In Europe it can be pretty difficult to get your hands on ethanol, I have seen people use 95% bio ethanol designed for fire places, but MOL’s 90% ethanol designed for motorsports with an octane rating of 106RON might be a better solution, called MOL DRX.
In my testing, I was able to get 100% ethanol and I used 100RON gas to achieve my E50 mixture. If I used 95RON gas, I would get a lower octane rating, which some people forget to keep in mind.
100RON
First let’s see the results with 100RON gas alone, boost is at 20 psi and at 5500 RPM I am able to run 8 degrees of timing, anything higher than that and corrections start to appear.
100RON + Boostane
Here is the 100RON gas + a can of Boostane to a full tank. At 5500 RPM I am able to run 12 degrees of timing.
E50 Mix
Now let’s see how much timing I am able to run on an E50 mix with 100% alcohol and 100RON gas.
With the E50 mix I was able to run 12 degrees of timing too, pushing anything more and I started seeing multiple cylinder corrections coming up, but the E50 mix testing happened way later than the Boostane testing, because I had difficulties getting my hands on ethanol, and my wastegates started to get tired, and with the E50 mix I was only running 19 psi instead of the 20 psi at 5500 RPM previously.
Conclusion
If you have Ethanol accessible to you and is fairly priced then the E50 mix is a no brainer, but you have to remember that ethanol puts a lot more stress on your fueling system than gas does, and this means on an N54 you might be able to make more power with the Boostane mix than with the E50 mix, because High Pressure Fuel Pump limitation is a real issue on this platform once you start running upgraded turbos or some serious boost. So with Gas + Boostane, you might be able to push boost further than you would be able to on an ethanol mix because of the reduced fueling requirement compared to Ethanol.
With the Gas + Boostane you are getting pretty much the same knock resistance that you would on an E50 mix, with the added benefit of some fuel system headroom, but you give up the cooling capabilities of ethanol.
Here is an example log, where running an E50 mix at 24 psi on stock turbos is getting close to the HPFP limits, anything below 1300 psi is no good.
Another thing to keep in mind, your O2 sensors and spark plugs will turn orange due to MMT, Methylcyclopentadienyl manganese tricarbonyl, which can be found in most octane boosters.
Some believe this to foul spark plugs and o2 sensors, but I never had issues during my testing.