He was running 15psi safely because he was using an Emanage Blue to control both fuel and timing.
There are actually three ways to reduce the probability of knock at full load on a turbocharged engine: reduce boost, adjust the AFR to richer mixture, and retard ignition timing.
Detonation is caused when the temperature in the combustion chamber exceeds the temperature of the air/fuel mixture. When exceeded, the mixture goes bang. Not a good thing, regardless of power. Detonation is the engine killer, not necessarily power.
If a system is detonation free, regardless of boost, rich/lean, power, etc., it will not fail due to bad combustion. But one knocking at a 10:1 AFR (rich) fail in a heartbeat due to an obvious over-heated air charge (think 10psi without an intercooler).
You either need to retard your static timing, invest in a Bipes ACU or MSD box, or enrich your fuel mixture.
The Bipes ACU (Auxiliary Control Unit) dynamically retards the timing of your engine to protect it from detonation or knock. The ACU uses three input parameters to control the timing: Airflow, RPM, and Intake Temperature. You can pull a total of 14° of timing. Not only will you help protect against detonation, or you gain low-end power back if you keep your static timing at 10* or advanced. The Bipes is a proven device in NA, turbo and supercharged Miatas. Aftermarket ECU and ?piggyback? usually have this function built in.
The MSD Boost Control unit specifically designed for the Miata. The Bipes actually originated as a mod for this unit for added adjustability. They can still be had, but usually for the same price tag as the Bipes itself. The MSD unit retards the timing 3° per pound of boost pressure with no more that 6° of retard being allowed. When no boost pressure is present, the ignition runs at the factory timing. These settings are fixed and cannot be adjusted. With that said, you can still run your Miata advanced to 14° of timing and when it boost it will retard back to a safe 8°. If knock is still present then set your back a little. It's a little basic but it gets the job done.
To just plain retard you static timing, you'll just need a timing light and a 12mm wrench. But by doing this you'll suffer in low-end power.
You're also trying to boost way more than those injectors are suited for. At most you want to raise your fuel pressure to 100-110psi. Anymore and you risk damaging your OEM FPR, bursting fuel lines, locked injectors, and even most aftermarket fuel pumps cannot produce enough flow to the injectors past that point.
You're using the supplied Vortech FMU, which comes loaded with a 12:1 disc. So we can determine your fuel pressure at full boost with math!
[tab:b6f6e1b73a]12 (rise) x 8 (boost) + 50 (fuel pressure at 0 ~hg.) = 146psi of fuel in the rail at full boost.
What does this mean?
[tab:b6f6e1b73a]You're pushing your fuel system to the brink of failure.
[tab:b6f6e1b73a]You're demanding more fuel than most FPs can provide.
[tab:b6f6e1b73a]You're running lean due to lack of fuel
If you want to boost 8psi you need a ratio of gain that will reach a target of 100-110psi in the rail:
[tab:b6f6e1b73a]7 x 8 + 50 = 106psi
Then you need an injector that can flow enough fuel to support your HP
at 106psi of fuel your 1.6L injectors (203cc) can only support 150rwhp. Which on a GReddy kit is only about 5-6psi.
[tab:b6f6e1b73a](317 / 10.5) x .8 / .55 = 44BHP on each injector
at 106psi of fuel 1.8L injectors (265cc) can support 190rwhp. On a GReddy kit that's around 7-8psi. So they should suit your needs perfectly fine.
[tab:b6f6e1b73a](413 / 10.5) x .8 / .55 = 57BHP on each injector
So to finally answer your question, yes...getting 1.8L injectors, retarding timing, a 7:1 ratio FMU disc, and a Fuel Pump that can flow at least 27 Gal/hr. at 110psi will allow you to support 8psi. Plus I hope at that point you have an intercooler as your intake air temps will be about 100* above ambient in the manifold at that point and the amount of ignition retarding it will take to battle ping will cause your EGTs to skyrocket.
I suggest you read my FAQ link a bit and rethinking your position on the answers you can recieve on Miataturbo.net.
Plus IIRC correctly you were asking suggestions on running a system at 215-245rwhp, in which case you really do want to consider engine management.
=D>
