Prechamber Mod "Flame" Front

OM616

10mm MW

572

01-29-2011, 06:22 PM #107

(01-29-2011, 08:22 AM)ForcedInduction
(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..

Why did MB inlarge the PC holes then?

(01-28-2011, 01:06 PM)OM616 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.

(01-29-2011, 08:22 AM)ForcedInduction Inside the prechamber, where the increased combustion pressure is completely wasted on immovable surfaces..

The higher pressure will increase the velocity of the gasses from the PC.

(01-28-2011, 01:06 PM)OM616 Also, if more air is allowed to enter the prechamber, then the pressure differential during compression would be lower, if the prechamber pressure is always higher than the cylinder pressure during combustion with the small holes, (high pressure differential during compression), then with a lower compression pressure differential, the prechamber combustion pressure would be even higher than the cylinder pressure, blowing out its contents even faster and with more vigor.

(01-29-2011, 08:22 AM)ForcedInduction Reducing the amount of fuel ejected into the cylinder.

(01-28-2011, 01:06 PM)OM616 blowing out its contents even faster and with more vigor.

(01-29-2011, 08:22 AM)ForcedInduction It would actually blow out slower with less fuel reaching the main combustion chamber. Larger orifice = lower velocity.

See above

(01-28-2011, 01:06 PM)OM616 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.

(01-29-2011, 08:22 AM)ForcedInduction Nope. The less air in the prechamber the less fuel wasted burning inside a non-movable chamber.

See above

(01-28-2011, 01:06 PM)OM616 If more air is allowed to flow into the prechamber then the swirl in the prechamber will be increased

(01-29-2011, 08:22 AM)ForcedInduction No. Swirl would be reduced, remember; Larger orifice = lower velocity.

Swirl is generated from gasses being expelled from the burn tube and then being deflected off the ball.

(01-28-2011, 01:06 PM)OM616 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.

(01-29-2011, 08:22 AM)ForcedInduction Also no. Injection time has no bearing on swirl or atomization. Fuel volume is what necessitates larger orifices.

But it does have bearing on the rate of pressure rise.

(01-28-2011, 01:06 PM)OM616 any extra air that is allowed to enter the prechamber, and is not used up, will be expelled

(01-29-2011, 08:22 AM)ForcedInduction Such a condition would defeat the entire purpose of a prechamber.
There is never leftover air in the prechamber (except possibly at idle).

So it hapens already

(01-28-2011, 01:06 PM)OM616 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.

(01-29-2011, 08:22 AM)ForcedInduction Incorrect. More energy would be wasted pushing on solid walls.

The larger holes will flow more in less time so extra energy will blow out the larger holes, and that is the point.

(01-28-2011, 01:06 PM)OM616 All in all, I see larger holes as a win win.

(01-29-2011, 08:22 AM)ForcedInduction If you're making over 100hp/cyl..

Agine, the engine needs to run well at power out puts and speeds well bellow full power, and they apparently do with larger holes.

(01-28-2011, 01:06 PM)OM616 And the reports, from other members besides me, support larger holes.

(01-29-2011, 08:22 AM)ForcedInduction 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...

I did not read anything about the prechambers in the information regarding the 240D. But lets say that he did not touch them, that does not mean that there is not some efficiency that could be had from scaling the prechamber to the higher output.

(01-28-2011, 01:06 PM)OM616 The increased air entering the prechamber will create a stronger swirl improving the mix of gasses and fuel.

(01-29-2011, 08:22 AM)ForcedInduction Incorrect. The air will be higher density and lower velocity, which will both work to reduce swirl..

The diameter of the burn tube stays the same, more air flowing out of it in the same period of time = faster flow that hits the ball and induces a stronger swirl.

(01-28-2011, 01:06 PM)OM616 Due to the lower cylinder / prechamber pressure differential, the result of larger holes, more pressure will be exerted on the piston sooner,

Corrected.

This post was last modified: 01-29-2011, 06:26 PM by OM616.