Duramax Larger Injector Discussion

[Fingers]

Smaller droplet size increases surface area and taken by itself will decrease the time it takes to evaporate the fuel. However, you have to have heat energy to make the fuel transition to a gas. As heat gets sucked out of the area the plume is occupying, the droplets stay in tact for lack of energy to allow them to transition. Essentially, the size of the droplet becomes moot while the surface area of the plume becomes the overriding factor when the droplets get below a given diameter. The only way additional heat gets into the plume, (remember, the O2 has been displaced by the fuel) is from outside the plume where the fuel meets the air. (FIRE!)

An advantage of the smaller droplets is they tend to produce a shorter/fatter pattern than a larger droplet. But as you see from the patterns on the pistons, not short enough.

 

[2500HeavyDuty]

they just need to make injectors with smaller holes and alot more of them to flow more than stock

 

[Fingers]

MDE did that with mixed results. More holes, at least at the same spray angle, is not the answer.

 

[McRat]

MDE did that with mixed results. More holes, at least at the same spray angle, is not the answer.

There is something else going on with the MDE's, not just more holes. They are difficult to tune. I had to give up because I had a race in a couple days out-of-state, but I will revisit them.

The maps I got for mine show the problem. At low flow, they are erratic. This affects spoolup when staging, ie- they struggled to light a GT42 and we were going up in altitude to Colorado.

At WOT they ran well. If I would have known we would be facing 10,000' DA and would have to use nitrous to stage, I probably would have left them in and continued to test. Then again, we would have swapped chargers if we knew. Nothing ever works as planned.

I think with some more dinking around, and some new spooling tricks I've learned, the MDE's might be right injector. More holes, more betta?

 

[malibu795]

so bassicly more hole.. current 7 ~.0059" say 10 @ .0040" would increase volume and maintian atomization no?

 

[2500HeavyDuty]

i suppose

 

[Brayden]

I don't have a cylinder pressure monitoring system ... yet (Waving at John)

We're running 45% over on a near stock pulsewidth. IMO pressure is going to make up for the poor atomization from the hole size.

To me it's dead simple. You only have xx number of degrees to get the fuel in efficiently. Otherwise the factory would have used even smaller nozzles than what we have now and just sprayed a 3300us pulse... But that isn't the case.

Now the dodge guys.. They just don't get it. They may as well be turbine engines.. But the Cummins is stout enough to handle it so they do it.

Here is a video of the truck this weekend running at near 650hp now on the stock bottom end. The goal here is to spin high RPM's to get more hp and lower the tq a bit. The 1-2 and 2-3 shift point are at 4400rpm and those two shifts were completed in 60ft or less it looks like.

www.fleeceperformance.com/Media/Jerrod_64mm_Cheetah_at_TS2.MPG

 

[Brayden]

You can control all 5 events on the LBZ and LMM also.

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?

 

[SmokeShow]

I don't have a cylinder pressure monitoring system ... yet (Waving at John)

We're running 45% over on a near stock pulsewidth. IMO pressure is going to make up for the poor atomization from the hole size.

To me it's dead simple. You only have xx number of degrees to get the fuel in efficiently. Otherwise the factory would have used even smaller nozzles than what we have now and just sprayed a 3300us pulse... But that isn't the case.

Now the dodge guys.. They just don't get it. They may as well be turbine engines.. But the Cummins is stout enough to handle it so they do it.

Here is a video of the truck this weekend running at near 650hp now on the stock bottom end. The goal here is to spin high RPM's to get more hp and lower the tq a bit. The 1-2 and 2-3 shift point are at 4400rpm and those two shifts were completed in 60ft or less it looks like.

www.fleeceperformance.com/Media/Jerrod_64mm_Cheetah_at_TS2.MPG

would have been nice to see how he did later in that class as the track really got better as the night went on... I mean a LOT better!


C-ya

 

[Brayden]

Malibu.. If you're talking about splitting injection volumes evenly I think you'll run into big trouble. Especially if you keep the pilot timing where it is currently. My guess is that the first 1500us shot would use all the available oxygen in the cylinder and the second pulse would be nothing but smoke or just wash the cylinders down.. but I have no idea.

