Engine Instrumentation Project - Page 9 - PeachParts Mercedes-Benz Forum

dieselbenz1 · #**121** 11-25-2015, 09:45 AM

Ok now I have a greater appreciation for your challenges and concerns. So you basically require a flow meter with a 15:1 turn down operating in a pulsating flow environment at a velocity through the meter to prevent meter stalling/ slippage.

I still am not convinced the float control valve is of adequate design to prevent on off control as I seem to recall the stem and seat to be fairly wide. You should be able to bench test that portion by supplying a constant liquid pressure, (pressure bottle) with a gauge on the inlet and a needle valve on the output empting into a graduated container. If that gauge bounces you have on off control rather than modulating control. This is interesting and if I had the Holley bowl and time I'd test this myself.

mach4 · #**122** 11-25-2015, 10:00 AM

Quote:

Originally Posted by dieselbenz1

I still am not convinced the float control valve is of adequate design to prevent on off control as I seem to recall the stem and seat to be fairly wide.

The float bowl aspect of the design definitely works. I had that exact setup installed on a Perkins diesel that I swapped into a Vega a long time ago. Then I was using the Zemco car computer that had a suite of fuel management functions. The only question in using it on the 617 is the heat issue...and a solution is available if needed.

funola · #**123** 11-25-2015, 10:39 AM

Quote:

Originally Posted by ROLLGUY

I disagree. The float bowl is acting exactly like the fuel tank. The fuel is taken from the bottom, and unused fuel is returned to the top. No extra pressure is in this system that would not otherwise be in the stock system, so no chance of blowing hoses. The fuel used is replenished by the stock fuel tank and added pump.

'''''''''''"The float bowl is acting exactly like the fuel tank""""''''''''

NOT EXACTLY!

1. The fuel tank is vented, the float bowl is not

2. The fuel tank is much larger in volume than the float bowl. Let's say float bowl is 4 oz, the tank is 672 times larger.

Your arteries has a given total volume, when it is clogged with plague, that volume decreases, pressure goes up= heart has to work harder. When clogging gets bad enough= heart attack. Not the best example but something that you may be able to visualize.

ROLLGUY · #**124** 11-25-2015, 11:00 AM

Quote:

Originally Posted by funola

'''''''''''"The float bowl is acting exactly like the fuel tank""""''''''''

NOT EXACTLY!

1. The fuel tank is vented, the float bowl is not

2. The fuel tank is much larger in volume than the float bowl. Let's say float bowl is 4 oz, the tank is 672 times larger.

You may be correct, and I am learning a lot by my reading of this thread. However, you say: "The fuel tank is vented, the float bowl is not". This may not be the case, as any float bowl can be made vented if needed. As far as "2, a float bowl can be made any size. Yes I know the float bowl in question is a Holly float bowl, but I am sure he can make a float bowl out of a #10 can if more volume is needed.

dieselbenz1 · #**125** 11-25-2015, 11:10 AM

Quote:

Originally Posted by mach4

The float bowl aspect of the design definitely works. I had that exact setup installed on a Perkins diesel that I swapped into a Vega a long time ago. Then I was using the Zemco car computer that had a suite of fuel management functions. The only question in using it on the 617 is the heat issue...and a solution is available if needed.

I must have had missed the Zemco car computer part in your earlier posting so that eliminates what I thought may compound the measurement issue. That's good to know.

funola · #**126** 11-25-2015, 11:12 AM

Quote:

Originally Posted by ROLLGUY

................ As far as "2, a float bowl can be made any size. Yes I know the float bowl in question is a Holly float bowl, but I am sure he can make a float bowl out of a #10 can if more volume is needed.

I don't think venting the float bowl is an option in his design. A #10 can is not enough. Just imagine taking a hose from your house faucet and filling a 4 oz non vented can with one inlet barb welded to it. It will fill partially, the air inside is compressed and pressure is built up . Do the same thing with a #10 can, it will fill with more water than the 4 oz can but same thing will happen= pressure builds.

Now if you return to the same (vented) tank that fuel is drawn from. No problems.

mach4 · #**127** 11-25-2015, 12:37 PM

Quote:

Originally Posted by funola

I don't think venting the float bowl is an option in his design.

A float bowl is by definition vented. If not, you can imagine the problems that would accrue in driving at altitude and then returning to sea level. If you don't understand what's happening ask questions about what you don't understand and I'll be happy to explain. Let me reiterate a fundamental fact in this discussion - the float bowl works as a strategy for eliminating the return line to the tank. I know because I did it - on a diesel engine ...with a fuel management computer...

