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DS4 pump mods

Away from them.
cylinders are everytime filled full and fuel solenoid controls that spill valve so when computer wants start injection sycle it gives pulse to pmd which closes fuel solenoid which closes spill valve and when injection has been on enough long solenoid opens and spills rest of fuel away from cylinders.
 
I looked at Bison's thread again,I finally understand it better. Is this solenoid normally open,and is there a delivery valve,or does the solenoid take care of holding line pressure also ?
 
I got a DS4 pump from a friend and removed the head and rotor and cam ring,the lobes are about 1/2 the size of a DB2 cam ring. Instead of a delivery valve in the center of the rotor it has a spill valve,and then has 8 delivery valves built in the injector line fittings,they will not interchange with the DB2 ,the DB2 cam ring will fit except for the cam pin hole which needs to be made bigger,also the plunger shoes and rollers will fit the DB2 and DB4 . The DS4 has the biggest cam pin I have ever seen, the entire pump is way heavier duty than the DB2 ,but harder to work on.
 
I didn't take the front of the pump apart yet,the shut of solenoid bolt seems to be seized ? I also thought that if you had a big lift pump and were able to circulate enough fuel through the injector pump, the pmd would be cooled from fuel.
 
6.2 turbo said:
I didn't take the front of the pump apart yet,the shut of solenoid bolt seems to be seized ? I also thought that if you had a big lift pump and were able to circulate enough fuel through the injector pump, the pmd would be cooled from fuel.
Click to expand...

The newer PMD's seem to be a lot more heat tough, maybe PMDCABLE.com will chime in... I woulnd't even bother. Mount it on the plastic mudflap or somewhere out of engine bay.

You may be able to enlargen the return fitting, and possibly raise pressure even more? Unexplored territory for most. I'm noticing greatly improved performance running at 10psi and pulling hard at 8 vs pulling hard at 4. Quieter, tighter engine feelings. Response is tit.

Forum rumor has max safe DS4 psi around 14psi into IP.

Keep these thoughts in mind as you rip one apart, thinking why too much may be bad, and what effect more pressure would have in the system.

PM Member BISON about some dealer take offs DS4's he had, he might still have a few left.
 
buddy said:
Fuel rates can be max at any RPM, the higher the RPM the more internal IP pressure so the more fuel gets metered for a given pulse width. And you have more cycles of that fuel rate, so you consume a lot more fuel at higher RPM and max fuel rates. Twice as much fuel consumed at 80mm3 5000rpm as 80mm3 at 2500rpm.

Key thing to remember is you've got 1/2 the time to get that 80 mm3 fuel injected & combusted at 5000 rpm - vs - 2500 rpm.

Time delay btwn injection & start of combustion doesn't change by a huge factor, so the faster it spins, the higher fuel flow rate/speed of injection you've got to have..... because you've got less & less time to get that done as rpm's go higher.

This is the same reason engine's torque curves always fall off at some point as rpms go up. Less & less time the intake valves & exhaust valves are open, so less & less time to fill or evacuate the cylinders. Same volume to fill.... less & less time to move the necessary air mass.
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Yes thats exactly why you need longer pulse widths at higher fuel rates, and pulse width goes down with RPM (because of higher IP charge pressure), and injection line pressure to the injector is higher with higher fuel rates, up to 11000psi.
 
Here is the charge pressure adjustment screw. It's inside the inlet just like the DB2,so the higher the lift pump pressure the higher the charge pressure,since it returns back to the inlet.
 

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6.2 turbo said:
Here is the charge pressure adjustment screw. It's inside the inlet just like the DB2,so the higher the lift pump pressure the higher the charge pressure,since it returns back to the inlet.
Click to expand...

What effect does higher charger pressure have in the injection process?

What about a near zero charge pressure?

Is that an adjustment screw or just an INLET fitting?
 
What he has there is the inlet fitting, the lower IP fitting that we bore those 4 little holes out to match the 3/8" line and upper IP fitting in the FTB upgrade. The 4 little holes that most people dont get around to doing.

The more charge pressure the more fuel gets metered during the pulse width. GM mapped the IP charge pressure over RPMs and decreases pulse width for a given fuel rate as RPM increases. So when PCM requests 20mm3 you may actually be pushing 25mm3 because there is more pressure than it mapped. Etc...

last time I took that off I did not notice a hex screw, is there one down in there on that lower fitting?
 
