Reasons for insufficient heat upon switchover

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Reasons for insufficient heat upon switchover

Postby grimey » Mon Sep 06, 2010 12:33 pm

im wondering what are some factors that might cause insufficient heat upon initial switch over to VO after engine is up to temp. My temp guage starts at 120F and after switching to VO, it normally takes a good few minutes of driving until it starts to read 160F.
Im worried that my first few minutes after switchover, im burning cold VO. Or are temp guages slow at indicating temp change.

I have a 92 dodge cummins. 2 tank system very similar to Sun's design.
Heated pickup, TIH / HOH heating, coolant wrapped filter, 26plate heat exchanger.

The filter is a racor 900 series. the heat exchanger is about a foot away from the IP and the hose leading to the IP is insulated together with the large radiator hose.

My coolant is plumbed the same as suns design except mine branches off to the VO side right from the block with 2 valves to adjust flow to the VO side or the cab heater side.

Also, if the FPHE is right by the IP shouldnt it be able to heat up the VO to close to coolant temp? or would the FPHE not be able to heat up the oil enough if supplied with too much cold VO?
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Postby dragonfly » Mon Sep 06, 2010 10:57 pm

The engine water pump doesn't have very much pushing power for a TIH. Thus, the longer time for the VO to heat up. To help the flow of block water, add a MB aux water pump ($80) to pump the water to the in-tank HE. I'd also suggest replacing the engine thermostat to a higher temp. Typicalli, by adding the aux water pump will cut the switch over time nearly in half. I will not switch over to VO unitl the engine operating temp of 180F has been reached. I replaced the standard MB thermstat to a "winter thermostat" which is around 195F. It has grately helped. To raise the VO temp, a coolant heated VW fuel filter was installed before the 32 FPHE. The above equipment is incorporated in my 1980 MB 300D.
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Postby SunWizard » Tue Sep 07, 2010 10:43 am

I agree about checking and replacing your t-stat, it makes a huge difference and is easy.

I find the water pump pushes very well through all my parts in a single loop on my Cummins. On my mercedes it is very weak and that's why they use a pusher pump stock for the heater core. What coolant temp are you switching at? where is your temp sensor? The few minutes could be simply the time it takes for the hot VO to warm up the sensor and surrounding metal tee. On mine the cheap mechanical sensor is right after the FPHE, and it takes about a minute to register the true VO temp.
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 grimey » Wed Sep 08, 2010 10:25 pm

So u can get a higher temp t-stat? And this just allows for higher coolant temps? Maybe I'll try one of those. Did you put one in your cummins Sun?

My H.E is about a foot from the IP and my temp sensor is in between the two.

Should I rule out the possibility that my large racor filter could still be holding cold VO even after the engine is up to temp? It does have a full coolant wrap but I thought maybe the few minutes it takes my temp guage to reach 160f is the remaining unheated VO in the middle of the racor housing.
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Postby SunWizard » Thu Sep 09, 2010 8:27 am

grimey wrote:So u can get a higher temp t-stat? And this just allows for higher coolant temps? Maybe I'll try one of those. Did you put one in your cummins Sun?

I put a new t-stat on, a stock 185F one which raised my temps.
Should I rule out the possibility that my large racor filter could still be holding cold VO even after the engine is up to temp? It does have a full coolant wrap but I thought maybe the few minutes it takes my temp guage to reach 160f is the remaining unheated VO in the middle of the racor housing.

It could be partly the racor. A coolant wrap doesn't heat the contents much.
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 coachgeo » Sat Sep 11, 2010 1:54 pm

get an IR meter. on different days with approx. same ambiant temps.. at approx same time into switch over.... stop and use IR meter to measure temps at different places such as at least at the racor's exit.. and right next to your temp sensor. Some readings along the line at marked spots would add more data to diagnose with. Record your data. Do this several times a week to get a common range of values. (hopefully it is common) If the two extreme ends show a deviation then it may be your racor does have cooler oil that is still being replaced by hotter recirqulating oil.


Next step is to measure same areas several times over a week like before but wait little longer into the cycle.

Comparing the results might indentify if you have a short time span of cooler oil coming out the racor as you suspect. For example if you have higher readings at racor exit and further up the line but values similar to previous from the marked spots further along and at the temp sensor... then that would seem to indicate you have a cooler slug of oil moving up the line as time goes on.
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Postby dragonfly » Tue Sep 28, 2010 1:34 pm

SunWizard,
Answers to your questions: I switch (within 4-5 miles) to VO at 175F indicated at exit of the engine coolant water just off the block where the MB aux water pump is installed and where a temp sensor is plumbed into the output line. I also have another temp sensor just before the IP. A third temp sensor is installed as the VO leaves a 16 plate HE. I have kept all the VO fuel lines are as short as possible and insulated to the fuel supply solenoid then on to the IP. Heat is the best friend VO can have. Get as much heat as possible. It takes 10 seconds, with the engine idling, to go back from VO to diesel. I can hear the engine's RPM change.
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Postby HoldOnTight » Tue Sep 28, 2010 10:58 pm

As I understand it, spraying cold oil in a cold engine is really bad. Spraying cold oil in a hot engine is not so bad if it is not long term situation. The fuel won't burn as efficiently if the oil isn't creating a fine mist, but it should also not create ring land coking as quickly as when the engine is cold. Short trips that occur often will make this situation worse. We just don't live in a perfect world. You could improve the temps by using an injector line heater after the IP to warm that cold VO slug if you really are concerned, and have a timer cut it out when the temp of the fuel entering the IP increases enough or when running on diesel.

Many people observe the same behavior as you and it doesn't seem to be causing failures. Will it shorten the life of your engine? Probably, but not by much if you change your oil more frequently.
Late 99 Ford F-250, Designed and installed at home, 30 kMi on VO. WVO temp at solenoid valve is 185-195+F, winter-summer.
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