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Old 11-22-2014, 07:39 AM
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Vandy Vandy is offline
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Default fuel psi d2/wvo?

I was reading a tread on .org about fuel pressure recommendations. So far we have yet to get a solid answer, but it made me start wondering. Does anyone know what psi my system "should" be at. Right now I have them both set at 74-75psi. Some are saying that's on the high side? I've read from 50 - 65ish is a good area. The truck seems to be running good where it is, but if it's putting unneeded stress on the injectors then I am going to turn it down a bit.

So for the obs guys, where are your pressures set?

Does the wvo side need to be at a higher setting than the d2 side?
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Old 11-22-2014, 05:04 PM
bbboomer bbboomer is offline
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Vandy,
I don't have any "facts" to back this up but here is my take.
The only downside to the pressures you have is the possibility of stress on the pump itself to produce the pressure. I don't think that is a problem at the pressures you are using.
Low pressure at the injectors is a problem that will damage the injectors. Again at the pressures you are using that is not an issue.
The OBS injectors are essentially the same as the later model 7.3 so I think your pressures are right where they need to be. Lowering them will not be an improvement but could be a problem.
Leave it where it is.
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Old 11-22-2014, 07:59 PM
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your pressure switch will trip at 55 psi IIRC. so the 75 psi was picked by jason to prevent this when you experience a pressure loss do to a plugged filter or cold oil, etc. The donaldson is rated for 90 psi so theres that. These systems are sent out already set to or close to 75.
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Old 11-23-2014, 01:35 PM
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Not 100% sure on the OBS D2 pressure in stock form, but you've converted to SD e-fuel now - which is ~55psi stock. Since we don't change D2 pressure, that is what most of us run.

Except for the Donaldson (rated at 100psi), nearly all of the VO filter options are rated for 75psi operating pressure and that is what most of us set the VO pressure to.

The delta between VO pressure and the (65psi?) pressure switch is what keeps the green light from flashing.

There is no need to set D2 over 55psi and no disadvantage to setting the VO to 75psi.

In my experience, there is no change in performance until pressure drops well below 40psi. I've seen trucks running 100psi that ran just fine - but there is no good reason to do this... It seems the 6.0 crowd has talked about higher pressure hurting power - but I dunno much about them new-fangled mils....
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Old 11-24-2014, 03:41 PM
Krause Krause is offline
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Vandy, for practical reasons IMO the veggi should be set a noticeable amount higher than the diesel side; this insures you know what fuel you are burning, regardless of what the light or anything else says. This has been made redundant somewhat by the SSB, but back in the day some weird things could happen with the control module, not all of which could (or ever did) get explained fully. Main tool you had for diagnosis was the 'green light', which could/can also do some weird things. Not so bad now because the switches dont see the load with the SSB, but I used to have issue where the green light would stay on no matter what (Auto/manual/off, truck off, all of them).. then go out after a couple key cycles. Another member here has switches that have seen so many miles, the green light dosnt always come on in auto, you have to jiggle the rocker a bit to make the green light up, but he is burning veg..

Anyways, I guess my point is my diesel is set at 65, veg is set at about 80. Green light SSB blah blah its all very exciting, but day to day I care about the pressure. If its at 80, I know for certain that's the veg pump. Make the gap large enough it wont fool you when a filter drags the veg pressure down a bit.

And on edit, your window for fuel pressure really is pretty lenient. Anything about 45 and below 100, your injectors wont know the difference. Dont get hung up by the guy saying it needs to be 68.454 psi, just set them apart from each other and beyond that you wont ever tell the difference.
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Last edited by Krause; 11-24-2014 at 03:45 PM.
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Old 11-25-2014, 01:36 PM
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^^^ What he said!!!!!
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Old 11-26-2014, 02:24 AM
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Valid points. I turned my d2 psi down to about 64. Can't tell a difference really.

Now if I can just get my coolant leak to go away before it gets cold again I'll be doing ok lol
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Old 11-26-2014, 06:45 PM
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I run my OBS at 55 PSI just because that is what the factory spec is. Veggie at 75 PSI. I use 75 PSI on veg because it gives me a 20 PSI window before triggering 55 PSI pressure switch.
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