injector washers affect on timing

[cougar]

Years back, when I change a set of injectors I wondered why the seals were not all the same thickness. I found a Bosch article explaining that different washer thicknesses were used to make up for machining variations in the depth of the injector holes and tip lengths placing the tips in a more uniform position above the piston. Granted this was part of a Mercedes article, but I thought it interesting.

[BC847]

I found a Bosch article explaining that different washer thicknesses were used to make up for machining variations in the depth of the injector holes and tip lengths placing the tips in a more uniform position above the piston.

That's what I believe. Assuming the crankshaft's center-line is truly parallel to the block/head interface, the washers are to dial-in the injector/piston-bowl relationship relative to the injection event.

The notion of the washers effecting the injection event timing is off IMO. The injection event timing is relative the the crankshaft position . . . so many degrees BTDC, etc. I think that landmark is about the beginning of the event (or perhaps peak combustion pressure, dunno for sure). The washers help ensure the best nozzle position relative to the piston-bowl, during the injection event . .. start to finish. And that's where our thinning of the washers comes into play.
Our turning up the fuel volume effectively lengthens the injection event as the injector's opening and closing is based on a set spring (POP-pressure). Without changing anything other than turning up the fuel, I think there's an issue of the flame being out of the bowl upon the nozzle's entry and exit (perhaps more accurately, the fuel spray pattern). Thinning the washers sets the nozzle just that much deeper in the bowl thus putting more of the flame in the bowl.

Anyway, that's what the voices say.

[RCCUMMINS89]

I would agree..... though it isn't changing timing, it is however changing the amount of time that it can spray into the bowl.

[Diesel Dawg]

DUH!!!! SORRY ABOUT THE BONEHEAD POST GUYS!!! I was thinking about the ntc cummins that places the inj. tip at the piston dome then read that about interferance. WELL IM BACK NOW!!! How are yall?

[cougar]

The sweet spot as it were. It's not just were the spray is in the bowl, but also were the event stays in the bowl over its duration.
Now for the next part. Timing variations between cylinders?
My thought would be to map each cylinder. Find TDC for each cylinder and record the IP lift. I would be shocked if they are all the same. I would then find the average lift and use that figure for my engine to base timing off of. You can't correct it, but maybe you can compensate for it by injector tip-to-bowl placement.

[DodgeFreak]

Wonder if there would be any gains from measuring all injector protrusion with say a .020 washer and then setting all injectors equal.

Ex. if one was protruded .250 inches another .239 so on and so forth with .250 the deepest and you set all of them to .250" so they are all spraying into the bowl the same depth. Is the machining difference great enough to notice a difference??

Kind of reminds me of the high hp gas guys that would shim the spark plugs so all the electrodes pointed the same direction for optimal burn time.

[ellis93]

Well....I got them and they are some kinda thin

I don't think I'll be sanding on anything
And I can also say there's no way these are on my 7x10s right now,so they've got to help the haze some

[cougar]

One thing that helped my low end haze was to add a spacer under the AFC cover. Spacer and gasket equaled about .120". This allows the fuel pin to come up higher off the ramp. Sense I also have the M2 pin, this might be helpful to you.

[ellis93]

One thing that helped my low end haze was to add a spacer under the AFC cover. Spacer and gasket equaled about .120". This allows the fuel pin to come up higher off the ramp. Sense I also have the M2 pin, this might be helpful to you.

Did you make or buy said spacer?

[RCCUMMINS89]

M&H makes one if you wanted to just buy it....

[cmann250]

They make them here: http://www.mandhinc.net/DPD-4-S.html

Or I could whip one out on the Plasmacam at my old high school.

RC beat me to it

[ellis93]

I'll be lookin in on them thanks