Injector preheaters, making your own

[rcavictim]

I have problems with my 1.5 liter Rabbit NA IDI diesel engine (now in a DIY power plant) coking up the injectors badly when I try to run on filtered WTF as opposed to clear diesel.  It has occured to me over time and reading here and elsewhere that one thing that would be worth my exploration would be providing heat to get the injector bodies up to a goodly warm temperature.  As they are now you can hold your hand on them when the engine is hot.

I haven`t yet coked the single injector of my freshly re-ringed 12 HP Petter directly injected air cooled single used only so far on new oil, but have smoking problems that sometimes clear after a good hard run.  I cobbled together a simple electric silicone strip heater around the injector last week and gave the plant a 6 hour run at half speed (900 RPM) and very light load (1.7 kW).  It ran very nicely and was not emitting more smoky as the run progressed.  I had the top part of the injector that I could reach at I`ll guess about 140 F., uncomfortable to hold after a couple of seconds.  Originally it ran cold.  I was encouraged by what I saw from this first attempt at injector preheat and believe this to be an idea worth persuing.

I would like to come up with a electric heater design that would be inexpensive and easy to apply to the injectors of both the VW and the Petter engines.  It would be a bonus if the heater design also lent itself to heating the injector high pressure fuel feed lines as well.

I have an idea that I want to experiment with.  I have some teflon insulated wire here, about AWG18 that has silvered, stranded copper inside.  I have been stripping short lenngths of this insulation to use as spaghetti insulation on under chassis electronic components like resistors and capacitors in the building I do of custom hi-fi tube amplifiers.  I have several colors in stock and the stuff will never melt in the applications where I employ it.  The teflon I have appears to have a working temperature range up to about 500 degrees F.  I was thinking that if I could somehow pull a good length of the outer teflon sleeve off my wire stock and snake a nichrome wire salvaged from an electrical heater down the center hole I would have a heating element that could simply be wrapped around the body of a fuel injector and associated piping.  A step down and isolating power transformer would be used to apply a suitable (lower than full mains voltage) current to the heater(s).  They could be safely heated to perhaps 400 F which might be enough to heat the injectors to the desired 200F target range.  Thermal insulation of some sort could be placed outside of the lines and injectors if necessary to increase the efficiency/heating capability of this system as needed.  Pink fiberglass or better yet, rock wool and self adhesive aluminum heating duct tape could do the job for an example.

I offer this in the spirit of sharing DIY ideas and invite comments and further suggestions from the readership.  I will report here when I have anything to add after my experiments begin.

[fuddyduddy]

The KISS principle is truly the best.

This has been covered many times, and is found in many forums. Heat, and/or treat, and/or dilute.

Is WTF waste trannsmission fluid?  If so, Power Service Diesel Kleen, a little dilution with regular pump gasoline (one gallon in twenty or so),  and Diesel 911 from Power Service will go a long way toward helping eliminate the problem.   

One forum that has great info on coking, wetstacking, etc, is http://biodiesel.infopop.cc/6/ubb.x?a   .

Dana Linscott has a great website to help us understand cures that work, also.  http://www.vegoilconversions.netfirms.com/    Yes, some will say those are mainly vegoils, not used lubricating (transmission) oil.  However, they are all hydrocarbons, and act similarly, and many of the same "cures" work for problems with using them in diesel engines.

[Mr X]

Yes I also have been wanting to make a injector line heater. I understand it is posible ,quite simple. I dont have supplies but have tore a toaster apart for the nicrome wire, maybe too thin. You need woven ceramic fiber 1800 and 2600 degrees f  . Silicone tape 500 deg f,, to wrap the wire and insulation to the injector line. Now as to ohms and length and gauge of the wire at 12 v,I found it sugested 20 watts/ injector line. A good sorce is Macmaster Carr but us here north of the 49 th cant assess this source due tio the growing security risk.

X

[biobill]

A good sorce is Macmaster Carr but us here north of the 49 th cant assess this source due tio the growing security risk.
   Our administration is well aware of plots to use Lister powered generators and resistance  wire to melt the polar ice cap and flood Manhatten
X

[Geno]

I've been thinking about the same thing and want to use AC as thats what I have easily available. Mcmaster Carr. $3.18 per ft. and it only uses 3 watts per ft. If you want to go to 250°F the other stuff is twice the price.

"You won't need a thermostat for this cable. The colder it gets, the greater the heat output; as the temperature increases, the heat output automatically decreases. A thermostat can be used, however, to turn unit on and off. Use on metal and plastic pipes for freeze protection and low temperature process maintenance.
     Cable can be safely overlapped. It's single phase. Not suitable for burying underground. UL listed, CSA certified, and FM approved Class I, Div. 2, Groups B, C, and D.
     To Order:  Please specify 20-, 30-, 50-, or 100-ft. lengths, or any length up to the maximum operating length.
     Standard Heat Cable— Max. continuous heat output is 150°  F. Can be exposed to temperatures from -40° to +185°  F. Cable with metal braid is approximately  13/32" Wd. x  3/16" Thick. Cable with metal braid and jacket is approximately  29/64" Wd. x  7/32" Thick.
High-Temperature Cable— Max. continuous heat output is 250°  F. Can be exposed to temperatures from -40° to +428°  F. Cable with metal braid  is approximately  3/8" Wd. x  5/32" Thick. Cable with metal braid and jacket  is approximately  13/32" Wd. x  13/64" Thick. "

When my engine is up to temp my injector housing shoots at 160°F. Logically, with a 6/1 fuel rate that should be enough to get the temp up but I've heard enough people who've done it say differently.

