Usable fuel In Tank?

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Usable fuel In Tank?

November 02, 2022, 07:22:10 pm

Our 99 U270 evidently came with a 149 gallon fuel tank. I figure that at a minimum 30 gallons must be spread across the bottom of the tank even when empty.
Then there is the slosh of fuel going to one side if a road has a camber or hill turn.
There is the issue of the fuel getting too hot as it circulates back to a nearly empty tank.
And the point that the generator starts to run dry.
So the question is what is the lowest usable amount of fuel should be considered as empty when programming silverleaf,?
I was thinking somewhere close to 95 gallons?
Any ideas?
Thanks
David

Re: Usable fuel In Tank?

Reply #1 – November 02, 2022, 07:35:49 pm

David,

95 to 100 will give you the cushion to cover both what is left in the bottom, slosh factor, and the air space that you can't completely fill (unless you turn the coach up on it's side) This should tell you that the tank is empty about the time your generator runs out of fuel.

Mike

Re: Usable fuel In Tank?

Reply #2 – November 02, 2022, 07:40:46 pm

Mike
Thanks for confirming that, it is a huge amount of waisted tank space with the flat bottom across the width of the coach

Re: Usable fuel In Tank?

Reply #3 – November 02, 2022, 07:44:31 pm

David,

On our 320 we have the 200 gal. tank and our Silverleaf is set at 150 gal. That is as close to the "W" on the fuel gage as I want to go. (walk)

Mike

Re: Usable fuel In Tank?

Reply #4 – November 02, 2022, 07:51:40 pm

On our single 150 gallon tank, it's 6 gallons per inch. We only have one filler so I can use an LED to make a visual check for contamination and a tape measure to get an exact amount for fuel in the tank with the coach level.

Since the fuel tank(s) are not out in the breeze like on a big rig, the fuel temperature can exceed the max allowed and since the fuel flows through the engine ECU, it can overheat it and cause early failure. Not good for the injection pump or unit injectors also. This is even more important on the Detroit 2 cycles as the fuel does not go through any lines to the injectors but through passages in the cylinder heads and is designed to remove heat from the engine and send it back to the fuel tank. So, a low fuel tank means a hot fuel tank and hot fuel heading back to the engine. With low fuel, I can't keep my hand on the side of the tank. Some members like Brett have installed a fuel cooler on the return line. Excellent idea.

The generator pickup won't supply any fuel to the generator with the tank below about one quarter tank. It's designed so the generator can't run the tank dry and leave the coach stuck somewhere.

For programming, probably empty at 75% or less of the 150 gallon total so you always have fuel for your generator.

Pierce

Re: Usable fuel In Tank?

Reply #5 – November 02, 2022, 09:35:33 pm

I use 100 gallons on the Silverleaf as empty on my 149 gallon tank.

Re: Usable fuel In Tank?

Reply #6 – November 02, 2022, 09:44:15 pm

I normally fill the tank within about 20 miles of the campground. Putting in 50 gallons each of two days seems to hurt less than putting in 100 gallons. Also, there is less chance for water to get into the fuel.

Re: Usable fuel In Tank?

Reply #7 – November 02, 2022, 09:45:08 pm

Does the Silverleaf give you a percent or number of gallons left? Does it give you a good idea when you fill up how much fuel you will be needing? ie 50% = 75 gallons on a 150 gallon tank.

My coach shows fuel in gallons left. With a 200 gallon tank when totally full it shows 198 gallons. The last trip I took I was down to 55 gallons. Instead of being able to put 143 gallons I was only able to put 105 gallons in. When it is showing around 100 gallons I can only get around 60 gallons in.

Re: Usable fuel In Tank?

Reply #8 – November 02, 2022, 10:26:36 pm

The fuel "gauge" n silverleaf is not connected to the coach gauge. You must set up how many gallons your tank holds, then it subtracts the volume used and tells you how many gallons are still in the tank.
The reason for this thread was that I had adjusted my tank size to read 100 gallons which is what is usable for reasons above.
When you fill your tank you must manually reset the tank gallons on silverleaf so it knows there is fuel there and your "gauge" will be correct

Re: Usable fuel In Tank?

Reply #9 – November 02, 2022, 11:54:45 pm

We have a 195 gal tank but set the Silver leaf to register 150 gallons. We refill when it shows around 90- 100 gallons, then reset the Silverleaf fuel gauge.

Re: Usable fuel In Tank?

Reply #10 – November 03, 2022, 12:04:34 am

I set my 180 gallon tank to 135 on the software.

Re: Usable fuel In Tank?

Reply #11 – November 03, 2022, 05:38:54 am

I found out the hard way that when you get to a 1/4 tank, the generator shuts down. In Texas summer, you don't want this. I wish someone would have told me about this when I was purchasing it. On our inaugural road-trip, I spent almost an hour in a Costco parking lot trying to figure out what was wrong with the generator post fill up before the MOT tech on call confirmed the low fuel behavior. I had to bleed the air from it, not hard but you want to avoid this if possible. I got 115-120 gal from that tank out of the 148.

I'd like to have a larger tank like the 320s, but they have extra that for the aqua hot. I'll change the silver leaf to show a lower tank volume, good suggestion.

Re: Usable fuel In Tank?

Reply #12 – November 03, 2022, 07:18:59 am

I have a 180 gal tank and set the SilverLeaf to 160. I've never taken the SilverLeaf below 30 and the one time I got close this past summer, I did run the generator dry about 20 minutes before we arrived at a campground.

