opinion on setup

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

Good morning,

I have attached a diagram of the setup I am planning to end up with.
The difference relative to the one I already have is the addition of a lift pump near the main tank (probably a Facet 11PSI), a second HE, a CAV filter and a bypass with antireturn valves.
The idea behind fitting the lift pump is to help the injection pump getting oil but mainly to "push" oil through the CAV filter to avoid frequent filter changes, even if I fit a second HE right before it.
However I have read somewhere that excessive pressure can damage the IP, so the purpose of the bypass is to relieve the pressure. In other words, I donīt want to create pressure at the entrance of the IP. Just want to be sure there is always enough fuel available to feed it.
Excess oil would just via bypass join the oil coming from the IP and going back to the tank.
The anti return valves would prevent the IP from sucking oil out of the main tank via the return line.

I would really appreciate if you let me know of any potential problems with this setup.
At the moment fuel starvation due to excessive filter restriction is an issue I donīt know how to resolve without fitting a lift pump, but I am concerned about excessive pressure breaking the IP.

Kind Regards
gonzalo

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: opinion on setup

The doc didnt open properly for me, (I found converting cars easier than posting attachments) but it sounds reasonable. I would use a return as you have suggested to avoid pressure at the IP. Make sure the the return line is free flowing, as if it blocks you will get pressure on the IP return.

If you get a "turbo" guage for a car (the inlet manifold vacume/ pressure guage from a turbo petrol car) you will have an excact idea on what pressure the injector pump is recieving.

When I had (2) cav filters one had no air going into it and heaps comming out. (the other seems to have some leaks, but only champane size, not the jaccuzi/ spa size bubbles of the other) I have no idea why or where. I think I know why most (paid for) conversions seem to use bosch filters....

[Guest Close David]

Re: opinion on setup

Speaking with all the ignorance of someone who has never done a conversion, I wonder about the nessicity for 2 HE's. Bio dosen't need to be heated so by eliminating the HE you have right before the pump now shouldn't make any difference. I can't see you would loose that much heat on the veggie side by just passing the oil through a CAV before the pump. If you found that you weren't getting the temps you want, you could insulate it and reduce any loss to a minimum.

I suggest you plumb your HE in SERIES in your heater line rather than in parralell so as you get the maximum heat which shoul be very close to the coolant temp going through it and may well be above the rest of the engine temp.

I would also suggest using a fuel pressure regulator and setting it to put 1-2 PSI at the inlet of the pump. This will not strain the pump, it would take some load off it and ensure that there is always an adequate fuel supply.
Your other option would be a surge tank which will allow you to put an amount of fuel in reserve after your filter at low load to be available to fill the extra fuel requirement at higher loads.

Without some sort of regulation with a positive pressure at the IP or using a surge tank, you won't get 0 pressure at idle and load. If there is zero pressure at low load, the pump will be pulling at higher load given the same diameter pipe going back to the filter which is what I think you are trying to eliminate.

I don't believe fluid dynamics make it as simple as just having a simple fuel circuit to do what you want. To make the system as problem free as possible, I think you need to lookat adding a regulator or surge tank.

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: opinion on setup

Speaking with all the ignorance of someone who has never done a conversion, I wonder about the nessicity for 2 HE's. Bio dosen't need to be heated so by eliminating the HE you have right before the pump now shouldn't make any difference. I can't see you would loose that much heat on the veggie side by just passing the oil through a CAV before the pump. If you found that you weren't getting the temps you want, you could insulate it and reduce any loss to a minimum..

On my merc with 2 heat exhangers, the one just before the engine gets it to about 35deg. I added another before the lift pump and CAV filter, and it takes over an hour before hot oil comes out of it, to heat the oil hotter. It appears to loose a lot of heat. I know its over 2 items, but I assume it takes a long time to heat the CAV. I have used 2 on each conversion, one to "pre heat" the oil before it goes through the filter, only to stop it plugging, and one before the engine to get it to the prefered 50-80 degrees. (with a flat plate type, it is between 40-75 deg.)

I suggest you plumb your HE in SERIES in your heater line rather than in parralell so as you get the maximum heat which shoul be very close to the coolant temp going through it and may well be above the rest of the engine temp..

