Cut Delivery Valves: Has anyone done it? - Page 4 - PeachParts Mercedes-Benz Forum

tomnik · #46 12-03-2009, 01:32 AM

"The descent of the plunger determines the end of injection"

No. End of injection is when the control edge of the plunger meets the filling port, which is at about 1/2 on the way to TDC of the plunger.

In general:
The volume that is taken out of the line by the DV is important. It is the volume below the cone to the collar.
The smaller this volume (collar narrow and sitting near the cone) the higher the residual pressure in the line, the more fuel is effectively delivered.
Going too far will not close the injector properly and it will open again caused by bouncing fuel column.
I posted somewhere a pic of a "tuning DV" that I bought. The difference is the a.m. I also have different springs but had no time to play with it.

And the lines are swelling! The pressure in the lines are way higher than the pop pressure of the injectors. The whole system is more acoustics than hydraulics. There are many parameters having an influence.
Either we create an action plan carried out by one or two persons step by step well recorded and discussed or everybody will do it on his own and we never get to a result.

I offer the different springs to throw in...

Tom

jt20 · #47 12-03-2009, 01:51 AM

Thank you,Tomnik for correcting me on these items. I realize there are many parts of this system I don't full grasp yet. I understand all of what you said and it makes wonderful sense to me.

great quote:

"Either we create an action plan carried out by one or two persons step by step well recorded and discussed or everybody will do it on his own and we never get to a result."

I will finish a reply to OM616 after I let this absorb a little and catch up on some other items this weekend.

Ian White · #48 12-03-2009, 04:37 AM

This discussion is very informative! I thank jt, tom, drew, and OM606.

DrewGerhan · #49 12-03-2009, 11:15 AM

We all have been bitten by the diesel bug!

I feel that a group effort would be way more productive than just one or two guys working by themselves.

In other news, would the pop pressure of the injectors have anything to do with cut DVs? Even partially cut ones? I'm getting my bottle jack and gauge later this week, so I'm going to make mine. I've probably got 20 spare injectors I'm going to test and what not.

What about this along with extrude honing.....?

mytmousemalibu · #50 12-03-2009, 01:15 PM

Im sure pop pressure will affect how the delivery valves are operating.

I have Extrudehoned the injector tips in my Dmax but they are an annular 7 hole type nozzle. The MB nozzles are a single hole pintle style so im not sure how having them honed will work? I would give Extrudehone (in Pennyslvania) call and talk to Jim, If they have and with good results, he'd know and could recommend how much %over. Id like to try some about 20%'ers. Pretty sure honing a pintle style will work, the seating surface is my main concern as the process is to pump an abrasive fluid through them. Love them on my Dmax though!

KarTek · #51 12-03-2009, 05:31 PM

I would be wary of extrude honing on an engine with stock elements because I would think that it would lower the nozzle velocity at lower injection quantities which would make for smokey/clackey idle.

In the D-max, it's a much larger engine so you're moving a lot more at idle.

Ian White · #52 12-03-2009, 06:06 PM

Quote:

Originally Posted by KarTek

I would be wary of extrude honing on an engine with stock elements because I would think that it would lower the nozzle velocity at lower injection quantities which would make for smokey/clackey idle.

In the D-max, it's a much larger engine so you're moving a lot more at idle.

Plus it is common rail injection, so the injection pressures are much much higher. Dmax is also direct injection...

babymog · #53 12-03-2009, 09:04 PM

Yes, the injection lines do swell, a pressure wave much like an old Bugs Bunny et al cartoon where the bulge moves down the garden hose. This phenomenon (known as "port effect") creates a delay between when the injection begins at the pump, and when it hits the injector, is why all injection lines are the same length, and as the delay is fairly constant regardless of engine RPM, occupies a greater degree of crankshaft rotation at higher RPMs.

As far as the delivery valves being pushed closed by the hydraulic pressure at the collar, I have some theory/speculation there. To displace the delivery valve you don't need pressure, you need a displacement of fluid equal to the volume of the metal/valve element displacement. A differential in pressures can cause the displacement, but it has to have some expansion or contraction as was mantioned above, to sustain that pressure differential and create the necessary flow/displacement of fluid. In short, I'm not sure that there is enough fuel backflowing to push the delivery valve back down.

