Injector preheaters, making your own

[SCOTT]

Below is a picture of the current version of my injection line heater,

I am using the Mcmaster heat rope mentioned in an earlier post, along with some automotive break line tubing and a few “T” pipe fittings.  The bottom “T” fitting houses the thermal switch, which is set: normally closed (on) open (turn off) on rise set point 120c or 248f.  I had to use black pipe vs. brass because the brass was a little too short for the probe.
The upper “T” houses the automotive temp probe I took my temp readings from.  In the background you can see another thermal switch for a radiator fan.  This one was to be set normally open, close on rise set pt 105c or 221f.  They sent the wrong set point, (150c or 302f) so I have not tested the radiator switch yet.



I ran the engine for about an hour and the temp gage registered a high reading of about 240f and a low reading of just above 200f.  I don’t remember what the dead band was rated as,  and am not sure of the accuracy of the temp gage, it is a sunpro from JC whitney.  The probe has a contact MTBF rating of 100,000 cycles @6 amps 120Vac.  I expect the temp range will tighten once the line is insulated and shielded from the “wind” of the flywheel.

More results to follow.

Scott

[rcavictim]

Anyone else find it impossible to view Scott`s picture on webshotz?  That site is a real waste of time if you have dialup. 

[Guy_Incognito]

I'm curious - anyone know what the injection pressure is on that engine?
Just wondering how well your temp sensor and thermal switch will handle pulses of "x" hundred (er, thousand?) PSI long term.

[SCOTT]

Rcavictim,
I posted the same pic in coppermine, at a much more compressed level, link below
 
http://listerengine.com/coppermine/displayimage.php?album=lastup&cat=10064&pos=0

Guy_Incognito
The temp switch is rated at 7000psi so I have no doubt it will be fine, the temp sensor is not of the same quality, I do not know what the psi rating on that is.  The pressure of the pump is the main reason I switched from copper tube to break line.  I would rather use the stock steel lines, but I did not have a good way to secure it to the block of steel that I had drilled and taped to accept the thermal switch and the temp probe.  I think the pipe is too small to weld and I never tried to braze or silver solder anything. 
Any suggestions?

Scott

[Guy_Incognito]

Never thought the temp switch would be good for 7000PSI 

What's the I.D. of the steel line? Perhaps you could flare (or double-flare) it and use standard brake-style flared fittings in your steel block? Don't know how standard steel compression fittings and olives would hold up.

[SCOTT]

Guy_incog..
As you can see in the picture below the ID of the copper is much greater than the original steel line, the steel is <2mm and the copper is around 5mm.  The break line is about the same ID.



Flaring is unfortunately not an option.  I think the only way to do this is by brazing or silver soldering.  I may try that on the next version.  The downside to using the break line is that the switch from VO to diesel takes longer

[Guy_Incognito]

I thought that would be the case  It's kind of indicative of the pressures they're under as to the amount of steel in that pipe. I know that contained volume in injection lines is a factor as well, but still... Makes me worry a little bit about the thin-walled pipe you're using as a replacement.....

But silver soldering should do the trick. If you drill a reasonably snug recess for the pipe (3/8" deep should do), use a goodly amount of flux, and sweat the silver solder + pipe into it.

[Geno]

Got my heat rope. 1', 50 watt, high temp. The same stuff Scott used just shorter. The rope shoots at 300-400°F Its diffucult to get an accurate reading where the housing enters the block but the housing on top shoots at 210°F with the power on and around 160°F with it off. Its to early to be sure but this amount of heat seems about right. Thanks Scott for breaking trail. I'll put another piece on the pump soon to thin the WVO in it.





http://www.warrensburgvendors.com/geno/listeroid/#engineroom

Thanks, Geno

[SCOTT]

Geno
Be careful with that heat rope.  The rope really needs to be in contact with metal over the whole length that is braided. If it is not in contact with metal it may get too hot and burn out, it needs to be able to sink the heat it is generating.  You may want to try wrapping the rope around the injector line vs. running it parallel, you will have a larger contact area between the rope and injector.

Or you could shorten the rope.

I like the clean simple install.

Scott

[Geno]

The exposed leads are the pigtails that do not get hot. The thicker, braided, hot portion is under the tape, in contact with the injector housing and not crossing over itself. I'm often wrong but I reasoned that getting the heat as close as possible to the injector tip will reduce losses. This is the first time I've tried it but I just can't get it out of my head that the large injector housing at 165 F will cool off the WVO. 165F or so is where it runs without any outside heat source. It would be easy to put the heat rope on the injector line, let it get hot and shoot the housing though.

Thanks, Geno

[SCOTT]

AHH

I can see in the second pic that the part of the rope with the heating element is in contact with the housing, my mistake.

I tend to agree with you that the fuel will take on the temp of whatever it is in contact with.  In my setup It takes on the temp of the heated injector line, but then most likely cools down once it reaches the housing which has no active heating.  I like the idea of heating close to the point of injection.  The only drawback is that I can't think of a good way to accurately measure the fuel temp and regulate the heating element.

It may be possible to add a surface mounted thermal switch to the injection housing as long as ther is a good flat surface big enough.  But then again regulation may not be needed if you can size the rope properly as you seem to have done.  I am interested in your wvo test results, keep the good info comming

Scott

[Geno]

The only drawback is that I can't think of a good way to accurately measure the fuel temp and regulate the heating element.
Scott

Agreed. I'll probobly peel back some tape near the bottom and shoot it after things have had time to warm up. Not perfect but should be pretty close.

It may be possible to add a surface mounted thermal switch to the injection housing as long as ther is a good flat surface big enough.  But then again regulation may not be needed if you can size the rope properly as you seem to have done.  I am interested in your wvo test results, keep the good info comming
Scott

I want to size the heat rope properly. Partially for simplicity and partially because I'm tired of getting nickel and dimed.

I should have time for some better testing this weekend

Thanks, Geno

[Joe]

Geno,
   I have to say I really enjoy your website…well organized…great pictures …easy to navigate…lots of facts and excellent detail in many different areas…it really makes for some nice reading….

Joe

[listerdiesel]

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!? 

http://www.oldengine.org/members/diesel/Ebay/Beads2.jpg

Peter