Veggiestroke/valveless RTT/loop switching.

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

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Veggiestroke/valveless RTT/loop switching.

Postby Welder » Thu Mar 20, 2008 5:47 am

Okay, first of all, I just made up the RTT acronym. I meant "return to tank". RTT seemed faster/easier, so if you agre, lets standardise the new acronym.

Anyway, when I convert my 88 F250 to SVO, I want to plumb the fuel system in the veggiestroke/valvless style.

Can anyone describe similar styled conversions and how they plumbed the return system?

You see, I have heard of this return style called something like "semi-looped" or "partially looped" or controlled loop", but I haven't read up on that yet. Since people do that on regular SVO plumbing styles, I just wanted to see if anyone ever did that on a veggiestrok/valveless system?

Also, some guys delay their return switching to minimise unintentional fuel mixing. Any input on that subject relative to this plumbing style?
"Is there anybody out there?"

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Postby SkySkiJason » Thu Mar 20, 2008 10:39 am

I think using (2) electric pumps and check valves on the supply side is the best design. This way you have redundant fuel systems and dramatically reduce chances of roadside problem solving. Switch over by turning on VO pump and turning off diesel pump.

I also beleive the hydraforce valves (I prefer the ones with a 'manual switch/override' on them) are quite reliable. Use one 3way to select tank to return fuel to and the second on the VO return, which will either return to the VO tank or return to the VO supply (anywhere pre-pump).

Kinda like this -forgive my fumbling attempt at drawing...

Image

Now, this could be wired so that when VO pump is on, the 3ways both switch to VO operation (looped) and when a purge button was pushed it turned off VO pump activating diesel pump and putting 2nd valve in return to VO tank. This could be semi-automated w/temp switches or a 'controlling' temp gauge.

my $0.02 8)
2001 F-350, DRW, 4x4, XLT Crew Cab, flat bed, 7.3, 6 spd, Dipricol Optix gauges, DP tunes - Single-Shot injectors! Vegistroke-style WVO conversion, 55,000 VO miles so far - 190 deg VO before the heads
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Postby Welder » Thu Mar 20, 2008 3:19 pm

Thanks Jason, that's great. Your drawing is actually pretty good, I thought. It may not win any art awards, but it is clear and simple to understand.
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Postby SunWizard » Thu Mar 20, 2008 3:43 pm

Thats almost the same as my diagram in the other "electric pump" thread and I will repeat here for clarity:
Image
Most pumps have check valves in them. And you can simplify to this and avoid your second valve with no change in performance.

A limited loop return is where you put a tee in the highest point of your looped VO return, with a needle valve which lets a small amount of flow (and air if any) return to tank at all times. They wouldn't do this on a Vegistroke or valveless since there is no return usually.
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 Welder » Sun Mar 23, 2008 4:04 am

SunWizard wrote:Thats almost the same as my diagram in the other "electric pump" thread and I will repeat here for clarity:
Image
Most pumps have check valves in them. And you can simplify to this and avoid your second valve with no change in performance.

A limited loop return is where you put a tee in the highest point of your looped VO return, with a needle valve which lets a small amount of flow (and air if any) return to tank at all times. They wouldn't do this on a Vegistroke or valveless since there is no return usually.


You don't do that, do you Sun?

You don't constantly bleed a small RTT off of your veg loop do you?

I guess that's one way of ditching air bubbles from your veg side, but I'd be concerned about the long-term effects on the Stanadyne DB2 rotary IP in my older F-250 IDI. You see, I'm not sure about in-line IPs, but I've been told that that rotary IPs often have their own built-in lift pump. I think that in the DB2, it's a vane style pump.

These second IP internal fift pumps step up the PSI from the first lift pump PSI, up to a higher pressure to "help out" the rotary IP a little. From what I've heard, if the first lift pump takes a dirt nap, then the second IP internal lift pump has to suck fuel all the way from the fuel tank all by itself. This isn't too good, fom what I've read. (you're lucky to have a 12 valve Cummins with an in-line Bosch IP!)

The Ford/Navistar 7.3 IDI is a good choice for SVO, but feeding fuel to the DB2 IP at a reliable PSI is apparently quite important. Since Delphi doesn't donate it's diaphragm lift pumps to Ford/Navistar for free, I think there is a reason why it's on my truck.

For clarity, I'm not saying that you're wrong to advise people to use the limited return system you've described. I'm only saying that it might not be the best option for rotary IPs, that's all.
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Postby SunWizard » Sun Mar 23, 2008 10:43 am

No, I don't do a controlled loop. You asked what it was so I answered. I haven't had trouble with air, but if I did, this might be worth doing.

I don't understand why you think a controlled loop wouldn't work OK for a rotary IP. Its only on the return, so has no effect on the pressure before the IP.
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 Welder » Sun Mar 23, 2008 5:32 pm

A looped return kinda shares the pressure of the IP intake doesn't it?

I mean, if the return is physically plumbed into the IP intake, I can't see how the whole thing wouldn't be at the same pressure.

