Carburetor information

[Admiral_dk]

PLEASE do NOT pay too much for that book .....

He gives a lot of hints, but not much in real info - especially in regard to fuel injection - I'm not sure I would have bought it if I've known how little "hard evidence" there's in that book. It's not a complete waste of money - he do give you a lot of ideas on how-to make crankshafts and certain other bits and pieces.

I'll try to give you an idea and the injection system that he and his son "invented". They claim about 20% power increase compared to carburetors on the same engines and easier starting.

Fueltank -> one way valve -> + return -> leaky fuelpump -> return valve (to fine adjust fuel amount) & -> one way valve -> to all injectors (each containing a one way valve and a adjustable jet) & a (probably adjustable) one way return valve -> fueltank. In other words, the fuel pump is short-circuited by the first ajustabled jet. The individual injectors are adjustable (and placed close to the air-entry into the engine) and I suspect that the last valve is connected to the accelerator, but I'm not sure - the drawing isn't clear, it just states that it's shown in "Leerlauf" ~ idle. There's about 100-150 words on how it works, and that's that ???

 

[mu38&Bg#]

Oh, You can get more info from the YS model engine patent.

http://www.google.com/patents?id=zcYMAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q&f=false

 

[Admiral_dk]

Thank you DieselPilot for that link - very informative, but also with (intentional ?) errors. :

I'm not sure this is a good system - it appears that it suplies the same amount of fuel no matter how much throttle is applied. Then there's the issue of isolating the fuel circuit from the lubrication circuit at the pump - it can be done, but it requires some very small o-rings. That's not to say that the camshaft (perhaps with an extra cam) couldn't be used as an intricate part of the pump with a perfect timing and the same could be said if you consider a diesel system.

 

[mu38&Bg#]

The only items not shown are the high speed needle and idle air bleed needle. The system has been used as described in their production engines for over 10 years. It works very well. The pressure regulator is referenced to manifold pressure, because the engine uses the crankcase to supercharge the intake at up to 9 PSI. In this type of engine there is no isolated lubrication circuit. The fuel carries the oil, total loss system.

 

[Admiral_dk]

You're right - I found a complete service manual on the DS 170 (never seen or heard about them before) .... but it do include the seals in form of o-rings.

I must admit that the regulator part confused me - I got it the wrong way around - it doesn't regulate at max revs, but lowers the amount of fuel injected as revs goes down. That and the "missing mainjet" confused me - now at makes sense.

As for using the crankcase two-stroke style to boost the input on a four-stroke - that's not new to me, it's been done to full size racing motorcycles in the eighties - just haven't seen on a model before.

 

[gbritnell]

When we first got on the discussion about fuel injection for model engines I had made the comment that anything is possible but given the size of our engines and therefore the size of the orifices and jetting the experimentation becomes almost impossible.

When I was growing up and fooled with race cars we had a Hilborn fuel injection unit on one of our engines. Being that the engine basically idled or ran wide open the injection system was quite simple. The injectors fed fuel to the cylinders through a jet which was changeable. To feed 8 cylinders and not overfeed or underfeed them you put another metering jet (pill) in the return line. This would maintain a somewhat regulated amount of fuel to the cylinders. Remember this was a race engine and only needed to run at one speed.

What has been said about this fellow's injection system reminds me of the Hilborn system, tweak this, adjust that, read the spark plugs and then start over. The only difference is that at least on a full sized engine you could 'read' the plugs.

Apparently there are no followers or contributors to this forum that are knowledgeable in miniature fuel injection systems. That's not to say that there isn't someone out there that is, it's just they haven't helped us along with this topic.

Not many years back we were all using automotive points, twelve volt batteries and coils and home made spark plugs to spark our engines. Now we have several different suppliers of electronic ignitions, spark plugs and the associated components. Who knows, in a couple of years maybe someone who has access to a lazer for making minute holes will come up with a miniature injector for our engines. Wait a minute, this will then require throttle position sensors and rpm readers and temperature sensors to adjust the fuel metering under varying conditions. Will it ever end!

