Help Electrical Questions

Hi Team, I’m doing electrical at college this week and I’m encountering a couple of teachers who seem to be more car-orientated and I’m starting to question some of what they are telling me. I know a few on here are pretty gluey on the sparky side of things, so any feedback, advice or links to good (accurate) knowledge/reading material would be greatly appreciated. For the purpose of my questions and comments, lets use one of our 4-stroke 250/4 bikes as the sample machine…2 coils and 4 plugs.

Question 1: I’m told the formula for calculating sparks per minute is F = Z * N/2 (F being the sparks per minute; Z the number of cylinders & N being the RPM). So, when my bike is doing 18,000RPM I calculate there are 600 sparks per second, which equates to a spark plug trying to fire every 1.2 seconds (two plugs in the wasted spark case). So given that, does that mean that at 18,000rpm the dwell period for each coil cannot be set any higher than 2.4 seconds?

Question 2: One teacher was telling me you need 80-90amps to turn the starter motor and a bunch of other “facts”. I went over to a bike and showed him the 12V9Ah battery it had and asked him how exactly did that battery generate enough amps to do that. His answer was okay, but then I remembered our bikes have 30amp main fuses. I didn’t introduce that into the conversation as I was becoming confused and annoyed all at the same time. So, do our bikes really generate that much amperage to turn the starter motor?

Question 3: The Stator/RegRec system… I was always under the impression (wrongly) that the power generated by this system just charged the battery and the batteries DC took care of all the needs of the bike. I now know (I think) that the Stator/RR system actually powers the bike while the engine is running and any leftover DC is then fed to the battery. Is that right? And, if so, what happens to the DC being created once the battery is fully charged?

Question 4: The spark advance for our bikes is built into the TCI/CDI units (right?). Does anyone know how to reverse engineer these settings or find out when in the rev range the advancing occurs? If I go to a programmable CDI to replace my TCI I will need (I assume) to program in the advance to make the bike’s firing function properly before trying to change it for different power delivery etc. The curriculum has touched on mapping, but only as far as to say it's built into the control unit.

I was going to PM these questions to certain people on this forum, but decided to make this a general post in case anyone else is interested. @GreyImport please move this to another forum if it's in the wrong spot.

Cheers

 

Thank you. I'll have to find the thread where you guys were discussing the Mosfet type R/R. Sounds like a good investment for all older bikes.

 

I've had an Ignitech unit for the ZXR250 for a couple of months now. That's what I was referring to as "a programmable unit". Looking at the Ignitech software will make a bit more sense now than when I got it. I can't recall ever seeing an ignition curve for the ZXR250A engine. They run the 21119-1263 TCI box on the A engine and I don't know anyone who has a Service Manual for the ZXR250A. The only manual I've seen is for the ZXR250C. If anyone has a ignition curve map for the A engine, please post it.

Thanks

 

Thanks Wozza. That Q4 response makes more sense. Not that it actually matters too much, but how would you know how much amperage is being used to turn the Starter Motor on any motor?

 

Too true. They don't like it much. Especially if when can't answer your question...that's when they suggest you go to the campus Library and read a book! Some teachers actually fess up and say "they're not sure"...I prefer that to misinformation.

 

That's a very good read Blair. Thanks for the link. I've started using an oscilloscope at college while testing spark/coils etc. I will have to get one as they seem like a necessary tool. At least the Ammeter is more affordable than an oscilloscope.

 

To be fair, I do ask a lot of questions and some of them can be painful. A couple of the teachers are absolute gold. When you ask them a question they articulate the answer(s) and check you've understood their explanation...beautiful. Some teachers you can ask "what's the time?" and they'll spend the next 40 minutes telling you how to make a clock; funny thing is, at the end of the explanation, I still don't know what the time is!