EBerspacher BN-4 Pressure regulator diaphragms

[Angleofattack]

Hello all,
I have managed to 3d print and assemble an acceptable BN-4 pressure regulator diaphragm, and using a copper river and brass washer. I am testing it in my heater today. Anyone in need of a new diaphragm, please let me know, I would be glad to ship one in exchange for material costs, postage and feedback on the part. I must advice that you should re calibrate your regulator and achieve the 20-21 ml in 2 minutes. Easy done in my Pinzgauer, the BN4 is installed behind the driver's seat.
Please text me, I do not check PM in this forum.
404 747 129Four

[ccowx]

This is great and I will be texting a bit later today! Much appreciated and if you wanted to secure a prominent place in my will, a diaphragm for the fuel pump would be great too. I believe they are made from the same material.

Thanks!

Chris

[Angleofattack]

You mean the BN-4 fuel pump? There are different types, but I have an old one sitting in my garage, I could take it apart and see about that diaphragm too.
That would require a second bottle of something that could both be used to get drunk but would also burn in the BN-4. 45% ABV?

[busdaddy]

That's really cool, care to share what the chemical makeup of the new part is?, have you done any long term testing with ethanol or slightly bad gas?
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[ccowx]

I meant to say regulator, my bad! I could use both, as a dedicated BN4 man.

[Angleofattack]

The material... this is a great question, that is why I want to share a few of these and see how they survive. A friend of mine told me it did great sitting in a cup of regular gas, and I assume it had some ethanol.
However, if you look into the specs of the brand... not good for ethanol. So I am taking the risk and see how it will survive. A good reason to take the risk is because this is probably a polyurethane based product (TPU), which is often described as partially or conditionally resistant to ethanol.
My previous diaphragm was made of two layers of nitrile gloves, and it is still in good conditions after 6 months. I removed it to test my new diaphragm made of Ninjaflex.

https://ninjatek.com/wp-content/uploads/2018/10/NinjaFlex_CR.pdf

The material expands upon immersion in gasoline, this is normal with most materials, including nitrile.
In six months we should have a good answer. if it lasts two winters, I am happy.

[Angleofattack]

Question...
I am running my BN4 on batteries with engine off, and after some testing of fuel flow, it seems like I run out of gas. I am wondering if the BN4 pump is sucking from my carburetors until they run out of gas or air gets in the line.

The question is, in the VWs, is the BN4 sucking gas from the line before the engine gas pump or from after the gas pump?

In the Pinzgauer, it sucks from behind the gas pump, i.e., from between the pump and the carbs.

Thanks for any comments on this.

JC

[notchboy]

Very interesting. I will PM you for a test one for sure. I'm about to finish a resto on an early one that I have a nos regulator for.

The big question though. The material for the gasket is available in sheets. So no need to print it. My take was that the brass center was the Achilles heel. I myself briefly looked into making suitable replacements.

I can send you some material if you want to share the brass trick you are doing?

Very cool as I love innovation.

Oh the BN4 should be between the tank and heater, tee'd off the line going to the motors pump. Maybe your heater is to far from the tank? Is it in a stock fitted position?
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[Angleofattack]

Gents,
Here is a picture of the printed diaphragms. The reason I find the printed part useful is because of the neck and the perfect fit. I fit the neck in the washer, then force the rivet through the neck and washer, and this produces a tight seal.

Considering the possibility of the material I use (Ninjaflex) not surviving the ethanol in most available gasoline, the option would be to cut the diaphragm from known resistant material and then place a nitrile O-ring under the washer.

I would try to find a brass rivet instead of copper, the valve pin may eventually dig a dent in the rivet as it is harder.

I will sink one of my new diaphragms in fuel today and see how it does.

My BN4 is stock, but I have changed my fuel pump and do not remember nor have documentation on the original configuration of the lines. It should be easy to change the split.

PLease dont PM, I dont check often them, text me at 404 747 129four.

[pittwagen]

When I rebuilt the pressure regulator and Hardi fuel pump for a BN2, I used Viton 70 - 1/32" for the diaphragm material. It seemed to work well.

[notchboy]

Completely get it with the seal. Looks good. I think the material I have is the Viton or similar like Pitwagen describes.
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[Angleofattack]

I just got back from a 10 day trip and first thing I did was to inspect the diaphragm material I left immersed in fuel. Looking good in terms of texture, resistance and flexibility, but as expected, it increased volume by about 8%.

I suspect this increase in volume is excessive for the current design thickness and because the diaphragm can not expand outwards because it is clamped, it expands inwards, creating a force that adds to the spring, therefore it will burn rich even with the spring screw all out.

I will try to print a thinner version and give it a try in my heater today. I will also print a couple more for Jason and Jay. I need help to improve the design.

Another thought I am entertaining is to print them at 92% scale so that a pre-soak would expand them to correct size.

[Angleofattack]

Jason,
Did you check the seal of the shutoff valve? Mine was dry and would not seal. Of course, I had the issue of sucking fuel from "after" the engine fuel pump, so my BN4 line was always pressurized as long as engine was running, not a good idea...
This is another entirely different project, but I managed to open the tip of the valve shuttle and replace the rubber.
Jerome

[notchboy]

[Angleofattack]

Jason,
I will put a new version of the diaphragm in the mail today. It is much thinner in the center. I took the one I had in my regulator out, which is a copy of the one I sent you already, and it is definitely too thick for the volume expansion of the material after it gets immersed in fuel.
Jeronimo

[busdaddy]

[Angleofattack]

Dear Busdaddy,
I carefully observed the soaked (One week) thin version as it dried up and it shrank back to exactly its original diameter.
The thicker one installed in the heater for a little longer seems to have shrank back to original diameter but center has stresses that maintain some waviness much like the 30 year old diaphragm I removed two years ago (I have been running a nitrile glove replacement for the last year)

So your assumption on over stressed clamped dry diaphragms cracking is a true possibility.

I do not take your comment as negative, simply because I am not selling these nor it is my intention. I'll be glad to accept a few bucks to cover shipping and the cost of the rivets and some feet of filament. My many days of design, printing and testing could never be compensated nor I ever intended so.

So anyone receiving one of these parts should be quite aware of the risks that come together with doing any type of manipulation of these old cans! Maybe I should send a disclaimer to Jason and Jay! Would you like one? I'd would appreciate your input!
Best,
JC

[notchboy]

Ha! A disclaimer?
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[Angleofattack]

I had so many leaks in my BN4... my truck smelled gas 80% of the times I started the damn can...! XD

That is why I finally got serious about it and replaced every single point of potential leaks. I am getting there!

For the ones or you getting the latest diaphragm... the outer portion that gets clamped is only about 0.75mm. My clamp ring is in ok conditions, but if you think yours is not, you may want to either cut one of the samples I send and double the edge, just to make it thicker and ensure good seal. Your call. Next version I will increase outer thickness to .8 or 1 mm. Anyone with the original diaphragm can guess the original thickness?

JC

[Angleofattack]

Just to report that my diaphragm is working great. BN-4 burning clean, starting every time, heating as expected, and no leaks, smells... just doing great for now.
By the end of winter I will take it apart and inspect it, but I suspect the Ninjaflex material is good for the job. I was concerned about the ethanol but I think it would have failed by now if it wasn't good enough.