What I don't know is whether heat will be a problem...or whether the fuel transducer I've selected will work...

mach4 · #**128** 11-25-2015, 12:54 PM

More information:

In another thread (MPG Computer) I posited a different design for a potential mpg gauge. This design was a "sealed" loop on the IP end and an open loop on the tank end. The main advantage to this design was that the surge tank was inside a jacket of continuously flowing tank fuel providing positive liquid-liquid cooling. I rejected this because of the potential for air to collect in the top of the surge tank over time and the need for occassional bleeding.

I actually think this would work, and work well, but have opted to go with the proven solution.

funola · #**129** 11-27-2015, 11:10 AM

Quote:

Originally Posted by mach4

A float bowl is by definition vented. If not, you can imagine the problems that would accrue in driving at altitude and then returning to sea level. If you don't understand what's happening ask questions about what you don't understand and I'll be happy to explain. Let me reiterate a fundamental fact in this discussion - the float bowl works as a strategy for eliminating the return line to the tank. I know because I did it - on a diesel engine ...with a fuel management computer...

What I don't know is whether heat will be a problem...or whether the fuel transducer I've selected will work...

OK so you say you did it on a diesel engine. Can you redraw your system diagram to include the carburettor diagram showing all fuel connections and how it is vented?

mach4 · #**130** 11-27-2015, 11:56 AM

I went searching for a Holley float bowl image I could use and stumbled on a kit that a guy in Australia sells that does exactly what I did. His application is a bit different - he needed a small "tank" to gravity feed a carburetor in a small generator - but the concept is the same. He doesn't have a return line as his is a carburetor engine, so I'll need to drill and tap a port for the return line - either in the backing plate or in the top of the float bowl, yet TBD.

Float Bowl Tank for little engines 01

Hope this helps...

funola · #**131** 11-27-2015, 12:02 PM

But where are you venting the fuel bowl to? Isn't the bowl under pressure?

mach4 · #**132** 11-27-2015, 01:27 PM

The fuel bowl vents to atmosphere - just like a float tank in a toilet bowl. The fluid goes out and the fluid is replenished in exactly the same amount - the float valve's job is to maintain the pre-set level in the tank. (Admittedly a poor example as the toilet bowl is designed to "restore" the level after a flush and the fuel float bowl is designed to "maintain" a precise level at all times.) The fuel coming into the float bowl is under pressure from the boost pump but it's essentially "gravity feed" to the lift pump (again not technically true as the lift pump "sucks" the fuel into the pump under vacuum)

What may be confusing you is the notion that the float bowl is not a "perpetual motion machine", it can never fill past the float level (if the float is working properly) because the return to the float bowl from the engine can never be more than it received from the float bowl. If the engine is on, it must return less fuel than used (by weight - by volume it could be very slightly more due to heating and the coefficient of expansion - but this is quickly rectified by the float and the system quickly returns to equilibrium.

mach4 · #**133** 11-29-2015, 06:29 PM

Today (Sunday, my new PCB boards arrived via DHL)....can't believe it. That's the good news - the bad news is I'm packing for the cruise we're taking tomorrow out of LA for Vancouver, so won't be able to test out the new boards until we get back. They look amazing.

The software development for the new MPG computer component of the system is moving along nicely. The image shows my test bed. I use one Arduino for a pulse generator, simulating the driveshaft (distance) pulse and the fuel transducer pulse. This data is collected, manipulated and sent to the EDMS Arduino over an I2C bus where it is incorporated into the rest of the data string which is sent to the tablet over bluetooth. The data portion all works, I've just got to get it rolled into the Bluetooth datastring, unpack it on the tablet and build a couple of screens for display. This too will need to wait a week

mach4 · #**134** 12-07-2015, 07:13 PM

Had a chance to start the assembly on the printed circuit board today and did some preliminary testing. So far I've got things working - the only known issue is that the silk screen of the DS18B20 component is backwards. Also did a trial mount in the case and everything fits nicely. Hopefully I can get it mounted in the car tomorrow - though I've got potential jury duty so it may have to wait...

mach4 · #**135** 12-09-2015, 05:14 PM

I now have the new system installed and running in the car. Its a lot cleaner than the original system. I've also been reviewing the code for some minor cleanup.

Here it is in it's new position.