Duramax Larger Injector Discussion

[mytmousemalibu]

For giggles i took a nozzle and stuck a can of brake spray to it before i sent it to see the pattern... wholly crap! 158* no kiddin! It almost is a flat spray, right into the cylinder wall! I'd be intrested to see some of the Mahle Monotherm steel pistons in a D-max if they ever make them for the D-max. Then the spray angle could be opitmized and sprayed into the piston bowl where it should be! At least that is how it plays in my head! IDK, im not an expert by any means!

 

[duratothemax]

Then the spray angle could be opitmized and sprayed into the piston bowl where it should be!!

or reseat the injector so it sits lower/deeper into the cylinder head.

 

[stacks04]

how low do they sit now. i see external, but i have never seen one bolted in place with the head off to visualize it. does the tip extend into the bowl of the piston the way it sits now? untouched

 

[Brayden]

We've had nothing but good results from a set of 45% over extrude hones. 2100us pulse, 26 degrees of advance, made 630/1147 on a stock motor LBZ with a 68mm cheetah. I don't have the cylinder pressure tools yet so I can't tell you what it has done if anything to the CP.. We are spinning the motor pretty hard though.. Shift points are at higher rpms etc to keep it from lugging.

 

[LarryJewell]

We've had nothing but good results from a set of 45% over extrude hones. 2100us pulse, 26 degrees of advance, made 630/1147 on a stock motor LBZ with a 68mm cheetah. I don't have the cylinder pressure tools yet so I can't tell you what it has done if anything to the CP.. We are spinning the motor pretty hard though.. Shift points are at higher rpms etc to keep it from lugging.

2100PW , I like it better around 3100

 

[dmaxtruck]

personaly i like the idea of increase INJ keep same pressure and cut pulse width

I think we're on the same page here. If you keep fuel at a constant, and make the size of the holes a variable, you have a whole new set of possible combinations.

My theory is that bigger injectors, same fuel rail pressure, much lower pulse width, and less timing will be a great combination.

I do see a problem of putting more holes in the stock injector tip and maintaing integrity of the tip itself.

I think that is the only problem with the theory of more holes in the injector vs bigger holes. If we think of the adjustable handles on garden hoses, it starts to make a lot of sense.

If you want a larger spray pattern you don't use the adjustment with bigger holes, you adjust it to where it has more holes. As long as the pressure is the same anyway, if pressure and hole size are both variables then that is a different story (which is where we are now with the injectors and rail pressure).

A modified cyl head and injector with a larger nozzle could support more holes. Then you could increase rail to whatever and atomize enough fuel.

I think that is exactly where the high pressure/stock injector combination is going to find its limits eventually. The reason is not going to be the injector, but aluminum.

 

[malibu795]

how low do they sit now. i see external, but i have never seen one bolted in place with the head off to visualize it. does the tip extend into the bowl of the piston the way it sits now? untouched

less then a 1/4" protrusiton form the heads deck towards the piston

2100PW , I like it better around 3100

yeah but he is getting more fuel ~2600 then you are at 3100

 

[McRat]

We've had nothing but good results from a set of 45% over extrude hones. 2100us pulse, 26 degrees of advance, made 630/1147 on a stock motor LBZ with a 68mm cheetah. I don't have the cylinder pressure tools yet so I can't tell you what it has done if anything to the CP.. We are spinning the motor pretty hard though.. Shift points are at higher rpms etc to keep it from lugging.

What did it do with stock injectors?

 

[LarryJewell]

We've had nothing but good results from a set of 45% over extrude hones. 2100us pulse, 26 degrees of advance, made 630/1147 on a stock motor LBZ with a 68mm cheetah. I don't have the cylinder pressure tools yet so I can't tell you what it has done if anything to the CP.. We are spinning the motor pretty hard though.. Shift points are at higher rpms etc to keep it from lugging.

Brayden, what has it done in the 1/4 mile with that setup, and also with the stock injectors just for comparison

 

[McRat]

My skepticism is based on customer trucks (and others) who put in injectors and showed no performance gain.

The CP3 is a fixed displacement device. It is entirely possible that bigger injectors will show no performance gain.

But I've been wrong before, and will be wrong again. In this case, I just don't know the answer yet. Most the testing has been SOTP only.

Let's get brutally honest. If I told you the stock LLY injectors would go 797rwhp on fuel (or anything) back 2 years ago, I'd be called an idiot. That's not saying I'm not one, but just the thought that stock 7 x .0059" sticks could push that power would be ludacris.

It didn't help matters that the Dodge shops claimed to make SuperMagicFuelMagnet injectors that would drop EGT's, increase mileage, make 1000HP, save engine parts, reduce smoke etc, etc, etc.

If making the holes bigger would do all that, then GM/Dodge/Ford/Bosch are staffed with dumbest Mofo's in the known universe. Why would they make the holes smallers and go UP in HP, if the real answer was to go BIGGER to make more power? How could one tractor mechanic using a $10k EDM machine wipe out all their research for the last 10 years?

But when you ask for REAL test info, it is never there. So far at least.

 

[malibu795]

i agree pat.. putting larger sticks in is pointless unless you can maintian pressure.. ie dual cp3 or moddified cp3

 

[1slow01Z71]

Ive read where injecting the same amount of fuel in a smaller amount of time contributes to lower cylinder pressures and lower EGTs, it seems that even if the injectors themselves didnt add any power they would be adding some cushion/longevity to the motor. It would be worth it to me to have them if this is truely the case.

