Fuel Temperature questions

[Hubert]

I am curious now and would like to know more about fuel temperature and performance.

Are there any problems with cold diesel fuel besides waxing and plugging filters? Living in SC I don't see either one of these that I know of. How cold is too cold for normal operation say 35F and above ambient temps? I assume manily affects ability to be pushed through a filter but is there a difference in filter performance or just flow. I don't know maybe when too cool parafins and/or lubricant additives seperate more in the filter?????

Assuming a good filter system what if any are the disadvantages of cooler fuel and excess flow to a DS pump to be returned to the tank?

What temperature does the fuel manager try to maintain? I thought I read once it was 70F???

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=009810

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=007702

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004681

[Hubert]

Ok searching google I found lots of info on cold diesel fuel not much on warm diesel. Except some stuff on SVO fuel.

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

I think 135F would be easily surpassed in the summer on most 6.5's.

I also saw else where there is a 1-7% drop in power from hot fuel compared to cool fuel. But it did not give specifics.

I found in the helm manual the fuel manager heater comes on when it "senses" 46deg F. Does not say when it cuts off. After thinking about it it must have been our IP's are calibrated at 70F temp.

I saw an article about a 6.6 having a diesel fuel cooler. Is that stock? Also some Volvo And several boats running coolers.

I saw a blurb in the manual that the LP should not pump too much. I wonder why. Is it not to foam the fuel or push stuff through filters?
I would think as long as its laminar flow no air bubbles too much fuel pumped to the IP would not hurt anything - it would just recirculate. Maybe the fuel manager can't heat more than a certain flow????

Anyone know of something I am missing on too much flow?

As hot as the underhood temps are on the 6.5 and location of the IP and fuel manager I think fuel temperature is too high and could be a source of a few HP performance increase at least in warmer climates.

Comments?

[tom.mcinerney]

H~
The 6.6 DMx has cooler because the higher pressure rail system creates more heat. The cooler is a radiator mounted front of fuel tank.

I've never had probs with fuel above 25*F. The big factors are what is the fuel like? Is it #1, or #2 , does it have additives to prevent gelling?
Below 20*F the fuel is problemmatic if not properly formulated for winter. First it will start run low-power, stall beyond ; if temp/fuel-mix real bad , won't start, or starts, then stalls as filter clogs before fuel heats enough to melt wax crystals.


A knowledeable fuel injection {Bosch/Stanadyne certified, etc.,} rebuilder who drove 6.2s in the '80s , suggested that a small fuel heater might be advisable year round , 'to make it easier' for the injection pump.

If you run continuously at high speed in hot environment, maybe add a small cooler. If you run short haul in north central Sasketchawan (sp?) add a continuous heater.

I run a small liquid/liquid (coolant/fuel) heater the first couple hours operation when ambient temps below 55*F , now , i may not turn it off until next summer. I plumbed it in to allow removal of electric heater from ignition switch load. I have more than twice the OEM filtration so that the warm (low viscosity) fuel is clean , hence not abrasive. I think the fuel tends to run about 110*F, but that's more a guess than measurement...

A loss of density/power/delivery is not a problem for my purposes, but it would be for high output apps. t m.

[damork]

I consistently get an SES code 36 with my 95 when starting in cold temps - especially when temps drop into the teens at the start of the winter season (and stations are still selling some of the thicker (higher viscosity #2) blends.

I mentioned this in the past and there was discussion that it is a failing pump, but I've talked to Stanadyne engineers who have agreed with my theory and ran enough tests to prove to myself that either warmer fuel or switching to #1 either reduces or eliminates the problem.

Fuel from stations that mix #1 & #2 seems to work better than #2 with a bunch of additives. The best combo I've found so far is straight #1 fuel with Stanadyne Performance Blue added to it.

[garre1tt]

My 95 also throws a 36 in cold weather. Once the engine warms up it always clears.

This truck has an aftermarket pre fuel filter heater. It uses antifreeze on its return trip from engine to the radiator. I would not recommend this but it did not seem to hurt.

Moving from Montana to California on many of the grades in S. Oregon and N. Cal. when the coolent temps were getting hot the truck would develope a miss like starved for fuel.

First thought was bad IP but now I wonder if I was just super heating the fuel.

Michael D.