Prechamber Mod "Flame" Front

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01-29-2011, 08:22 AM #99

(01-28-2011, 01:06 PM)OM616 I agree that smaller holes = quieter operation, I am interested in more power.

Enlarging the holes will not do that.

Quote:If the size of the holes were increased to allow more air into the prechamber, the prechamber air temperature, (before, and at the time of injection), would be higher from the additional pressure, (increasing the conditioning of the fuel), aiding in combustion.

Inside the prechamber, where the increased combustion pressure is completely wasted on immovable surfaces.

Quote:Also, if more air is allowed to enter the prechamber, then the pressure differential during compression would be lower

Reducing the amount of fuel ejected into the cylinder.

Quote:blowing out its contents even faster and with more vigor.

It would actually blow out slower with less fuel reaching the main combustion chamber. Larger orifice = lower velocity.

Quote:The faster the engine is running the less time there is for air to make it into the prechamber, lowering the prechamber pressure and reducing the amount of vigor. Less vigor, bad, more vigor, good.

Nope. The less air in the prechamber the less fuel wasted burning inside a non-movable chamber.

Quote:If more air is allowed to flow into the prechamber then the swirl in the prechamber will be increased

No. Swirl would be reduced, remember; Larger orifice = lower velocity.

Quote:If larger elements are used, then the length of time that the fuel is injected in is reduced, and the holes will need to flow at an increased rate to keep up.

Also no. Injection time has no bearing on swirl or atomization. Fuel volume is what necessitates larger orifices.

Quote:any extra air that is allowed to enter the prechamber, and is not used up, will be expelled

Such a condition would defeat the entire purpose of a prechamber. There is never leftover air in the prechamber (except possibly at idle).

Quote:The closer the prechamber and cylinder pressures are during compression, the less energy that is used to raise the prechamber pressure above the cylinder pressure during combustion.

Incorrect. More energy would be wasted pushing on solid walls.

Quote:All in all, I see larger holes as a win win.

If you're making over 100hp/cyl.

Quote:And the reports, from other members besides me, support larger holes.

Except the ones that do it correctly are making 100hp/L on top of what any OM61x has ever achieved. Even the "245hp" Norwegian 240D doesn't meet the need for modifying the prechambers.

Quote:The increased air entering the prechamber will create a stronger swirl improving the mix of gasses and fuel.

Incorrect. The air will be higher density and lower velocity, which will both work to reduce swirl.

Quote:Due to the lower cylinder / prechamber pressure differential, the result of
larger holes, more pressure will be wasted inside the prechamber

Corrected.

(01-28-2011, 02:59 PM)Volker407 concerning the atomization the common rail DI is better than IDI

Not for those up to the current generation. Current pressures are still too low to vaporize fuel to the extent a prechamber can.
They haven't even caught up to the pressures generated by early-90's unit injection systems. Thats why VW went with unit injectors (pumpe duse) in the previous generation of TDI. The primary reason for common rail today is unit injectors can't have multiple injection events beyond the compression/power strokes. Which is why manufacturers that have stayed with unit injectors, like Cat, use a "7th injector" post-turbo to produce the heat needed for DPF regeneration.

(01-28-2011, 10:40 PM)OM616 they are just numbers that might inspire a member to post.
...
In order to have a 21:1 compression ratio the total combustion area needs to be a little over 1.7 cuin.

Your math is significantly off because you forgot to include headgasket thickness.

Quote:Get the 85yr. Turbo ones, Injector moved deeper ,better atomization,less smoking.

There were no changes to 85 core engine. All changes were to bolt-on equipment (turbo, emissions system, air filter). The only change to the injection system was the addition of a rack position sensor to the injection pump and possibly a change in the governor settings.

ForcedInduction