I don't think I have seen a suggestion on what max fuel temp should be. Does anyone have an opinion?

Rich

Re: Usable fuel In Tank?

Reply #13 – November 03, 2022, 07:42:06 am

Diesel fuel starts to vaporize at elevated temperatures and become ignitable with an open flame or spark. The lowest temperature at which the vapor will ignite is the fuel's flash point. Diesel fuel #2 as specified by ASTM D975 has a minimum flash point of 125.6°F. For diesel fuel #1, the minimum flash point is 100°F. (Winter blends of #1 and #2 are allowed to be 100°F minimum as well). If the flash point falls below these values, the fuel becomes potentially unsafe to handle.

Re: Usable fuel In Tank?

Reply #14 – November 03, 2022, 11:02:13 am

Quote from: Rich Bowman – November 03, 2022, 07:18:59 am

I don't think I have seen a suggestion on what max fuel temp should be. Does anyone have an opinion?
Rich

All manufacturers have a maximum fuel temperature listed but I can't remember where it is. Our Pro-Link also reads out the fuel temp. It's not only to avoid injection pump damage but if your fuel goes through the ECU to cool it like ours does, this is another big reason to have it cool. Big rigs just don't have this potential problem with the tanks located outside.

Pierce

Re: Usable fuel In Tank?

Reply #15 – November 03, 2022, 02:38:03 pm

So at what point does it start to threaten our ECUs?

Rich

Re: Usable fuel In Tank?

Reply #16 – November 03, 2022, 04:31:28 pm

Quote from: Rich Bowman – November 03, 2022, 02:38:03 pm

So at what point does it start to threaten our ECUs?
Rich

Use your engine model and year and look it up online. Lots of info but here are a few considerations:

Quote:
Why is There a Temperature Limit?
There are many reasons why the fuel temperature needs to be limited:
1. Modern HSDI engines for passenger cars are designed for operation at an optimum fuel temperature of 45 oC.
2. Increased temperature reduces the density of the diesel fuel. Since a constant volume of fuel is injected on each stroke, the reduced density means that a smaller mass of fuel is available to be burned, affecting the stoichiometry of combustion and also reducing engine power.
3. Increased temperature reduces the viscosity of the diesel fuel. The reduced viscosity increases the leakage flow past the pistons of the injection pump, which increases the drive power and pumped volume of the injection pump.
4. Increased temperature increases the bulk compressibility of the fuel. The pump must therefore do more work to pressurize the fuel at a higher temperature. It also affects the pressure wave dynamics.
5. A limit exists on the fuel tank temperature due to the use of plastics. As well, other material compatibility conflicts arise with the use of elastomers.
6. Fuel lubricity is reduced at elevated temperatures. This is very harmful as the fuel itself is used to lubricate the injection pump.
7. There is also incorporated integrated electronic circuit chips onto injection pumps, which must be cooled below their 120 °C limit.
8. Due to the extremely precise and small volume of fuel per injection event, each injector must supply the same volume of fuel at the same temperature.
End Quote

Start your search here:

do you need a fuel cooler for diesel engines - Google Search

Pierce

Re: Usable fuel In Tank?

Reply #17 – November 03, 2022, 08:04:28 pm

Just out of curiosity, is the SilverLeaf temp data taken on the input from the tank to the engine, somewhere in the engine flow path, or somewhere on the return to the tank, or at the tank?

Is the stock fuel cooler on the supply or return side of the plumbing?

Rich

Re: Usable fuel In Tank?

Reply #18 – November 03, 2022, 08:16:34 pm

Quote from: Rich Bowman – November 03, 2022, 08:04:28 pm

Just out of curiosity, is the SilverLeaf temp data taken on the input from the tank to the engine, somewhere in the engine flow path, or somewhere on the return to the tank, or at the tank?
Is the stock fuel cooler on the supply or return side of the plumbing?
Rich

Ours on the U300 comes from the DDEC ECU and is read by the ProLink.

No cooler on our coach. Should be on the return side.

Pierce

Re: Usable fuel In Tank?

Reply #19 – November 04, 2022, 06:51:45 am

Thanks. So the fuel in the tank should probably be a little cooler than the reading on the SilverLeaf.

Rich

Re: Usable fuel In Tank?

Reply #20 – November 04, 2022, 09:40:02 am

The hottest fuel temp I've seen on the SilverLeaf is 144º. This was at the end of a very hot day.

I fill up at half a tank in hot weather just to keep the temps down. Doesn't seem to work that well. It does drop the temp 20º to 30º but it's back up in the 140s in less than an hour.

Has anyone installed a fuel cooler on a 6v92? I've given it thought but don't know where the return fuel line comes off the engine.

see ya
ken

Re: Usable fuel In Tank?

Reply #21 – November 07, 2022, 05:45:20 pm

Quote from: Jason – November 03, 2022, 05:38:54 am

I found out the hard way that when you get to a 1/4 tank, the generator shuts down.

Generator fuel pick-up on the fuel tank is higher than coach engine pick-up so the generator use doesn't leave you without the ability to drive away...

Re: Usable fuel In Tank?

Reply #22 – November 07, 2022, 06:27:31 pm

But never believe the dash fuel gauge. A good way would be to have the coach level with a low tank, run the generator until it stopped and then dip the tank allowing 6 gallons per inch.

Pierce

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