Anyone using injector line heaters?

[Gen-Erix Senior Member Find all posts View Profile Close Gen-Erix]

Re: Anyone using injector line heaters?

Hello, Im in Hawaii where the temp never falls below 60F (15C). Im planning to get a old Mercedes 300 and outfitting it with injector heaters and a fuel filter heater. Im eager to learn but am still learning about the process so talk slow and simple from time to time. So far I have found this info:


The nichrome wire used in fattywagans heaters was 316 stainless steel 30 inches long, 76.20 centimeters long. .031 inches dia for 80 watt heaters, .035 inches dia for 100 watt heaters.


1. I want it to function at 200F (93C) which seems to be a good temperature. What would I do to make it stay at 200F instead of going up to 2000F (1093C) Fuse, Temp Regulator, Thermistor?

BUT...
Quote: "the acrevo study does recommend 302F (150C) for canola oil for it to atomize similar to petro"


2. Ive seen kits that were already insulated with some sort of wrap. What is that?


3. What about injector lines cracking?
(at 150deg C, the issue I have is that the existing fuel lines are not manufactured for such extremes and, such rapid heating (and cooling) could lead (and has with some) to the fuel lines cracking.)


4. What about a second battery for the heaters?
How would I wire that up? Especially if I do some minor audio improvements as well.

[Vegiecars Member Find all posts View Profile Close Vegiecars]

Re: Anyone using injector line heaters?

1. I want it to function at 200F (93C) which seems to be a good temperature. What would I do to make it stay at 200F instead of going up to 2000F (1093C) Fuse, Temp Regulator, Thermistor?

I had a similar problem and so installed a thermoswitch to turn it off at 90 deg. This allowed me to make the elements shorter which therefore heat up quickly and are easier to install. Now, it may be difficult to get the thermoswitch to properly measure the temperature of the heating element as it is only in contact over a small part of the surface area of the switch, so we wrap the section with pure copper tape to conduct this heat over a greater surface area.

2. I've seen kits that were already insulated with some sort of wrap. What is that?

The elements that we make up are a nichrome wire in a very thin silicone coated fibreglass sleeve. It wasn't easy to get! The Fatty Wagons system used a bulky fibreglass sleeve that tended to thermally insulate the wire and therefore took a long time to transfer the heat to the injector line.
We then cover this with a high temperature split sleeve tubing (loom tube) and coat that in a high temperature fire retarded lagging for thermal insulation.

3. What about injector lines cracking?
(at 150deg C, the issue I have is that the existing fuel lines are not manufactured for such extremes and, such rapid heating (and cooling) could lead (and has with some) to the fuel lines cracking.)

None of my customers have reported this problem, as we are not heating them to such extremes of temperature. If you were to heat the oil to such extremes you may end up with impurities in the fuel building up on the walls of the injector line, so it's best to not overheat the oil.

I Have heard of lines cracking under the "old" system due to the excessive temperatures that were achieved. I measured over 180 deg C under the "old" system.

4. What about a second battery for the heaters?
How would I wire that up? Especially if I do some minor audio improvements as well.

The injector line heating elements that we make up use 2 amp per cylinder when they are on, which is less than half of the time, so a second battery is only necessary if you intend to start the engine from cold, in which case you are likely to want top preheat the injector lines, the fuel before the IP (maybe the IP itself) and the filter. This will draw significant load from the battery and is not the most reliable system to employ, although should be fine in Hawaii with a non- direct injection engine.

The easiest way is to just set up a second battery where there is space, and run a positive line to it from your existing battery. You can purchase an isolating kit from your local automotive parts shop.

Regards
Marcus

[Gen-Erix Senior Member Find all posts View Profile Close Gen-Erix]

Re: Anyone using injector line heaters?

My plan is to use:
fuel injector heaters
fuel filter heater
12v fuel pump


I just wanted to add that once the system is up and running
I would be starting with a 50/50 mixture of wvo/petro-diesel
and working from there (not pure WVO) although I would be
cold starting on that mixture


(currently the indoor temperature reads 75F with no heater/air conditioner)

[Vegiecars Member Find all posts View Profile Close Vegiecars]

Re: Anyone using injector line heaters?

Cold starts are not recommended for Direct Injection motors due to many factors, the main being coking and glazing in the cylinder bore. Pre-heating the oil before starting will help to resolve these issues but may not resolve them altogether as the engine is cold. Having said that, I operate my Direct Injection engine as a no purge system, but ensure that the fuel is well heated both at the injectors and before the IP prior to starting, and so far haven't had any problems. I do believe that the odd long trip from time to time will help to give the system a good clean out.