 

[02freighttrain]

This is a great thread and a lot of expensive trial and error experience, along with theory is being revealed.

I am convienced that the stock injectors with enough rail pressure can get the job done. The numbers that have been posted prove it.

I have heard the "Death Rattle" of many trucks on the dyno. They were rattleing like hell and it just sounded wrong. This concerns me. I run 26* total timing on my current tune. This is the same tune that went up against some trucks on Dunbars Dyno. I had a very reputable tuner in the truck on the dyno, trying to improve on Graig's tune and had no success in bringing the numbers up. For now my motors still lives with a short dwell, late timing tune and if Injectors allow this to happen, then is all good with me.
I could go on about my theory, but it's just that. I wish I knew more about the combustion process. I do know that fuel sprayed early hit's the lip of the piston in a greater concentration.

It's really a catch 22... It's nice to start the compression stroke early and make lot's of power with a early shot, but there is a price to be paid. It's called Rod bending, bearing pounding, pre-ignition. Just my theory.:hug:

 

[ripmf666]

We've had nothing but good results from a set of 45% over extrude hones. 2100us pulse, 26 degrees of advance, made 630/1147 on a stock motor LBZ with a 68mm cheetah. I don't have the cylinder pressure tools yet so I can't tell you what it has done if anything to the CP.. We are spinning the motor pretty hard though.. Shift points are at higher rpms etc to keep it from lugging.

Thought that was the 70mm cheetah from the video of the dyno of 630/1147.

 

[Sean8816]

If making the holes bigger would do all that, then GM/Dodge/Ford/Bosch are staffed with dumbest Mofo's in the known universe. Why would they make the holes smallers and go UP in HP, if the real answer was to go BIGGER to make more power?

They were increasing the amount of pressure via a stronger CP3, so smaller holes could be used to create better atomization for efficiency/emissions? Just my very uneducated guess. As far as a duramax making serious power, 2 trucks come to mind. Kyle's and Keith's. Nasty girl runs very large injectors, and Climax runs REALLY large injectors. If you can maintain the same fuel pressure w/ 6 larger holes as opposed to 6 smaller, obviously you will have more fuel to burn. These guys have massive twins able to burn this extra fuel, nastygirl @1000 had practically no smoke once spooled on dunbar's dyno. I don't know what % over injectors it takes to start draining rail pressure below 26k w/ 2cp3s (obviously depending on duration), at that point you might be hurting power. What prevented you from making more power than 800? Were you running out of fuel? The charger can't support more power? I hope this comes off the right way. If you had made 1200hp I'd still ask, so why not 1201? Good to know stock inj make 800, something you'll never see fords or dodges claim. Thanks for all the testing, I'm curious to see how this all plays out.

 

[LarryJewell]

Thought that was the 70mm cheetah from the video of the dyno of 630/1147.

I think the 68mm and the 70mm are the same , pretty sure I saw that in a recent thread.

 

[Brayden]

68 is a 4094 compressor... That is the old 70mm.. I now have a true 70.3 mm inducer Cheetah assembled and ready to test.

That truck made 596hp Pat on the smaller charger.. 64mm....

BUT...... 32 degrees timing and 3300us pulsewidth.

New tune has 26 degrees timing, and 2100us pulsewidth and runs considerably lower EGT's.

I would have to attribute that to the shorter duration.

Also, if you look at the gas world, they have a fixed pressure that they try to run on a FI setup. The logical answer is to increase injector size when they run out of fuel instead of raising the pressure... It also keeps from saturating the coil's of the injector. They can only open so quickly and then the response will degrade. If you have a short pulse you aren't working the coil so hard.

Different fuel but similar delivery method. I would say that if the engineers were going to work towards a 500-600hp reliable engine, injectors would definately be in the recipe. There is just no way to make a diesel run cool EGT's with fuel chasing the piston down the bore.

So if you look at our case, the injectors made 30hp and 75lbft or possibly that was just the combo of larger turbo and sticks, but we've never had an LBZ 68mm w/o sticks over 600hp.. yet. And at high rpm, you have even less time to spray so injectors become a necessity...

 

[stacks04]

to me rail pressure wont be an issue. especially guys running dual pumps. if they keep up with a 3300ms shot with stock injectors, what would prevent them from keeping up with the same shot at 2200ms. same amount of fuel just less time for it to come out. i agree with pat in the performance gain may be minimal if you are tuning the same power as you can make on stock sticks, but once you reach the limitations of the stockers, when it comes to the timing, what then. a third cp3 to make more rail pressure? most agree that timing can be bad in big doses and causes bent rods noise ect, than if nothing else they may make the engine live longer at 5-6-700hp.
maybe a cylinder pressure test would be the tell all in how well they perform.

 

[dmaxtruck]

I love this thread, and this board for that matter. Where else can you have a thread 6 pages long, on a controversial topic, and it NOT getting turned into a horrible craptasm of "my epeen is bigger than yours"?

Pat & Kat, good job guys. Keep up the good work.

 

[1slow01Z71]

SO Brayden and Pat have a cylinder pressure tester correct? When do either of you believe you will have time to test this theory? I like what Brayden is putting up, and like I said before even if the injectors dont add power, if they can allow lower timing and EGTs to be ran then I think that will contribute to a longer living stock longblock. I would love to get in the mid 500hp range and 1100ish ftlb area and not have to worry too much about cracking a piston, I realize bending a rod is a good posibility but I can live with shortened rods for a while a cracked piston would really rain on my parade.