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DS4 pump mods

Can customize how long the pulse width is for any given rpm and fuel rate. Are you thinking we would have to be shorten the pulse width to lessen the amount of fuel at lower rpms.
 
buddy said:
Where is the separation of charge pressue and transfer pressure? Are those synonomous or is there is specific place they are separated?
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Sorry to confuse my point is liquid can't compress and any change in volume will immediatly increase pressure exponentially unless its relieved. Its very dynamic flow the transfer pump continuously pumps but the plungers fills/injects/spills in "pulses".
I guess transfer / charge pressure are synonomous depending on clock time of port alignment. Yes the transfer pump is what supplies the flow to build charge pressure. But I consider charge pressure only when plungers are filling. During times when plungers are full or closed intake port alignment (time to pump output) I consider it transfer pump pressure not "charge" pressure.

Because this is a relatively short time it might take some kind of hydraulic pressure measuring device to measure the lowest pressure dip ???? Bison mentions accumulators and this would soften dips/spikes but I missed the mechanism when I took mine apart so fast and sloppy looking at other areas.

It appears there is some overlap to the transfer pump pressure/spilling pressure such that when plungers are "spilling" (after fuel injection commanded stops - solenoid opens and plungers dump remaining fuel internal to IP and not injected) it mixes with transfer pump pressure and this is where I would think the transfer pump pressure would spike and the pressure regulating relief in the bottom of the inlet mechanism would open???
 
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Great info guys.

I will add that when I'm at 10psi It almost seems if the moment I feather the APP and idle control is transfered to pump operation it perhaps gives it more fuel than desired, resulting in acceleration.

Perhaps all my gains are just premature fuel vs APP movement, so the largest gains I'm feeling are just that I'm using less APP movement to supply the same fuel, resulting in earlier shifting (tcc ETC) basd on throttle position.

My routes are NEVER the same, my locale is EXTREMELY hilly, and shitty roads, and my right foot can't stay out of it. All that said, my MPG took a hit with the last tank, netting the lower end of 12mpg vs the upper end of 12mpg. However, this means little as I leave it idling at the dump, and at customers houses for the first few minutes (during customer introductions)... (let the oil/egt's cool down before shutdown).... These idling amounts always vary, and I've been pushin the ol' girl a tad more, so I'm not surprised.

Perhaps all the gains I've been feeling are the similar to a reflash.

It is odd how my fuel pressure changes so often. One day I was pushing a tad over 10, the next day around 7 (with both pumps). Another day I never used the 2nd pump and it never dropped below 6 (hard throttle 5) and another day idled at 6 and dropped to 3 hard throttle single walbro with only 6-7 hard throttle, with instant recovery to close to 10.

Walbro's warming up, filter restrictions fluctuation? Ambient temps, and perhaps something inside the IP making these numbers change so often.

I pulled an all nighter last night trimming out the house I'm moving to in a few weeks, so hopefully before the end of this long weekend I will bore out the inlet fitting of my pump and see what that does to pressure/performance.
 
To buddy,this what I was thinking,and also if it might not work with the stock program. To schiker I always thought that transfer pressure was just another name for charge pressure,and after the plungers it will be injection pressure,but that could be called transfer pressure I guess ,and the accumulators are in the head on the plunger end behind allen screws that have a hole in the middle, same as the DB2. On my one pump I turned them in against,because I decided that they bled fuel at high charge pressure, some of the DB2 pumps don't even have them. To Matt, higher lift pump pressure will do pretty much the same thing as cranking the charge pressure screw,you are pushing down on the regulator valve with fuel pressure instead of more spring pressure,but the valve will still be able to open fully so at higher rpms it probably won't be as noticeable a differance as actually turning the screw or modifying the regulator. I would say that 10 psi lift pump pressure should be fine,and if you want more just turn the screw,but at your own risk,I would maybe do it on a pump that is a little iffy ,and on a good pump be a little conservative,and use a gauge, I believe the charge pressure is capable of some serious psi , I had a DB2 over 200 psi,and that don't have injection pressure feeding it also,so be careful . Any one getting carried away with adjusting should make the relief slot wider so enough fuel can still be bled off at high rpms,but this might make it very touchy and possibly even lope at idle . I'm surprised no one has adjusted this before.
 
