computer to controll sequential turbos

[Andrew Theurer]

Hello list,

I am working on a Toyota Supra (1998) sequential turbo, and in the process
of replacing stock exhaust manifold and turbos with a nice header and turbos
still designed for sequential operation, I would like to research modifying
it's sequential timing.  Right now, it has a very nice system of
pre-spooling the second turbo (with interesting placement of the first
wastegate/exhaust bypass and a reed valve), which usually happens through
2500-4000 rpm, then two valves, like throttle blades, (after exhaust wheel
on exhaust, after compressor housing on intake) open at 4000rpm.  This is
done with a Vacuum Switching Valve, or VSV, which is triggered by the ECU.
Now, normally I would not mess with any of this, but there's a good chance
my new turbos will flow a LOT more, and subsequently, they are going to
spool differently than the stock ones.  The prespool operation works very
well, and has really no computer influence.  What I want to modify is the
timing of these throttle valves at my desired rpm. First thing I thought of
doing is using a rpm trigger (summit, msd, etc) at xxxx rpm to open the VSV,
which opens the valves.  Only one problem, the stock ECU opens the VSV at
4000rpm, BUT it closes the VSV only after rpm falls below 3500rpm...  So..
maybe I could use two rpm triggers and some sort of flip-flop to control
this... or what I'm really getting at.. a nice simple ECU for sequential
operation.  Either commercial or home built, but something that can read
rpm, maybe MAP, and control a vacuum switching valve or even better cycle a
solenoid like ones found in electronic boost controllers.  The algorithms
would be pretty simple, as rpm increases beyond x close circuit a, if rpm
falls below y, open circuit b.  Eventually I'd like to incorporate boost
control, with a couple of solenoids run inline with the wastegates, but
that's not necessary right now.  Anyway, If you have any suggestions for
what I can use, commercial or home built, please let me know.

Thanks

Andrew Theurer