What is the vehicle that your intending to convert?

[zigparacingtadpole Senior Member Find all posts View Profile Close zigparacingtadpole]

Re: Anyone using injector line heaters?

G'day Bryan,

As you are using a two tank system I dont percieve a second battery to be necessary as you dont start the car cold on veg oil. At the time you switch over the oil should be up to or close to operating temp, which means that the battery should be being charged by the alternator and replenishing what the start took out of it. The draw of the heaters you have is similar to having the low beam lights on, not a huge problem. You have a huge battery and reasonable size alternator fitted.
The idea of using a thermal switch to control the turn on turn off points is a good one.
If you need help wiring the heaters up I can help you, but you will have to wait a couple of weeks as work has me sitting out the next couple of weeks on Groote Eylandt.
I also think there are some gains to be had by improving the transfer of heat from the heater hoses into the veg fuel line.

[Gen-Erix Senior Member Find all posts View Profile Close Gen-Erix]

Re: Anyone using injector line heaters?

If you are planning on running a 50% blend, you don't need any heating at all. On a 300D in the climate you describe, this is the easiest and most hassel free veg system for you to run. I have been running a 10-20% Unleaded blend in my 300D with no problems at all.

You have to remember, with a blend you have already thinned the oil. The biggest advantage to heating the fuel on these cars is to thin it to make it easier to get through the filters. Once the car has warmed up, it will have to go through the hot fuel pump and then the hot injector pump before it even gets to the injector lines. Once it hits the injectors sunk in the head, No matter what temp the oil is before it gets there, it will instantly assume the temp of the injectors and that is it. After half an hour of running, the fuel tank in my car has also been significantly warmed by the return fuel.



I would love to see injector line heaters get the temp to 150oC on a cold running engine! They would be pulling some significant current to accomplish that!

You could heat the oil to 1000oC to make it atomise like Dino Diesel but once it hits the head sitting at 80-90oC or whatever, you will be lucky if it sprays through the injectors at more than a degree or 2 above the head temp. As such, I would suggest that you would be a lot better off with just a coolant heater and that is not nessacary for a 50% blend anyway.



I see this question posted all the time about injection line heaters but it is just not a practical concern. Often the question seems to be answered by people with little apparent knowledge of Automotive electrics and as such, they give very misleading and incorrect answers.

Where are you going to put a 2nd Battery in a 300D anyway?
Only place I could think of would be the boot and then you are going to have to run a heavy, double insulated cable back to the main battery or wire in an isolator system and use this to feed the line heaters. Big job ( and frought with danger if your not savvy and understand car wireing) and totally unessecary.

If as suggested previously, you are going to run heaters that pull 2 A each, that is only 10 amp total. The batteries in diesel cars are usually more like truck batteries than the Flashlight size batteries some small cars have. My own merc has a 55amp alternator which was standard, and a battery that puts out 800 cold cranking amps and has a reserve capacity of 150 Minutes. This means the battery will supply a 25Amp load for 2 1/2 Hours!! Putting an extra 10 amp load on it for even half an hour isn't going to put enough of a dent in the charge level to make 1 iota of difference. You could triple or quadruple the load and run it 30 minutes and it still wouldn't make any difference to normal starting where you are going to be lucky to crank the engine for more than 10 Seconds.

I have calculated that if you turn everything on in a stock 300D ( lights, Wipers demister, fan blower etc) you still have capacity on the alternator charge rate to spare. If you are going to add a " Normal" type sound system, it still wouldn't make a scrap of Difference.

Instead of the impracticality of adding in a second battery, Just make sure you have a good large battery in the first place. The biggest battery you can get here is around 200 of our dollars which is going to be heaps cheaper than a decent second battery, an isolator and all the wiring and bits and pieces you will need to set it up without causing your car to catch fire. I imagine the pricing will be proportionally similar in your part of the world and installing a large single battery is still your best soloution. If you want a bit of extra margin on the alternator, the standard Bosch types of around 80Amps would be more than overkill and easy to get anywhere I imagine.

I have gone in to a lot of detail on this to clear up a few misconceptions but I would suggest that line and filter heaters in your climate are a waste of time. If you were really pedantic about heating the fuel, you would be far better off with a run of the mill coolant type heater such as the one Mercedes made as original equipment for these cars or the much used flat plate type.

It has been stated by several members that using a fuel pump is completely unessacary on a Mercedes as the stock pump is recognised as being stronger than any electric pump available on veg oil.

