 

[catman3126]

Only about 1500 ft ish

Oh yeah? I thought it was higher maybe not

 

[Cknight199]

All I know is single turbos up here have a harder time making power. No question IMO


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