Yes that is where it is. Also the relief hole for charge pressure is a long slot,which makes the pressure vary more instead of more constant. If the slot is enlarged at the bottom ,and a stiffer regulator spring is used the pressure won't vary as much and will not waste as much charge pressure. I would think any adjustments to charge pressure will advance timing,unless the computer will compensate. Also the fuel is metered after the plungers,so that is not a restriction. The only gain I see here would be if the plungers are not always getting filled,then more pressure is better. On the DB2 too much charge pressure is supposed to seize the head and rotor,but I would think the DS4 will handle more since its already higher than the DB2. I would recamend a liquid filled charge pressure gauge for anyone that is going to adjust this screw more than just a little. A regular gauge will get ruined from pulsing ,unless maybe if you put a restriction in the line. So far the best idea I had for circulating more fuel would be putting the inlet where the pipe plug is,on the pass side and using the stock inlet for a return,but would need a pressure regulator on that ,this would help cool the pump some what,and would flow great,It might be 3/8 pipe,not sure but the hole is drilled very large and goes directly to the inlet fitting. How do I get the shut of solenoid off must the bolt on the top come out,it won't budge ,I think I'll just cut the head off,I probably won't use this pump anyhow ,but its is good experiance.
 
The shut off solenoid twists off with that top hex head. Its not a bolt but part of the solenoid housing and it all spins off.

Where would you install the gauge to read charge pressure? I have a 100psi electronic sender and gauge that would at least be good up to 1500 rpm, before pressure goes even higher than that. But I could monitor idle rpm charge pressure of 45psi at least and modify that screw to see where it ends up.

The fuel gets returned to tank from that bottom hole right, and into the IP via the 4 little holes that are behind that screen.
 
Yeah, the FSOS just unscrews std right hand threads. There is a passage connected from the inlet and the FSOS shuts off the inlet to the transfer pump to kill the IP as a safety.

What I still don't quite get is how the charge pressure stays smooth to control timing. The transfer pump is going to be pretty smooth GPM flow dependant on RPM. But is going to be dead headed during timing events that close off the filling of plungers and when the plungers are full.

Does the charge pressure surge during spill events and this is when that valve opens on the bottom of the inlet mechanism??? Or do you think it opens during time that the transfer pump is dead headed??? Charge pressure has been posted to vary with rpm. So the valve should be closed during low rpm low pressure and could open at max charge pressure (during high rpm).

The slot in this relief valve would allow it maintain a more consistant pressure with variation of GPM flow wouldn't it? Say for instance the quicker pulse of filling at high rpm vs low rpm plus different transfer GPM and frequency of dead head events ???

I have read the IP can vary output balance near max fuel rates I think due to slight variation of plunger fill. Such that can be the main advantage to feeding the beast is best consistent filling during high fuelrates under all conditions.
 
I got the shut off solenoid off by clamping it in a vise and turning the pump,the hex head was rounded off. I also took apart the charge pump,and was debating if it can pump a lot or not,kinda think it can because of the large diameter. All the ports on the pump are charge pressure except the pipe plug,which is not 3/8 or 1/2. Charge pressure comes from the internal pump and into a passage on the ip housing pass front,then goes straight back to a rear bolt hole,which goes directly into the head which has a internal passage that goes the whole way around and has 8 holes that line up withe the 2 holes in the rotor when the plungers are between lobes on the cam, it is then pressurized by the plungers, then enters a hole in the center of the rotor, and can go one of two places,depending on the fuel solenoid,with it closed it will go directly out a hole in the rotor,and to which ever cyl hole it lines up with in the head,when the fuel solenoid is open the high pressure fuel goes into two holes in the head,which are charge pressure,and then goes into a passage in the pump body, and goes straight front to the inlet where the regulator is,and returns towards the lift pump. The charge pressure is sealed from lift pump pressure,by the oring at the bottom of the inlet fitting except what is passed through regulator valve,which is probably open most of the time since it is slotted. Since the high injection pressure is dumped into the charge pressure it looks like it could easily get very high at light loads,and higher rpms.
 
If I were to put a DB2 cam ring in a DS4 would the computer hold the fuel solenoid open long enough ,to still operate some what normally? The available fuel would probably be about triple.This pump looks easy to get a lot of fuel,it only shares one restriction with the DB2,the rest,except the cam ring and electronics, looks way better than the DB2,even the input shaft is way bigger in diameter,pretty much the only thing good about the DB2 is that it is simpler and mechanical, but not heavy duty at all, no wonder I broke so many cam pins. The way the plungers get fuel straight from the charge pump is so much better than trying to get it through a metering valve that is very tiny,like in the DB2.
 
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