v2.0 Fuel APC (was OFV)

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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philip
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v2.0 Fuel APC (was OFV)

#1

Post by philip » 13 years ago

Adjustable Pressure Control

Overall view.
Image

A very small orifice vents possible second air from the injection pump. The nozzles still have a very tiny fuel leak (a couple of drips per minute ... normal). (from old VW diesel)
Image

PRIMARY fuel sent back to the tank. Any of that air sent back to the tank also. Any last minute of air from injection pump and/or nozzels sent back to tank. (Cummins stock part)
Image

The APC "thumps" while moving fuel back to the tank so .... a cushioning (without, you'd hear "thumping" while driving with the engine below 2000 rpm! (ACE Hardware. Grommets and longer bolts)
Image
Last edited by philip 13 years ago, edited 1 time in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

exsimguy1
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#2

Post by exsimguy1 » 13 years ago

Philip,
First of all, let me say how good it is to see and hear you are on the road to recovery. It seems you are doing better each day (or post!).

Now that you have changed your fuel system again (looks promising by the way), please note any changes in "cackle" with any of the fuels that you may burn. Primary pressure can affect timing in subtle ways. Since most everyone else is probably running the stock OFV, with probably stock (or late relatively) timing, their results with fuel related "cackle" may be different. I am interested in any comments you may have in driveability, noise, or any other changes you may see now.

Take care,
Terry
1987 D21 w/1983 SD25 drivetrain

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philip
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#3

Post by philip » 13 years ago

exsimguy1 wrote:Philip,
First of all, let me say how good it is to see and hear you are on the road to recovery. It seems you are doing better each day (or post!).
Thank you. God forbid it happens again.
exsimguy1 wrote:Now that you have changed your fuel system again (looks promising by the way), please note any changes in "cackle" with any of the fuels that you may burn.
During cold temps, you can do much more with preheated air than you can with various fuels . Don't ask me.
exsimguy1 wrote:Primary pressure can affect timing in subtle ways. Since most everyone else is probably running the stock OFV, with probably stock (or late relatively) timing, their results with fuel related "cackle" may be different. I am interested in any comments you may have in driveability, noise, or any other changes you may see now.
Take care, Terry
People are far more fascinated about "free fuels" who then spend a lot of time and money and engine damages. After reading about bios ... I limit to such fuel that I can buy cheap at a pump. That's it! There is no "free lunch" fuel out there. I find better to fine tune.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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asavage
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#4

Post by asavage » 13 years ago

Gawd help me, I've driven something like 600 miles commuting in three days, and not easy commuting either (training classes in Tacoma).

I've switched back and forth the last week between D2 and B99 a couple of times (running the tank way down past 'E' on the gauge), and my '82 Wagon smokes significantly more on D2 under hard load. FWIW, and that's only one difference.

It also starts harder on B99; the existing GP poor performance (for whatever reason: bus bar, GP timer, deteriorating GPs) that makes it run poorly when first cranked is much worsened on B99. My gut feeling is that if I got it starting well on D2, it would start well on B99 (as did my first 720 SD22), but that is not yet proven.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

exsimguy1
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#5

Post by exsimguy1 » 13 years ago

Phil,
I am not too concerned about "other fuels". We have had previous conversations about ULSD and additive use changing the audible "cackle" in your engine in particular (possibly cetane value related). I was wondering if your results were different / or have changed (from everyone elses) since you have deviated from the OFV scheme. Primary pressure does affect timing, audible sound, and driveability in subtle ways, as well as, and in addition to, cetane value. I am merely wanting to see if the latest rendition has changed any of these noticably.

Your testing frequently adds altitude to the mix also, so is great data for the overall SD diesel data collective.

Thanks,
Terry
1987 D21 w/1983 SD25 drivetrain

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philip
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#6

Post by philip » 13 years ago

asavage wrote:SNIP- I've switched back and forth the last week between D2 and B99 a couple of times (running the tank way down past 'E' on the gauge), and my '82 Wagon smokes significantly more on D2 under hard load. FWIW, and that's only one difference.
Lots of people fill smoke their kitchen when they cook eggs. It is gourmets who turn down the fire ... thereby making the best eggs.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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asavage
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#7

Post by asavage » 13 years ago

Philip, your pedagogy is too subtle for me. Got a brick handy? Can you throw it at me?