If you have dont have a heater tap go series. If you have a heater tap, I cant see how turning off the heater wont turn of the heat exhanger as well, despite being assured its not the case (I would put them in parallel if you have a heater tap)

I would also suggest using a fuel pressure regulator and setting it to put 1-2 PSI at the inlet of the pump. This will not strain the pump, it would take some load off it and ensure that there is always an adequate fuel supply.
Your other option would be a surge tank which will allow you to put an amount of fuel in reserve after your filter at low load to be available to fill the extra fuel requirement at higher loads.

Without some sort of regulation with a positive pressure at the IP or using a surge tank, you won't get 0 pressure at idle and load. If there is zero pressure at low load, the pump will be pulling at higher load given the same diameter pipe going back to the filter which is what I think you are trying to eliminate.

I don't believe fluid dynamics make it as simple as just having a simple fuel circuit to do what you want. To make the system as problem free as possible, I think you need to lookat adding a regulator or surge tank.

Both could work, the advantage of using a return line is any air can be returned to the tank, rather than going through the IP

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

Re: opinion on setup

Gonzalo,
It would help to know what vehicle / engine you plan to convert, it does make a difference.

If your veggie pump operates from startup, you could get by without the second FPHE if you monitor the fuel temperature at the CAV filter outlet, but I believe that you will have a shorter warmup period using both FPHE. The biodiesel is not compromised by the heating, and it pre-heats the IP as well as ensuring that the oil from the CAV is hot at the IP.

I do not believe that 4-6psi would have any negative effects on a Bosch rotary IP (based on discussions with HCII of Infopop and Vegoil diesel forums).

Tony

[Guest Close David]

Re: opinion on setup

and it takes over an hour before hot oil comes out of it, to heat the oil hotter.

Hi Chris,

I am not sure if I am understanding your comments correctly. Are you saying it is taking an hour before your oil gets up to temp in your car when you are using 2 HE's? Are you running FPHE's?

If you have dont have a heater tap go series. If you have a heater tap, I cant see how turning off the heater wont turn of the heat exhanger as well, despite being assured its not the case (I would put them in parallel if you have a heater tap)

This is a very valid comment and thank you for pointing it out.
It would be important to ascertain if the heater line is a constant flow type and the air is diverted away from the heater core or the heater tap diverts the hot water from reaching the heater core. Either way, it would be best to determine which way the coolant flows and put the HE between the engine and the heater core or a T so the HE receives the hottest water from the engine in a constant flow.

I believe in a 300D the water flow is constant even if it is diverted around the heater core. Fitian has arranged his HE's in series and has experienced a much faster warm up time and a higher temp in his WVO than with his previous T configuration.

When an opportune time comes up, I will drop into the local radiator place and see what info they can give me on this.

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

Re: opinion on setup

Thank you all for your comments. I am sorry the document cannot be viewed. I will try another way.

Chris, your comments about the CAV filters leaking air are making me think twice about this brand. I already had enough about leaks, so will have a look at Bosch filters too.

David, the second HE is to heat up the oil right before the filter. Since there is already a HE down the line, I think I will just leave that one there. If as a side effect I get a quicker change over time, thatīs good enough.
That pressure regulator you mention I should really have a look at. Thanks for that.

Tony, the car is a poor Peugeot 205 diesel. The 2 tank conversion was done some time ago and I have already covered 40.000km on WVO. However, most of the time I have been experiencing filter clogging problems, so tired of replacing elements I want to put some pressure on the oil. The pump I am ordering is the Facet PRO59SV Gold Flow. I have read many good comments about it. It reaches pressures up to 8PSI. This is before the filter. After the filter I am not sure how much the pressure will drop. If you say that the IP can withstand up to 4-6PSI, maybe it should be fine after all without the bypass. Iīll give it some more thinking.

Cheers
gonzalo

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: opinion on setup

Hi Chris,

I am not sure if I am understanding your comments correctly. Are you saying it is taking an hour before your oil gets up to temp in your car when you are using 2 HE's? Are you running FPHE's?
.

