VW Beetle engine 1/5 scale

[Arild]

Nice. So in that picture
- is it driving regular spark plugs like commercial RCEXL 1/4-32 type (or home made equivalent)
- are the taser modules divided one per 2 plugs because of the duty cycle = time required to charge = 'dwell? (sheesh, you can tell I am NOT an electrical person haha. Do those specs translate into some kind of max RPM per cylinder?
- does your Arduino sense RPM & then you have some kind of programmable advance/retard curve mapped in the background?
- what kind of battery / power requirement for a typical

Sorry for all the ignition related questions. I'm slowly getting my head around spark ignition from other model engineer contributors & this seems quite unique. If it wasn't for you smart electrical guys, I'd be using glow plugs forever!

I will use Rimfire Z2 sparkplug. The "rcexel" has a ignition module that you need! I use microcontroller from Microchip, because then I can use assembler programming that I know quite well (in my first job, I worked programming for Electrolux)

 

[Arild]

Back to your push rod tubes, To save some headache, you really on[y need to have a spring on one end of the tube. I assume you are installing valve seats. It looks like you machined a domed chamber. The VW uses a flat chamber top, your seats are going to be machined mighty deep in the head and you are going to have a lot of unshrouding around the valves. It looks like your valves are not centered enought in the chamber.

I'll use spring on each side, its not necessary, but it looks more like the original then...
Yes, it has a dome combustion chamber, and that is not original, but I cannot make a original, because I dont have an CNC mill. The valves are not in center, and that is for make better room for the sparkplug. (Z2 Rimfire). As traditionary model engine, I'll use valve seat and valve steering in one unit..
I will make a fillet to transition between the seat and chamber.

 

[petertha]

The "rcexel" has a ignition module that you need!

Yes I am aware of them. Now, I only know enough knowledge about model ignitions to be dangerous & some of this has been discussed in other ignition / cdi / distributer posts so I don't want to detract from your nice VW build.

But my understanding is even though the RCEXL (brand name) CDI ignition modules may provide suitable spark energy for our shop made engines, they also have an embedded retard/advance curve, because their intended application is RC models & hall pickup signal on the crankshaft. And largely intended for 2-stroke RC applications firing every revolution, which fortunately translates to a waste spark on 4-stroke in specific cylinder layouts. But its when you try to implement RCEXL module on a multi-cylinder 4-stroke with mechanical distributer the hard wired advance/retard curve does not scale properly because of its timing curve relating to crankshaft trigger. It just so happens to work on certain multi-cylinder 4-stroke layouts like 2-cyl opposed boxer, but not uneven firing requirement like a 2-cylinder Vee. Or higher cylinder counts. They sell different, dedicated CDI modules for that. And RCEXL also have specific features for RF suppression, cable shielding, grounding layout, resistor in the spark plug boot etc. Now there are other (non-RCEXL) CDI sellers & board builders that do not have advance/retard integrated into the design & less concerned by RF noise for bench running engines. Maybe you know all this stuff already but I thought I'd mention just in case. OK back to VW building!

example RCEXL multi-cylinder
https://www.justengines.co.uk/produ...cexl-multi-cylinder-ignitions/?v=5435c69ed3bc