AFN Engine running veg oil http://homepage.ntlworld.com/c.caldow/Elsbett/ another interesting website http://www.brevardbiodiesel.org/Elsbett/Elsbett.htm
Well, someone has to be first I like the idea of having heat available before the engine has warmed up. Less strain on the pump and faster warmup? Tricky if the battery is low, but that's an easy problem to solve, IMO. Bought one!
I was wondering, would heating the fuel help with combustion efficiency generally - maybe get a more complete burn, if the fuel has less cooling effect (although probably minor) when it hits the hot cylinder? Any benefit on doing this in a car running regular fossil diesel - might help atomisation and prolong the life of the pump? I'm wondering about this, because I think my car does better MPG in the summer than the winter - could be explained by colder, denser air that the car is having to push through, but I wonder if it's better combustion from warmer fuel as well? Anyway, I'll report back if I see any improvement in MPG when I start running fuel heaters. Been getting about 47-48mpg on fossil diesel in the winter. Was 49-50 in the summer. Too early to tell on bio blend.
Most modern, and semi-modern (i.e. ecu driven) diesels will compensate for fuel temperature through injection timing. As the fuel warms the injection retards. This might have an effect on performance, and thus economy.
Yep, that's why you need to wait for it to warm up before you check the timing in VAGCOM. To put it another way, they run more advance when cold, so maybe this is to allow the cold fuel a little more time to hit the cylinder, warm up, and ignite. Is the fuel temp sender in the fuel pump assembly, I wonder? - I'm thinking that warmer fuel would help quicker warmup, but if the fuel is ignited too quickly due to being warmer than expected, this could potentially cause pinking, but if the sensor is in the pump then the ECU can allow for that based on what it gets from the sensors. Had the opposite problem this morning. The combination of a cold morning and a fresh fill of fuel - around 20% veg - meant that the car really struggled to start, and was very sluggish on warm-up. I'm guessing this is due to cold veg oil settling in the bottom of the tank. I started wiring in the glow-plug type fuel heater last night, but didn't get it finished. I think I'd better get that done tonight if I want to keep the car running as the weather gets colder. I'm placing that heater in the feed pipe, just after the fuel filter, to quickly warm the fuel before it gets to the pump. The instructions suggested it should be before the fuel filter, but I think it's going to take a fair bit of time to feed warmer fuel to the pump, on that basis.
Done some more thinking on this... I think the best solution is a hybrid approach. 1. A coolant/fuel heat exchanger just before the fuel filter, or wrapped around it as per Brooky's suggestion (tricky on the audi, as it's in a metal case with a foam lining, so would tend to insulate it.) 2. An electric heater between the filter and the pump, for initial start up and warm up heating. I was thinking of putting in a relay based timer to switch off the electric heater, but once the engine is warm, the extra heat from the coolant should mean that it tends to shut off using the thermal cutoff on it. I'll have a switch on the dash, but even if I forget to switch it off when up to temp, it should tend not to run the electric one much anyway. Advantages of the dual heater system should be: - Fast heat from the electric heater for startup. - Residual heat of fuel in the fuel filter hopefully stays warm overnight, meaning there's only a 'total cold start' if the car hasn't been used for over a day. - Reduced use of electric heater should extend the life of the glow plug that fires it. If I get a chance, I'll draw up a diagram to show what I'm on about.
Fitted the glow plug powered heater tonight. It gets bloomin' hot, so hopefully it'll do some good, but without setting fire to the fuel lines I've installed it on a temporary basis for now. I need to think a bit more about the layout in the bay, once I know what other heater to install. Following on from some of the chat earlier in the thread, I'm thinking of wrapping copper pipe round the downpipe, use that to heat water from the coolant return pipe to the expansion tank, and use that in turn, to heat the fuel via a heat exchanger. The thought of wrapping fuel pipes round the downpipe is a bit too risky, I reckon, but wrapping a water pipe round the downpipe will get heat early in the engine warmup cycle. It is a bit of a long route round the engine bay though, so I'm going to have another think before I do anything.
After a long night and day stood in the freezing cold, I ran the fuel heater for 30 seconds before starting, and cycled the glow plugs 3 times. Started after about 5 cycles of the engine, compared to taking about a minute on Tuesday. It idled happier and pulled much more smoothly on warmup. I ran the heater most of the way to and from the 10 mile trip to the man cave. It seems to run a lot smoother too, with the warmer fuel. When I got there the clear fuel pipes were warm to the touch, but not hot. Seems to make a difference so far, but it needs a bit more use to get a better feel for it. It's properly cold today as well, and I'm on the train to the London office, so I'll try it again tomorrow after sitting for 30+ hours.