In practacality, you are going to a lot of extra and unnessacary trouble with your planned setup. Mix the blend, pour it in and drive around happily.

you have a lot of good info there
thank you

let me add more stuff
(im sure ill be glad i did)

i was going to start on a 50/50 mix but then I was going to gradually increase the amount of wvo and see what happens.
with my fingers crossed i hope to get to about 75% wvo. (or more)
I just want the injectors/fuel filter heaters to make sure that blend gets heated.

(especially since Hawaii is relatively small, and I hardly ever drive more than 30 miles at a time)

(another reason why I chose the heater method as opposed to a dual tank or a fuel exchanger as
by the time everything is heated up "Coolant-wise", Id be shutting down and going in the house)


regarding the fuel pump. like i mentioned above, i plan to gradually increase the amount of SVO. (hopefully this makes any sense) ?


and regarding the battery. the injector/fuel filter heaters I have been looking into to, draw about 16 amps total.
Plus ill no doubt be upgrading the stock deck, all speakers, and possibly adding an amp+sub.
Do you think the stock battery would be able to handle the load?
(what about getting a more powerful battery? optima/etc?)


thanks again
I look forward to learning more!

[zigparacingtadpole Senior Member Find all posts View Profile Close zigparacingtadpole]

Re: Anyone using injector line heaters?

Guys please stop obsessing about the size of batteries. The size of the battery is only relevant in so far as it must be able to run the vehicle as the maker intended. The size of the charging system is more important. To illustrate, if your vehicle sucks 100Amps from the battery, and your charging system can only supply 80Amps your battery will eventualy go flat . Adding a bigger (or more) batteries just means that it will take longer for the battery to go flat . In this instance you will be better spending the money on a higher capacity alternator. If your battery is having 100Amps sucked from it but your charging system produces 120Amps then you have a charging excess and your battery will not go flat .

and regarding the battery. the injector/fuel filter heaters I have been looking into to, draw about 16 amps total.
Plus ill no doubt be upgrading the stock deck, all speakers, and possibly adding an amp+sub.
Do you think the stock battery would be able to handle the load?
(what about getting a more powerful battery? optima/etc?)

My suggestion would be to use the force and go talk to a car audio (I.C.E.) supplier/installer in your local area to sort out your audio requirements.

[Gen-Erix Senior Member Find all posts View Profile Close Gen-Erix]

Re: Anyone using injector line heaters?

i have never known a car audio person to talk about alternators (foremost)

batteries always proceed it

thanks for the input though

[Guest Close David]

Re: Anyone using injector line heaters?

Guys please stop obsessing about the size of batteries. The size of the battery is only relevant in so far as it must be able to run the vehicle as the maker intended.

I'm pretty sure Mercedes never intended their cars to be running on Veg oil with electric heaters all over the fuel system and a sound system that would have the output of a PA system in a public hall!

While I concede that a good Merc size Battery will do the job here, the situation would be that the battery would have to support the load of the glow plugs in the engine and an extra load of line and filter heaters as proposed BEFORE the engine was running to charge the battery back up.
I am led to believe that diesels are relatively sensitive to slow cranking and if the battery did not have enough capacity to spin the engine up fast enough, starting difficulties may occur. While in this case the battery will operate in warm conditions, just about everyone reading this will experience much lower temps at some time and this diminishes battery capacity as well. As I said, in this case that would not be a problem with a Good heavy duty battery installed but my reply was written in a way that would cover a broader scope of usage than just this one scenario.

One thing to be aware of, Batteries are rated as the current and capacity they will supply when in NEW condition. It is always a good policy to fit an over rated battery where practical so that when the battery is 2 years old, you are still getting all the juice you need.

You are right about the alternator though Adam, it is imperative to have excess charging current. The way alternators are specified, they will only supply their rated current when the battery is very low or the draw is very high. Sometimes they will then exceed their rated output IF they are up to the required speed. As many modern large cars often don't get over 2500 rpm in normal circumstances these days, the alternators are over rated so as to give sufficient charge at these lower engine speeds.

In a merc diesel which does relatively high engine speeds, this would be less of a problem. One nice thing about the mercs is that they use the standard Bosch alternators which are fitted to about 1000 other cars and are easily found the world over in a range of capacities. I believe the latest ones are capable of 200 amps but more typical units are 80 and 100 amps.