Terry, can you summarize how IP inlet pressure to a Bosch-design inline IP affects injection timing?
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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philip
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#8

Post by philip » 13 years ago

exsimguy1 wrote:SNIP- Primary pressure does affect timing, audible sound, and driveability in subtle ways, as well as, and in addition to, cetane value. I am merely wanting to see if the latest rendition has changed any of these noticeably.
In the beginning, I was looking to minimize frequent fuel foaming to the injection pump at times the tank dropped to 8-10 gallon level. Satisfied now considering the long, shallow having no liquid windages.

The cackle research has moved in a different direction. But you just gave me a idea today. :)
Last edited by philip 13 years ago, edited 1 time in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

exsimguy1
Posts:27
Joined:13 years ago

#9

Post by exsimguy1 » 13 years ago

Al,
We have all experienced a plugged fuel filter in a diesel vehicle. The vehicle gets lazy, generally exhibiting poor mileage, and possibly higher EGT (N/A). The filter exhibits a pressure drop across it, limiting pressure to the IP. The SD produces little excess fuel at the return, even at original OFV pressures, possibly as high as 30 psi. At reduced pressures, each piston cavity in an inline pump may either not fill, or fill at a lower pressure(density) than normal. When the delivery valve pressure is reached, the density of the fuel may change exactly when the injected fuel actually fires. This is after the pop pressure is reached at the injector also. Small differences, but enough to change sound and power.

Terry

Higher compressibility = retarded firing point
Lower compressibilty= Advanced firing point
1987 D21 w/1983 SD25 drivetrain

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#10

Post by asavage » 13 years ago

exsimguy1 wrote:We have all experienced a plugged fuel filter in a diesel vehicle. The vehicle gets lazy, generally exhibiting poor mileage, and possibly higher EGT (N/A).
Low power, yes. Altered injection timing? High EGT? Do you have a collaborating reference?
At reduced pressures, each piston cavity in an inline pump may either not fill, or fill at a lower pressure(density) than normal.
Liquids, in general, do not change density appreciably in the pressure range we are discussing, so toss that right out.

If we were discussing a housing-pressure-activated-injection-timing-mechanim-equipped-IP, such as a Bosch VE or Stanadyne/Roosamaster DB-series, I would unequivocally agree that changing the housing pressure changes the injection timing (and I have personally experienced this), but unless I'm missing something in the design of the Bosch Inline IP, the housing does not require the pressurization it is receiving and is so insensitive to IP housing pressure that some have successfully run it gravity feed.

I was hoping that you have some insight into the Inline IP's internals that I lack.

I've run an Inline IP with a plugged filter to the point of 11" vacuum and inlet lines collapsing, not once but several times, and did not seat-of-the-pants experience what I would translate as injection timing changes -- but that is certainly not proof that they weren't occurring. And while I did not have a pyrometer installed in the 720, I am skeptical that reduced fuel injection quantity combined with pretty much any injection timing change available in the full range of possibilities even with a VE or DB2 would raise EGT; on the contrary, I'd think.

Please do reply if you can educate me further on this, I'm interested.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

exsimguy1
Posts:27
Joined:13 years ago

#11

Post by exsimguy1 » 13 years ago

Al,
I will reply with better info after further contemplation. I am speculating presently on experience (as are you) and cobweb encrusted data of yesteryears reading. There is (2004) some good research comparing compressibility of different fuels and their changing of firing points related to static timing settings in Bosch inline pumps found here.

http://pubs.acs.org/cgi-bin/abstract.cg ... 9880j.html

and here.

http://www1.eere.energy.gov/vehiclesand ... oehman.pdf
1987 D21 w/1983 SD25 drivetrain

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philip
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#12

Post by philip » 13 years ago

exsimguy1 wrote:Al,
We have all experienced a plugged fuel filter in a diesel vehicle.
Al and I have found how LOTS of people use the gasoline paper filter (cheaper) than Nissan's require of using the wire screen. All told in another forum here.
exsimguy1 wrote:The vehicle gets lazy, generally exhibiting poor mileage, and possibly higher EGT (N/A).
Not possible. When a fuel delivery is reduced ... ALL diesels simply slows down and with less heat in the combustion.
exsimguy1 wrote: The filter exhibits a pressure drop across it, limiting pressure to the IP. The SD produces little excess fuel at the return, even at original OFV pressures, possibly as high as 30 psi.
Huh? It is the Lift Pump pump SPRING that limits fuel line pressure. The OFV is only a SMALL ORIFICE ... starting at ... 20 psi.
exsimguy1 wrote:At reduced pressures, each piston cavity in an inline pump may either not fill, or fill at a lower pressure(density) than normal.
Huh? When you see SD22 / Bosch C.A.V. having the diaphragm fuel pump type (lever pump alongside cam gear house), they are normal at only 5-8 psi. Works fine.
exsimguy1 wrote: When the "delivery valve" pressure is reached, the density of the fuel may change exactly when the injected fuel actually fires.
May. The Lift Pump at (saying) 25 psi but ... the nozzles are popped at 1500-1600 psi. But for certain, if foam fuel is present then ... the nozzles will pop-off when the piston is closer to TDC.
Last edited by philip 13 years ago, edited 3 times in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

