DS4 max fuel rates at X rpm

[SmithvilleD]

Not to worry at all about thread hi-jack. You're adding good info & pics to the knowledge base. Takes a little work & time to learn & understand new things. No doubt the most knowledgeable DS4 inj pump guys weren't born w/ their knowledge, but took the time to learn it.

 

[schiker]

If the fuel metering solenoid doesn't close the IP just pumps the plunger charge to the cam ring area (I think called the spill chamber) Or can also send some down the excess inlet path.

I think its called a spill/fill chamber because as long as the transfer pump can supply enough fuel to this whole combined area the plungers can vacuum some fuel due to centrifugal force slinging them outward. But it is also checkvalved such that if the tranfer pump closes inlet a high vacuum will form quickly due to the check valves mechanisms and the plungers will stay vacuumed inward and not charge with diese fuel.

I think this why feeding the beast helps at high fuel rates. Since the plunger charge is more fully evacuated for injection rather than expelled into the spill area the transfer pump has to charge the plungers via the forward ports only that are angles and maybe why they are angled (to encourage that flow direction).

pic 1 shows flow towards "excess feed port" 2nd pic show straw exiting towards camring area. There is another port leading to this cam ring area in pic 2. But I can't be for sure of of some of the internal porting of the distributor. It looks like 2 pieces from manufaturing but not really serviceable or any need for servicing. I would need a good spanner wrench and they may permantly bond them somehow then finishing maching.


Again once the spill chamber is filled (really its always full) but when it over pressurized (any pressure over 15 psi iirc) it relieves volume back to the fuel tank.

This why its so important to overfeed the IP with plenty of LP volume and adequate pressure so it makes life easier for the transfer pump and ensures the internal pressure and flow of the diesel through the IP flushes the IP and keeps it cool and lubricated while allowing the plungers to fill and evacuate thier full charge volume.

That is about it for good pics unless someone wants more (again let me know specifics and I'll try). I might try to add a few more later but pictures won't do some of the orifice sizes justice. Jim over on the page suggested when the pump is pumping fast through some of these small orifices (and I'll add the injector orifice thinking its also a factor) the pumps pressure really increases comparing 1700 rpm to 3400 rpm. And this is why the output is limited so it doesn't require so much force to turn the pump and shear off any drivetrain pins or componets etc. I'll try and show I think there is one little roll pin that could shear off and mess this all up.

 

[schiker]

Uhhg as soon as I type it and read it something hits me differently.

Well the plungers would evacuate their charge volume the same wether or not its injected BUT I think its different somehow when max fuel rates are delivered to injectors. Maybe the tranfer pumps flowrate is near max too and the spill/fill chamber pressure drops some. Such that when all fuel is injected into engine such that with better fuel supply the transfer pump can better recharge the plungers better. While the rotary vane transfer pump is positive displacement and they are pretty constant when wet there is some slippage and the vanes can float somewhat in there slots. So I still suppose that feeding the beast allows the transfer pump work better.

Note:
I have noticed my old ford tractor return fuel line seems to surge a little when I gun it then let off. I wonder if something like that happens.

 

[ak diesel driver]

Great write up thanks for the pics and info.

 

[6.2 turbo]

That interested me greatly,I have my hands full with the db2 pump, high injector line pressure is something I overlooked, the marine injector orfice is same as all the rest ,the pintle tip that you see from the bottom is simply ground off ,orfice is.043, I drilled mine to .065 thousands. If you would increase plunger travel on the ds4 and figure out the most binding problem, getting them to fill you would have something. Fitting bigger plungers is very tricky ,and they should be plated or coated,Columbus Diesel is the only place I ever heard of ,that puts 1/2 plungers in a db2 pump ,theirs are 4 and 6 cyl tractor pull pumps.

 

[schiker]

The actual "end hole" may be the same but I believe the restriction to flow or the pintle cone open cross section (effective flow cross section) area is different and/or something that the spray pattern is different marine vs on road.

I have read blurbs that actual factory bosch marine injectors are "different" and or are unique comparing nozzle and pintle different places different forums. I may be remembering wrong that the end hole was different but again think I have read that before too. Also read there may be several ways to mimic marine injectors with street parts ie with different shim(s)? in the injector as one approach I have read about iirc.