 

[Brayden]

You're telling me!

I think he could have pulled 330 or better...

would have been nice to see how he did later in that class as the track really got better as the night went on... I mean a LOT better!


C-ya

 

[LarryJewell]

Nice run Brayden

 

[malibu795]

Malibu.. If you're talking about splitting injection volumes evenly I think you'll run into big trouble. Especially if you keep the pilot timing where it is currently. My guess is that the first 1500us shot would use all the available oxygen in the cylinder and the second pulse would be nothing but smoke or just wash the cylinders down.. but I have no idea.

i typoed 15* for pilot and 0* for main... it was an off the wall thought i had dont knwo how practicle it is....

 

[dmaxtruck]

Ok I'm going to paraphrase these two as they're much smarter than me and I'm going to put it into laymans terms so I can understand it...

This one:

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.

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

And this one:

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.

If CP = bent rods, and CP is highest ATDC, then the "safest" way to tune would be the smallest amount of timing possible?

If that's the safest way to preserve the internals, then wouldn't bigger holes (or more of them) at higher pressures be the best way to accomplish that? ie same amount of fuel, in a quicker shot (again, as long as the pressures are increased)?

If that's true, then the opposite should be true. ie small holes (or less), at low pressure, in a long/slow shot = disaster.

If all of that is true and there's not another variable (total assumption, based on the only cause being CP), then it seem to me that the key variable is the duration of the fueling event. Low pressures, and low amounts of fuel don't seem to bother the engines much at idle.

 

[Mike]

Ok I'm going to paraphrase these two as they're much smarter than me and I'm going to put it into laymans terms so I can understand it...

This one:



And this one:



If CP = bent rods, and CP is highest ATDC, then the "safest" way to tune would be the smallest amount of timing possible?

If that's the safest way to preserve the internals, then wouldn't bigger holes (or more of them) at higher pressures be the best way to accomplish that? ie same amount of fuel, in a quicker shot (again, as long as the pressures are increased)?

If that's true, then the opposite should be true. ie small holes (or less), at low pressure, in a long/slow shot = disaster.

If all of that is true and there's not another variable (total assumption, based on the only cause being CP), then it seem to me that the key variable is the duration of the fueling event. Low pressures, and low amounts of fuel don't seem to bother the engines much at idle.

Outstanding Chris.

Lite a match and spray diesel on it at 15 gallons a minute and 60psi. Light a match and spray diesel through a pressure washer at 4 gallons a minute and 4kpsi. If the match doesn't blow out because of the air displaced with the spray of the pressure washer, which method would burn the fuel.

5 gallons of diesel in a bucket has less surface area around the fuel than 5 gallons of diesel sprayed into the air under high pressure. If the air space does not become saturated then kaboom.

 

[Fingers]

Unfortunately, that is not a good analogy. You are comparing an open system to a closed which does not account for the close quarters, limited heat available and ignition process that exist in the chamber. So on and so forth, blah, blah, blah. We can theorize it to death.

From the little that I have done on my engine and the CP rig, the larger injectors are more sensitive to timing changes than stock. I look forward to the day when others can add their 2 cents worth based on their own logging.

One thing I do not have a handle on is how much more CP, if any, is needed to generate X HP with stock VS bigger injectors. After all, THAT is what we are after. Max HP with Min CP. Right?

But, what do I know...

 

[McRat]

Yup.

I'll be on the dyno tomorrow trying to collect data for stock injectors, so I can go forward to injector testing.

 

[Brayden]

I guess we "FPE" need to get a chamber pressure monitor on the LBZ and see what kind of data we can get.

 

[McRat]

Maybe, maybe not. Nobody even knows if this data will helpful yet.

We do know that these kinds of sensors will be stock in couple of years. They will be used to control emissions.

 

[Fingers]

My read on the chamber pressure monitoring coming down the pike is that they will be peak pressure only monitors. That would be fairly easy to do and does not require the level of sensitivity that the Oprand or my system's sensors have. Nor would they incur the costs either.