RPM, spray angle, bowl design

[BluegrassDiesel]

that is my 2.6 piston design, the net one will go right up to 20 to 1 compression.

With that much compression at high power levels, what about reliability of the crank, rods, bearings, etc?

 

[Signature600]

.....um to clear the valves with a big lift.

I believe he meant why have reliefs when you are designing a piston...design it shorter to not need reliefs. I can't imagine a relief does much for swirl and combustion with those sharp edges.

Chris

 

[SHughes]

But diesels don't need swirl....

Epically post by a dumb phone.

 

[VanillaGorilla]

I believe he meant why have reliefs when you are designing a piston...design it shorter to not need reliefs. I can't imagine a relief does much for swirl and combustion with those sharp edges.

Chris

Right on, I'm with you now but don't you need as much of a lip as possible for promoting propagation? That's the only reason I can think they would keep it.

 

[COMP461]

With that much compression at high power levels, what about reliability of the crank, rods, bearings, etc?

Compression is relative. When talking about 2.6 engine programs, the limited turbo’s chargers, hence limited air flow it’s the dynamic compression that occurs during the combustion event. As to the valve reliefs, I leave the small amounts of piston to accomplish quench. In reference to fuel and air mixing, and swirl, it’s not even a consideration, if the injector design, compression, and timing are correct and then the flame front starts as the fuel plumb is happing.

Everyone needs to understand that the dynamics of a stock diesel engine have very little to do with an engine optimized for better performance. A better designed shallow and wide bowl will work better on any diesel engine. The down side is emissions where more complete and efficient combustion created nitric oxides.

Now to the real world benefits of all of this. If you want a good running street truck, compression is a wonderful thing. You must be real with your goals. The person that wants 1000 hp tow with it , sled pull and drag race, while getting 25 mpg, and do this without killing the motor in their daily driver on a working man budget is unrealistic.

 

[Signature600]

But diesels don't need swirl....

Epically post by a dumb phone.

:lolly:

Right on, I'm with you now but don't you need as much of a lip as possible for promoting propagation? That's the only reason I can think they would keep it.

Not gonna say that's over my head, but at the same time, I've seen examples of where flycuts are said to hurt, and I've seen it said that they help. I think it is all about design and application.

Chris

 

[Fahlin Racing]

What are we seeing as a lip VanillaGorilla?

Edges in terms of mixture movement within the chamber, sharp edges create more turbulence right at the edge. We not only have propagation going into the chamber center but we have turbulence generating right below the flow moving toward or flame front at the edge itself, where ever this edge may be. An easy way to visualize is take a flat rock and place it in a stream/creek, position it so the flow is across the flat surface. As you watch it, once the water reaches the end of the flat area and then there is no surface you should see a vortex/turbulence.Wether or not this edge(s) can be beneficial with having a radii or staying sharp, only R&D will tell.

Any edge on the piston or on the head will act as a heat sink unfortunately, if we round these, what we call, stress risers down. Our heat absorbtion rate is reduced going into the crown, hopefully.

 

[VanillaGorilla]

Bad choice of words on my part, I should have said as much of a bowl design as possible within the current trend of flatter-wider bowls. I was refering to the outer edge of the bowl. lol, for all I know, flat-tops might work.

 

[oldestof11]

So, when it comes to diesels and RPM, what is affecting the limitations of obtaining a wider powerband and still being able to carry said powerband above 4-5k?

 

[oldestof11]

Bump.

I am wanting to also know how fuel atomization affects the powerband in higher (+4k) rpms.

 

[Franz]

Take a look here: Home - Big Bang Injection

 

[Fahlin Racing]

Fuel atomization is only a piece of the puzzle Oldestof11, you have to look at your cam profile, you timing and your displacement along with the size of your fuel injection quantity, injector nozzle design, amount of injector orifices, injection pressures as well as cylinder pressures. Not forgetting your in-cylinder mixture motion that can improve or create a poor combustion situation. I am sure there is more out there you can look up as well on just this aspect.

I think this should give you a good initial start on studying. Remember, there is a difference between engine builders and engine assembler. The builder taylors each and every part to work among the rest while if you assemble it, you are only fastening things together.

 

[oldestof11]

I am wanting to build, not assemble.

Thanks for helping!

 

[Fahlin Racing]

Found this old trunk-type Cummins heavy truck piston in my truck box. Noticed the spray pattern still on the crown even from sitting outside for numerous years. Just another piece to chew on.