If you are just fiting something like a cd player, sub and an amp, you will not have any trouble with your electrics.
I have played with this uprated sound gear and the electric ratings on a lot of it is a complete crock. I have seen endless amps and head units that specify a certain minimum gauge wiring and have massive terminals on the power inputs.

Many units specify a power cable as thick as you little finger but when you open the units up, Inside the wire going to the circuit board is the size of a piece of thin string! Sure you don't want voltage drop in the cable but you would never get that much!
Like most things, big numbers sell product in this game. Before you let some audio type salesman tell you that you need to supply 50 Amps to your setup and have an expensive bullshit battery.... Errr, sorry, I mean 1 Farad CAPACITOR to keep the voltage up, do the mental math as to how many REAL watts ( not hollow RMS or peak ratings which mean nothing) at say 6 volts the units can actually supply in audio power to get a closer estimate of the real current draw.

Even if you do get caught in a storm on a hot night and have the air, wipers, aircon, stereo , lights and every other electrical devise in the car going, any undercharge by the alternator would be supplied by the battery for more than the short distances you say you travel and once you got home, switching everything off and running the car for a few minutes at fast idle will top the battery off enough to get you started in the morning.

I would suggest the best and smartest way to go would be to do all your modifications and add in all your electrical gear and then take the car to an auto electrician and have them test the charge rate with everything in the car turned on and the car running around 2500RPM. IF the alternator can't keep up and you think that you may have the need for every electrical devise in the car to be on at once, install a bigger alternator. If you think this is an unlikely scenario and you can be mindful of it on the occasions it does occur, no need to worry about a thing!

With your Fuel System, You have to realise that the best you can do with a cold engine is heat the fuel a bit to get it through the filters easier.
If you heat before the filter the oil will pass through nice and thin right till it gets to the big lump of a cold injection pump which will cool it back to the temp of the cold engine almost instantly. From there on the fuel is engine temp which is cold. The amount of oil you would be heating to any temp simply does not contain enough BTU's to make any change to a great lump of thermal mass like an engine or IP.

If you heat after the pump such as with line heaters, the oil will then hit the injectors which are set in an even bigger thermal mass being the Head and again will virtually instantly assume the temp of whatever the engine is Plus maybe a little extra after maybe 15 seconds of running as the injector tip picks up heat from the combustion chamber.

These problems on a cold engine are compounded by the fact that at 16 amps, you are only putting 220 watts of heat into the system. This is not enough to have any influence on the engine or components the fuel will flow through till they themselves have warmed up at which time you don't need the heaters ( especially in your climate) anyway. I have been taking notice of the warm up time on my 300D and I would suggest that 1 minute after warm up, there is useable warm water flow coming out of the heater connection in the head to make a lot more difference to any fuel heating than what any practical electrical heating could supply. Sure it takes a minute where the electric is instant, but putting hot oil into a cold engines is futile and in fact a suggested cause of damage on some engines and pumps.

I have been looking into all this heating stuff a lot and even with one tank systems using SVO, the cold starts are still more reliant on engine and fuel system tolerance than anything else. This is why they don't ( with one exception) do single tank systems for rotary and inline/similar type pumps. Luckily the Bosch type pump found on a 300D is considered the most robust type pump of all.

The bottom line is, in your climate and in a 300D, with the blends you suggest, the modifications you are proposing are not going to be needed and not going to be effective. I believe you would be far better off forgetting the electrical heating and using a coolant type exchanger. While the engine is cold, its going to be cold till warms itself up no matter how much heat you try to put into the fuel.

I do understand that what I am saying goes against a lot of the accepted theories but simply thinking the process through will let logic tell you that putting a small stream of hot oil through the workings of a big cold lump of metal isn't going to allow the oil to stay warm for a second. In some areas where temps are freezing, electric heating may thaw/ thin out the oil but it is not going to make any difference in those first moments of startup to the engine or the pump.

Instead of using Diesel, you may like to look into blending with Unleaded gas. You would only need to run 15% max in your climate during winter and 10% in summer as I have seen a guy on another forum state he has been doing for the last 2 years without problem.

Hope this helps and yuor still awake after reading it.

[Vegiecars Member Find all posts View Profile Close Vegiecars]

Re: Anyone using injector line heaters?

Hey David, it's really hard to reply after such a great long spiel, as a short reply just simply doesn't do justice to the content that you have provided.

In practice, I believe your theory on heating the fuel for a cold motor to be incorrect. I live in the Dandenong Ranges where it gets very cold in winter. I have one vehicle that would not start at all on Vegetable Oil under these conditions, requiring bleeding the fuel lines to replace with diesel if purging had been forgotten.

