Interesting thread on greasecar.com about heating oil...the topic came up about how much oil goes through your veg filter in an hour...one guy says 1 gallon, based on engine consumption, another says, no the injection pump pumps way more than it uses...
My thoughts: if it's a looped system where the loop comes back between the veg filter, and the injector pump, this is true, the amount of fuel through the veg filter would be what you consume...comments??
however, if you Tee back in on the other side of the veg filter (between tank and veg filter, like the other thread here), the filter would then circulate much more....
this could be good and bad...if you tee in between veg filter and tank, then you run more fuel through the filter...pros: the veg that recirculates is heated again...keeping it hotter...cons: the new veg oil going through that filter spends less time being heated, therefore is colder on the otherside...what's more efficient, and keeps the oil hotter...
my opinion: the new oil has gone through the hose in hose all the way from the tank, therefore is very hot when reaching the filter, at this pint, it just needs to stay the same temp...however the oil coming from the loop and injector pump will be cooler, as it has been running through just rubber fuel line for a little bit...
conclusion...tee in between veg filter and tank to get oil at a higher temp...
however, i like the idea of backflushing the filters also to keep the crud out of the paper, as stated before...
comments, anyone experimented with this...it'd be interesting to tee in on one side, check VO temp, then tee in on otherside and check VO again...next project.

Mine Tees back in after the filter, making a shorter loop. My temp sensor is at the IP inlet, and indicates hottest when in looped mode. Obviously the IP and Injectors are heating the fuel more than the HIH can.

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Originally posted by 91jettawvo:
SNIP
however, i like the idea of backflushing the filters also to keep the crud out of the paper, as stated before...
comments, anyone experimented with this...it'd be interesting to tee in on one side, check VO temp, then tee in on otherside and check VO again...next project.

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I always thought that the filter was supposed to trap all of the "crud" so that when you replace the filter all of the "crud" is removed from the fuel system.'
If you are trying to backflush the contaminants from the filter,
1. It doesn't work well, when you loosen a little of the blockage, the differential pressure drops, so the other contaminants stay put.
2. Anything which does dislodge from the filter will be right back there when you start up again, blocking the filter faster than ever.
I have tried bacckflushing, but it only had marginal success and a very short time before tha filter has a high pressure loss again. I used petrol and compressed air to remove the "crud", it only took about 20 km before I was having fuel starvation problems
p.s. I have a fuel pressure/vacuum gauge at the IP inlet.

johno, is that true that the injectors will heat it more than the HIH?? I've heard this theory, but wasn't sure what the actual numbers were...I was worried about in the winter, at 80 mph, that the "looped" oil may get cold...but i guess with the volume of the pump, and the injectors, most of the oil is being heated by the engine block anyway...when it's 10 below zero, how cold is the air around the engine??

tony,
i've always had the same theory as you on the backflushing of the filter, and have never done it...i figure i'd rather get the crud out of the system for 10 bucks, then reintroduce it, however, i've heard differntly on this issue in here...i'll go with the non-backflushing.

The injectors are at least partially directly exposed to the combustion flame, at their tips. They're also carefully surrounded by the water-jacket, and also are intended to have extra fuel pumping through them to help cool the internal parts. That's the logic presented in my textbooks, but I don't have direct measurements or numbers. The return hose doesn't get hot before the engine though, so I take that to indicate the injectors aren't causing the heat, they're passing it on.

1. It doesn't work well, when you loosen a little of the blockage, the differential pressure drops, so the other contaminants stay put.

* I think removing enough so the differential pressure drops is the goal of backflushing.

2. Anything which does dislodge from the filter will be right back there when you start up again, blocking the filter faster than ever.
I have tried bacckflushing, but it only had marginal success and a very short time before tha filter has a high pressure loss again. I used petrol and compressed air to remove the "crud", it only took about 20 km before I was having fuel starvation problems

*When you say you "removed the crud", where did you remove it to? Sounds like you flushed it back down the vegy line and sucked it back into the filter again ... or was this new crud that clogged the filter again in 20 km.
If the fuel vacuum starts to get high, I backflush it at around 55mph for 1 mile (no slow idling backflush this time) when I'm done driving and drain the crud out the water drain in the bottom of the filter.
Pressurise the tank for faster flow from the water drain and to push air out the top air bleed on the filter.
Good for another 1000 miles.
The injection pump will add some heat to the fuel but when I was idleing with a return to the front of the pump setup, the fuel temp would just drop off, even in the summer. Ran the return to the output of the filter, where it was heated again before entering the pump and I could idle long time again ... down to 35F.

