We had a chance over this past week on our trip to Texas to mess a bit more with the shop’s 997.1 GT3. What began as a simple training trip to Cobb Plano lead us to a few new discoveries with the .1 GT3 platform! What we found was surprising and will save you guys countless dollars on race gas if you choose to use it!

Cobb Plano, located in the Dallas Metro area, was gracious enough to let us come by and test a few things and while we were there we brought their in house tuner, Calvin Dotson, up to speed with all of our new developments with the Porsche platform. Calvin is a very talented calibrator with all the tools necessary to perform a stellar tune for your Accessport equipped Porsche! While we were going over some 100 octane calibrations on Cobb’s .1 GT3 we got to thinking about how buff the stock fuel system was and how hard it could be pushed. One thing lead to another and we tossed in some E70. The results were surprising to say the least. Over the factory tune on 93 octane, the GT3 picked up 25whp and 14ft/lbs of torque on a 100 octane protune, furthermore the car picked up an additional 13whp and 4ft/lbs of torque on the switch and tune from 100 octane to E70. That is a 38whp gain over the stock tune in this particular case! Keep in mind this is all done on a 100% stock car with only an ecu reflash via the Cobb Accessport. I plan on evolving what we learned here into a release OTS map version for the GT3 in E85 form. Please note that the car must be calibrated properly for high ethanol mixtures.

On to the data! Below is a comparison of the stock 997.1 GT3 calibration vs. a 100octane Protune vs. an E70 Protune.





Here is a link to the datalog taken with the Accessport for our final E70 run from the dyno run above.

So for those of you looking to edge out your buddy running 100octane in his GT3 know there is a bit more on the table running ethanol! Ethanol is also a cooler burning fuel so your car will remain much happier for longer on the track. Fuel economy will come down about 30% however.

Let's move on to a little bit of math to make sure we are not running on the limits of the stock fuel system.

Using the Injection time and the RPM you can calculate Injector Duty Cycle or IDC. IDC is a percentage of on/off time of an injector. 100% is always open, 0% is always closed. In a broad sense, the closer you are to 100% IDC the closer you are to maxing out your fuel system. You can find IDC using the following:






Using that formula you can see we are only hitting a peak IDC of 77.183% at an engine speed of 8146RPM all on stock injectors and fuel system. Plenty of headroom left in the fuel system!

Thanks again for reading! If you have any questions regarding ethanol in your GT3 please don’t hesitate to reach out to us or your local Cobb Protuner!

Thanks again to Cobb Plano for opening up their facility to us for testing

- Jon Hebbeln jon.hebbeln@cobbtuning.com
- Porsche R&D Calibrator

 

Hey how do your dyno numbers compare to the SoCal dyno? Mitch built the base gt3 tune with my car back in December and these base numbers are a lot lower than mine. My car is stock minus cup car exhaust. He's been wanting to do an ethanol tune with bbi for the car for a while. Problem is access to the fuel at the tracks. 100 and 91 easy to get. Ethanol we have to carry and consumption goes up with it. Already burn 20 gallons of fuel a day.

 

An apples to apples comparison can't really be distinguished because we have never had the same car on each dyno. What we always look for when we put cars on the dyno is the delta percentage that is gained. This percentage should stay pretty consistent regardless what dyno is used.

In this case the car's peak power increased by 11.7% over the factory calibration. Just by switching to ethanol and a bit of custom tuning with the Cobb Accessport. I would estimate your car's increase to be similar as well with a custom ethanol tune over the factory calibration. The guys at BBi are more than capable of getting this sorted out for you!

However, like you said, the logistics of running it at the track are a bit tough. that 20gallons of 100 octane fuel a day you burn would turn in to 25-30 gallons of E85. Which means lugging that fuel around in your support/tow vehicle. Which for some guys is just too much hassle, but you can fill up on 30 gallons of E85 for much less than what 20 gallons of 100 will cost you.

Since we support both fuels we are simply providing more options for anyone who chooses to use them!

-Jon

 

I'm hoping to do an E85 tune on my .2RS at BBI in the near future. This is pretty damn exciting. Will be interesting to see what kind of power the car makes with a full race exhaust and 4.0 style intake.