With the installation of Injector line heaters, this vehicle will cold start. We call it our insurance policy as it does make a huge difference.

Regards
Marcus

[Gen-Erix Senior Member Find all posts View Profile Close Gen-Erix]

Re: Anyone using injector line heaters?

It's really hard to reply after such a great long spiel, as a short reply just simply doesn't do justice to the content that you have provided.

With the installation of Injector line heaters, this vehicle will cold start. We call it our insurance policy as it does make a huge difference.

David, I agree with the first part as you got some great info there.

I also agree with the "insurance policy". Like I said, I mostly drive short distances. (Example: its about 3-5 miles from my house to all the outlets, grocery, gym, etc) So a coolant heated tank wouldnt be prudent. The injector heaters should do the trick as since diesel has a return line the tank would no doubt get a little warm and stay that way due to the weather. I could always add one of these later.




My oil would be dewatered and filtered down to at least 5 microns.
Then mixed with diesel. (50%)
But I do want to increase the amount of WVO as time goes by.
Personally 90% WVO would be awesome, but we'd just have to see.

[Guest Close David]

Re: Anyone using injector line heaters?

With the installation of Injector line heaters, this vehicle will cold start.

Hello Marcus,

This is very interesting.
Can you tell me what the line heaters actually do to cause the Vehicle to start? Could you also give some more infomation as to the temprature this vehicle is operated in, what sort of vehicle you are refering to and the type of oil you are using? Also, how much Amperage draw do the heaters you are using have?

I have looked but never found any tests showing how much temp rise line heaters create at the injectors. Have you done any tests on this yourself or know of any such tests on this?


Gen-Erix,

I agree that if most of your driving is over such short distances, a heat exchanger would not be a wise choice in the long term.
I would also suggest that if indeed you do a lot of such short trips that you would want to be careful using almost any veg oil blend as you are never going to get the engine right up to temp.

If you were making a lot of short trips say monday to friday and you are able to give the car a good run on the weekend, hopefully this will work out OK. Bear in mind that due to a number of factors, Veg oil works best in engines that are fully warmed up to operating temprature. Even if line heaters are able to warm the oil somewhat, the combustion chamber and cylinder walls will never get properly warmed up and will be at greatest risk for causing you problems.
If you were blending 50/50 I would think you should be OK but I would certainly save any higher veg ratios for long trips where the engine is properly and throughly warmed up or blending with unleaded.

If you are looking for peace of mind and insurance, then I would suggest the very safest option where you are virtually gauranteed no problems is to use Biodiesel. For short trips, this is by far your wisest choice.

With the oil returning to the tank warm, I very much doubt this will occour in 3-5 miles. The oil will still be going back through the cold filter fittings and fuel lines which will suck any heat ( and I don't think there will be much to speak of) out of them and in any case, the distance traveled is not going to circulate much oil back to the tank to warm it and the remaing contents very much at all.

In the end, I still think this is all a moot point. I'm sure you will find line heaters work simply because in your climate I don't believe they will actually do anything and therefore couldn't be seen not to work.
You may like to look them up on infopop where there are plans and descriptions that show how you can make the things yourself for $15-20 and there are people selling them there premade for not a lot more.

Hope you find a nice car and it all goes well for you anyhow!

[Gen-Erix Senior Member Find all posts View Profile Close Gen-Erix]

Re: Anyone using injector line heaters?

i would make BioDiesel but...

i live in a townhouse
i have no front yard
i have no garage
my room is bigger than my backyard

svo is the logical way to go

[Vegiecars Member Find all posts View Profile Close Vegiecars]

Re: Anyone using injector line heaters?

This is very interesting.
Can you tell me what the line heaters actually do to cause the Vehicle to start? Could you also give some more information as to the temperature this vehicle is operated in, what sort of vehicle you are referring to and the type of oil you are using? Also, how much Amperage draw do the heaters you are using have?

I have looked but never found any tests showing how much temp rise line heaters create at the injectors. Have you done any tests on this yourself or know of any such tests on this?

Hi David, thanks for your questions.
On cold mornings here it may have reached zero temperatures overnight. The vehicle that I was using as an example is a Toyota Tarago with a 3c engine. If this vehicle is left overnight on WVO, there is no way of getting it to start in the morning. One can turn the engine over until the battery is flat.

