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Hit and Miss Engine

Hit and Miss Engine

(OP)
Hi everyone,

I wish to convert a 4 stroke engine into a hit and miss engine - or something similar.

I have made a flux generator that is powered by the small (Carburetor) 4 stroke using a flywheel. I wish now to make the engine more fuel efficient.

My plan is to use an Arduino and solenoid to shut the fuel and spark on & off so it fires once every 2-3 seconds.

I am a bit green with 4 stroke engines and would love to hear any suggestions.

Thank you

RE: Hit and Miss Engine

More efficient??. Looks to me like you just mean used less fuel but this will be accompanied by less power out.

What is this thing powering?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hit and Miss Engine

Buy a smaller engine - more fuel efficient.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Hit and Miss Engine

Couple a flux capacitor to the flux generator - use the stored flux to add efficiency.

RE: Hit and Miss Engine

Carbureted hit an miss engines have very low efficiency. All those revolutions sucking in air and fuel without producing work are just about the worst thing you can do for efficiency.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Hit and Miss Engine

Hit and miss engines were a way of regulating engine Rpms with the primitive carburetors available in the early days of engine manufacture. R.A. Lister used this system on their early engines, which had massive flywheels to compensate for the engine inefficiency. Are you sure you want to go this route?
B.E.

You are judged not by what you know, but by what you can do.

RE: Hit and Miss Engine

They do have low efficiency, but they don't suck in air and fuel on every rotation; automatic intake valves (check valves) only open when there's a vacuum in the cylinder, which only happens on firing cycles because the governor holds the exhaust valve open otherwise.

see 'how hit-and-miss-engines work' in https://en.wikipedia.org/wiki/Hit-and-miss_engine


Fifty plus years ago, I saw 'Rumely Oil Pull' engines running at Henry Ford Museum. I think they worked by exploding kerosene and air in a large external combustion chamber, and expanding the hot gas through what was mechanically a steam engine. The sound was essentially the same as that produced by a regular h+m engine.


Mike Halloran
Pembroke Pines, FL, USA

RE: Hit and Miss Engine

OK I'll ask the obvious - - WHY?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Hit and Miss Engine

Sounds cool... even cooler than a Harley? ponder

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Hit and Miss Engine

We had one of those monster single lunger H&M engines in our power mechanics class in high school. You could start it with a bar in a hole in the flywheel. It was crazy. The flywheel was about 4 feet in diameter and had monster spokes. The flywheel probably weighed a thousand pounds.

It was salvaged after a fishing boat that is was the motive power for sank, in the harbor. Seems the starting bar got jammed in the starter bar hole in the flywheel on starting. The bar went around with the flywheel and plowed a huge smile in the lowest point of the hull. The boat sank fast.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Hit and Miss Engine

2
wayneoz - the issue you will face is that carburetors don't like having fuel turned on and off. They usually have some sort of float system and bowl which holds enough fuel for a few seconds, so turning the inlet fuel on and off won't make any difference to the fuel out, but can affect the re-start as the bowl fills up again.



Also systems like this actually lightly coat the inlet chamber in a thin film of petrol. If you manage to cut off the fuel, this film dries out, but then on re-start the engine coughs a lot. I remember on a car some time ago where they used carbs and tried to cut off fuel on the overrun, they found when you put your foot on the accelerator it wouldn't go properly so had to actually cycle the fuel on and off when on overrun.

Fuel injection now, especially electronic FI, is a different thing.

All up no one can work out why you're trying to make your engine less efficient than it is at present....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hit and Miss Engine

Little inch,
What is that carb ? It looks a bit like a Stromberg.
B.E.

You are judged not by what you know, but by what you can do.

RE: Hit and Miss Engine

Very typical constant-velocity motorcycle carburetor. They're all like that.

RE: Hit and Miss Engine

Be. Dunno. Just the nicest picture I could find to demonstrate that turning the fuel off on a carb won't end the fuel supply for several seconds.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hit and Miss Engine

In our mech eng power lab, we had a very tired National Gas engine, I think the data plate was dated 1915. Four men cranking on the flywheel with a crank handle for all their worth to get it started. The experiment was to adjust the compression ratio via shims in the conrod to find the highest output and efficiency. Blowby was so bad on that tired old beast that MBT compression ratio came and went pretty quick with more shims. Flyball governor cut the ignition when governed speed was reached, classic H&M governing. For fun I held the governer down for a few seconds and let the engine accelerate, but I quickly lost my nerve. bomb

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Hit and Miss Engine

I'm thinking I've heard pumpjack engines that were hit-and-miss, but no idea how old they were. Heard them in recent years, I mean.

