Should I purge my FPHE?

[Aaron Berk]

I'm in a conundrum, should I purge my final 30 FPHE in my engine valley?

I'm torn and can't make up my mind.

The FPHE is a Rover Hybrids 30 plate SS copper brazed HE.

If I purge the HE, then my purge times get extended, and my fuel flow diagram gets more complex and expensive. But my piece of mind goes up.

If I skip purging the FPHE, would I run into any issues?

[erbilabuc]

Id say yes.

[tubular031]

Make sure you purge up to it. My thoughts are if there is VO in the FPHE it will heat up as the truck is heating up. when you flip to VO the oil in the FPHE will be hot and exit hot on its way to the motor. It would not hurt to push a little diesel into the FPHE

[Aaron Berk]

Here is my issue, if I go the simple route, I will bring my D2 and WVO feed lines up to the valley then Check Valve on both, then y block, then FPHE.

My problem is when I run diesel it will be hot diesel because of the FPHE. and hot D2 loses it's lubricating properties real quick.

So then I was thinking about putting a normally open solenoid valve on my coolant loop (feed side) so that I can shut off the coolant to the fphe so I don't cook my diesel for the times when I drive extensively on diesel.

So that all works for me........ but I don't like it because purging the fphe extends my purge time.

Does any one have the knowledge to tell me how long it would take to purge a 30 fphe with 65 psi of fuel from a 3/8 feed line?

If I could purge the fphe in 30 - 40 seconds I'd go for it.
My purge flow is like this -----Yblock----FPHE---4" of line---Yblock---(2) 6" lines to heads ---- heads --- (2) 8" lines -- FPR --- 3-way solenoid--- done

I'm not sure how long this takes to purge, but if the fphe adds a 60 or more seconds to my purge time..... I might skip it.


Uggg, so many options. Muns!! where you at man??? didn't you add a purging FPHE to your setup?

I love this stuff

[Clay Henry]

the FP shouldn't add more than a few seconds.

[simone0414]

If you feel you need to then go ahead & purge the HE. The D2 will get heated but I find it hard to believe that small amount of heated D2 will do any damage. I don't feel it is necessary to purge it but I could be wrong. I purge up to mine. I have my VO temp sender right after the FPHE so when I see my temp gauge drop I know that I have purged to it.

If you are not going to be running veg for a while( weeks) I would purge it & shut your coolant flow off to your whole system.

[Aaron Berk]

All right, I've made my mind. And thanks a million to yous guys

Where would we be with out internet forums?


Purge it is! and I'll have a solenoid valve on the coolant flow so I can shut it off when on diesel.

Sure am glad these OBS's have big engine bays.

Any one mount a FPHE in their engine valley yet? (I need pics please)

I'll be mounting mine in a vertical position using a bracket that bolts to the old fuel bowl mounts.

Coolant will be fed into the top, and fuel in from the bottom.

Thanks for the input guys.

[muns53]

Aaron, I'm a little late to the table, sorry. Also, I don't completely understand your DIY setup, but IMO you should definitely purge your FPHE (so should you simone). Poly problems appear to be cropping up with folks using FPHEs - I've seen threads on several forums about it, some with pics. I don't know if it's because they're not purging them or because it's going to happen to all FPHEs b/c of the copper brazing. But one sure way to slow down the poly formation is to "clean it out" with diesel upon every shutdown.

FYI, I didn't have to change my purge time of ~12 seconds when I put my 16-plate FPHE in - that still clears mine out on my setup. The way my auto-purge cycle works on the V3 is: the veg pump stops, a valve on the manifold opens and the diesel pump turns on. So, the diesel is being pushed through the fuel lines on the head, back through the veg fuel lines (no check valve on the veg lines), through the FPHE, into one of the channels in the V3 manifold and then into the return line on the veg tank. (The secondary function of that return line is to allow a small amount of veg oil to regularly flow back through it from the manifold through a tiny little orifice. This keeps the lines forward of the manifold free of air.) My veg system bypasses the stock fuel bowl and the veg lines are connected to the unused fuel "test ports" on the engine. So, because it's deadheaded, I have one-way check valves on the D2 fuel lines on the head. These make sure no veg can be pushed into the diesel lines when the veg pump is running.

So, the upside of dead-heading with some type of small air bleed orifice is a very short purge. The downside is there's a pressure spike every time you start up the motor (pegs my 100psi guage, so not really sure how high it goes). Then, the only thing left to do on shutdown is to let the motor idle for a minute and 1/2 to burn out any veg oil remaining in the motor and refill it all with diesel for the next startup. The V3 does this automatically with a run timer card, but you could do the exact same thing automatically by installing a "turbo cooldown" timer.

I also wanted the option to run diesel through my veg system if I ever ran out of veg. So, I just set up ball valves on my coolant lines. I can shut off a valve at the front end of the system (right after where the hot coolant line is tapped into) and also at the back end of the system (on the return coolant line after the veg oil tank). So, if I close the valves, the FPHE, manifold, tank, etc. get no heat. I'm not sure I understand how you intend to use a normally closed solenoid/valve to do it. Does that mean it would only come open when your turn the system on - or are you putting in a seperate on/off switch to close it automatically?

Regarding the mounting position, I went back and forth on that a lot. Frybrid recommends mounting it with ports up because there's less chance of air in the veg fuel lines causing poly to form. The manufacturer states you get the best heat exchange mounting vertically (like you're describing) or next-best is on it's side. I ended up mounting on it's side because I put mine under the truck and there's no room for vertical orientation. I won't have any air in my veg fuel line, so I figure that's the best of both worlds. You won't have any air in your line either, so you should be good to go mounting vertical - especially since you have the room under the hood.

Hopefully this gives you some ideas and my description was clear. I have a thread on here about changes I made to my system before the winter with lots of pics - hopefully you can see what I'm referencing.

[Clay Henry]

Originally Posted by Aaron Berk

The FPHE is a Rover Hybrids 30 plate SS copper brazed HE.

I think this is a bigger issue that whether to purge or not. This thing will polly up inside.

[muns53]

Originally Posted by Clay Henry

I think this is a bigger issue that whether to purge or not. This thing will polly up inside.

Yeah, I'm coming around on my thinking on that. At first, it was a major concern for me and I was considering doing the more expensive nickel-plated one. But, I think it's still up for debate. The guys having poly problems aren't purging them and/or don't have an air orifice in their veg fuel lines to keep the air bled off.

Consider the veg fuel ports/fittings we have... they are either brass or mild steel. I can tell you when I completely cleaned out my system in the fall, the fittings that were washed with diesel on purge had no poly. However, every other fitting that came into contact with veg had a nice coating of poly on it. All the aluminum channels were clean and so was the tank. But not the fittings. That's why I changed them all out for stainless.

But I've also read many other posts (some with accompanying pics) where people have checked their fittings that are "cleaned" with diesel on the purge cycle and they have all been poly-free.

Either way, even if the copper-brazed FPHE polys up, they are 1/3 the price of the nickel-brazed. So, let's say it only lasts 2-3 years... you can replace it 3 times over 8-10 years and be even with a nickel-brazed unit. And nobody has any experience with a nickel-brazed to say whether it's less succeptible to poly than an copper-brazed. When I was trying to make up my mind about which one to buy, I learned that nickel is an element added to vegetable oil to cause polymerization to occur when making plastic/rubber from it. So, is it any better a solution? Dunno. The only "best" solution would be an all-aluminum or all-stainless heat exchanger. But that ain't going to be cheap.