 

[6.2 turbo]

Could be, mine were knock offs . Mine had the same size hole ,when the pintle is open there is still a little tip sticking out on the 6.5 factory one, the marines have this cut down so that its not restrictng as much of the hole. If you take a 6.5 nozzle and grind the pintle tip untill flush with the bottom of the nozzle you will have made your own marine injector. Be careful with to high pop pressure if your pump is weak it wont start hot.

 

[SmithvilleD]

I've read they use 0.5 orifice plate in the test injector to calibrate the DS4 & 250 hp DB2's.

Use 0.6 orifice plate for the 310 hp rated DB4831-5722 marine pump.

Obviously this spec isn't an actual injector, but would have to think if they're using a bigger orifice for calibration, there's a reason.

 

[6.2 turbo]

Ive never seen any with bigger than stock orifice ,not saying there not out there,maybe Heath Diesels are the big ones.

 

[SmithvilleD]

The 0.5 mm & 0.6 mm specs aren't from actual injectors on an engine.

They're little orifice plates put into test injectors on a test stand they use to calibrate the inj pumps. So the same test injector body/plumbing can be used for different rated pumps. Bacharach is the brand test equip I've seen at a pump shop.

It would seem logical if they're using a larger orifice to calibrate the higher hp 310 hp pump, the marine inj's spec'd/designed to be used with the 310 hp pump must be capable of passing more fuel. This is only my theory though. Would love to hear from knowledgeable pump/injector folks?

 

[SmithvilleD]

Ive never seen any with bigger than stock orifice ,not saying there not out there,maybe Heath Diesels are the big ones.

Does the 500 hp # for Heath's LSR effort come from an estimate needed to put that amount of drag/weight to the max mph? Or dyno data? Chassis, or engine hyd brake, etc.?

 

[Woody35]

im pretty sure its calculated not dynoed

 

[buddy]

The larger orifice would keep fuel line pressures down. More volume in less time through the same orifice means line pressures go up with fuel rates. With larger orifice, the peak line pressure will be lower. DS4 goes up to 11k psi or something like that, but with a standard injector at 80mm3 line pressure might go up to 8000psi, while the marine injector line pressure may only peak at 7000psi. So start pushing 100m3 and they might want larger nozzles.

 

[SmithvilleD]

The article I've read gave the following numbers that were reported to have come from Stanadyne pump spec sheets (also where the orifice plate size specs came from). It was an April 2009 article associated w/ Jim Bigley's The Diesel Page.

250 hp DB2833-4979m = max fuel rate of 81.5 mm3/stroke @ 2000 rpm & 68.5 - 73.5 mm3/stroke @3600 rpm

310 hp DB4831-5722 = max fuel rate of 79.0 mm3/stroke @ 2600 rpm, 73-77 mm3/stroke @ 3500 rpm

DS4831-5521 = max fuel rate of 89.9 mm3/stroke @ 2000 rpm, 65.2 - 75.2 mm3/stroke @ 3400 rpm.

It's interesting to me that the lower rpm spec is 1 volume/rate, but the higher rpm spec is given as a range in each case. I don't fully grasp that yet, but it jumps out at me as relevant in trying to understand what the limits are at higher rpm.

Don't know if at the 3400-3600 rpm, the 80 mm3 fuel rate is getting anywhere near how much can be injected within the available time window/correct crank angle/piston stroke range. As well as can it combust cleanly as the time window for that to take place gets smaller as rpm's climb?

Inquiring minds want to know! Would be great if any pump guru's would share, although I get it, if they're keeping their knowledge sequestered & more valuable.

 

[6.2 turbo]

I thought it was dynoed probably on an engine dyno If it was calculated I feel suddenly better about my 6.2. I experimented with pop pressures as high as 4800 psi looked awsome on the tester the truck would not start hot, once running it seemed smoother, top end was also better ,was curious of injector line pressure so I brazed a fitting onto an old injector line and hooked to a 5000 psi liquid filled gauge, using 3/16 brake line ,cranking pressure was never near enough for my 4800 psi pop pressure to start hot, we reved it a couple times and pegged the gauge, ruining it, this was with marine nozzles, and .370 pump plungers, DO NOT TRY THIS AT HOME ,IT WAS NOT A SAFE TEST luckly nothing happend , my brazing didnt even leak, you should have seen and heard that brake line rattle,and vibrate. Im running 1500 psi pop pressure now account of loose pump and plungers.