Not sure if trying to leach heat from the exhaust downpipe will work - sure it probably warms up fairly quick, but it also gets a lot hotter than is useful for water heating - you'll need a way of moderating the heat transfer into the coolant water - I think you may end up boiling it. If you want a warm start in the morning and you have mains handy, consider investing in a block-heater (kenlowe or similar)*. Combine this with your coolant-fuel heat exchanger and I think you'll be on a winner - until it gets so cold the fuel solidifies in the tank You may want to work out a bypass mechanism for the temperature sensor on the glow-plug control circuit, a warm block might convince the glow plugs not to fire. edit: fairly sure the fuel temperature sensor is in the injection pump
I don't have mains power to the car at home, unfortunately, and that doesn't necessarily work if you're away from home. So far the simple glow-plug heater in the fuel line is working fine. I do need to add a coolant type heater to avoid running the electric one full time, but there's not actually an easy place to 'tap in' on the Audi, other than the small pipe that runs back to the expansion tank, and there are a couple of issues with that option. - It doesn't flow a lot of coolant, so doesn't warm up very quickly. In fact, it doesn't seem to flow any coolant when the engine is cold - maybe only used when the thermostat is open. - The route to run coolant to a heater just before the fuel filter, or around the fuel filter, goes right across the engine bay. I'm wondering if a simple solution is just to extend the bracket to move the fuel filter closer to the engine, so it gets a bit more heat soak from the block (note, I'm not talking about strapping it to the exhaust manifold here) - OR... thinking about how air cooled VW and Porsche heat exchangers work, just take some ducting from the downpipe up to the fuel filter to warm it up from exhaust heat.... a thin casing around the downpipe would trap the heat... if I use the lower part of the downpipe then it should rise up towards the fuel filter without any sort of fan assistance.... Maybe I need to play about with some old bits of exhaust boxes and ducting. There's a bit of room around the downpipe in the audi. Downside would be higher engine bay temps in the summer - maybe? I probably need to have a closer look at the pipework out of the back of the head/ block that goes to the heater, and figure out where I can get a T-piece into it. With the longitudinal engine, there's not a lot of room in that area, and only short runs of pipe to play with. The heater connections on the bulkhead are probably the best bet If the fuel goes solid in the tank, I'm knackered anyway! Hopefully I'll be OK at 20%, even up in the Highlands over Xmas. I don't fancy lighting a fire under a plastic fuel tank!!
Your best bet for a coolant heater would be in series with the cabin heater matrix - this is a non-optional part of the heating loop- unlike the radiator, and not a one way overflow, like the expansion tank. It'll have to go in series, otherwise you may end up loosing any flow through the heater matrix. Personally I'm wary of relying on the starting battery for axillary purposes, especially when the engine isn't running - if you're battery is healthy and over-specified then you're minimizing the risk, but you're not really going to know until it turns -12 and you're suddenly trying to crank a mostly cold engine with half the current you're used to. Instead of an electricity driven water heater, have you considered a diesel fired one? I guess it depends how deep your pockets are though.. Your exhaust heating scheme sound more feasible, it's a common setup on smaller cross-flow petrol engines to warm the intake air - my old polo had this arrangement, as well as a bizarre pair of exhaust ports on the inlet manifold for heating that as well. I don't know how much heat you'd actually transfer - I'd be tempted for a fully ducted approach, driven perhaps with a forward mounting ram-air style intake, and some form of veined heat-exchanger around the fuel filter to maximise heat transfer.
Yep... was looking at the heater connections for those reasons. Lots of flow, open all the time for faster cabin heating in the morning. The electric heater is on a switch. If the starter struggles then the option is there to switch it off. It's just one extra glow plug though, at the end of the day. After 4 days, the little electric fuel heater is definitely helping - it's easy to start, drives better on warmup, smoother on light throttle, and I reckon it pulls better as well. I reckon this is a winner, but I still want to add a coolant option to take over as it warms up.
Phatty has just fitted a Eberspacher D5W Diesel powered wate heater to his T4 to heat the van when camping , it heats the coolant so the blowers can be run with the engine off, but also preheats the engine etc also in winter i run 95/5 mix SVO 95% and 5% petrol plus 100ml of veggie boost. i got a barrel of svo out this morning and it was like jelly in the freezing temperature , added the petrol and it was as thin as standard diesel.
How much or how quickly does the fuel settle out if the car's been sat still. I was wondering if the reason I had the starting problem was because it hadn't done enough miles to mix properly (10 miles since fill up) or if it was because the veg oil settles out to the bottom of the tank... so if you mix in petrol does it stay mixed or separate if the van is left standing for a while?
Totally mis-read the above: also in winter i run 95/5 mix SVO 95% and 5% petrol plus 100ml of veggiemite wonder how that'll run? lol
yes it will run great, it will just wear the seals out at some point if it hasn't got Viton ones fitted.