IIRC Slim and TD have mentioned turning the hex screw 1/8 of a turn on older pumps.
 
You don't want to turn the screw in the IP inlet fitting more than a half to full turn. Timing changes and case pressure goes up at idle and exponentially at rpm. Case pressure can range from 10 psi to ~ 135 - 145 psi at high rpm.
Any more and you risk blowing the shaft seal and dumping fuel into your engine oil, ask me how I know):h.

Don't let me stop anyone though, a half turn on older pumps is all I have ever done. I have played with this for about 3 years now, amongst other things on the IP.
 
Slim Shady said:
You don't want to turn the screw in the IP inlet fitting more than a half to full turn. Timing changes and case pressure goes up at idle and exponentially at rpm. Case pressure can range from 10 psi to ~ 135 - 145 psi at high rpm.
Any more and you risk blowing the shaft seal and dumping fuel into your engine oil, ask me how I know):h.

Don't let me stop anyone though, a half turn on older pumps is all I have ever done. I have played with this for about 3 years now, amongst other things on the IP.
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So are you saying youve only done it on a DB2, or on older DS4 pumps?
 
The housing pressure is regulated by the return line fitting. The charge pressure regulator is in the fuel inlet fitting,and has nothing to do with housing pressure. The fuel in the housing is just from internal leaks.
 
6.2 turbo said:
The housing pressure is regulated by the return line fitting. The charge pressure regulator is in the fuel inlet fitting,and has nothing to do with housing pressure. The fuel in the housing is just from internal leaks.
Click to expand...

Hmnn, not quite what I observed on test stand when doing some R&D @ a IP shop in FL when testing my FTB setup/experiments; not doubting your statement, but I have seen 1st hand observations after making some inlet pressure regulator adjustments that make me say hmnnn.
 
Turbine Doc said:
Can't let all our secrets out :D, we have collectively been playing with some different ideas with the DS-4
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Keeping secrets from your community, not very nice. I thought this was all about sharing. everyone else is sharing. Who is the collective, we have made a lot of progress with just a couple people on here.
 
I dont know why anyone would say a different turbo is impossible, thats just nonsense. Its just a turbo, it spins. When things are based on science its easier to explain.
 
Buddy you have no idea of flak from "experts" at other sites that said no way would it work, there are still some doubters out there, "math/science" says it can't work, yet it does, defying the "experts" in real world application. Science gets you close, sometimes you have to "just do it" as was done with the ATT.
 
I'll bite. I have had so many hooks in my mouth snatched out and some swallowed it don't bother me much anymore I just like the intellectual stimulation.

The spill/fill chamber is sorta seperate from housing pressure is what 6.2 turbo is saying I believe. But fill/spill chamber "vents" or flows to the housing chamber and out the return fitting in a few paths. One through the advance piston path and the other through the head from spill I think. Also, maybe some high pressure leakage from plungers "blowby" due to clearances I imagine. Which might be appreciable at high rpm high line pressure???

I can see appreciably higher transfer pump pressure elevating housing pressure if it wants to exceed expected output mechanism flow/pressure and the return fitting is restricting flow. Its looks like a realitively small output hole (at least smaller than input hole) and I imagine Stanadyne designed the pump to recirculate most fuel and just return enough to flush a little bit and allow some pressure bleed off. But change internal flowrates and pressure could rise easy enough. The GM DB -DS IP's were suppose to live in the V-8 valley and be designed to like warmer fuel than traditional IP's of its generational birth. Might have been a design feature to return less fuel to the tank than traditional. Note guessing about maybe the longer GM fuel filter maintenance schedule /smaller size compared to others???.
 
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