Tuning ignition map for a Porsche 928 S4 with E85 fuel

Bonjour,

I have a Porsche 928 S4 since 2011 and I really enjoy it. Sometimes I use it on track. I started using E85 fuel since 2014 and my feeling is that she works better with E85, in particular during hot season.

Last month I bought a tool in order to be able to modify the fuel and ignition maps.

I have a WBO2 sensor since 2013 on the car. I can run it open (no cat) or close (cat) loop. To run E85 fuel I run it close loop so far. Now remapping it, I plan to prepare an open loop map for track use so I can have better control on the target lambda I would like to get.

In the attached file you will find the 3 stock ignition maps : 2 for 98 octane fuel (cat and no cat) and one for 91 fuel.

I prepared an ignition map to start testing with. It is also in the attached file. I can verify the knocks on the car and I will make some runs on an open road, verifying power with the sensor of my iphone. I have a track day soon. It will be helpful to feel a difference or not. I plan to tune with E85 at about 70% ethanol.

As a start, I removed 2 or 3 degrees at low load as I understand that E85 fuel burn faster. For higher loads I compared ignition map between 91 and 98 fuels and supposed that where advance has been removed by Porsche for 91 fuel it was because they would like to prevent knocks... so should be knock limited? At high load and RPM I put also more advance : +3 degrees before 28 degrees and +5 after.

I also added 5 degrees on WOT map. To prevent any issue with knocks, I plan also to retard more in case knock occur (max knock retard of 14 degrees instead of 9 set by Porsche) to be conservative till I make sure the map is correct.

Comments based on experience will be appreciated!

Best Regards

While you can make changes, and confirm that you aren't getting knock with audible knock detection on the road. The only way you are going to know if you are optomizing power will be to tune the ignition timing on an actual dyno. The changes may be to subtle to detect with a phone app, but feel free to try it anyway.

Good Luck!