And just to keep it going....Alp racing, the guy with the fastest naked frame Triumph 650 LSR in history, 157 mph on gas, 175 mph on nitro....Single plug with a Morris magneto... Of course a street bike has different requirements....
650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
"direct ignition"? Do you mean coil on plug? HB is running separate construction twins. There is nothing to mount the coils to on top of the plugs. If he wants to build a mount the ignition will still work with them. Coil charge time is programmable and can exceed 360° crank angle if needed. The ignition curve is programmable - advance, constant or retard with RPM, so make it what you want. It is also re-programmable so the same ignition can be used on a single, twin, triple or four with only a change of pickup and loading the correct program. Bigger inductance coils can store more energy which allows a longer duration spark which extends the lean stability limit (Heywood -Internal Combustion Engine Fundamentals).
No aggression intended. I had been using the Atmel mega88 at 8MHz which left plenty of time to check the USART for the handlebar control but for this I needed more 16 bit timers to handle the two engines so I am using the mega328PB at 16 MHz. I never bothered learning assembly since compilers are so good and Atmel's Studio lets me write in C. I have not had the need for the SAM chips yet but maybe when I work on the fuel injection.
Both Boyer and Pazon supply twin plug kits with modified advance curves to suit.
john, I would buy one of these today if i could find one. I'm running a 30-year-old Boyer with twin plugs and it's suffering from excessive retard at idle because I'm limiting total advance.
the Boyer websit doesn't list anything that I can detect for a twin plug british twin needing less total advance than stock, although I may have missed it?
pazon has been out of rotors for their twin plug smartfires for over a year. I bought one of the last ones available. they will work with you to provide a custom rotor if you send them assembled measurements of your exhaust cam nose (for a triumph) but that's the best they can do at present.
how would I come up with a Boyer system that has a shorter advance curve for a twin plug? I already have dynatec coils at 2.2 ohms each, and just need the box, rotor, and stator.
funny you should suggest returning the points. I've considered it, because brazing up the advance slots would be so easy. lots of similar-sized springs are available in different tensions for the old delco remy distributors too, so changing the advance rate would be cheap.
I missed the spot about the microdigital being adaptable to this. its not expensive, either, compared to the pazon. I'm looking at it and the micropower both.
The Micro-Digital system is designed to use the original coils where possible, the time these coils are switched during the ignition cycle is programmed into the microchip. With older machines, the coils have a high primary resistance and require a long switch on time. If the coils are replaced, it is important that coils of a similar resistance are used.
This system is designed to work only with our special digital power ignition coils (type 00007 single output, or 00008 dual output). Up to three of these coils may be run from one ignition box, providing very high energy sparks for single, or twin plug cylinder heads. The ignition cycle is produced by a high current pulse lasting for a short period of time; this is controlled by the microprocessor program. The total current consumption is reduced by over a half and the spark energy is greater; average current consumption is less than 1.5 amps at maximum r.p.m.
I have a dual plugged BSA 441 running points and no battery. When I retarded the timing for optimum timing, I found that it was ATDC at idle or for starting, which made kickstarting difficult. I brazed up the slots in the advance unit to lessen the amount of advance (actually, in this case the amount of retard!)and it worked great. Before doing so, I asked Ed V (BSA unit singles guru) about using an ET advance unit. His advice was not to. He said that the different points cam would likely end up causing problems. I am, however, using a dual tower coil. If I am understanding correctly, I would be better off with 2 single tower coils. While my 441 fires right up and goes fine now, it would not be hard to wire up a couple of my spare Lucas coils and see if it makes a difference.
Wow! Thanks for all the input,some of it I don't even understand but it was fun reviewing all the responses. After talking to John Healy over the phone I decided to send my points assembly to Ed V and have him modify it to retard the advance as several have advised. I also ordered two twin tower mini 3ohm coils. I think this way the stock wiring harness will be easy to modify although I will use a tympanium regulator/rectifier. Any more imputed would be appreciated. THANKS