Duramax Larger Injector Discussion

[McRat]

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.

While I'm confident that we can go past 800 uncorrected with stock sticks, it's time to do injector testing. 800 ponies is lots of fun, but useless for anything but racing.

First test is going to be 10% from Dynomite Diesel. Next will be 29% from MDE, then we will open up the injectors further, 50%, and ??? until we see harm.

 

[McRat]

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.

Yeah, but my data collection from it sucks so far. My TDC mark is questionable.

 

[LarryJewell]

While I'm confident that we can go past 800 uncorrected with stock sticks, it's time to do injector testing. 800 ponies is lots of fun, but useless for anything but racing.

First test is going to be 10% from Dynomite Diesel. Next will be 29% from MDE, then we will open up the injectors further, 50%, and ??? until we see harm.

will you be selling injectors if you come up with anything good

 

[McRat]

will you be selling injectors if you come up with anything good

I've had injectors for sale for about 2 years now? But I talk people out of them. Guess I suck at business.

Like always I try to only sell the "good stuff", and try to keep the price low. Most everything I sell, I've tested first. Not everything, but most. Stuff I can't test I send out to others to test for me. Neutral parties.

 

[LarryJewell]

want me to test some injectors since I have the turbo referenced above

 

[Killerbee]

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.

That is impressive considering that the same injectors can deliver 20 mpg when toting the family around, making only 25 HP for a 70 mpg cruise.

I am betting that aftermarket injectors lose big economy benefits.

IMO, (and as a statement that wreaks of impracticality), the modified sticks are necessary for you guys reaching levels over 500 HP on a regular basis.

Cylinder pressure is what destroys rods. Namely the required early timing that comes with 3300 us. It creates such huge spikes at TDC, and that is where the damage is being done...negative torque. A shorter PW, and the consequential retarded timing is going to be much much safer, and permit an otherwise stock duramax to go higher before failure.

at 4000 rpm, 3300 us consumes 80 degrees of CA travel (check my math). That is just a huge span that wastes so much of the fuel. The first 10 deg or so is combusted opposing the direction of travel, the last 10 degrees adds little to no effort in the torque curve, and comes out mostly in increased EGT, as Brayden points out. Also, the cylinder is descending too fast at that point ATDC.

Getting more fuel atomized in a shorter time frame, beginning closer to TDC, is surely the way to go.

 

[Fingers]

Brayden has a Chamber Pressure Rig? ?

I have not sprayed for more than about 40* on my engine since the bigger injectors. I don't have the fuel to make it worth while. But the data I do have indicates that you are hard pressed to have a pressure peak much past 30* ATDC with any size injector.

As far as safety is concerned. Remember, the peak cylinder pressures are After Top Dead Center. At least if your making good power. The closer the peak is to TDC, the harder it is to control. That is, the closer the peak is to TCD, the more impact timing, chamber temp, Boost,..... make on the peak pressure. A 1* change in timing might move a peak from an original 30* to 29*with only a mild pressure increase, but will move a peak originally at 20* to 16* and increase the pressure drastically.

Since bigger injectors tend to make better power with the peak closer to TDC, I think they might have a greater tendency to break things with a tune that is a little off. That is, if chamber pressure alone is killing engines.


I have noticed that my exhaust is more "stinky" since the bigger injectors and as such, I don't think as efficient at the lower rail pressures and RPM. But I am still getting comparable fuel economy from the truck. So it has to be more of an emissions thing. JMO

 

[slowlmm]

John do you think tht your testers will work in a lmm? i know a little while back i think you said there might be a isse with tht. thansk tommy

 

[McRat]

It's interesting to watch the Dodges with very large sticks.

Combustion is happening inside the exhaust system after the turbo.

You can see the flames or the glow inside.

I imagine this means there is both fuel and oxygen inside the cylinder when the valve opens. Droplet size so big the fuel doesn't have a chance to use up all the air? No idea.

In a perfect world, having peak pressure occur when the rod is perpendicular to the crank throw (81.3° ATDC) would generate the highest torque with least stress on the piston and rods. Not sure how you could ever achieve that, except perhaps with variable flow injection, ie - flow changes during the fuel shot. That doesn't exist. So we normally have to put up with higher stresses ATDC than we really want.

