Comments/opinions on my 2 tank design

[Turbogeno]

I have 1300 or so WVO miles on it.
It is for mild weather only.
All valves are manual.
The parallel FPHE and main filter are the only insulated components.
I don’t plan on burning WVO or even using the car much for short trips so the manual valves won’t be a problem for me.
I centrifuge my WVO and will see how long the filters last.
Purge time is about a minute and shorter once the veg tank warms up.

In operation it seems to be working very well. Within 2 minutes of turning on the FPHE the main filter is very hot and the oil leaves it at around 150°F. The injection line heaters get the oil up to 180°F right before the injectors at highway speeds and a bit hotter during slower driving.

One thing which surprised me very much was the amount of WVO returning to the veg tank and the temp at which it got there. I don’t have the hard #s but my 12 gallon veg tank in the trunk will increase 40°F or so in 1 hour of highway driving. The body of the return valve in the trunk is very warm to the touch. That is with no insulation on the lines or tank and I live in upstate NY. It hasn’t gone above 85°F here in over a month.

I got great mileage on my last trip. 8-19-08, 333 miles, 10.875 gal. 30.62 mpg, 90miles highway, 240 mi. back roads, ~4% rug.

Sorry about the poor diagram.



Thanks, Geno

[VinDiesel]

Most would place the supply valve between the FPHE and the pre-filter. That way the diesel never goes through the HE. Then coolant can flow through the HE all the time and not have to be switched or valved (except in case you want to run diesel in the VO tank).

You're also sharing the original diesel filter; a definite no-no, as it will cause cross-contamination and a gulp of VO upon a cold start. Much better to set the system up with a separate heated veggie filter.

[Turbogeno]

I wanted as simple a system as possible while still giving me some options. One of which, as you state, is switching the fuel in the tanks. Also, while the car is shut down there is no WVO in the FPHE or most of the fuel lines.

I can see the fuel in the trunk right by the return valve and switch when it’s the correct color. There will be a little cross contamination but I do not think it will be much and I’m not using the car for a lot of short trips. After I switch back to diesel I drive at least 5 miles before shutting down and I would be very surprised if there was any WVO in the filter or anywhere else other than the tank.

If I’m missing anything please comment, that is the intention of my post.

Thanks, Geno

[VinDiesel]

Geno,

If sharing a filter, there will always be some veggie that will not wash out. After sitting overnight, some will settle out. That will give the engine a gulp of VO when it's cold and when trying to start. Not good.

As has been said before, you can have cheap and simple, or you can have a good system; not both.

Since your proposed system includes an additional pump, you might as well just make it dedicated to VO only and add a VO only heated filter. That way, you would never have to worry about accidently heating the diesel (very bad for your IP and injectors). Purge time would be much less.

Maybe engine longevity doesn't matter on an older Mercedes so much...

[Turbogeno]

I put 40 miles on the car today. 10 diesel miles to warm up, 22 on WVO and 8 miles on diesel back home. I pulled the main filter, poured it into a glass and let it drain for at least 10 minutes. While it was draining I pulled 2 samples from the diesel tank. I added 20% WVO to one of these samples.

On the left is the fuel from the filter, middle glass is fuel from the tank and the glass on the right has 20% WVO.

The sample from the filter is slightly darker than the sample from the tank but both are much lighter than the sample with 20% WVO added.

I let the samples sit for over an hour to equalize temps before doing the viscosity test. 14 ounces of fuel was used for each test.

Main filter sample 165 seconds

Diesel tank sample 165 seconds

Diesel tank sample with 20% WVO added 176 seconds

These tests show me with near 100% certainty that there is no significant amount of WVO in my filter after 8 miles.

This test is only valid for my vehicle with my setup, as always YMMV.

Thanks, Geno

[VinDiesel]

Geno,

Eight miles is nothing. What about after 300 miles? 1,000?

BTW, I said not all of the VO would wash out of your filter. That means draining it will not yield all the VO that might be in there.

Just because something will seemingly work in the short term, doesn't mean it's a good idea in the long run. It seems to me that your time (distance) to switch-over is about twice what it should be. You definitely could have a much shorter purge time with a better-configured system.

Of course it's your choice- your vehicle/engine and you are free to do anything you want. Most of us here are interested in the most efficiently operating system we can have, not the cheapest. So our advice follows that thinking.

Regards,
Vince