How hot is hot enough?

[geewizztoo Senior Member Find all posts View Profile Close geewizztoo]

Just recently I bought a second diesel vehicle (a Triton ute) with the intention of adding a 2 tank conversion so that it could run on straight veggie oil. Then someone told me that this type of vehicle was not the most ideal candidate, something to do with type of Injector pump. But I couldn’t fathom why there would be any problem if the veggie fuel were heated sufficiently so that the viscosity was lowered to match the intended fuel - mineral diesel.

This got me thinking, how hot does the oil need to be? Can the veggie be heated to the point where the viscosity matches that of cold diesel? As it turns out, I have access to a Brookfield viscometer, which is a laboratory instrument for measuring viscosity, and I managed to borrow it for the weekend and I ran some tests.

I picked a random sample of clear, runny, WVO and compared this to brand new veg oil, biodiesel and diesel. The result is shown in the graph. The maximum temperature used in the tests was 85°C as it is unlikely that many water-cooling systems in cars will ever go above that in normal operation. And as you can see, the viscosity of both the new veg oil and WVO came quite close to matching the starting point of room temp mineral diesel, but not quite. So my conclusion is that I’ll be adding the best heat exchanger that I can afford to my WVO conversion.



The thought of using a blend has also crossed my mind, so I ran a few tests with new veg oil diluted with mineral diesel in the range of 100% SVO to 50/50% in steps of 10%. I picked these two fluids in an attempt to cut out the variability between different WVO’s and diluent samples. I would also liked to have included Kero, Petrol and Biodiesel as the diluent but I didn’t have the time, maybe later. But I figure the trend will be much the same.



You can see that as the percentage of diesel increases the viscosity reduces, no surprises there, since this is whole reason were adding it. But you can see that we need to add a sizeable proportion of diesel (30-40%) to even halve the starting viscosity of WVO. And since the critical condition is the cold-start, that figure would be better off approaching the 50% mark as the nights get frostier.

Maybe if I can get my hands on the instrument again, I’ll get a chance to try different diluents and also cool the blends to zero to replicate a frosty morning start.

[W123 x 2 Senior Member Find all posts View Profile Close W123 x 2]

Re: How hot is hot enough?

Great work! Just what we need on the forum, some facts and figures.

A couple of points; 24 centistokes is the max figure before the lucas type rotary injector pumps start internal cavitation and self destruct. To allow a safety margin for these pumps, 10 or 15 centistokes is probably wise. This means that any unheated blend of used veg and diesel probably isn't safe with this type of pump, especially as the temp drops. Furthermore you would have to be sure straight veg oil was at 80 degrees Celsius before change over with a two tank system. A 50/50 blend and heating, or a ulp veg diesel blend might work, but caution is the word.

The bosch in line type pumps are apparently OK to 60 centistokes or more. Which is why the old Benz's do so well on WVO or blends unheated. But even the mighty OM617 MB engine and pump benefits from a reduction in viscosity via heat or blending.

Here's hoping you can get the machine again and test some other blends. It sure beats the 'Dr. Pepper Viscosity Metre" I've been using.

Thanks again,
Michael

[clackdwack Member Find all posts View Profile Close clackdwack]

Re: How hot is hot enough?

good info mate, just one thing you should think about is dont forget by the time the wvo gets to the IP and its sitting there for a few seconds its probably over 100 -150 oC, and also once the wvo is at the injector tip it will be hotter again, the engine temp will be a lot hotter around the top end due to the explosion of wvo/Diesel, i wouldnt worry to much about getting the visco to the exact same as diesel, if you have a infared temp gun run your engine and see how hot the IP and Fuel lines and injectors and so on get, the thing that i have been keeping in mind is making sure it passes through the filter (thin enough WVO)

i havent been doing this for to long,so i dont want to sound like a big cheese

cheers mike

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: How hot is hot enough?

