Two Cylinder Engine

[Roger B]

Thank you both 

The 7806 has been in use for some time on a couple of engines. It has the two small ceramic capacitors between the input to ground and the output to ground as well as a 2200 microfarad 25V electrolytic across the output. This is sufficient to maintain the voltage when the engine is running although it goes into current limit if the engine is stopped with the points closed. Maybe the new ones I have are of lower quality.

I have ordered a 12V coil with the same small 44mm diameter. These are not so easy to find as there was a small window between when motorbikes moved from 6V to 12V before they went for ignition systems without the traditional style coil in a metal can.

The 12V coil can be connected directly to the battery with no need for a regulator 

[Admiral_dk]

Do you have a diode across from the Output to the Input ?
If not, you will damage the 7806 (when you turn Power Off), as it do not like a higher Output Voltage than Input Voltage ... 
So Anode to Output and Cathode to Input.

I hope you will have a long life with your new Ignition 

Per

[Brendon M]

Roger, will you eventually convert the kid's car to diesel electric?

[Roger B]

Hi Brendon, only as an experiment to confirm that the engine power is sufficient 

Still having fun with this one  You get a few excellent runs with a model engine and then they go off song for a bit while you check and improve everything 

I received a 12V motorbike coil from a German bike spares company. Unfortunately it was 44mm diameter rather than 40mm so I had to make a new fixing ring. I kept the original circuit board and just moved the coil connection to the input as it was used as a junction board for various supplies. This seemed to run better but there was still some arcing in the distributor so I took the cap off and cleaned it again.

There was still significant misfiring, although no obvious arcing, so I checked the plug gaps, 15 thou, and the valve clearances, 6 thou.

<a href="https://www.youtube.com/watch?v=XWqidUQrSKw" target="_blank">http://www.youtube.com/watch?v=XWqidUQrSKw</a>

I then wondered about the fuel system and if the plunger/rack could be sticking as there was no way to lubricate then, not a problem when there are just short runs followed by dismantling for modifications. I decided to drill a 45° 3mm oil hole in the side of the body so I could lubricate the rack gear and plunger.

This required removing the pump body and then the gear and plunger, carefully recording their positions. The hole was started with a 3mm end mill and then finished with a drill. It was all carefully cleaned, reassembled and lubricated. Priming the pump, as ever was a bit of an effort due to the very small volumes compared to the pipe size.

It runs better but still it hasn't got the crispness of earlier trials.

<a href="https://www.youtube.com/watch?v=xUeGdfnsgUU" target="_blank">http://www.youtube.com/watch?v=xUeGdfnsgUU</a>

[Admiral_dk]

I can't say that this is what is required here (and remeber that it can be Detrimental) .... But in my youth I got a lot faster Throttle respons by adjusting the Ignition Adwance to about 5 degrees earlier than stock 
 But it also makes the Engine run hotter + more load on the Pistons, Conrods and Crank + Bearings ...!!!

Per

[Kim]

Wow, Roger!  It sounds really good to me!
However, I do hope you get it running to YOUR satisfaction soon.

Kim

[Roger B]

Hi Kim, I just want to get it back to how it was in May.

<a href="https://www.youtube.com/watch?v=7RVp_fwLo0o" target="_blank">http://www.youtube.com/watch?v=7RVp_fwLo0o</a>

It was running how I wanted it to and then the performance just dropped away and it wouldn’t rev.

My first diagnosis was wear in the brass injector eccentric so I made a case hardened steel version. With hindsight this could be a problem as the pump plunger would be operating in a different part of the stroke.

Next I found that the 6V regulator feeding the coil had failed and the spark voltage was much to high. Fixing this removed the symptoms of arcing in the distributor but didn’t really improve the running.

I don’t, as yet think that it is a problem with the engine mechanics, both cylinders have compression and grounding either spark plug brings equally bad running.

I need to check the various aspects of the fuel injection system:

Is it injecting on the induction stroke?

Is the fuel delivery pump under pressure when the injection pump  inlet port is open?
 
Is the inlet port fully opening?

At what point in the stroke does the inlet port close and injection commences?  Maybe it is important that the plunger is moving with maximum velocity at this point.

Plenty to think about, but I will play with the diesel for a bit now.

[RReid]

One thing I'm learning in my own twin build is that vs. a single the population of potential gremlins seems to increase not linearly but exponentially.

[Admiral_dk]

Earlier this year I learned that some very succesful Fuel Induction Systems, actually don't Inject the Fuel during Induction, but for instance during Combustion, so the cool Fuel hits the Hot Valve. This helps with Cooling the Valve and increases the Fuel Evaporation ...! Others have more than one Fuel Injection Period, during the 720 degrees.
This is of cause an very easy experiment, when you just change som values in a piece of Firmware and quite a bit more complicated in your System ....

I can only agree on your other Considerations, having an Influence on the result.

Per

[Roger B]

As the next step I decided to raise the injection pump a little to match the wear on the original brass excentric. The slots needed to be milled away to give enough additional movement. This seems to be promising  I can move the pump up till the engine barely runs (which is what I think happened in May as the excentric wore away) I can then lower it which improves the running considerably. As I lower it further operation then becomes worse again somewhere is the 'sweet spot'

<a href="https://www.youtube.com/watch?v=BaKZGobENqc" target="_blank">http://www.youtube.com/watch?v=BaKZGobENqc</a>

I need to try and understand what is happening, but it maybe an additional dwell time for the pump cylinder to refill with fuel      The plunger is limited in it's travel so the inlet port is just fully open. If I lower the tappet the port remains open for longer and the tappet is travelling faster when it meets the plunger.

[Admiral_dk]

Even if you can't explain the exact reason, why it made the difference it did - it still sounds and runs better now   

Per

[Roger B]

Thank you Per 

Another known problem is that there is a tendency for air/fuel vapour to collect at the outlet from the fuel tank. If the air bubble stays there no problem, if it gets to the injection pump the engine will stop and I will have to bleed the system again  This could be due to the lower pressure where the fuel is sucked to the top of the tank or could be due to an air leak  I searched for another style tank with a bottom outlet. This has a floating sintered filter but the outlet is around the fuel level.
The first attempt was not successful  The pipe to the sintered filter was not compatible with Alkylate fuel and swelled enormously  I replaced it with a piece of my petrol/gasoline compatible pipe, bled the system and all seems ok so far 
Maybe time for some more load trials 

[Roger B]

I finally got around to another load trial. This was rather more successful although the generator characteristics are not really suitable. I could drive it with a belt reduction or find another generator with a lower voltage output but at least I have proved the principle.

<a href="https://www.youtube.com/watch?v=FGwGoNfH2zk" target="_blank">http://www.youtube.com/watch?v=FGwGoNfH2zk</a>

[RReid]

Now That's a fun test! Well done, Roger!

[Kim]

Very cool, Roger!     

Kim