I will be the first to admit that when I bolted the OS 2a carb on my 302 and fired it up I was amazed, astonished, even flabbergasted at how it ran. What type of fuel to air ration it has at any given rpm I haven't a clue, but I'm extremely happy with it. I have been keeping track and I now have over 7 hours of running time on my engine and it still starts and runs great so for the time being I will continue to use a variation of this type of carb on my future builds.

I would love to have some type of EFI on one of my engines but I'm afraid that's way beyond my resources.
George

 

[Lakc]

Apparently there are no followers or contributors to this forum that are knowledgeable in miniature fuel injection systems. That's not to say that there isn't someone out there that is, it's just they haven't helped us along with this topic.

I have had that engine and fuel system three quarters done for the last 12 years. I have since sucessfully overcome many skill, material, and design challenges, and while its been a labor of love, there has been much frustration along the way. Last year, I managed to convert the existing napkin and graph paper sketches to CAD, but I had to change laptops and can no longer run cad off my thumb drive. It was perhaps an overly ambitious first project. (understatement of the year) The biggest challenge, one which I am failing to overcome, is finding time. Between home, work, family, etc., all my spare time seems to evaporate.
I have the fifth or sixth iteration of the cylinder heads ready to build, and have already played with the injection pump design and block cavity. Once I get finished cylinder heads that I am happy with I can cast another block (would be the seventh or eighth one of those) and then get to the FUN part of the job, the fuel injection.

 

[stevehuckss396]

I have had that engine and fuel system three quarters done for the last 12 years. I have since sucessfully overcome many skill, material, and design challenges, and while its been a labor of love, there has been much frustration along the way. Last year, I managed to convert the existing napkin and graph paper sketches to CAD, but I had to change laptops and can no longer run cad off my thumb drive. It was perhaps an overly ambitious first project.

I see you are in the Detroit area. Maybe I could interest you in combining our spare time and work together to get the injection project back on track. I have good cad skills and machines to make prototype parts. I would love to inject one of my V8's

PM if interested!

Until then i will stick to my original plan with the drum style carb. This one will have to be adjusted with a small screw driver. There will be a 4-40 screw in the front that will be drilled to allow the air bleed. I will be able to swap out different screws (jets) with different hole sizes. If I over shoot the bleed size I will be able to go back unlike the carbs where you drill the carb body.

 

[Lakc]

Nice looking carb there Steve! Thats not too far off of real life practice, as a lot of Japaneese carburator designs use replaceable screw in air bleeds. Holly uses pressed in brass bleeds, we would measure and swap them on the dynomometer with a kit of gas orifice plug gauges.

Continious flow fuel injection is simpler then a full-size carburator, but very similar to the model carburators we use. In fact, its essentially identical to adding a Perry oscillating fuel pump, to a barrel carb that moves laterally pulling the needle further from the seat.
http://www.perrypumps.com/prod02.htm

It gets a little trickier when you want to produce maximum power into a variable load at different throttle openings. With the possible exception of the Chevrolet Rochester fuel injection of the late 50's, most of the remaining fuel injection systems are designed for drag racing, not driveability. The trickiest part to build is either the pump, or what they refer to as a barrel valve spool. On the Hillborn systems I worked on, that was a V shaped depression machined onto the outside of a rotating valve, which linked directly to the throttle. I couldnt find a picture of that exact valve, but there is a slotted type barrel valve spool, along with some other information at this site.
http://www.kenlowe.com.au/LFS_injector_hardware.htm

 

[mu38&Bg#]

The only system I've read anything about is the Bosch Jetronic. Bosch calls all of their fuel injection Jetronic. There are many versions, the earliest open loop mechanical. There is some good information about the system on the net. There is even manual available for download.

http://www.jc42.dial.pipex.com/alpina/Injection/kugelfischer_injection_Description.htm

http://www.bmw2002faq.com/content/view/66/32/#section1

http://www.scribd.com/doc/3299223/Bosch-KJetronic-Fuel-Injection-Manual-