Thanks, Geno

[Mr X]

Geno It depends on what your burning, wvo acording to Fatteywagon site requires hot hot, in the range of 180- 300 f . I think the stuff your looking at is for melting the snow in your roof gutter. Check out wvo site http://www.fattywagons.com/fwlinks.htm.
   Poke around Forrest Gump site and get some ideas. Ive heard its not good to get your dino diesel real hot, but it is for wvo.

[Geno]

Mr_X, I agree with what you say, Alternate fuels need to be hot. McMaster had many other options for heat cable.
Heres a copy of the page. Let me know what you think.
http://www.genedevera.com/temp/mcmaster/Mcmaster.htm

I haven't seen it with my own eyes yet (and others who have say differently) but it still *seems* to me that the fuel will be the same temperature as the injector housing. Its a decent size chunk of metal with about a quart of fuel an hour going through it.

Just exploring the possibilities.

Thanks, Geno

[dkwflight]

Hi I wanted to use a/c for my injecter heat too.
I ordered part no. 36005k35 from mcmaster-Carr.

http://www.nelsonheaters.com/
This is a self regulating heat tape with a draw of 15 watts per foot. runs on 115v.

I thought this stuff would heat to 250f per mcmasters  description.
What I get is 100- 105 by my infared thermometer.
It does heat up to this level fairly quickly.
It turns out that this is the top limit for exposeing the heat tape to an out side source of heat.

Siince I bought this stuf I will try it out on veggie oil.  I will wrap the heat tape with friction tape to try to keep the heat in and transfer to the injecter line better.
 I will post my results when I have some.
Dennis

[Geno]

I thought this stuff would heat to 250f per mcmasters  description.
What I get is 100- 105 by my infared thermometer.
It does heat up to this level fairly quickly.
It turns out that this is the top limit for exposeing the heat tape to an out side source of heat.

Thats good info Dennis. Where does that top temp limit info come from? Also the tape you bought is "self regulating" I wonder what the "constant wattage" tape would do.
Thanks, Geno

[dkwflight]

Hi I have an e-mail in to Nelson              http://www.nelsonheaters.com/

For more information.
Nelson says this tape can be exposed to up to 250f from extrenal sources like steam heat. The Mcmaster-car info implies the tape is good for 250f. A completely different thing.
Nelson heaters have several different products that are good for up to 11oo degrees. Most need thermostatic control of some sort.

The constant wattage stuff is good for much longer lengths the heater wire is connected every so often so you can cut it to length.
Dennis

[rcavictim]

Well by golly I have it!  What one needs are a whole handfull of tiny ceramic beads with a hole through the middle.  Slip them onto a piece of nichrome wire and wrap that around the injector.  Use a step down isolating power xfmer from the mains voltage to power it safely.  Operate that heater incandescent red if you need to without worry about melting it.  Pack a wad of rock wool and some aluminum HVAC or HVDC tape around that for outside protection and to keep the heat in.

Brilliant or what!? 

[Mr X]

There is some tape I think it is silicone tape it has no adesive on it but bonds to itself  good for 250 or maybe 500 f not sure its in my shop and aint running out ther.Try wrapping with that. This stuff is easily avalible seen it in the building supply and Canadian tire. And Macmaster Carr.

[Guy_Incognito]

How about a 12V 100W H1 or H3 halogen bulb in close proximity to the injector, wrapped in rockwool or whatever you've got to insulate it? There's a hundred watts of heat in a package that's pretty small as opposed to 15W per ft of tape or nichrome wire.

Easy to put in, gets plenty hot, safe voltages, relatively small, a couple can be added around the injector as needed.

Main issue is that you'd probably want a small air gap around the globe - it's quartz envelope is designed to run at a high temp to allow the internal halogen cycle to work properly. But still - all the heat's got to go somewhere and if the metal body of the injector is the only thing near it that will transfer the heat away, it'll go there.

[rcavictim]

How about a 12V 100W H1 or H3 halogen bulb in close proximity to the injector, wrapped in rockwool or whatever you've got to insulate it? There's a hundred watts of heat in a package that's pretty small as opposed to 15W per ft of tape or nichrome wire.

Easy to put in, gets plenty hot, safe voltages, relatively small, a couple can be added around the injector as needed.

Main issue is that you'd probably want a small air gap around the globe - it's quartz envelope is designed to run at a high temp to allow the internal halogen cycle to work properly. But still - all the heat's got to go somewhere and if the metal body of the injector is the only thing near it that will transfer the heat away, it'll go there.

I don`t think the filament will take the engine vibration for long which can be very severe on some of the singles like my Petter, and full wattage rating would likely melt the bulb if the heat was not allowed to escape through the design open air radiation process.  Less than proper operating temp and the halogen cycle wouldn`t work, leading to filament evaporation.  Too sum up, I don`t think that will work.

[Guy_Incognito]

Too sum up, I don`t think that will work.

You'd be suprised. Allow me to let a little bit of experience with underground mining equipment slip through:

- Low voltage filaments are rather thick. I use 24V dichroic halogen bulbs on mining equipment in solid metal frames that gets shaken enough to break any loose wiring on the brackets in a day or two and hot enough in the tiny metal frames that it will eventually burn the connecting wiring off the pins. In those conditions they run about 400-800 hours before bulb failure.

- I've run 24V bulbs at 12V for hundreds of hours without deposits forming on the envelope (used as low intensity tail lights). In a confined space next to an injector, envelope temp should be high enough to allow the halogen cycle to work ok at 12V.

Anyway, it's cheap enough to experiment a little with it.

Otherwise, as you mentioned, there's beaded ceramic heating wire you can use. I didn't recall it until you mentioned it, but I used to use it for large solder pots that ramped up to 500 deg C.