Bad news - the switchover times on this car are quite lengthy. This appears to be due to the common rail being thermally tied to the engine's head. With ambient temps at about 70*F, it takes me 11 miles / 20 minutes to get the returning diesel fuel temps up to 140*F. The coolant is at full temperature at about 4-5 minutes, but the entire engine takes much longer to heat up.
A block heater or some type of aux 120v coolant heater should help, and that's my plan of action going forward.
Wednesday, June 18, 2008
Monday, June 16, 2008
Valves replaced
I took out the experimental valve set I had installed that was leaking quite a bit (41ml/min on the return side) and replaced it with a set of boring old Hydraforce SV-10s. The leakage rate is much lower (5ml/min on the return side), thank goodness. This means I can finally run WVO with getting huge amounts of cross-contamination.
One thing I've noticed is it does take a *long* time for this car to get up to temperature, at least fuel wise. The coolant temp can be up around 165*F or so while the fuel coming out of the common rail is around 110*F. If I keep driving around the fuel coming out of the common rail eventually gets to around 175*F, but it takes a while. Switching to heated VO does NOT make the fuel temps coming out of the common rail increase faster.
The conclusion is that the common rail fuel temperatures depend mostly not upon the fuel input temperatures, but rather upon how heat-soaked the head and rail are. This, of course, does not negate the need for heating the fuel before it enters the high pressure common rail fuel pump, but it does mean a much longer wait before a safe switchover can be made. I imagine this is true with most or all common-rail based vehicles.
To counteract this I'm going to purchase and install a block heater and put it on a timer, even in the summer. This should (hopefully) shorten my switchover distances.
I'm also going to update the controller logic so it is more suitable for common rail based vehicles. This update will mean that the controller will only switch when coolant AND fuel temperatures reach certain points. I'll most more on the controller software update in the weeks to come.
One thing I've noticed is it does take a *long* time for this car to get up to temperature, at least fuel wise. The coolant temp can be up around 165*F or so while the fuel coming out of the common rail is around 110*F. If I keep driving around the fuel coming out of the common rail eventually gets to around 175*F, but it takes a while. Switching to heated VO does NOT make the fuel temps coming out of the common rail increase faster.
The conclusion is that the common rail fuel temperatures depend mostly not upon the fuel input temperatures, but rather upon how heat-soaked the head and rail are. This, of course, does not negate the need for heating the fuel before it enters the high pressure common rail fuel pump, but it does mean a much longer wait before a safe switchover can be made. I imagine this is true with most or all common-rail based vehicles.
To counteract this I'm going to purchase and install a block heater and put it on a timer, even in the summer. This should (hopefully) shorten my switchover distances.
I'm also going to update the controller logic so it is more suitable for common rail based vehicles. This update will mean that the controller will only switch when coolant AND fuel temperatures reach certain points. I'll most more on the controller software update in the weeks to come.
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