Big problem discovered with long-term WVO use in PD-TDI

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

Moderators: SunWizard, coachgeo

Postby chasee » Fri May 23, 2008 4:33 pm

SunWizard wrote:I am not talking about an electric heated pickup. I am talking about coolant heated. They are common. Look at kits by Plantdrive, Frybrid, Vegpower, Goldenfuel systems, and the hotfox and arctic fox which are used by many others. The links to all of these are in the sticky at the top of this forum.


Yea, I know about the Hotfox. I thought all it does is heat the tank more slowly. Am I correct that after a given amount of time, it will still result in the tank heating to 180F or so, as that is the temp of my engine/coolant? Remember, PD engine here. It gets hot, fast, and the return fuel is actually even hotter due to the high pressure injectors. Did you know the stock fuel return line has a radiator under the passenger side to keep the stock tank from getting too hot?

Am I missing something on Frybrid's site? All I see is heat exchanger coil for tank just like mine, excepting of course for the copper. :wink:

As for lift pump, already got one since the PD stock tanks have one and the IP is not really an IP anymore, the injectors do most of the work. Not really interested in mixing D2 or Kero in winter, kinda defeats the purpose. Plus, that study showed that the winter anti-gel additives for D2 can actually accelerate polymerization.
2005 Golf GLS PD-TDI, 5-speed. Grease Car kit installed right off the lot when brand new. Running on WVO about 85% of the time.
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Postby SunWizard » Fri May 23, 2008 4:47 pm

chasee wrote:Yea, I know about the Hotfox. I thought all it does is heat the tank more slowly. Am I correct that after a given amount of time, it will still result in the tank heating to 180F or so, as that is the temp of my engine/coolant?

A hotfox and most heated pickups will not get the tank to 180 even after 8 hours. Thats why they are better, you don't want or need that much heat in the tank.
Remember, PD engine here. It gets hot, fast, and the return fuel is actually even hotter due to the high pressure injectors. Did you know the stock fuel return line has a radiator under the passenger side to keep the stock tank from getting too hot?

Yes.
Am I missing something on Frybrid's site? All I see is heat exchanger coil for tank just like mine, excepting of course for the copper.

Yes you are missing that they surround the coil in an aluminum enclosure that keeps the heat limited to the VO inside the pickup area.

Another problem with the greasecar setup is there is a coolant connection in the tank that can leak coolant into your VO, you should fix that too.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby chasee » Fri May 23, 2008 4:56 pm

SunWizard wrote:
chasee wrote:Yea, I know about the Hotfox. I thought all it does is heat the tank more slowly. Am I correct that after a given amount of time, it will still result in the tank heating to 180F or so, as that is the temp of my engine/coolant?

A hotfox and most heated pickups will not get the tank to 180 even after 8 hours. Thats why they are better, you don't want or need that much heat in the tank.
Remember, PD engine here. It gets hot, fast, and the return fuel is actually even hotter due to the high pressure injectors. Did you know the stock fuel return line has a radiator under the passenger side to keep the stock tank from getting too hot?

Yes.
Am I missing something on Frybrid's site? All I see is heat exchanger coil for tank just like mine, excepting of course for the copper.

Yes you are missing that they surround the coil in an aluminum enclosure that keeps the heat limited to the VO inside the pickup area.

Another problem with the greasecar setup is there is a coolant connection in the tank that can leak coolant into your VO, you should fix that too.


Hmm... I dunno. The physics of heat transfer seem to dictate that my tank would ultimately hit 180F with a Fox. The tank is in the spare tire well, so the top is insulated by floor mat and cargo mat. Insulation like this on top is what really counts in keeping the heat in the tank, side insulation is not really effective one way or another. Same for the FB coil. It might heat more slowly, but its not made of a magic substance which does not allow any more thermal energy to transfer after a given temp is reached. I'm going to pick my local installer's brain about this. Are there any members here with a PD like mine, a tank like mine, and either an FB coil or Fox? I'd love to chat with them and have them take a couple spot readings with a point&shoot digi-thermometer after some long drives.

Yea, I know about the possibility of a coolant leak. That seems to be exceedingly rare, unless the initial install was not done properly. The weak link I see is the pex line possibly degrading over time in the HIH, causing the cross contamination there.
2005 Golf GLS PD-TDI, 5-speed. Grease Car kit installed right off the lot when brand new. Running on WVO about 85% of the time.
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Postby chasee » Sat May 24, 2008 6:37 am

Just got a suggestion on the Greasecar forum that a solenoid could be employed with a bypass loop for the coolant. This actually could satisfy my fantasy of a system which gets the tank to whatever desired temp you want and then keeps it there.

If one of the computer units, like the Frybrid or Greasecar controllers, has the ability to control a solenoid like this based on the tank temps, that would be super trick. No need then for an expensive Fox-like product (which still may overheat WVO over time) or overpriced Frybrid coil. Just a simple coil like I already have, just non-reactive metal.

