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Placement of Flat Plate Heat Exchanger
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Well I finished installing the FPHE today. I used the smaller pex valves (2 of them) where I tapped out of the coolant line where it exits the block. I put the coolant return just after the water pump, near the turbo. Currently I have the fuel always running through the FPHE and the coolant laved on or off. If anyone sees potential issues with this scenario please advise.
As soon as I mix up another batch of veg oil blend, I'll give this setup a road test.
Right now I am running on straight diesel.
I am also happy to report that I have secured another source of WVO, after my old supply decided to start giving it to his nephew. This new source is much cleaner oil anyways, so it worked out for the best.


1983 Mercedes Benz 300SD
290,000 miles. 50K on alt fuels.
 
Location: North Shore Vancouver | Registered: October 22, 2007Reply With QuoteReport This Post
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I put the coolant return just after the water pump

the return should be on the suction side of the water pump



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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Why is it that the coolant return should be on the suction side of the water pump?
I am also trying to wrap my head around a looped fuel setup, so that I am not always returning heated fuel all the way back to the tank. Do I need to tee off the "cigar" fuel hose and back to my input line, before the filters?
 
Location: North Shore Vancouver | Registered: October 22, 2007Reply With QuoteReport This Post
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Why is it that the coolant return should be on the suction side of the water pump?

So the pump will suck hot coolant through the FPHE.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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In my opinion, if you're operating with a single-tank system where you aren't heating the tank, you're not going to want to loop. I've done 4 two tank systems, each of which had an open loop to the diesel tank and switched to closed loop for veggie oil. But I had coolant lines running back to the tank through a discrete heat exchanger.

Problem with a single tank system is two-fold:

1. you probably don't have heat going back to the tank.
2. the fuel lines from the tank to the engine are not insulated

Consequently, it's going to be like sucking a milkshake through a straw.

I've had best luck with a single tank system by leaving the open loop intact so hot fuel is routed back to the tank. It takes, at idle, about 30 minutes for every bit of fuel to run from the return lines back to the tank. That'll be warm fuel.

In addition to leaving the open loop intact, I've added a 15 PSI thumper pump right at the fuel tank pickoff. Pumps always push better than they pull. So this pump will ensure that the fuel makes it up to the mechanical lift pump which, again, is better at pushing than pulling.
 
Registered: January 31, 2006Reply With QuoteReport This Post
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Bemore:
Suggest the return line be " T " just BEFORE the LP. There is an advantage, i.e. saving as much heated VO going into the LP, especially in a one tank system, . I agree that pumps are more efficient pushing than sucking fluids. Air leaks are a bugger to find under suction vs leaks under pressure.
 
Registered: October 30, 2005Reply With QuoteReport This Post



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Just so I am absolutely clear on this; You are advising the same as John G., to return the coolant just before the water pump, correct? Thanks.

quote:
Originally posted by Dragonfly:
Bemore:
Suggest the return line be " T " just BEFORE the LP. There is an advantage, i.e. saving as much heated VO going into the LP, especially in a one tank system, . I agree that pumps are more efficient pushing than sucking fluids. Air leaks are a bugger to find under suction vs leaks under pressure.


1983 Mercedes Benz 300SD
290,000 miles. 50K on alt fuels.
 
Location: North Shore Vancouver | Registered: October 22, 2007Reply With QuoteReport This Post
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I could be mistaken, but I think he was replying to my post about fuel loop, not coolant loop. Although I could've mis-read the post.

Anyway, my post was definitely about fuel loop and not the coolant loop.

Some might argue by closed looping fuel, you'll simply require less fuel in total. But I think any advantage you might gain in this respect would be offset by the disadvantage of never looping hot oil back to the tank, especially if you're like me and you start the car some 30 minutes before driving it. In the case of an open-loop, you'll have a nice warm tank from which to route fuel through the copper lines to the front.

Else, if closed loop, your tank's still going to be like a frozen milkshake. And I have found getting fuel from the tank to the front is every bit as challenging as pushing cold fuel through a filter. I didn't think that'd be the case, but it turned out to be true (trial and error).
 
Registered: January 31, 2006Reply With QuoteReport This Post
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your tank's still going to be like a frozen milkshake.

With a single tank system the VO in the tank should be diluted with diesel and petrol, adjusted for ambient temperature, so that it's never going to be like 'a frozen milkshake'.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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Why pay extra for diesel for something a small 15 PSI pump, a heat chamber with a glowplug, and an open loop can't solve? A little extra work is all it took.
 
Registered: January 31, 2006Reply With QuoteReport This Post
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Why pay extra for diesel for something a small 15 PSI pump, a heat chamber with a glowplug, and an open loop can't solve?

Reliability !!

It all depends on the ambient temperature where you are. You don't want a 'frozen milkshake' in the fuel tank.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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I would assume that somebody would already have opted for a single tank system over a dual tank system based on climate exigencies and reliability.

I'm no scientist, so I don't think anybody should rely on my posts if they're looking for data; however, I've got some amount of experience with both dual tank systems as well as single tank.

In Michigan, I was driving in -17 degrees in January on a dual tank system. It was closed loop for WVO with a 'triple bypass hose' routing back to that stainless tank. So the WVO line had coolant lines as its companions on the way to the front. Closed loop made sense. And I went the entire winter without mixing diesel and WVO (which has its own hazards if encountering WVO with high FFAs). I used diesel only in my 'starter' tank.

In Atlanta, and because I have a wagon that I wanted to remain relatively unmolested (due to resale being much higher if all the WVO sundries can be stripped off when I sell it), I opted for a single tank.

Open loop made much more sense so I didn't need to re-plumb anything. It also made the most sense because like the other respondent, I'm using a flat plate heat exchanger which gets oil sizzling hot.

