[Grantmac]

Hello all,

I registered here specifically because of this and the open source thread, the thread popped-up over on miata.net. I drive an MX-5 which I dual purpose as a DD and STR car. I'd love some more power on the street but don't want to add a full-time SC and end-up in SSM class. Being able to revert to NA in 10 minutes is a huge draw for me.

I also like the idea of storing potential energy over a fairly long period of time and then releasing it over a short period of time. I think if I datalogged my average spirited drive I'd be at full throttle for less than 5% of the time, even less on the daily commute.

As I understand it: right now the system uses cascade charging from the 12v system to charge the 24v SC batteries and keeps the systems separate.
Why not do a Series/Parallel system like this:
http://www.the12volt.com/installbay/forum_posts.asp~TID~128392~PN~1

It would eliminate one of the batteries, or allow you to run a 36 system with the same number of batteries currently used and retain the 12v charging system. Your recharge time would also be reduced because you wouldn't be limited by the cascade charger but rather the alternator and battery itself.
Of course you'd want to isolate the batteries with the key off, but if you ran them parallel with the key on that would allow for twice the starting battery amperage. Which is something you lose going to a smaller starting battery. Then run series when the SC kicks in and completely isolated from the alternator (which would run the onboard electronics).

As for the bigger battery/alternator/road racing question:
This idea is actually pretty good, but not in the way that many people are considering. In the current scheme the alternator doesn't power the SC at all, it only charges the battery when the SC is NOT engaged. That is why people are getting such good numbers at low boost. It also means the engine is actually under less load for a given output with the SC engaged, which is good for the engine. Going to a larger alternator to try and drive the SC directly would result in much lower peak HP numbers for a given level of boost.
Where a bigger alternator comes in would be in getting the batteries charged faster when off the SC. For street driving the system is currently capable of doing this, maybe even for AutoX or time-attack as well.
Ideally the batteries would be sized to use 50% of their capacity during the longest time of full-throttle on the track. The alternator would be sized to recharge 50% of the batteries capacity in the braking and partial-throttle zone after that straight. This would likely require a 24v alternator to keep things efficient, maybe even a completely separate charging system.
Think of it as regenerative braking but instead of storing efficiency (like a hybrid), you are storing HP.

I don’t think this will compete with traditional forms of FI for maximum power applications in a race environment.
But a race environment which they are ideally suited for is certain classes where the cars are classed by HP and weight. This system produces massive low-end torque with moderate HP gains, basically ideal.

I’ve got some ideas for an improved control system but I’ll save that for another post.

-Grant