3 min read


100% E85 IN THE F80 M3

Now that we've maxed out the power output on the stock turbos with 93 octane, the next step was to tune the S55 for E85.  Off the shelf maps using E-Blends are common, such as 30%-50% E-85, but we wanted to go 100% E-85 for the extra power, and if nothing else, the simplicity of filling up with only one fuel type.  

To handle the tuning for the E85 map, we selected pro BMW tuner Cary Jordan.  We knew he would be able to safely and precisely dial in a custom  E85 tune for our S55.  In preparation for this we needed to upgrade the spark plugs.  We opted for the NGK 97506, gapped to .020. There is some debate on how to gap these, but we can say these worked flawlessly gapped at this spec.  Our S55 was already equipped with the following modifications:

ARM Catless Downpipes
ARM Intake System
With the spark plugs properly gapped and installed we were ready to flash our baseline E85 tune.  As is typical with remote tuning, there were multiple datalogging sessions and tune revisions.  Communication from Cary and his team was first class.  Revisions always came with feedback on how the car was running and the adjustments that were made with the new tune.  After approximately 12 revisions were ready to bring our F80 M3 back to the dyno to see how much power was gained. 

S55 Charge Pipes


The best numbers we were able to pull from the E85 setup were 556WHP and 524WTQ.  86whp and 105wtq over our stock dyno numbers.  At 5,700RPM is where this tune really shines, making over 100whp more than stock.  Using our standard correction factor of 20% that puts the crank numbers at 667hp and 629tq.  

S55 E85 Dyno

Compared to the BM3 OTS Stage 2+ map, the custom E85 tune was able to squeeze out another 13whp, and actually showed a loss of 23wtq.  However, at 5,700RPM to redline is where the E85 tune stands out, making 30-40whp over the Stage 2+ map.  While the peak numbers don't really show massive increases, the performance testing does show a good bump in improvement.  


With 100% E85 fueling the S55 our best 60-130mph time was 7.92 seconds.  The 60-130 times had a good grouping which ranged between 7.92 - 8.15 seconds consistently. 

S55 60-130 Full E85 Stock Turbos

This cut 1.26 seconds off of our BM3 OTS FBO Stage 2+ 60-130mph.   Putting the S55 roughly in the same category as a stock Hellcat, Viper ACR, 997 Turbo S, Huracan, and many other respectably fast cars. 

Overall, going to 100% E85 over the OTS Stage 2 tune made a measurable improvement to our 60-130 time while keeping the simplicity of fueling up simple.  The only hardware modification that was necessary beyond our Stage 2 FBO setup was the spark plugs. 

There is some "maintenance" which requires you to run a tank of 93 octane through the vehicle roughly every 1,000 miles to keep the injectors healthy. Also, at this stage we highly recommend upgrading the crank hub to avoid the notorious S55 crank hub failure.  Once this upgrade is performed you will be ready to max out the stock turbos without the risk of spinning your crank hub.

With these items sorted out, our next phase will be to install and test upgraded turbos and compare the results to these. 

If you would like assistance with building your S55 powered BMW, let us know and we'll help you with your build!

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