What do you all think?
2005 Golf GLS PD-TDI, 5-speed. Grease Car kit installed right off the lot when brand new. Running on WVO about 85% of the time.
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Postby jburke » Sat May 24, 2008 8:42 am

REducing coolant flow wa swhy I suggested a valve in series w/ your coil.
A thermostatically controlled valve would also work.
The bypass is so you can maintain coolant flow I guess.
[Not sure why your PD needs that]

So then the question is, what is the max. viscosity your stock PD lift pump
can handle?

If you have to replace the copper coil anyway, why not try the Frybrid or HotFox? But I agree, I'd like to see some data demonstrating the effectivness of the shoield.
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Postby chasee » Sat May 24, 2008 9:57 am

I just have a "feeling" that inhibiting coolant flow in any way is not a good idea. I like maintaining as many stock parameters as possible. That's the main reason I have not made any mods to my car whatsoever, other than the basic kit.

At this moment, I'm thinking a coil the same size as mine, just not reactive, and the solenoid temp sensor bypass. I just assume get the WVO up to my specified temp ASAP since it will then just hold it there.

I've thrown it out there on the Greasecar forum too, and it might get posted to Fred's (by someone else of course :wink: ). Let's see what the masses come up with.

I'm happy to get this experience out there. I think the issue of poly is still not much addressed in the WVO community. Probably because it happens so slowly, and not many have run WVO for the hours/miles I have.
2005 Golf GLS PD-TDI, 5-speed. Grease Car kit installed right off the lot when brand new. Running on WVO about 85% of the time.
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Postby SunWizard » Sat May 24, 2008 12:42 pm

A heated pickup is not restricting the coolant flow in any way. The simplest solution is to run an aluminum line, with a single 6" diameter loop around the pickup pipe at the bottom. This is what is in my tank, and its been fine to -10F with PHO. Cost was about $3. No connections inside tank. No added cost and complexity of computer control, relay and another solenoid. Doesn't overheat the tank. Pics are on this thread:
http://www.burnveg.com/forum/viewtopic.php?t=28
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby jburke » Sat May 24, 2008 3:25 pm

"I just have a "feeling" that inhibiting coolant flow in any way is not a good idea. "

Is the tank heater circuit flow in series with an existing engine component?
I was assuming you'd T'd into the cabin lines and created a new path for coolant, and there wouldn't be a problem shutting it down.

Since most commutes are short, maybe the shield does insulate the rest of the tank. Hard to quantify. Better if it's a thermal insulator.
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Postby jburke » Sat May 24, 2008 3:26 pm

"Doesn't overheat the tank. "
Any guesstimate on temp?

Do you use a supplemental fuel pump?
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Postby SunWizard » Sat May 24, 2008 4:51 pm

jburke wrote:"Doesn't overheat the tank. "
Any guesstimate on temp?

Depends totally on the ambient temp, this time of year 70F, the tank gets about 100F.
Do you use a supplemental fuel pump?

No, stock piston lift pump, plumbing described in the linked thread.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby chasee » Sun May 25, 2008 4:03 am

SunWizard wrote:Depends totally on the ambient temp, this time of year 70F, the tank gets about 100F.


So uninsulated bed mounted tank, 100F when its 70F outside. I'm pretty sure that means my worry about a setup like mine getting to 180F is well founded.

Just for reference, if I park in my garage overnight, even on super cold winter night, next morning my tank is still a nice hand-warmer if I lift the mats.
2005 Golf GLS PD-TDI, 5-speed. Grease Car kit installed right off the lot when brand new. Running on WVO about 85% of the time.
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Postby BMW Fan » Sun May 25, 2008 5:44 am

Why make things so complicated?
If the source of polymerization is your intank heater and you got plenty of heat....why don't you just take of the dam thing and go only with a plain return to tank ?

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Postby jburke » Sun May 25, 2008 7:31 am

Re: BMW Fan's suggest to just heat with the return fuel.
The worry would be the PD's lift pump. It might not be able to handle thick vo. Several have been reported failing using B100. It might only be a design or manufacturing flaw, but I've always wondered if it was due to too thick fuel.
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Postby SunWizard » Sun May 25, 2008 8:32 am

chasee wrote:Just for reference, if I park in my garage overnight, even on super cold winter night, next morning my tank is still a nice hand-warmer if I lift the mats.

Too much heat + insulation = even more poly! 24 hours a day even in winter. Oxidation rate doubles for every 18F increase.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby SunWizard » Sun May 25, 2008 8:34 am

BMW Fan wrote:Why make things so complicated?
why don't you just take of the dam thing and go only with a plain return to tank ?

You need some heat in the tank around the pickup to liquefy a small amount so it can be sucked up the pickup tube. VO will be gelled at 0F.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
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