Just a little recap on our Fiesta ST. We have tuned it on 91 octane with a COBB intake and no other engine performance modifications. It made very nice power and the little car is just tonnes of fun to drive! Now it was time to see what E85 will do and that meant strapping it on the dyno. 

A little run-down on E85. E85 has a high resistance to knock (high octane) and we love this about it because it allows us to push both boost and timing higher without reaching the dreaded knock threshold and thus make more power with no other hardware changes other than an E85 specific tune. The Fiesta ST uses a high pressure fuel system since it is direct injected and while E85 adds octane, it also takes away fuelling headroom. We were able to watch knock response as well as all fuel pressures using the COBB Accessport.

To run full E85 the fuel system would need to flow 30% more fuel and the high pressure fuel pump would have a hard time keeping up. Because of this we chose to run an E85 blend. That means we mixed 3 gallons of E85 and topped off with 91 octane. The effective mix is around E30 and it adds enough octane such that we can reach MBT (meant best torque) on the stock turbo. What that means is that we were able to advance timing until no additional power was being made and the engine remained knock free.

So this trip to the dyno served several purposes. First, it allowed us to search for and find MBT on the Ecoboost 1.6l in the Fiesta ST. Secondly, it helped verify that the E30 mix offered enough octane to reach MBT on the stock turbo while not depleting the OEM high pressure or low pressure fuel pumps. Finally, it allowed us to build our Stratified E85 Flash Tunes and also verify that by switching to an E30 blend and tune, you will gain approximately 15whp and 15wtq with no other hardware changes. 

On such a light car, those power gains can definitely be felt and add to the enjoyment of an already fun car!