Max PSI for a DS4 IP?

[Will L.]

With the db2 is wasn't hard to maintain pressure. It would be 6psi idle and floorboarded on hill 3psi. That was on my one of my old trucks way before I heard of TTS. Had the fuel screw maxed out and ran twin gm4. Both up front, one of each van exhaust manifold flipped backwards. Bottom end let loose from bad harmonic balancer. Little 1/2 ton would scoot for a 6.5. Can't remember what fuel pump I ran, I think it was a Holley red, and yes regulated. Still hate that truck, it was cursed.

 

[JayTheCPA]

With the db2 is wasn't hard to maintain pressure. It would be 6psi idle and floorboarded on hill 3psi.

Even though that was on a mechanical pump, it tends to reinforce that regulating the fuel pressure at 5 psi for the DS4 is actually good presuming it remains at 5 psi during WOT; correct?



And in terms of reconciling the community's experiences with Stanadyne's spec, here is my take:

> The DS4 wants 5 psi at the inlet under all loads (idle to WOT).
> What we are doing is working to the WOT part by over-pressurizing at lesser loads. Specifically, to end up with at least 2 psi at WOT to maintain power (per common experiences), we are starting out with 10+ psi at idle.


Looks like I am going to dig a bit more and see if there is something like a bleed-off valve versus the ~$700 regulated systems available for the DI motors.

 

[Will L.]

Yes, keeping it up to pressure while WOT under load is the desire. What does greater than 5psi anywhere in the power band do? Idk.
Could be it helps,could be it hurts. So many people on forums like the higher pressure I just would be hard pressed to go by that 5lbs statement.

Just too much pressure on seals, or more complicated like what messing with intergration of parts like the db2. Maybe the bell curve of pressure for the "fill" stroke looses performance?

Maybe John from uniquediesel.com can teach us a little?
Personally, ds4 knowledge to me will just get passed on, I'm db2 4 life.

 

[Burning oil]

Again, Stanadynes own service manuals call for 9psi. I think your over thinking the issue. In real world driving having 9-13 psi at IP is perfect for DS4.
I understand you want to have a constant predetermined psi, but think you will over spend/make things complicated to do it. JMHO.

 

[THEFERMANATOR]

The outlet fitting of the injection I believe has a spring loaded check ball in it to maintain and regulate the pressure in the system. I know that CUMMINS used this style setup with all the BOSCH pumps. And you can get a return style EFI regulator for not that much money. Or build your own low pressure one out of a HOLLEY regulator(theres a diy somewhere on how to modify one).

 

[schiker]

OK it was pretty crude but I measured the outlet fitting on the IP. I poured a little diesel fuel in a hose to lube it up and help keep a wet seal then Tee'd in a hand pump and slowly pumped. The IP outlet valve appears to start flowing around 5 psi.

This one has sat out in a box a long while so I don't know if its 100% and the first time I did it pumped up a little higher then blasted out (up near 12 psi) like it was stuck. So I refilled the hose and tried 2 more times and it starts to flow at near 5 psi. I wouldn't argue if someone said it was suppose to be a little different. 4-8 psi (or a little more). But its not 16 psi like I thought.

It seemed to blast out pretty quick upwards of 8-10 psi. It might seep at 4-5 psi again its a crude set up.

I can't say that means much but optical sensor is probably not sitting in very high pressure.