Can fuel get too hot from coolant heat exchanger?

[sedecrem]

I purchased a stock Mercedes fuel heater(connects to coolant hose) on eBay and the previous thread on WVO heaters got me wondering about the installation instructions. The instructions say to install the heater in the hose run from the head to the heater core. It states that this is necessary because "In the summer the car heater is usually turned off at temperatures above 70 degrees, stopping the flow of coolant through the fuel heater as well. This prevents the fuel from being overheated, which could otherwise result in a loss of power." I am sure the instructions are intended for vehicles running on regular diesel rather than SWO/WVO or biodiesel. However, I was under the impression that even with diesel # 2 that higher fuel temperatures would result in more complete combustion because of faster ignition and better spray pattern from the lower viscosity. Also, If the fuel was heated by coolant from a system with a working thermostat, how could it get that much hotter in the summer?

Thanks

Sedecrem

[airbus]

Where do you live? Unless you reside in northern Alaska, you probably won't need a fuel heater for diesel. And even up there it should be sufficient to thin it with kerosene if it's getting really cold.

[sedecrem]

I am in the Sacramento area. I got the fuel heater because I may want to run biodiesel and was also under the impression that in Winter, even in Sacramento, the car would run better with heated fuel.

Thanks

[airbus]

I went to Vermont last week at 7F below and (with a block heater, though) my 300SDL started and ran just fine. A fuel heater is required only if you want to run your car on vegetable oil.

[Matt L]

Originally Posted by airbus

A fuel heater is required only if you want to run your car on vegetable oil.

OM606 comes with one from the factory, and it's not for vegetable oil.

[Old300D]

Fuel heaters for diesel are required in very cold climates, for below -20 degree operation. Even in Alaska when they run pure Kerosene, the fuel can gel below -40 or -50. If you are heating biodiesel you can still install the heater in the heater coolant circuit, but vegetable oil will need heat all the time, at least to get through the filters.

And I can't imagine a fuel heater on all the time would affect how the regular diesel fuel burns. As soon as fuel gets into the injection pump it heats to engine temperature.

[pizzachef]

The fuel is cold when you start the engine, even if the block heater is plugged in, the fuel in the lines and tank are going to be cold until the engine is up to temp. So if the fuel can get too cold to flow or whatever, how is the engine supposed to run until its warm enough to heat the fuel?

[wheelguru]

the 300sdl has a fuel heater already.

[Old300D]

Originally Posted by pizzachef

The fuel is cold when you start the engine, even if the block heater is plugged in, the fuel in the lines and tank are going to be cold until the engine is up to temp. So if the fuel can get too cold to flow or whatever, how is the engine supposed to run until its warm enough to heat the fuel?

In Alaskan winters, you never shut the engine off. Or you can keep the car in a heated garage to start it.

[Mister Byrnzoil]

maybe a better question is... what is the optimal fuel temperature for CI?

I've read on frybrid that Vegoil needs to be 180 degrees F.

I don't know about #2 diesel or BD, but I'd like to.

[sedecrem]

Robert

You make a very good point. It would be usefull to know the optimum temperatures for several fuels. Diesel # 2, Biodiesel, and SVO/WVO. It would seem to me that as long as you did not start vaporizing the fuel in the lines or heat it to the point where it became a fire/saftey issue the hotter the better. Less viscosity at higher temperatures should make for better atomization. and the hotter the fuel the less heat energy it would need to pull out of the air in the combustion chamber to start burning and burn more completely. But, I am new to all of this so it's all just a SWAG on my part.

Best regards to all!

Sedecrem

[Old300D]

My point was that it hardly matters what the fuel temperature is before it hits the IP. It it's hotter than engine temperature, you will shed that heat in the IP, possibly damaging it. If it's colder, the fuel will cool the pump. The fuel will be close to engine temperature when it exits the IP.

There have been folks that rig heaters to the hard lines, after the IP, and that has been shown to improve emissions when burning vegetable oil.

[biobenz240d]

Originally Posted by Mister Byrnzoil

maybe a better question is... what is the optimal fuel temperature for CI?

I've read on frybrid that Vegoil needs to be 180 degrees F.

I don't know about #2 diesel or BD, but I'd like to.

The minimum temp. for WVO to enter the injectors is 160F to prevent coking of the rings and valves. The optimum temp. for biodiesel is 80F to 120F for best fuel economy and power, but will run well down to 60F, with a greater loss of power and economy at and below. Petro diesel will run fine at much lower temps. but will run best at 40F to 100F for best fuel economy and power. Power and economy start to suffer at temps . over 120F. I have put in many hours of testing to arrive at these values, keep in mind that these temps. are recorded at the injector lines prior to entering the injectors, measured with an infrared thermometer.

[psfred]

All 603 and later engines have a thermostatically controlled fuel heater.

Peter

[sedecrem]

Good information guys! Thanks. Sounds like the instructions with the fuel heater were pretty much right on for diesel # 2. A little more help for biodiesel in cool or cold weather, and pretty much heat all of the time for SVO/WVO.

Best Regards

Sedecrem