I have a 93 miata and I run in autocross STS class, so I am limited with many of my mods.

Is it possible to run E85 with stock injectors and Fuel Pump? I am not allowed to mod these in my class. And can the fic handle e85? it says +100% fuel duty cycle for injector, so I assume if the the injector and pump can handle the extra fuel, it would work.

My other option is to use high octane pump gas (100+octane).
But I firgure if the E85 work, I would net more power.

 

It will not work on stock injectors/pump unless you jack up the pressure, and even then you'll run out of pump/injector.
Even if it did, you would not gain power on an otherwise stock'ish car with e85.
FIC is pretty limited in what it can do as well.

 

I have a 1991 STS Miata and am planning on trying E85 with the FIC also. I logged a maximum of ~68% duty cycle on gasoline so the injectors should have capacity. I'd be surprised if the pump didn't. If it doesn't it should only be at very high rpm.

Higher octane won't provide any power gain because on pump premium the engine is not knock limited even at MBT spark and low rpm. The E85 should provide a 2-3% torque bump due to charge cooling. From what I've read MBT E85 lambda's are similar to those for gasoline.

 

Update: E85 works fine with the FIC in my 1991. The injectors get max'd out but lambda is holding at 0.90 all the way out to 7100 rpm. The mods are limited for STS class autocross to blueprinting, CAI and a full header and exhaust with catalyst and straight through muffler. It fired right up and ran fine right away. A little testing and calibration and all is good. Now to schedule some dyno time.

 

.9 V on a wide band or narrow band?

If narrow band, I don't think that would be very accurate, since narrow band switches at ~14.7:1

I believe E85 need to run around 9.5:1 to be effective

 

Lambda is not volts, it is a ratio of the actual AFR to stoichiometric AFR (~9.76 for E85). Lambda of 0.90 with E85 is an AFR of 8.8. This is measured on a wide band sensor, of course. Best torque lambda for gasoline is ~0.90. For E85 many suggest it is a bit richer. The dyno will tell.

 

misread your post. my bad.