No the merc has 2 "home made" heat exchangers. One is about a meter of 8mm copper hose coiled in some 2" copper pipe. Coolant goes in the 2", oil in the 8mm. This heats to about 35 deg by itself. My car uses closer to 15L/100ks, which means the oil goes through quicker than normal, meaning it does not get the same chance to heat up.
I added another heat exchanger, which was just a piece of 12mm copper pipe silver soldered to an 18mm copper pipe. Coolant through the 18mm, oil through the 12mm, this is about 1.1M long (and goes under the car) nd is encased in foam to stop air cooling it. The oil travels more slowly through this one as the 12mm has a lot higher volume than the 8mm (duh)

When I added the extra one, and set off, after the first 2 ks, swapped over, and after a few more was up to its normal operting temp (35 ish) Great, no difference I thought. After about 1.5 hours the temp had increased to 55 degrees. My interpretation was it took 1.5 hours to get the cav filter and lift pump up to temp?

gonzalo.
How do you filter your oil before putting it into the car, and did you flush the tank out before you started on veg oil? Tony suggested putting a cheap disposable filter (a small clear cheap petrol filter) in front of the CAV filter. I replaced about 10 of them in the first few months as all the gunge from the old diesel tank disolved and flowed down to the filter. I have not had to replace a CAV one yet (I did, but it was clean) I put 2 in paralell and it took longer to clog.

On my first car I had problems clogging filters, and discovered my filtering method was flawed.

[Guest Close David]

Re: opinion on setup

Hi Chris,

I would be absolutely certain that your slow oil temp rise is due to a flow problem with the coolant. The cars engine temp would be pretty stable after only 15 minutes and would be at or near max temp and its ability to heat the coolant given your thermostat is working properly. If the oil isn't up to temp in 15 min, then it has to mean that your HE's arent getting enough hot coolant through them.

This could be because of the reported poor coolant flow in the merc engine heater lines, it could be the location of your HE's and it could also be that having a 12mm pipe through a 18mm pipe causes too much resistance through the HE being that you only have 6mm total clearance which could work out to only maybe capable of flowing the same as a 10 or 12mm pipe. Even this I would think at a reasonable coolant flow at 80o+ would be able to dump some considerable BTU's into you oil and certain'y stabilize itself way inside of 90 Minutes.

There is kilowatts of heat available from the coolant and certainly enough to heat your fuel flow no matter how thirsty your engine. If it takes 90 min for your oil to reach max temp and then it stays there, I would really have to wonder if it is the coolant adding heat to your oil or the heat is coming from somewhere else. Possibly this could be from a heat transfer through the brackets from the frame or some other part of the vehicle which takes a long time to heat up due to thermal mass but once to temp, transfers heat constantly.

If your HE's are plumbed in parallel with your heater, I'd be really interested to see what happened if you put them in series. This may add some extra heat but I would think the solution most likely to give the best results is to add one of those small electric merc coolant pumps so you know you have a positive flow of hot coolant. Even if your HE is a bit tight in the coolant path, increasing the flow with a pump has to help.

I have a rudimentary knowledge of thermodynamics having researched it for past projects and I would be quite certain a CAV filter has neither the thermal mass nor ability to dissipate heat anywhere well enough to drop the oil temp more than a few degrees.
The contact area of the mounting bracket is very limited and so is the ability to transfer heat this way. The element is smooth and of limited surface area and the bowl, if made of glass, is a very poor heat conductor and again, whether made of glass or alloy, has a limited area to dissipate any heat.

When one considers the underbonnet temps of a vehicle once it has been running a while, even at highway speed where the radiator is still heating the underbonnet, let alone the heat soak of sitting in traffic, the difference between the temp in the CAV and the surrounding air may only be 30o or in fact higher, than the CAV temp.

Looking at it another way, if you were to put the CAV in a bucket of running water, it isn't going to be able to drop the oil temp much because it dosen't have any properties of a good heatsink or radiator. It's ability to cool a constant flow of hot oil in an enviroment that is for the most part, not that different in temperature, is very limited.

If you are interested in getting your oil up to temp a lot faster, I am quite certain if you try the things I have suggested here you would get a much better result than what you are now. If your prepared to give it a go I would love to hear how you get on with these modifications.

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: opinion on setup

YEah I hear what you are saying, I guess a good place to start would be to measure the coolant temp as it exits the engine and rejoins it? I guess if there is not enough flow, then it will cool a lot.

The 18 and 12mm heat exchanger are brazed next to each other, not one within another, which although has a better coolant path, has of course a much worse heat transfer.
I think perhaps a problem is the time the oil spends in the heat exchanger. After doing some maths (which I now forget) I think the oil spent only about 30 seconds in the (8mm) heat exchanger whilst using 15l/100 (this was worked out calculating the volume of the pipe and how long it would run the engine for. If this is wrong lets know) Also 8mm does not have much surface area for heat transfer.

