Hit and Miss Engine 2

[wayneoz]

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

 

[BrianPetersen]

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.

 

[JohnRBaker]

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

 

[wayneoz]

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

 

[LittleInch]

100W!!

Try something like this

https://www.stevewebb.co.uk/index.php?pid=LE41F&area=Engines

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.

 

[BrianPetersen]

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!