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Discussion Starter · #1 ·
I’m adding a shut - off thermostat to control flow of engine coolant to the in - tank “hot stick” heater put in a couple of years ago for biodiesel. I’ve been just turning the coolant loop on for Winter and shutting it off in Spring – Fall. I’m worried I might be overheating the fuel at times. Running pretty much straight petro this last year.

Arctic Fox http://www.arctic-fox.com/ sells 2 temperature ranges: 78 – 90 degrees Farenheit, or 104 – 125 F. When the fuel is heated past these temps, the thermostat shuts down the coolant loop. Question for you experienced guys: How hot is too hot for the DB -2 injection pump? I had a new (reman) pump put in last fall at 109K and don’t want to damage it.

Thanks!
 

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I could be out in left field, but I think it's more of a viscosity issue, not so much as temp... at least with the veg oil.

...again I could be on the wrong track
 

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Don't know if this is ok but cut and paste from somewhere else:

quote:
Diesel fuel has a Specific Gravity of .82 @ 60F
Raise the temp to 90F and it suffers a .9754 increase in volume and thus a reduction in viscosity, by 120F there has been a 1% change in volume.

These figures are from a diesel fuel distributor who uses industry standard tables to calculate volume for adjusting delivery pumps. With VO we are trying to lower the viscosity and do so by nearly 12 times by heating it to only 160F, since oils all loose viscosity when heated, heating diesel the same amount will not be very good for the IP. Several companies I have spoken with say that diesel fuel temps greater than 135F should be avoided.

Chris
end quote

This topic interested me concerning through put to a DS-4 pump. While not the same as a DB-2. Some things could be similar.

The DS-4 and ECM monitors fuel and has a range up to 285F IIRC on the sensor. It says in the Helm manual 159 F is a typical value. Its measured near the opitcal sensor. Pretty big difference from above paragraph!

I looked over the internet and saw several coolers on high hp and higher pressure IP's diesels. And several statements that hot fuel has less power, less efficiency, and looses some of its lubricity at higher temps. But I could not find real good numbers on max temps for the 6.5. Note the duramax has a cooler on the return fuel line.

I had started a thread over on the page. Just a couple of threads on the subject. I did not search here yet though.

Looking forward to others comments. I think too warm of fuel can contribute to loss of a little power under heavy load.


 

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If my memory serves me right, you want the WVO to be at 160 degrees. It is not about keeping it warm, WVO is thicker and need heat to make it less thick. Biodiesel does not need any heat at all except in winter time but you could mix 50/50 with regular diesel.
 

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Heat won't hurt pump. You get it to hot or in this case thin, the vehicle may have hot start problems.
 

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Discussion Starter · #6 ·
"Normal" warm weather fuel temp for DB-2 I.P.?

Next question: Anyone know the "normal" range of fuel temperatures going into the DB-2 mechanical I.P., with say 80 deg ambient air temperature under light load?

Heat won't hurt pump. You get it too hot or in this case thin, the vehicle may have hot start problems.
:exactly: I have had hot start problems. I want enough heat to keep B50 or higher biodiesel blends from thickening up too much - yet not too much that will thin out straight dino diesel too much. It seems like a compromise / balancing act. I probably want just enough heat when needed to raise fuel temp "normal" summertime range. I see running the heated fuel only late fall to early spring when average temperatures here are below 35 - 40 F.

Also: schiker, you bring up good points about specific gravity & viscosity. I'll see what the biodiesel experts know about heating it to 90F vs 125F.

John
 

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John,

In the original post you said you ran pretty much straight diesel last year. I would not heat straight diesel unless temps were 45 F or cooler.

A fair and semi educated guess I would expect fuel temps to be 100F-125F at the IP on a 80F day light load just due underhood temps and location of IP and fuel filter. Everything under my hood is warmer than you want to hold at normal operating temps - sit and idle with ac on and its hot under the hood. The temperature in the tank and most of the line would be closer to the 85-90F (after circulating a while). If you ran a heater then fuel temp at IP would be higher mabye 135F (or higher maybe what coolant temps ~ 145-165F ish at the heat exchanger).

Over heat diesel fuel and it looses lubricity I think that can hurt IP! At least it would wear more and reduce life. No not kill an IP overnight but it aint good. Biofuels blends and WVO have much more lubricity as you know so its a different and fuel temp should HEAVILY depend on blend and type of fuel.

Good luck with research and look forward to more info.

Hue
 

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Discussion Starter · #8 ·
Thinking through fuel heating

Hue,

You are dead right about fuel blend and temp being related. I'll be talking with Arctic Fox this week to get their recommendations on thermostat temperature.

************************
I'm not a mechanical engineer or diesel tech, but see a couple of scenarios:

Spring/summer/fall: Coolant loop shut off, no heat added at fuel tank; stock setup. B50 to B100 is warm enough from ambient temps and heat introduced at the engine, and lubricates IP better.

Winter: Coolant loop opened. Inline thermostat after lift pump & secondary filter limits max. temp of heated fuel to: a) 90F+ b)120F+: Some heat would be lost going the 8 feet or so from t'stat to IP. Some heat gets reintroduced at the IP (How much?).
-> 120+ degree t'stat should be OK below freezing, with B20 or greater. IF the temp spikes into the 50s (It happened here just yesterday) and if I'm running pure dinodiesel because it was -5 F two days earlier, I could be thinning out fuel too much, which isn't good for the IP.
- > 90+ degree t'stat would introduce less heat, and be safer for times when the outside temperature goes on a roller coaster. With less heat added to the fuel, I depend more on a conservative blend in winter, say B20 with anti-gel additive. And if I'm running B0 / dinodiesel anywhere below the arctic circle, I just shut the coolant loop off.

The 90 degree approach looks like the safer bet, especially for the "shoulder" seasons and when temps swing wildly, like they have this year.

Anyone else with info or opinions on this?

John
 

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Sounds like you are headed in the right direction, Nuzz.
 
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