 

[SmithvilleD]

I'd love to see engine dyno data.

Chassis (typically inertial) dyno data can be useful. But it's often tough to make great comparisons btwn different dyno's. Whether the dyno tech knows/understands temp/baro pressure compensation seems to vary place to place.

The way different setups come up w/ diesel engine rpm also seems to be a common confounding/confusing issue. Lots of chassis dyno charts on diesels out there w/ hinky rpm data.

 

[Matt Bachand]

Found this quote in some off-truckstop link the other forum. This stood out at me as something I've never read, nor heard much about.

Injection Pump Housing Pressure
If the fuel return function in the injection pump becomes restricted and the internal pump housing pressure rises above the normal 10-12 psi, the injection timing will be affected. Housing pressure partially controls injection timing. More pressure retards timing, and less pressure advances injection timing. The engine will probably produce more white smoke due to lower combustion temperatures with a retarded timing. An incorrect housing pressure also interferes with the injection pump's ability to correctly meter fuel. Installing a "T" fitting in the injection pump fuel return line will allow you to test the return line pressure. The pressure should be below 12 psi. A higher reading would indicate a restricted fuel return line

Full article is here
http://flashoffroad.com/Diesel/injectionpump/injectionpump.htm

A nice link from member Curt.

 

[schiker]

That sounds like a DB pump mechanical issue not a DS pump????

And I am not sure I understand the Tee into the return line diagnostic. I think the return line is at 0 psi or no restriction drain back to tank (minus pipping losses). I have read the IP return check valve opens at something like 15 ish psi so that is close to the 12 psi mentioned. You shouldn't really see much pressure Tee's into this line so it would be a partial test. It wouldn't diagnose a bad relief valve holding housing pressure.

As far as I know the stepper motor clocks the camring should be the only thing that affects timing. Unless they are saying this housing pressure is restricting the FSD from closing the metering port in time (which should code).

A few psi shouldn't matter here but yeah a lot might??? I am not sure but am supposing this is some differential pressure that the FSD plunger has to overcome between plunger filling pressure/housing pressure andor very beginning injection pulse vs injector opening pressure??? Solenoids usually have a much higher holding force than closing force and I think the FSD is suppose to close the metering mechanism before appreciable cam lobe rise. Such that the holding force really is what contains or holds the IP injection pulse pressure. Then depending on fuel rate the FSD releases the mechanism for the rest of the injection to be recirculated. So would a few psi make a difference in timing comparing ~ 10-20 psi housing pressure to ~ 2000 psi injector opening pressure ???? At least I don't think the FSD actually controls the exact timing pulse in that it closes independant of cam lobe pump action when it wants the IP to begin the injection ??? I don't know but don't think its strong enought for that ???? Maybe it can for a couple of degrees cam rise variation in which case significant housing pressure might retard timing due to slowing the plunger closing the metering mechanism. But again I THINK the clock orientation of camring is what actually controls timing not the FSD its just a metering compensator ???? It was the forerunner to the common rail system that the injector actually does time independant to the pumping action.

 

[schiker]

I guess they are saying if housing pressure is too great the FSD can't close the metering mechanism fast enough such that some initial cam lobe pump volume is lost and it then takes a few 0.00X-X? more degrees rotation to build up enough volume pump compression to pop the injectors. I can see something like that but I think there are codes for too long of lag for the plunger to close???

 

[schiker]

Worst case is if you block return line. Then the transfer pump would build high housing pressure and the FSD couldn't close the metering mechanism and the IP would build even more housing pressure up to the injectors opening pressure (which would probably blow past IP housing gaskets/seals). Or more probably the transfer pump/IP pump pulse would back feed some against the lift pump or something wierd like that and dependin on if the FSD could close the metering mechanism at all then it might inject. ????

When FSD's totally fail you either get a runaway (all fuel is injected solenoid stuck shut) or a no start solenoid not closing and thus no injection.