exsimguy1
Posts:27
Joined:13 years ago

#13

Post by exsimguy1 » 13 years ago

Phil,
1. Was talking about fuel filter between lift pump and IP
2. Not less heat if at different time
3. You were the one saying your OFV was allowing 30psi from your new lift pump
4. you're right
5. Foam or a lower density liquid

The differences between D2 and Bio (in multiple formulations) in firing time vs. static timing are documented, but .... what is D2 right now? Certainly not what it used to be. And may not be the same tomorrow.

Trying to keep an open mind,
Terry
1987 D21 w/1983 SD25 drivetrain

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#14

Post by asavage » 13 years ago

exsimguy1 wrote:There is (2004) some good research comparing compressibility of different fuels and their changing of firing points related to static timing settings in Bosch inline pumps found here.
Um . . . yes & no. At injection pressures (let's say, over 1500 PSI), there is some measurable difference in the compressibility of various diesel fuels.

However, we are not talking about varying the output pressure of the IP, only the output volume, and the feed pressure range is something around zero to something above, say, 30 PSI. Fuel in the IP housing is in that range (excepting the plungers area high sides and on out). Perhaps even a bit below zero in a plugged-filter circumstance.

In that range of pressures, diesel fuel's density does not change (to any appreciable degree; we are talking really, really hard to measure differences now).
Not much but one paragraph, unless you register, but it's a good paragraph nonetheless.
This 2003 abstract is fun, lots of colored lines and terse summaries.

One of the two listed test engines they used (the other being a Yanmar DI One cylinder air-cooled) is a Cummins 5.9 ISB, which seems (five minutes Googling did not yield a definitive answer) to have been available with at least three low-pressure IPs: A Bosch VE, a pretty much similar-to-SD inline IP, and a Bosch VP44. After that, they went common-rail. I probably have part of that wrong, but in any event at least the common-rail (HEUI) and the VE will not be applicable to any discussion of IP housing pressurization effects as relevant to the SD IP.

I noticed some overlap in the staff of both publications, so it would be fair to say that pretty much the same people came to pretty much the same conclusions in 2003/2004. Interesting stuff. What Andre & Rick say is that they've measured the static & effective timing changes when mechanical factors are held constant but the fuel composition is changed. Vegetable oil and various blends of biodiesel and other fuels (LSD, ULSD, COP FT) show differences in static and effective timing (and peak cylinder pressures, brake-specific fuel consumption, NOx, output to later diesel particulate filtration systems).

A fair summary would be to say that BD does not compress as much as D2, at common injection pressures, and that this "stiffer" liquid column allows the action of a IP high-pressure plunger to be transmitted to the injector in less time.

The left chart on page 6 is filch-worthy:
Image

About 1.5° advance is what is indicated. That's just the mechanical difference in the fuels: independent of cetane/ignitability factors. Which is a number I'd heard before from other sources, so I'm not surprised, and it ties in neatly with Philip's cackling too ;) Oops, I meant Philip's cacking problem . . . um, the cold cackling of Philip's SD. There.

(I want to take this opportunity to say, "kilo-joules per degree". That's not a phrase I see on the legend of a graph very often!)

None of which seems to relate to IP housing feed pressure affecting injection timing.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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philip
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Location:Southern California, USA

#15

Post by philip » 13 years ago

exsimguy1 wrote:Phil,
1. Was talking about fuel filter between lift pump and IP
Because ... incorrect primary filters cause a LOT more failure of fuel delivery than the Secondary filters -- we find. Once you do have the correct screen type primary filter, then you can site infrequent failed secondary filters.
exsimguy1 wrote:3. You were the one saying your OFV was allowing 30psi from your new lift pump
We know that 28 psi is expected to be the fuel line pressure. Not the OFV 16-20 psi. Lift Pump from Nissan page. At normal idle, a very pulsed fuel line of 10-15 psi.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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