Kinda makes me wonder if SVO converted Ford Powerstrokes running a looped return are in any way slowly damaging their IP (for lack of a better term) with the 60 or 70 PSI backpressure the lift pump must be pushing into the IPs return outlet?
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Postby SunWizard » Sun Mar 23, 2008 5:39 pm

A looped return is best done before the pump so its not sharing any pressure, see my diagram above. Another reason for that spot for looping is with many pumps you don't want to deadhead them, which would damage the lift pump not the IP. Stock Ford powerstroke lift pumps are designed to be deadheaded. And you get a really quick purge by looping as I show, and a really slow one if you loop after the pump.
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 BMW Fan » Sun Mar 23, 2008 7:55 pm

Hi,

a controlled loop works just perfect with rotary pumps.
I personally prefer a full return to the tank and locate the return line just opposite the tank outlet. That helps melting down animal fats or shortening under winter conditions.
By the way I love animal fats for their energy and don’t get it why most people want to get rid of them.

...and yes, all rotary pumps have the low pressure pump built inside.
That is the reason why some people can't find this pump. :)
If you measure the condition in front of your pump that will allow you to decide if you want a “ helper” pump or not.
Read the values running on Diesel and compare with running on veggie.
For my Bosch rotary pump the small 4-7 psi version is just ideal.

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Postby Welder » Sun Mar 23, 2008 10:36 pm

Hi Klaus. Thanks for confirming that all rotaries have built in lift pumps. I actually asked that question on a different thread though, not this one. At least I got an answer. Thanks again.
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Postby Welder » Sun Mar 23, 2008 10:49 pm

SunWizard wrote:A looped return is best done before the pump so its not sharing any pressure, see my diagram above. Another reason for that spot for looping is with many pumps you don't want to deadhead them, which would damage the lift pump not the IP. Stock Ford powerstroke lift pumps are designed to be deadheaded. And you get a really quick purge by looping as I show, and a really slow one if you loop after the pump.


Whether the IP return loop is inserted before or after the lift pump will certainly effect a difference in the IP intake pressure. Thanks for pointing out the difference in loop insertion points, Sun.

Since pressure is directly related to flow (and flow restriction), I'm wondering if constantly bleeding veg flow off of the veg line wouldn't decrease the pressure availabe at the IP intake.

I would think that bleeding a small trickle of veggie off the main veggie line immediately before the IP would decrease veggie fuel pressure available at the mouth of the IP intake.

Although I like the idea of recycling available heat by recycling hot veggie, I like the simplicity of a full return, like Klaus mentioned.

Hey Coach, wasn't it you who once mentioned the idea of recycling available heat by running the return veggie through a FPHE to impart that heat into incoming veg? (maybe that was someone else on infopop?) That would allow a full return with minimal heat loss.
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Postby SunWizard » Mon Mar 24, 2008 9:43 am

Welder wrote: I'm wondering if constantly bleeding veg flow off of the veg line wouldn't decrease the pressure availabe at the IP intake.

No since the return line where we are bleeding has very little pressure (<1psi), and it will not effect the pressure at the IP at all. Think about it, if a limited loop lowered pressure a little, then a full return would lower it a lot since its wide open to the tank.

A full loop is the simplest since you save another pipe run and tank fitting, and I have never had air problems. A full return is less simple since you need to run another pipe all the way back to the VO tank (same with limited loop.) And you then are pumping, heating and filtering about 5x as much fuel as you would if looped. Which means you will get slower switchover times since you are consuming your coolant heat much faster and having to heat much more volume. And you will have to change your VO filter more often since it needs to be cleaner to flow 5x as 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 BMW Fan » Mon Mar 24, 2008 10:53 am

[/quote]
Which means you will get slower switchover times since you are consuming your coolant heat much faster and having to heat much more volume.
And you will have to change your VO filter more often since it needs to be cleaner to flow 5x as much.[/quote]
I got same questions.
Would you mind to elaborate how temperature effects switchover time ?
Volumne does ...but temperature does not if I run a full loop.
My FPHE, well insulated is not effected by a little more or less flow at all.

Lets state that I use your famous centrifuge technique and filter down to
0,5 micron or 1 micron absolute.
The finest filters used are 2 micron.
That means there are no particels which could be kept by this filter, correct ?
So is it "nothing " times 5 ???
For older cars like the Mercedes or the BMW I run,
the filters are 10 micron.
My full return can not ...all of a sudden....create particles which have past the filter already the first time.
My filters last app. 10.000 km.

What do you think?

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Postby SunWizard » Mon Mar 24, 2008 11:32 am

The VO temp is affected by 5x more flow during the time when we are trying to get up to temp to switchover. Since you are consuming the engine heat at 5x the rate and sending it back to the VO tank, it takes longer for the engine to warm up. I notice a difference in switchover times by shutting off the heater core flow even when the heater fan is not on. And longer switchovers when I run the cab heater. The heat you are sending back to your VO tank with a full return exceeds that.

After you get up to temp then there is little difference with increased flow since the engine heat plus FPHE capacity far exceeds the heating needed so it doesn't matter that you are sending much of the heat back to the tank.

A 2 micron filter will still catch some particles <2, and eventually it plugs as do all filters. They will plug much faster with 5x the flow. Better pre-filtering makes the filter last longer but requires more work. While changing to a looped return requires no work. On a large truck it matters more than a car since they consume 2-3x as much fuel.
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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RTT

Postby sanderlings » Mon Mar 24, 2008 8:42 pm

Hi Welder,

I hope your pump project is on track. I don't know what kind of connections are on your return, but on the 6.2L there is a daisy chain of push-on tubes that connect all the injectors with the return line. I have run a looped return before without problems, but I got cold feet about the push-ons being in the loop with the IP and return to tank on my revised "valveless" system.
todd
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