With the addition of our injector line heaters and some time to allow the fuel to be pre heated, the fuel will atomise allowing the vehicle to start. The injector line heaters draw just over 2 amps per cylinder. Now if you were to just turn them on while trying to start the car, of course nothing would happen. Our heating elements heat up very rapidly and are spiralled around the injector line just before the head of the injector, turning the steel of the line into a conductor of heat to the fuel. Our system also includes thermal insulation to avoid heat loss to the atmosphere.

Some of this heat is transferred directly to the injector at start up but not enough to cool the fuel completely, and the glow plugs of course will have had an effect in the bore.

Another vehicle which belongs to a customer would not operate effectively on Vegetable oil at all because of air cooling. He had the fuel temperature before the IP at 90 deg but found that the fuel was less than 50 deg by the time it got to the injectors. He tried insulating the lines which helped a little but not enough as the vehicle would billow smoke and just run really badly.

We installed a set of injector line heaters on this vehicle which immediately rectified the smoke issue, obviously having an effect on the heat of the fuel.

In one vehicle, we tested the temperature of the injector head (that's all we can get to) after operating the vehicle for 30 minutes on a 20 deg day. Without the line heaters active, the temperature was at 65 deg C, with the heaters on and running for 15 minutes the temperature was up at 85 deg.
Of course this test could not test the temperature of the fuel or the quality of atomisation, and was only for personal interest not for evidence in a debate.

I have found in the Nissan Patrol that running the heaters for a couple of minutes before starting greatly assists in starting and engine operation. The engine starts quicker, soot from the exhaust is greatly reduced, and the engine doesn't carry on like it does if the fuel is not heated. I have now been operating this vehicle as a no purge system on 100% WVO since July 2006 to see how the injectors and bore will be affected in the longer term, and to date havn't had any trouble (I haven't stripped the motor yet). I wouldn't have been able to do this without the injector line heaters.

Overall I have found our injector line heaters to work efficiently and effectively at assisting to offer a clean burn and assisting with cold starting as they have a very thin silicone coated fibreglass sleeve and heat up rapidly. They are thermostatically controlled so that they don't overheat the fuel or cause heat stress on the fuel line and are very well thermally insulated to increase their efficiency.

Hope that helps to answer your question.

Regards
Marcus

[Guest Close David]

Re: Anyone using injector line heaters?

Hi Marcus,

Thank you for your very interesting accounts of your line heaters.

I have to say that I still find that they appear to defy Physics as well as logic. At 2 amps, the heat they are generating is only a few watts more than a tail light globe and even one on each line would seem to supply an insignificant amount of heat even over a practical period of time.

I find it a struggle to come to terms that an injector that makes very good contact with the head through the use of special sealing washers would not bleed a significant amount of heat straight into the cold head.

I have worked with electronics and just now looking up an engineering catalouge, I see that a large heatsink weighing around just 1Kg has a thermal resistance of just 0.552 oC/W. This means that for every watt of energyput into the heat sink it's temperature will only rise .5 of 1 degree celsius. I can think of no components that would have any greater thermal transmission area than that of the contact area of an injector in a head with the head having a thermal mass of around 100 times more than the heatsink referred to.

Dumping say 28 watts of heat into one of these relatively tiny heatsinks would cause a temperature rise of 14 oC.
It is hard for me to fathom how an injector in a head would allow anywhere near this temp rise but perhaps what heat does get through may be enough to create a difference in critical applications. Even without any air cooling, the thermal mass and contact area of the injector in the head would seem to me to be able to dissipate hundreds of watts of energy very effectively.
A few seconds after engine start up, I still believe the injector would be supplying more heat to the fuel than a line heater of 2 or 10 amps could.
Of course as soon as the engine does turn, at cold start up the area surrounding the injector location in the head would also then see a movement of cold water further removing any accumulated heat.

I do understand how over time a line heater could cause a temperature rise of some amount into a line on a non operating engine but how much heat rise a 2 amp heater could impart into a line of moving oil is also something that I have great difficulty getting my head around. I realise that the amount of oil is small but it would only have around half the heat conductivity of a similar collum of water and would be moving relatively quickly with only a short residence time in the injector line.

Certainly if these heaters do allow cold starts where the engine would not fire otherwise, or do add enough heat to make a difference to the engines operation, they would be a worthwhile accessory. I am always willing to learn and change my thinking, however until I can find suitable materials to make and fit a set to my own car and do my own tests, I am afraid I will continue to have reservations about line heaters based on the principals of Physics I do know and understand.

Out of interest, is anyone aware of any tests by any universities or labs on these heaters? There are loads of tests published about running diesel engines on veg oil, anyone know of any similar type tests on line heaters that have been done?