 

[Killerbee]

The biggest problem with 80 ATDC, is that the cylinder is moving as fast as the flame front (or thereabouts) and CP quickly disappears. Almost none of the torque is generated by fuel that is still burning at this stage. Something like less than 10%.

IIRC, the LPP is around 14 degrees, +/-, mathematically. The exact number, is pretty much a constant for each motor. This is the peak we look for, if so equipped, by adjusting timing, to maximize torque. The more fuel that can be finely atomized in a shorter time, the better HP will result.

The variables that change LPP, location of peak pressure, are many. I really appreciate how the Bosch generation of trucks monitors post CAC temps and pressure. After seeing my LLY range from 120 F to 300 F, with no PCM adjustement for timing, I see why the towing crowd loses power on the hill. There is no retard for these thermal excursions in the LLY code.


When you think about it, the ICE is a real efficiency dinosaur.

 

[malibu795]

off the wall thinking here..

we can effectivly control two injection pilot and main..

can we split the injection between them?

i know hte LLY/lb7 can controll when if at all the pilot shuts off.

split the inj between 15+ and -15 useing the two systems?

 

[Fingers]

Only issue with using my system with the LMM would be making the proper adapter to replace the glowplug.

Heck it could be used with any engine that provided access to the chamber.

 

[McRat]

You could try something like this if you had 5 pulses and wanted the fuel to come in slow, then ramp up fast.

open	100	50% duty cycle
closed	100	50% duty cycle
open	200	66% duty cycle
closed	100	66% duty cycle
open	400	80% duty cycle
closed	100	80% duty cycle
open	800	89% duty cycle
closed	100	89% duty cycle
open	1600	100% duty cycle

Total Fueling	3100 microseconds
Time Duration   3500 microseconds

 

[mytmousemalibu]

That is impressive considering that the same injectors can deliver 20 mpg when toting the family around, making only 25 HP for a 70 mpg cruise.

I am betting that aftermarket injectors lose big economy benefits.

IMO, (and as a statement that wreaks of impracticality), the modified sticks are necessary for you guys reaching levels over 500 HP on a regular basis.

As for a daily driver/work/street/play truck with a good extra dose of power, I would say 15-25% would be just fine and thats what ExtrudeHone will recommend for such applications. 50% is way overkill for street IMO, im runnin 50%, but its for the future grand scheme of things! 50% is equal to about a 95-110HP i belive. Dosnt sound like much but belive me it is! As for MPG, see my list of mods. I drive with a heavy right foot and im gettin 19MPG!!!
Thats on the McRat 20/20 tune with no additional fine tuning
and NO meth/H2O!!! If i fine tune the EFI and drive nice and run the M/W i would say
20+MPG is very possible, Not to shabby IMHO!

The exhaust does smell more "rich" IMO. I can accelerate the same with less throttle than before, so there streetable but it will roll coal with no tune in the ECM. Feels like a 75-100 hp chip just as the injectors alone.:hail2:

 

[McRat]

Here's a thought. If big injectors increase droplet size, the fuel will burn slower. The fire doesn't know if the injector is closed or open. It just knows the presence of fuel vapor. For those who do not know, liquid fuel does not burn. Only after it has vaporized into a gas will it combust with oxygen.

What is the difference if the fuel takes 5000 ms to burn with small injectors or 5000 ms with big injectors?

 

[2500HeavyDuty]

atomization?

 

[McRat]

Smaller droplets burn faster. Atomization is the key to fuel injection. And why injectors are getting smaller and pressure climbing.

 

[2500HeavyDuty]

well yeah, like one gallon of water boils faster than 10 gallons of water.

But pressure means heat and warmer fuel.

 

[McRat]

well yeah, like one gallon of water boils faster than 10 gallons of water.

But pressure means heat and warmer fuel.

Perhaps more like, a cup of water in a glass takes forever to evaporate. Dump it on the ground and it evaporates faster. The smaller droplets have alot more surface to them than a few big drops.

 

[2500HeavyDuty]

Perhaps more like, a cup of water in a glass takes forever to evaporate. Dump it on the ground and it evaporates faster. The smaller droplets have alot more surface to them than a few big drops.

yeah thats what i meant