The lengths of pipes (for fuel between heat exhangers) are also a bit of an issue on my car, they are longer than they need to be.

I guess also the car (well used to) do only long trips, (5-6 hours at a time) so the temp hasnt been an issue. Probably the nextstep with it will be an elsbett conversion, as it is likely to become the "around town" car, as the other car is better suited to long trips (functioning air cond, 1000-1500 K range, and a heater that is not stuck on )
If this was the other car, indirect injection and the engine is aout 70% of the cars value, I would worry more. However if it dies, I know of a turbo engine (that comes with, but not in a car) so it may be enough to get the wife to consider it.....

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

Re: opinion on setup

No the merc has 2 "home made" heat exchangers. One is about a meter of 8mm copper hose coiled in some 2" copper pipe. Coolant goes in the 2", oil in the 8mm. This heats to about 35 deg by itself. My car uses closer to 15L/100ks, which means the oil goes through quicker than normal, meaning it does not get the same chance to heat up.
I added another heat exchanger, which was just a piece of 12mm copper pipe silver soldered to an 18mm copper pipe. Coolant through the 18mm, oil through the 12mm, this is about 1.1M long (and goes under the car) nd is encased in foam to stop air cooling it. The oil travels more slowly through this one as the 12mm has a lot higher volume than the 8mm (duh)

When I added the extra one, and set off, after the first 2 ks, swapped over, and after a few more was up to its normal operting temp (35 ish) Great, no difference I thought. After about 1.5 hours the temp had increased to 55 degrees. My interpretation was it took 1.5 hours to get the cav filter and lift pump up to temp?

gonzalo.
How do you filter your oil before putting it into the car, and did you flush the tank out before you started on veg oil? Tony suggested putting a cheap disposable filter (a small clear cheap petrol filter) in front of the CAV filter. I replaced about 10 of them in the first few months as all the gunge from the old diesel tank disolved and flowed down to the filter. I have not had to replace a CAV one yet (I did, but it was clean) I put 2 in paralell and it took longer to clog.

On my first car I had problems clogging filters, and discovered my filtering method was flawed.

Hello Chris,

I filter the oil with a pair of thick jeans. Each leg is inside a metallic container. 2 containers on top of a 200l drum. Everything sealed.
I didnīt flush the tank before using WVO.
I will go with a prefilter, as you suggest.

Chris, would you be able to tell me if the stock lift pump fitted in your Merc is electric? Is it inside or outside the tank? If it is outside, where about?
I am really struggling to find the Facet Pro59SV or even a Master E8012S in Spain, so perhaps the best alternative is to buy a Merc lift pump from a wrecker, as these appear to work well with cold WVO. What do you reckon?

I am preparing a second HE these days. I will take some pictures. I thought it was going to be heavy duty, but then I read about the 1.1m HE you have fitted to your car!!

Cheers
gonzalo

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: opinion on setup

Hi Gonzalo.
The mercedes lift pump is not electrical, it is mechanical and attaches to the side of the injector pump. It pumps well, but I dont know how to get it to work on another car.
If you put some clear hose going into and out of the filter, is there air going in and air going out? (on one of mine there was ir comming out, but not in) Did you have any luck with the bosch filter?
After mucking around with CAV filters I dont think I would use another.

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

Re: opinion on setup

Hi Chris,Thanks for the info about the pump. Bad news for me.When you say you wouldnīt use another filter, do you refer to the CAV or to the Bosch? I will go with what you say.I already know what cars fit the CAV and the Bosch as standard, so will go to the wrecker this weekend.Thanks again for all your help.Regardsgonzalo

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: opinion on setup

I have not used a bosch, but would give it a try. As a mechanic asked "did you choose the cav because you like leaks?" Unfortunatley he seems accurate. The other car which operates under pressur always seems oily inthat part of the engine bay. Perhaps there is something I am forgetting in the way of a seal, but I cant find it.
I would use the clear pipes going into and out of the filter. If there is no air going in, but it comes out, you have the problem narrowed down to one part, the same that I had with one filter(and may have on a lesser scale with the other filter, I had 2 on this car, but could not stop one leaking air)
If this is the case visit the wrecker.
Best of luck