Second, I believe that the delivery valve has two functions: A check-valve to allow the pump element to draw fuel into the barrel for the next injection event, and a (hydraulic) damper to absorb the returning pressure wave and avoid chattering the valve. The spring returns the valve, along with some energy from the returning pressure wave to overcome the inertia of the valve, and the collar in the bore limits its speed.

Last, and again theory/speculation, the sealing surface of the delivery valve has a much greater surface area and thus takes much less pressure (psi) to lift it from its seat, than the collar. If the collar were the piston lifting the valve, it would create a higher pressure in the pump barrel before opening, creating a more abrupt pressure change in the injection lines. This I don't believe is the case however, going back to my above point that the amount of fuel displaced (especially at idle) isn't great enough to lift the collar from the bore. Further, if this were the case, cut delivery valve collars would allow the valve to open at significantly lower pressures and reduce the abrupt pressure change to a sinusoidal surge.

jt20 · #54 12-03-2009, 11:13 PM

Quote:

Originally Posted by babymog

Yes, the injection lines do swell, a pressure wave much like an old Bugs Bunny et al cartoon where the bulge moves down the garden hose. This phenomenon (known as "port effect") creates a delay between when the injection begins at the pump, and when it hits the injector, is why all injection lines are the same length, and as the delay is fairly constant regardless of engine RPM, occupies a greater degree of crankshaft rotation at higher RPMs.

this is what I imagine, as well. There is a change in dimension, but the injector[/quote] line does not 'swell' to the shape of the cigar hose...

Quote:

As far as the delivery valves being pushed closed by the hydraulic pressure at the collar, I have some theory/speculation there. To displace the delivery valve you don't need pressure, you need a displacement of fluid equal to the volume of the metal/valve element displacement. A differential in pressures can cause the displacement, but it has to have some expansion or contraction as was mantioned above, to sustain that pressure differential and create the necessary flow/displacement of fluid. In short, I'm not sure that there is enough fuel backflowing to push the delivery valve back down.

right, there is a quantity / flow of fuel involved. Not pressure.. pressure creates the flow. That is the relation previously mentioned. This all makes sense if the lines to 'stretch' to accept additional volume as Tomnik suggests.

Quote:

Second, I believe that the delivery valve has two functions: A check-valve to allow the pump element to draw fuel into the barrel for the next injection event, and a (hydraulic) damper to absorb the returning pressure wave and avoid chattering the valve.

I'm with you here.

mytmousemalibu · #55 12-03-2009, 11:33 PM

Lotta good info going on here guys! Thanks! I think its becoming more and more apparent how much stuff is at work here. I like the idea of gathering up all of this and attacking it mythodicaly! Kartek brought up a good point on honed nozzles, I too think a pressure/volume increase would be needed to take advantage of them. Again to refernce the dmax, we can get away with quite a bit of fuel/power before larger nozzles become needed on them. All that was done was uping the pressure and duration. Same applies here. Unless the stock delivery valves are hindering our stock pumps maximum output potential, Now kinda leaning towards cut DV's are more of a "sloppy" way of getting more fuel in. Not saying we cant fine tune them somwhat to get some more power without the cons, but to make them really shine, we need bigger pump elements.

tomnik · #56 12-04-2009, 12:12 AM

The whole system for me is like a concert. All the involved components are playing together in a harmony of pressures waves running up and down the lines, of controlled flow out of the nozzles and of course the IP elements as the master of the concert.
What I want to say is that it might not work if we change just one single player.
I.e. I really custom made nozzles. I did not extrudehone but increased the needle lift to keep the geometry of the cone and the throttle effect (pre-spray).
They flow approx. 40% more compared to the 261. In the injector bodies at 145 bar the spray pattern is perfect also the "sound" ? clattering ?.
On a stock 603a these injectors simply just don't work. To be honest I did not hear it but my friend told me that the car was not drivable not even 20 km to my garage so I could hear it. But as the spray pattern is perfect I am sure it can work with changing some other "players". Now I like to go step by step like increasing just the pop pressure to see (hear) what will change. Fixing one pop pressure then changing i.e. just springs of the DV,...
I don't have the equipment to see where is the issue, so I have to change step by step and learn about influences.

Tom

OM616 · #57 12-05-2009, 07:13 PM

This discussion has restored my faith that multiple people with different experiences and understandings can have a polite discussion, exchanging and challenging ideas and experience in a civilized manner. Bravo to all!

