Twin tanking.

[Rotary-Motion]

I'm not, because.......
Although my engine (smiley transit) is a direct injection, this particular engine, a York, doesn't have the same tendency to suffer from ring gumming.
The main reason to run twin tank is to mitigate the risk of ring gumming in a direct injection engine.

At some point, in the imaginary future, I'm going to twin tank, and have the second tank heated, to help with winter running of veg and bio.

not sure about veg tank heating or not??? I have never had a problem there so to me seems a lot of expense and time and a pain in rear to fit. when for me not needed. don't forget the fuel is running round in a loop it picks up from the sender unit and dumps back to the sender unit, the sender unit is usually from my experience located in tank in another plastic housing localizing the warm veg return so in an effect the fuel is running in a loop (vented no air locks - standard) so dumped warm return fuel is being sucked back up again! this seems to me enough to keep tank oil warm enough for even the coldest winters, and after all its only the veg just before the injection pump that needs to be hot when going in to be used.

this leads onto the cold start veg being on very cold days thicker than normal and harder to pull through the pipes, for this I don't use original pipes on main veg tank (original van tank) mine are uprated to 8mm ID. also depends if your fuel tank is plastic or metal I guess plastic being more sympathetic and not get as cold and quicker to heat up...

rather than heated tank, insulated fuel in and return pipes maybe better, although I don't have this.

[Rotary-Motion]

Who, Me?
Voice activated, ha ha ha.
Sorry.........

I'd just have switches, changing over three way valves, to change the fuel source. I'd have the veg oil in an insulated tank, and pump it through a FPHE. No need to go very hot. 40c would be fine, IMO. It would stay hot for days like that, even in the winter, I think.
I'd have all the gubbins in the back of the van, rather than under the bonnet, and run the pipes through the cab.

all under the bonnet is tidier I think except aux tank although people do use a water header tank under bonnet for a small amount of startup diesel, mine is set to 40c to switch but soon rises to 80/85c while fully running/driving.

60c veg in my shed tank insulated (160 ltrs) stays warm into the third day, 4th day back to normal near enough, plus no wind chill in the shed a van would have this to add to cooling

the main FPHE needs to be as close to IP as possible I think on the pipework I only have a short run of pipe so less heat loss when oil is leaving FPHE and hitting IP (6 inch of rubber pipe) which you could insulate but I don't need it.

[Rotary-Motion]

So what would be your ultimate wish list control system?

FULLY automatic would be nice I say fully as the car doesn't know when you will be stopping to purge out...

can be done but way to much hassle for what its worth

[Rotary-Motion]

Had to Google PMSL.

So ...

Switch valves when fuel temp reaches a preset temp.  (where would you measure the temp?) From my little knowledge they need switching back in time for the engine to stop on diesel.

Monitor/display oil tank temp and ... control a water valve?  Any other temperatures useful?  Ambient?

Any trace heating required?

my relay/temp controller part has its probe on the FPHE

[Rotary-Motion]

I'd just have the temp gauge in the second tank. If I was really getting sophisticated, I guess I could rig a thermostat to the pump, that takes it around the FPHE, instead of a switch.
Even better would be have it so the pump only comes on when the coolant is up to temp.
I'd jsut have to remember to purge with diesel a mile or so from home.
What usually happens with my best plans and ideas, is that it ends up cobbled together with binder twine and duct tape.........

in the past I have wired a buzzer to the twin tank system, if I haven't purged and I open the driver door buzzer goes off (live or neg) taken from interior light switch in door frame

[Rotary-Motion]

Temperature is really secondary to the fact.

What I'd want to see is a measurement of viscosity, along with fuel pressure of diesel, pressure of veg, pressure at IP inlet, filter differential pressure, and engine coolant temperature.

I'd want it to automatically switch to veg when viscosity gets within a certain band, and I'd want it to blend it in slowly to allow the IP to warm up with the warm fuel.

In fact, I'd probably redesign the plumbing a bit and have the heat exchanger in the looped fuel return with a proportional valve on it to be able to regulate the temperature/viscosity of the fuel going around the loop.

mine blends it, starts on diesel so pump and lines and injectors have diesel in them and as the veg comes in mixes with veg gradually changing from diesel to 100% veg, so no hard shocks...

also IP gets warmer as engine runs anyway

[Julian]

The reason I'm asking is that having seen what the Arduino board on the printer is capable of, I've bought a spare to play with.

Many sensors can be had VERY cheaply and getting a load of sensors to interact and give outputs is no significant cost beyond the cost of the controller as it a matter of writing code (sounds easy!!!).  Arduino mega boards can be had for around a tenner, but other versions can be as little as five quid.  Multi line LCD displays can also be had quite cheaply.

Thermistors for temperature weigh in at a few pence each.  There are numerous other sensors available which could be employed ie a sonic distance sensor could, in theory, monitor tank level but I doubt it's suitable for the duty.

Unfortunately I haven't seen any cheap viscosity or suitable pressure sensors.  Do you know of any, James?  I can see that monitoring viscosity makes sense, but I'd have thought the viscosity/temperature relationship was quite uniform in our simplestic world.  I guess at the end of the day as far as the controller is concerned, it's just an input so, as far a writing the code is concerned i makes no difference, the input pin just needs setting to the appropriate signal.

