M5KILLR

make more power. before or after renntech ecu make a difference?

elboricua

I think it all depends on what your ecu was set at.

Dr Chill

When at the track I filled up with a tank of 100 octane and didn't notice a significant improvement.

E55AMG99

In my experience, there are many variables that you should test to see what octane range works under each condition. My W210 E55 with PowerChip upgrade runs fine on 91 octane. I saw a .1-.2 sec improvement (G-Tech)from 0-60. The times were very inconsistent but not noticeable while driving. If I top off the tank with 5 gallons of 100 octane (approx 93 mixed), the results are much more repeatable and closer to the .2 second mark. Higher ratios of 100 octane did not improve times nor consistency.

Drivability on 91 octane is not an issue on cool days with my 190# butt in the car. However, if temps get over 80-85 and I drive the car hard, power begins to drop off over 5500 RPM. Again, raising the octane to 93-94 solves the problem as far as my butt can tell. Same goes for a full load of people or high altitude driving. 93-94 octane eliminates the high RPM power loss (ping and subsequent timing retard).

These are seat of the pants estimates but pretty close to what octane is required for my car to perform best. I've tried 96-100 octane and found that the only thing it does faster is drain my wallet. Other considerations are humidity, gasoline quality and makeup, engine tune, etc. I can only suggest that you give the car some time to get used to the new ECU and then start experimenting with different blends until you find the one that works for you.

Curious to hear about your experiences with the upgrades.

Greg