Converting to E85

Finally I had the time off to test E85 on the MSM.
Since I already have a programmable EMS and bigger injectors everything was set.
The advantages are obvious:
- 104 octane rating
- Alcohol (85%) cools the intake charge. No need for water injection.
- It’s cheap and the consumption is less than 30% more than gas when at cruise.

There are a lot of hysteria about E85 destroying hoses and injectors.
Hoses on modern cars can take E85. Actually, gasoline is quite good at eating rubber too. My RC550 injectors don’t have aluminum parts and can be used with E85. I will not run E85 permanently as there are no E85 pumps close enough to any of the local tracks around here. With the added fuel consumption at WOT I would be forced to bring 1 or 2 cans in the car. Not too smart in a two seater MX5 if I was to crash on the way to the track.

I started off richening my current 98 RON map with 30 % and filled her up.
The first minute was a little rough as there was still gasoline in the system. After a while I could smell the alcohol ( top down, cruising) and it started to idle normal again. The lambda showed rich at idle and midrange so I had to lean it down quite a bit at lower revs. At the top it was more or less spot on.
I ran without boost control the first half tank which limits boost to approx 0.5 bar.
Even at this boost pressure I could feel more crispy ness at lower revs and more bite in the top end.
After a lot of datalogging and verification that everything engine related was ok I upped the boost to 15 psi. The car definitely feels faster. The sound is different above 5K and pulls harder. Knock i no where to bee seen.

Here is a datalog comparison between a 4th gear pull on 98 and E85.

E85 4th and 5th pull (woups, 125 mph on public roads..) :

The duty cycle is at 95% at red line in fifth gear. I’m sure I could lean it out a bit but 550cc injectors are pretty maxed out.

Here is the data log for 3rd-4th pull from my last track day at Rudskogen:

Here duty cycle is about 65-68%. It would have been more in fifth. On E85 DC is about 90% in 4th.

I think E85 has seriously good potential for high boost as everything runs cooler.
For more good information about E85 and tuning for turbo cars see


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