Clackdwack,
The most important temperature for the oil in a diesel engine is the temperature inside the injection pump. Coming a close second, is the temperature of the oil in the oil filter (must be above the melting point of the oil) That is the main reason for these tests.

geewizztoo,
Can you please re-label your graphs with the type of new oil and the type of new oil which was later used for the used oil tests. This will assist others who could have different oils and may expect the same figures to apply. Obviously, oil with a different fatty acid profile (esp. proportion of high melting point oils) would have a different curve.

Please keep up the good work.

Here is one for you to consider testing,
Relative viscosity of new oils of different types.

Palm oil (non-hydrogenated & hydrogenated if you can obtain both), soy, canola, cottonseed, grapeseed, safflour, sunflower, etc

Keep up the good work.

Regards,
Tony

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: How hot is hot enough?

Geewizztoo,
I have revisited your graphs. Would it be possible to perform the tests to 0°C or lower, so as to allow those in colder climates the opportunity to use these results without extrapolation.

Thanks,
Tony

[Fitian Was here Find all posts View Profile Close Fitian]

Re: How hot is hot enough?

Great work mate , Thanks for putting the time and effort and sharing these results with us.

After running my 300D on wvo for the first two months using only 20 flat plate heat exchanger I then realized that it was not giving enough heat. Lucky it was in summer.

I used to take too long to change over too.

After adding the twin coil heat exchanger things got much better. and the engine sounded more comfortable.

Would be even better to use 30 plate.

I have used 2 twin coil "total of four coils" units in one conversion and they gave a very good result.

Also there are some flat plate heat exchangers in the market right now with ready fitted barbs size 3/8''. I doubt that they are any good for wvo application because the 3/8'' barb will restric the coolant flow.

Please keep us updated

THANKS

[gwalker Senior Member Find all posts View Profile Close gwalker]

Re: How hot is hot enough?

This is really great info. Thank you for taking the time to do the tests.

It suggests adding a temperature sensor in the fuel line prior to the injector would be worth considering.
Has anybody done this?
George

[clackdwack Member Find all posts View Profile Close clackdwack]

Re: How hot is hot enough?

i have placed a 2'' temp guage the sender is just before the injector pump, giving pretty good readings that close to the IP.
cheers mike

[gwalker Senior Member Find all posts View Profile Close gwalker]

Re: How hot is hot enough?

i have placed a 2'' temp guage the sender is just before the injector pump, giving pretty good readings that close to the IP.
cheers mike

Mike,
What type of guage is it?
George

[Fitian Was here Find all posts View Profile Close Fitian]

Re: How hot is hot enough?

Sounds great Mike, Where did you get them from? Any photos please?

Cheers,

[geewizztoo Senior Member Find all posts View Profile Close geewizztoo]

Re: How hot is hot enough?

Michael,

The units shown on my graph are Centipoise, which is a measure of dynamic viscosity. The Centistoke is a measure of kinematic viscosity. To convert between the two, just multiply Stokes by the oils' specific gravity:

Poise = Stokes x specific gravity.

The two values will be pretty close (~10% difference) as the specific gravity of veg oil is around 0.88.

So for veg oil: 10 cP = 11.4 cS, 20cP = 22.7 cS, 40cP = 45.5 cS, etc.


Tony,

My apologies I do not know the type of the new oil, I suspect it was a blend, but I dont have the original containers. It was that stuff kindly donated by Fox Studios. But the same oil was used in both series of tests.
And yes, as I said in my original post, I'll try to do some tests at 0C and some other types of blend when I get the chance.
I take your point about the different types of VO, my hunch is that there will be a large range of viscosities at lower temps but as the temp rise the values will converge in a similar way to the curves of WVO and new oil in my graph. Palm or tallow oil maybe a different story. I'll try to get round to testing them.


Clackdwack,

Thanks for your comments and I appreciate that there will be regions in the fuel system where the temps will be considerably hotter, but when designing a SVO system you need to pay attention to the weakest link areas, such as the small diameter fuel lines, filters and changeover valves to determine the lowest temp that these components will perform their desired function. The goal of both blending and SVO systems is to lower the viscosity to within the operating range of the vehicles original equipment.

