Diesel flow meters

[oldbeaver]

Ok, send me a private message for the Futurlec ...

Oldbeaver

[mechatronica]

Dear sirs! We are manufacturer of fuel meters for diesel engines (including differential flowmeters with supply and return chamber). Experience in installation on various engines for 10 years.

Differential fuel flow meters not come cheap (from 380 USD) but easy in installation.
Also we have an option of built-in LCD display.

But usually they are used here in Russia together with GPS tracking systems.
(we can provide turn-key solution if someone need).

ask in PM if someone interested.

[mach4]

It's not necessarily a requirement to use two flow meters to get a suitable flow reading on diesels. Years ago I used a Zemco car computer which was designed to provide mpg readings by calculating fuel flow using a single sensor comprised of a plastic ball in a race and an optical sensor. I installed this on a vehicle which I built that had a Perkins diesel in a Chevy Vega. My solution to dealing with the return line issue was to use a float bowl from a Holley carb. The return line dumped into the float bowl and the IP drew its fuel from the float bowl as well. Thus I was able to put the fuel sensor on the make up line to the float bowl and only read fuel used at the sensor. This actually worked very well and gave accurate readings.

There are two issues with going this route. The first is that many, maybe all diesels use fuel for cooling the injectors. It's possible that the fuel in the float bowl would become overheated after awhile and cause problems. The other issue is that many diesels use a lift pump which draws fuel from the tank under vacuum. It might be necessary to use a small "clacker" low pressure pump to feed the float bowl.

Another potential solution would be to use a surge tank of sufficient size and construction to provide cooling of the return fuel. By dumping return fuel into the surge tank the lift pump would automatically replenish the tank as needed. There could be a problem in using a lift pump for this setup related to getting air into the system that would collect in the surge tank creating a problem. It might be necessary to use a small boost pump to deliver fuel to the engine under pressure rather than under vacuum.

Creating a system that doesn't need to do differential calculations of two low flow rates is significantly more accurate than differential systems.

[oldbeaver]

Hello Mach4,

Sounds interesting. But, I dont understand well your system, as the engine uses less fuel than the one received from the IP. Then the floating thing bowl may explode with fuel... or not?

Please, can you make a draw or a diagram of it?

tks.

Oldbeaver

[mach4]

Originally Posted by oldbeaver

Hello Mach4,

Sounds interesting. But, I dont understand well your system, as the engine uses less fuel than the one received from the IP. Then the floating thing bowl may explode with fuel... or not?

Please, can you make a draw or a diagram of it?

This should help.

First, here is a diagram of a typical carburetor. The float bowl allows new fuel to flow into the bowl at exactly the same rate as fuel is used by the engine. This is necessary as air flow across the venturi creates a vacuum which pulls fuel out of the float bowl proportional to the flow rate and atomizes it for use in the engine. A constant head pressure is necessary (or fuel flow would vary) hence the use of the float bowl to maintain a constant level.



In the system I was describing to allow the use of a single flow meter, the float bowl is removed from the carburetor and mounted stand alone using an aluminum backing plate. Two fittings are added to the float bowl, one for fuel to the engine and one for fuel returning from the engine.



It is impossible for the engine to return more fuel to the tank (or in this case float bowl) than the engine receives from the tank. If this were not the case, we would have a perpetual motion machine where the tank would continually [magically] be filled by the engine. Our gas stations would be places we would dump excess fuel rather than refueling.

The float bowl needs pressure to fill so a boost pump is needed somewhere between the tank and the float bowl. The lift pump on the engine would then pull fuel by vacuum from the float bowl to the IP.

Just for reference, here is what a Holley float bowl looks like.

[Gasoline Fumes]

Is the float bowl even necessary? People have been using looped returns for WVO systems for years. Often with no additional pumps. If heat's an issue, add some sort of heat exchanger. I'd be more worried about the injection pump due to reduced lubricity of the hot diesel than the injectors.

[mach4]

Originally Posted by Gasoline Fumes

Is the float bowl even necessary? People have been using looped returns for WVO systems for years. Often with no additional pumps. If heat's an issue, add some sort of heat exchanger. I'd be more worried about the injection pump due to reduced lubricity of the hot diesel than the injectors.

I do believe that a float bowl is not necessarily required as I pointed out above.

"Another potential solution would be to use a surge tank of sufficient size and construction to provide cooling of the return fuel. By dumping return fuel into the surge tank the lift pump would automatically replenish the tank as needed. There could be a problem in using a lift pump for this setup related to getting air into the system that would collect in the surge tank creating a problem. It might be necessary to use a small boost pump to deliver fuel to the engine under pressure rather than under vacuum."

I referenced the float as a known good solution I used in a Perkins swap years ago. I'd be reluctant to use in on my Mercedes swap without some sort of cooling system added. Mostly I wanted to prime the pump for thinking about how to setup a system without trying to rig one based on differential flow meters.

[oldbeaver]

Dear Mach4,

The carburetor diagram is very clear. Brilliant idea, I like it. It would allow to use only one fuel meter, instead of a differential one, which is very expensive for what I have seen.

The temp issue is a concern to me, though. You suggest using a "surge tank" as remedy, where I think fuel will be kept for a while for cooling. However, this would alter the measures on the fuel meter.... won´t it?

Or am I not understanding this well?

What I don't understand for sure is "the lift pump would automatically replenish the tank as needed" .... this will be the same as I have now. Am I wrong?

Please, show some more diagram to understand.

Thank you !

Oldbeaver

[mach4]

Originally Posted by oldbeaver

The temp issue is a concern to me, though. You suggest using a "surge tank" as remedy, where I think fuel will be kept for a while for cooling. However, this would alter the measures on the fuel meter.... won´t it?

Please, show some more diagram to understand.

This might help...