So at this point, taking into account the above, it would seem that;

1) If one changed the length or diameter of the Injection Lines, that the DV Collar would need to be altered in accordance to the increase or decrease in Injection line volume?

For example, if the stock lines were lengthened, and the stock post-injection/pre-injection line pressure was to be maintained, taking material from the top of the Collar, (directly under the Taper,(Cone), making the Collar thinner, leaving the Diameter alone), would increase the area from the Tamper, (Cone),to the Top of the Collar, which would accommodate the additional volume in the longer lines and maintain the same post-injection/pre-injection line pressure?

2) If one increased the pop pressure, the Collar would need to be altered to counter act the increased delay from the start of injection till the Injector Pintle lifts off its seat?

I have been informed by a reliable source that the DVs are different in a 115bar IP than in a 135bar IP. The 135bar DVs do something, (rise the Post-pre-injection line pressure?), so that when mechanically timing the IP, (Drip method for example), both the 115 and 135 bar IPs are static timed to the same speck.

I am guessing that taking material off of the bottom of the Collar, (making the Collar thinner, leaving the Diameter alone), would raise the post-injection/pre-injection line pressure in a manner that might have the least impact on idle quality? Stronger springs may do the same?

If seems to me that the DVs have an influential control of the total duration of the injection event, (Pintle off its seat), at a given rack position, in regards to the time from the start of injection, to when the actual beginning of the event takes place, (Pintle off its seat). Where as the rack limiter has control of the total duration of the injection event in regards to when the end of injection take place.

Is this a reasonable understanding?

tomnik · #58 12-06-2009, 11:17 AM

Hi,

if you don't mind let's stay at the DVs not mixing it up with the rack limiter.
I suggest to make a common plan what to do first.
Just one thing and see what changes.
What should be fix? Timing, pop pressure,..?
Attached my work up to now.

Tom

jt20 · #59 12-06-2009, 12:21 PM

Quote:

Originally Posted by tomnik

I suggest to make a common plan what to do first.
Just one thing and see what changes.
What should be fix? Timing, pop pressure,..?
Attached my work up to now.

Tom

I will be installing a full set of OM603 injection lines on my stock '85 om617.

I don't have a very good means of video, so you may have to trust my reporting.

As stated, the injection line volume / length is highly correspondent to the DV relief cut. by changing only this parameter, I hope to officially report the relationship.

This will be after 12/8/09

jt20 · #60 12-06-2009, 12:38 PM

Quote:

Originally Posted by OM616

1) If one changed the length or diameter of the Injection Lines, that the DV Collar would need to be altered in accordance to the increase or decrease in Injection line volume?

I agree. It is well stated that this is the case in the Diesel Engine Reference book.

Quote:

For example, if the stock lines were lengthened, and the stock post-injection/pre-injection line pressure was to be maintained, taking material from the top of the Collar, (directly under the Taper,(Cone), making the Collar thinner, leaving the Diameter alone), would increase the area from the Tamper, (Cone),to the Top of the Collar, which would accommodate the additional volume in the longer lines and maintain the same post-injection/pre-injection line pressure?

I am on the same page

Quote:

2) If one increased the pop pressure, the Collar would need to be altered to counter act the increased delay from the start of injection till the Injector Pintle lifts off its seat?

again, the terms are confusing.

Beginning of delivery: this is what we use to spill time our engines. It is the moment when pressure begins to be created by the plunger.

Start of injection: this is when the pintle lifts off the seat.

I am not sure about this statement. The more I read what others have written, it appears that this function is maintained by the elasticity of the lines. The relation b/w the DV and line appears to based on volume vs. length. The pressure inside the line can be overlooked by focusing on these parameters.

Quote:

I have been informed by a reliable source that the DVs are different in a 115bar IP than in a 135bar IP. The 135bar DVs do something, (rise the Post-pre-injection line pressure?), so that when mechanically timing the IP, (Drip method for example), both the 115 and 135 bar IPs are static timed to the same speck.

this may be due to the effective volume of the elements, since one is for the turbo engine, and the other is N/A. The fuel volume requirements must be higher on the turbo.

Imagine the demand for more fuel at higher RPM.. how do we keep the lines pressurized before events? If it is the lines storing this "potential energy" the turbo lines will have more fuel volume stored in them before the DV closes, this requires a different DV than that of one for N/A.

Quote:

Is this a reasonable understanding?

I think so