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Originally posted by Fatmobile:
1. It doesn't work well, when you loosen a little of the blockage, the differential pressure drops, so the other contaminants stay put.

* I think removing enough so the differential pressure drops is the goal of backflushing.

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I thought that the goal of filtering was to remove the contaminants from the system when the filter gets changed

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2. Anything which does dislodge from the filter will be right back there when you start up again, blocking the filter faster than ever.
I have tried bacckflushing, but it only had marginal success and a very short time before tha filter has a high pressure loss again. I used petrol and compressed air to remove the "crud", it only took about 20 km before I was having fuel starvation problems

*When you say you "removed the crud", where did you remove it to? Sounds like you flushed it back down the vegy line and sucked it back into the filter again ... or was this new crud that clogged the filter again in 20 km.

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The prefilter was removed from the car and blown out using HP air. It was reinstalled and primed, but the pressure differential was never as good as a new prefilter,
then it got worse,
and worse,
and worse,
until I stopped and replaced the prefilter with a clean one.
Hey presto, full pressure again.

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If the fuel vacuum starts to get high, I backflush it at around 55mph for 1 mile (no slow idling backflush this time) when I'm done driving and drain the crud out the water drain in the bottom of the filter.
Pressurise the tank for faster flow from the water drain and to push air out the top air bleed on the filter.
Good for another 1000 miles.
The injection pump will add some heat to the fuel but when I was idleing with a return to the front of the pump setup, the fuel temp would just drop off, even in the summer. Ran the return to the output of the filter, where it was heated again before entering the pump and I could idle long time again ... down to 35F.

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I have experimented with backflushing as well in have found that as filters begin to clog backflushing them seems to push off a lot of the "cruyd" which has accumulated on a filter element. But if one waits for the filter to seriously clog smaller bits of crud seem to be drawn deeper into the element material and become so tightly stuck that nothing will dislodge them. Not backflushing, solvents, or high pressure air....nothing works.

To be effective backflushing must be done regularly. The optimum backflush cycle I experimented with seemd to be one that gently pushed vegoil back through the filter and then allowed the filter to sit in solvent(such as dielse fuel) for a long period of time. The majority of crud that dropped off of the filter seemed to drop to the bottom of the filter shell and stay there with this cycle. If I backflushed and did not allow the crud to setle it only fell a small distance and then was sucked back onto the filter. This reseulted in a small area at the top of the filter element being cleaned of loose crud...which allowed the fuel to pass through that area of the element easier but clogged with new crud faster.
And a high pressure flush did seem to just send the crud back down the fuel line and into the tank where it slowly accumulated in the bottom and caused problems if I allowed the tank to get empty enough for the "slosh" to stir it up.

I believe that backflushing has its' merits but it requires timing and "technique" to make it really effective.

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I thought that the goal of filtering was to remove the contaminants from the system when the filter gets changed

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I think that's the original idea from the factory but I think the main goal is to keep the crud from entering the injection pump regardless of how or where it is removed to.

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The prefilter was removed from the car and blown out using HP air. It was reinstalled and primed,

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I think hot vegy/diesel does a much better job of backflushing a vegy filter than air would.
I was on a long trip and the vacuum gauge started to rise. I backflushed it and pulled into a rest area to drain the filter. Got back on the road and it started to rise again ... backflushed again, pulled into a truckstop to drain the vegy filter into a plastic bottle I brought along. Got back on the road and the vacuum stayed low all the way home.
Sometimes the filter does get alot of crap gathered into it and I've had ones that I gave up on and replaced with a new one but a serious high speed backflush ... or 2 will usually work for me.

interesting idea brewing.

screw a fuel hose to the filter bleed. Put a pollik valve on this hose and when you back flush open it. Run this to a tiny tank.

hmmmm. Use this tiny tank to inject fuel into the exhaust to smoke out the Jackarses behind you....LOL.