RE: Hit and Miss Engine

Every time you cycle off, you will waste most of the fuel in the carburetor bowl. When you cycle on you will will have to wait for the bowl to fill enough to supply a fuel mixture.
There are after market kits that add fuel injection to small gasoline engines. You can then simply cycle the injection off and on.
The big question is "WHY?"
Most small engines have a serviceable governor.
If your engine does not have a governor, you can probably make one with a flapper that the cooling air blows against. The faster the engine the more force on the flap. Use a spring to hold the throttle open. Use linkage from the flap to close the throttle at the speed that you want.
It will take some cut-and-try and trial-and-error to get it right but there have been many small engines governed in this fashion.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Hit and Miss Engine

The emissions/pollution profile of any H&M would likely prevent it's commercial application.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Hit and Miss Engine

Skipping firing events (provided the fuel is shut off as well as ignition) is a more efficient method of reducing engine load than throttling.

je suis charlie

RE: Hit and Miss Engine

That depends whether you can successfully shut off ALL the fuel.

The old school hit and miss engines worked by cracking open the exhaust valve and the intake valve was purely suction operated, so it did in fact successfully shut off all fuel (and air) ... although the nature of operating an intake valve in this manner severely limits the RPM and operating pressure (compression ratio) of the engine.

The various late model engines that use "cylinder de-activation" leave the intake and exhaust valves shut, which obviously shuts off supply of all air and fuel.

Shutting off a direct-injection injector will shut off all the fuel.

Shutting off a port injector won't because the inside wall of the intake port is wetted with fuel during normal operation, and if you leave the intake valve working, that's going to gradually get drawn in over the following (skipped) cycles. The air/fuel mixture will be too lean to fire, but the fuel is still going through the engine being wasted.

Carburetor, same problem but even worse.

Any emissions-regulated strategy that involves shutting off the fuel but not the air will screw up the operation of a 3-way catalyst. The cylinder-shutoff mechanisms that completely shut off valves don't have an issue. "Deceleration fuel cut" on a normal port-injected engine isn't a problem because whatever bit of fuel that was wetting the port walls goes through the engine and gets oxidized by the catalyst and it only happens the moment you take your foot off the accelerator - not continuously the whole time the engine is running (in hit-and-miss mode).

The original poster has not showed up in this thread to explain WHY he wants to do this doomed experiment.

RE: Hit and Miss Engine

I'm not sure that I would use the word "doomed". Perhaps highly "dubious" would be better since we don't yet, as previously noted, have any idea why this solution was being considered.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Hit and Miss Engine

(OP)
Thanks for those who kindly replied thus far. I expected some criticism and most of you definitely haven't held back.
The reason I am doing this project is because I have successfully built a small electro/magnetic generator (100W). Naturally my next step was to have a quite, efficient engine to run it. I actually have a brand new Honda GX35 Motor available (1kW which means its 10% efficient = poor). I am also an admirer of the old Hit and Miss engines of the past. So that is how I came up with this concept. Bringing new and old technology together. I'm not sure if this is even conceivable but was hoping to get some insightful feedback.
Wayne

RE: Hit and Miss Engine

100W!!

Try something like this https://www.stevewebb.co.uk/index.php?pid=LE41F&am...

Engines running continuously work much better than one starting and stopping.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hit and Miss Engine

Where is your assumption that a 100W generator connected to an engine of 1 kW output is 10% efficient coming from?

and I will grant that the real efficiency is probably pretty lousy because the engine will be running at such a small fraction of its rated load, but it's not determined by 100 W / 1 kW ... if the generator only draws 100 W from the engine then the engine will simply run at 100 W output - part load - not full fuel delivery. You don't have (or haven't provided) sufficient data to establish what the efficiency of this powertrain will be.

Running the engine in hit-and-miss mode won't make it better, though!

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