Hey Ryan, thanks and awesome to hear your taking a spin with a turbo setup! Do post up a build thread when you start getting some picture fodder generated. I think you're spot on with the GT15. The current setup with the slightly larger Chinese turbo is in my opinion lacking a bit with the delay in boost. Granted it's easy to find (boost) and a hellva blast when in it, but I would dig to have it just a bit more accessible, where you could get a good nip at it when more causally going through the gears. In any case as mentioned I think you'll see just that with the GT15.
As far as the detonation goes, it's something that's always been on my mind. How much more boost could I get away with, is one more redline pull going to break her back???
I haven't been that daring to push it any further. I've gotten away with stock timing for enough miles to be comfortable with the current boost pressures that it's running, but would not consider raising the boost any further (with out at least race gas, a stout motor would be nice insurance too
. I've checked the plugs on occasion and as far as I can see and or tell there have been no deposits or specs of aluminum or other signs indicating detonation but don't feel too comfortable pushing my luck with the stock motor.
As you've noted with the points ignition we're limited as for what can be done; shifting static timing you flatten your bottom end. As we force feed the CBs cylinders via a turbo the combustion rate is increased due to the increase in cylinder pressures/load, with this the need/desire to retard the spark event to keep within the optimal torque range (and motor efficiency) which has moved closer toward top dead center would be a great benefit. At the present with 8 psi I could benefit from pulling a bit of spark timing to keep up with that optimal spark territory, or hit up the dyno to find where it's at. Keeping it as it is with stock timing is playing to impending preignition. The ignitions that are out on the market that have ignition retard/advance don't come cheap. The Dyna 2000 is probably what I would be pushing myself, but that leads me to another fun project I'm playing with.
One of the toys that I'm working on that I've vaguely made mention of recently in this thread is something to combat just this situation that you brought up. On the conception of building the turbo bike I thought a microprocessor controlled iggy would be the perfect compliment to the turbo. So off and on with the help of some friends I have been pushing forward a processor controlled ignition that has timing control as one of its features. I don't really like to speak of vapor ware, and technically that is what it is as of right now, but the first proto circuit layout out is for the most part done (final tweaking yet) and first round of software just about there as well. Hoping that by spring time, no later than early summer (knock on wood), there will be something fairly solid; it has some useful features as well (rev limit, shift light, tentatively more battery efficiency at low RPM, and a few others) . If it turns out to work well I hope to offer it to the community with the goal of making it a good value for the feature set it has. I'll speak more of it if and when it comes closer to becoming a reality.
Hope I answered your questions, if not fire back with some more!