The biggest problem, as has been pointed, out is purging the system.  Arduinos will accept a signal from a GPS module and could be programmed to automatically switch within a certain radius of a "home" location.  Great for inbound journeys, but would require lat and long coordinates for each outbound.  Anyway, the cost of a GPS module, although cheap for what it does, is high compared to the other components.

I may never build a working version, perhaps only a prototype, but just want a project to play with, the main aim being to learn a little in the process.

Thinking on this purging business, when I've pulled IPs appart in the past, I was surprised at the volume of fuel they held ... probably about ½ a litre at a guess.  Is the considered opinion that this volume, along with all the interconnecting pipe work needs to be purged?

[julianf]

Legal issues aside, with a twin filter setup, the car could just be idled for x time before stopping to purge.

[Julian]

What about forcing a purge through the IP with a pump ... would mean drilling and tapping the IP casing if there's a convenient point, but a back flow of pure diesel to the oil tank might only take a few seconds.

[Head Womble]

What about forcing a purge through the IP with a pump ... would mean drilling and tapping the IP casing if there's a convenient point, but a back flow of pure diesel to the oil tank might only take a few seconds.

This may protect the pump, but would not protect DI engines against ring gumming.

Think about a turbo timer, these keep the engine running for a while after the ignition has been turned off.
If this function could be added to the controller it could be used for purging, thus completely automatic.

[Julian]

What about forcing a purge through the IP with a pump ... would mean drilling and tapping the IP casing if there's a convenient point, but a back flow of pure diesel to the oil tank might only take a few seconds.

This may protect the pump, but would not protect DI engines against ring gumming.

Think about a turbo timer, these keep the engine running for a while after the ignition has been turned off.
If this function could be added to the controller it could be used for purging, thus completely automatic.

I say easy (won't be for me), but theoretically it would be easy as far as the controller is concerned, just an input from the ignition switch and an out put delayed by time, temp, viscosity, whatever.  Making that work with the vehicle's system might be another matter.

Do vehicles have delays built in when they are turned off ... I'd have thought there may have been safety issues?

[therecklessengineer]

Unfortunately I haven't seen any cheap viscosity or suitable pressure sensors.  Do you know of any, James?  I can see that monitoring viscosity makes sense, but I'd have thought the viscosity/temperature relationship was quite uniform in our simplestic world. 

Sadly not. Viscocity sensors are pretty hard to come by. There are a few pressure sensors around that would probably do the job - "MPX pressure sensor" in eBay turns up a number of hits. They're designed for air, so you'd need some sort of isolation diaphragm.

Really, my last post was just splurting out what I'd like in an ideal world.

[Head Womble]

What about forcing a purge through the IP with a pump ... would mean drilling and tapping the IP casing if there's a convenient point, but a back flow of pure diesel to the oil tank might only take a few seconds.

This may protect the pump, but would not protect DI engines against ring gumming.

Think about a turbo timer, these keep the engine running for a while after the ignition has been turned off.
If this function could be added to the controller it could be used for purging, thus completely automatic.

I say easy (won't be for me), but theoretically it would be easy as far as the controller is concerned, just an input from the ignition switch and an out put delayed by time, temp, viscosity, whatever.  Making that work with the vehicle's system might be another matter.

Do vehicles have delays built in when they are turned off ... I'd have thought there may have been safety issues?

On older cars a delay would not be hard, modern common rail engines may be a different mater though.

Safety issues are something that would need to be taken into account.
Something like my old merc would be fine as being an electronically controlled auto you could not take it out of park without the ignition being on.
On the other hand it had a vacuum controlled stop solenoid so not so easy there.

[Julian]

Unfortunately I haven't seen any cheap viscosity or suitable pressure sensors.  Do you know of any, James?  I can see that monitoring viscosity makes sense, but I'd have thought the viscosity/temperature relationship was quite uniform in our simplestic world. 

Sadly not. Viscocity sensors are pretty hard to come by. There are a few pressure sensors around that would probably do the job - "MPX pressure sensor" in eBay turns up a number of hits. They're designed for air, so you'd need some sort of isolation diaphragm.

Really, my last post was just splurting out what I'd like in an ideal world.

I understood it was an "ultimate" wish, and probably not economically viable.  But all input is valid, very often an unattainable idea sparks other ideas which are.

One place I worked at we occasionally had what we called a "silly half hour" down the pub.  Suppose they call it brain storming these days, but we just used to throw stupid ideas around about the products and go off on tangents.  Amazingly one or two really good ideas sprung out of this nonsense.

Would pressure against an orifice plate equate to viscosity?

[therecklessengineer]

Would pressure against an orifice plate equate to viscosity?

Yes, but it also depends on flow rate. So unless you've got an accurate measure of that, your viscosity maths will be out.

I suppose it wouldn't actually need to be normalised or calibrated. You could just use diesel flowing through the orifice as your base line and use it as a point to aim for.