Sunday, January 03, 2010

Small tank = warm diesel

Since I drive short distances and don't always switch over to SVO on these short trips I've noticed that the diesel fuel tends to get warm. I think this is because of the small 4.5 gallon doughnut tank and the fact that the fueled is warmed by the engine (via the return loop). Since my trips are short I tend to drive on the smaller tank for longer than what it was meant for - the idea of the tank is you switch over as soon as you can for the longer drive on VO. As stated my drives are short.

The other issue that complicates this is that as I drive over the course of the week the quantity of fuel is reduced (obviously) but that makes it run hotter as there is less fuel to be heated and recirculated.

I generally refill the doughnut tank once a week and it usually takes about 2.5 - 3 galllons irregardless of how many miles I drive - because on the longer trips I switch to veggie.

On most drives it seems to balance out in the the sense that if it is a longer drive I will switch over before the diesel gets too hot. It's the shorter trips that become longer - more or less local errands- that aren't practical to switch over for because of the loss of fuel through purging.

I don't know offhand what the diesel temperature gets to but on the VegControl I can see it rising because I placed the fuel temp sender in the return line so it reads the temperature for both diesel & VO.

UPDATE: I noticed today that for my 7.5 mile drive home that is about 20% freeway and 80% surface streets that the coolant made it to 170ish degrees and the diesel made it to 104ish with an outside temperature at night of approx 64 degrees