Cheers for all the input and I'll try to add to this data when time allows

Wayne

[Guest Close David]

Re: How hot is hot enough?

This is great factual info Wayne that is scientifically based. While we mostly read of experience and impressions which are valueable, factual infomation like this is very rare and of a great benifit to all.

Obviously the variations of oils tempratures and blends is endless and completely impractical to test every one given how long these tests take to run. I think what you have here gives a great indication as to what other similar oils will be. Obviously one oil may be slightly different to another but I think it is the likely charateristics that are important, not the actual centipoise of each and every oil.

I would suggest that rather than testing each and every oil that won't have that much variation between useable and not at certain temps, If you are able in the future to test some blends with petrol or kero, that would be more helpful. As you say, oils are going to follow a similar curve and I think we can already see from the tests you have done what temps are going to be needed. The current thinking with WVO usage is the hotter the better and this is born out by what you have tested here.

Great work, thanks for taking the time and putting in the effort to make it available. I'm sure you will see refrences to your findings popping up all over the net now!

[Alga Senior Member Find all posts View Profile Close Alga]

Re: How hot is hot enough?

Hi Wayne, your graphs are great. With regard to your triton, I've got a 94 ute and have been running 15%ULP, 20% BD and the rest WVO. Its done more than 2000 klms on this with no trouble at all pump wise. The temperatures have dropped down here (4-18c), but it still runs really well and no pump noise. My only Problem has been gunk in the fuel system, when it comes back from the mechanic ( gearbox), will install a 20 plate FPHE and will drop the ULP.

Your graphs have given me a bit more confidence in my blends, which I really appreciate, thanks.

[Guest Close David]

Re: How hot is hot enough?

But even the mighty OM617 MB engine and pump benefits from a reduction in viscosity via heat or blending.

I installed a home made Heat exchanger on my Benz and found it did make a huge difference to the way my car runs on blends. No doubt in my mind the heat and thinning has helped significantly although I do not know if it is because the fuel can flow through the filters easier or it makes some difference to the IP itself. As the improvement is evident even when the engine is throughly hot, I tend to think the main effect is on the filters but whatever the reason, the improvement is very noticeable.

i have placed a 2'' temp guage the sender is just before the injector pump, giving pretty good readings that close to the IP.
cheers mike

After running my 300D on wvo for the first two months using only 20 flat plate heat exchanger I then realized that it was not giving enough heat.
After adding the twin coil heat exchanger things got much better. and the engine sounded more comfortable.

Would be even better to use 30 plate.

I have thought of putting a temp sender on the fuel line before the pump along with a turbo gauge but have yet to find a fitting for the temp sender to do so. Could you tell us where and how much the one you got was Clack?

I would be really interested to see what difference heat exchangers do make to the inlet temp of the pumps. If Fitian can fit a temp gauge, maybe we can get him to do some tests between 20 and 30 Plate FPHE's and the twin coils etc.
The temp the oil arrives at the pump at is something I have always wondered about with the different types of HE's and even the way they are plumbed in. It would be great to see some actual data on this.

[W123 x 2 Senior Member Find all posts View Profile Close W123 x 2]

Re: How hot is hot enough?

David,
I'm fairly confident that the improvement you noticed is in the fuel flow though the filters. The IP is quite warm to the touch after a 15 minute run (haven't measured it but guess 50 degrees plus externally) and the 20 FPHE made a noticeable before and after difference to horse power when fitted.

I didn't want to run any heat exchangers, as I don't like all the plumbing and hoses, but the improvement made me. As you know, ANY improvement in HP in the 300D is to be grabbed with both hands

Alga,
I'm still running the ulp in my blend (10-15ulp 85-90 WVO) because I run a single tank and need the reduction in viscosity at start up. I forget, are you running a two tank system? If not, I wouldn't be in a hurry to ditch the ulp from the blend - not as the temps are dropping.

cheers, Michael