So it made sense to me to route back to the tank. But oddly, the amount of fuel returning to the tank lessens as you go faster. Plus the copper lines get colder. I have had extremely good luck with this combination for assisting when I'm going fast in the cold:

1. FPHE right before the lift pump
2. 14 PSI thumper pump right after the tank pickup
3. a heat chamber using a glow plug - the heat chamber has a 130 degree thermister that closes above that temperature to prevent runaway. The thermister sets a DPDT relay which then disables power to the glow plug until the thermister resets again, at which point the relay resets, and glow plug gets power once again. I have a lamp under the dash so you can see it turn on and off all the time.

Anyway, I've run on straight WVO about 32 degrees F with no clogging. I'm still unsure if this would work reliably below that.

So I haven't yet tested out your 'reliability' thesis yet. But hopefully we'll have some cold days.

But again, using a FPHE, I see no reason NOT to recover some of the hot oil to the back tank. And then simply augment with diesel or kerosene or even ethanol free gasoline where the above setup doesn't satisfy climate demands reliably.

Does anybody think otherwise in terms of open loop? I'd be interested to know the rationale for closing the loop on a one tank system.
 
Registered: January 31, 2006Reply With QuoteReport This Post



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What do you all do to catch the spillage when you cut into your coolant lines around the water pump? Simply put a large basin of some sort beneath your incision or what? Perhaps a clamp ot two on tne hose will be the ticket.
P.S. Dana wasn't it you who allows your vehicle to warm up at idle for like 30 minutes? That seems like a very long time to me. Or perhaps you were simply stating it takes 30 minutes for the contents of your tank to get up to temperature. If so pardon me.


1983 Mercedes Benz 300SD
290,000 miles. 50K on alt fuels.
 
Location: North Shore Vancouver | Registered: October 22, 2007Reply With QuoteReport This Post
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What do you all do to catch the spillage when you cut into your coolant lines around the water pump?

I can't speak for anyone else, but I simply clamped the hose shut with vice grips, made the cut and inserted the 'Tee' which was already attached to the hose to the FPHE. Very little coolant was lost.
To feed the FPHE I 'teed' into the coolant line that comes off the block to feed the cab heater, and the return from the FPHE is 'teed' into the return line to the pump. The FPHE is on it's own coolant poop in parallel with the cab heater loop.

I run a single tank system keeping Toyota's OEM tank return, with the FPHE added between the lift pump and the fuel filter. It uses a fuel mix of ULSD, VO, BD, and jetB [or petrol]. The proportions are varied for the time of year and ambient temperature. I use the diesel truck to about -25°C, and in colder temperatures I run a gasoline vehicle.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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Hey. Yep, 30 minutes. I've been driving the w123 and w124 for about 10 years. And there's nothing they hate worse than running down the road cold. Since it's straight WVO, the cost of a good warm-up is small
 
Registered: January 31, 2006Reply With QuoteReport This Post
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Prolonged cold idling is a good way to 'coke-up' an engine.

Plug-in preheating is much more effective.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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Originally posted by Dana Shields:
Hey. Yep, 30 minutes. I've been driving the w123 and w124 for about 10 years. And there's nothing they hate worse than running down the road cold. Since it's straight WVO, the cost of a good warm-up is small


The amount of time taken and fuel going through the engine in a 30 min warm up would be far more than a 1 min idle and then driving the vehicle. The fuel would have a lot better chance of causing guming or coking than if the thing was driven moderately where it could have some load and get some turbulence and real heat into the Cylinders, injectors, IP etc.

It is well known the fastest way to warm up an engine is to drive it carefully till it gets up to temp. Extended warm up was a good thing 50-60 years ago when engines and Oils etc were totally different but not today.


Also in the case of Benzes, do not think that because the temp gauge shows they are up to temp they actually are. Drive the thing a few min till it shows normal operating temp then jump out and put your hand on the IP, block and gearbox. You will find they are lukewarm at best.
As the IP is engine oil fed, it's easy to see the COOLANT is up to temp but the engine is not.

I doubt anything is warmed up much at all with a 30 min idle. On my truck I can idle the thing from cold almost indefinitely and still put my hand ( just) on the exhaust manifold. at idle the engines have about 98% excess air which helps keep the Cylinder temps down.

I Run straight WVO most of the year and did away with HE's and 2 tank systems years ago but there is no way in this world I'd idle an engine from cold for 30 min on Diesel let alone Veg. To me that sounds like a recipe for trouble.

I'd put it down to a lot more good luck than management that some have got away with it so far.
 
Registered: July 30, 2010Reply With QuoteReport This Post
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I would think a block heater would be cost effective vs the current price of electricity for 30 mins. To clear up the my post about " T" connection, yes I was talking about the VO return to the input side of the pump.
 
Registered: October 30, 2005Reply With QuoteReport This Post



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The plug-in preheating on my truck [block, FPHE & injectors] costs about 6¢ an hour and is much better for the engine. Warm-up time depends on ambient temperature.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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I live on an extended 1-in-3 grade hill in a town called Mountain Park. Transmission hates it, and it's pretty obvious from the way the drive train acts and smells, it's not a good thing to do cold.

The block heater would DEFINITELY be a better solution but the cord is busted. I bought a standard block heater cord and for some reason, it doesn't fit the recepticle. The heater cord's plug is rectangular while the one on the block is a big round one.

I'll need to have my mechanic get up there and bust the old one out. Apparently, they're not that easy to break loose.

But I acknowledge that a long warmup isn't ideal.

I have had the idea that taking it out on the highway at 75 MPH for 30 minutes would take care of it, along with Diesel Purge every couple months, but again, I'm no expert mechanic. In terms of the engine coking, does anyone else have any opinions on either?
 
Registered: January 31, 2006Reply With QuoteReport This Post
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