94 octane/e10 base map, e85 flex tuning

Hi All,

I have an R33gtst with rb25det. My car performs double duty, it spends most of it's life on the streets and sees a track day every other month.

Recently I've been thinking about setting up the base map to run e10 (about 94 octane in Australia, our best pump fuel is 98 octane) with a flex sensor.

The idea being, I could run a 4 port boost solenoid and really low gate spring pressure, say 3 or 5 psi base. Then when the car is on e85, run full boost 20psi.

That way when I'm simply commuting to work for the week, the car would drive around essentially as an NA car making 3ish psi and I can trow e85 in it when I want to enjoy the drive.

My concerns are primarily around any risk of engine knock as I'm only running a Haltech Pro Plug in and I'm not happy with the knock control function of this ECU.

My main questions are, is this a crazy idea? should I not be a tight arse and run the base map on 98 octane like everyone else? (even though I'll just be cruising down the highway for my 100km round trip)

If this isn't a completely mad thought, any ideas on knock detection for the boat I'm in? Ideally I'd like to use the factory knock sensors.

Your idea is pretty sensible really. While I generally always advise to run the highest octane fuel that you have available to you, I understand that cost needs to be factored in. Provided the boost and timing are safe on your E10 94 octane you're fine. You probably don't need to pull the boost down to 5 psi either - I'd see no reason why you couldn't achieve a safe tune at 10-15 psi with conservative timing.

As for the knock control I don't have a good solution as I never found the Haltech Platinum Pro knock control to be effective. in my mind it is really a primitive 'noise' control system rather than proper knock control. So if you want closed loop knock control then you really need to consider a better ECU. That's not to say it's essential though. I spent probably 2/3 of my career tuning ECUs with no knock control at all and you can get great results by tuning the timing using audio knock detection. You'll need audio knock detection equipment anyway even if you had a more advanced ECU so that you can properly calibrate and validate the knock control settings.