What do most run in these cars? PMNA claims they can run on 93. My shop said race gas is recommended. Currently running 96 in my car, but if not necessary, it would be good to know.

 

If you actually race the car, particularly in summer, keep using the higher octane race gas.

 

Had this chat this weekend with the Merit Partner guys. You can run 93, but they highly recommend 100 or else you likely aren't getting everything possible from the car.

 

Plus the higher octane pays benefits in engine and cylinder head cooling in extreme conditions

 

My race shop gave the same advice as above. 93 octane will work but they strongly recommend 100+ octane as the engine should run cooler.

BTW, I love your Gulf inspired wrap. Care to share a few more pics?

 

What the 100 unleaded does is allow more timing advance and a better burn before the knock sensor kicks in, We did a lot of testing in 2016-2017 to see what the difference was, and the performance level improvement and consistency, while negligible, was measurable.

 

I’ve only run my 981 GTS4CS MR at one event at Road America. Ran it on 93 until they ran out, then on straight 100, then a 50/50 mix of 91/100. All combos yielded the exact same power and the Motec logs show timing was never pulled. I also didnt see any difference in engine temps. It was not very hot this event, only around 80, but I personally doubt that 100 will make any difference at all. I’ve done the 93 vs 100 comparison in at least a 6 track cars, and none actually performed any different. If anyone has contrary data, I’d love to see the timing change and engine temp delta when running 100 vs 93.

 

Wouldn’t negligible changes in performance and consistency support 38D’s results at Road America? It would suggest that it’s not necessary like PMNA claims. They told me the recommended octane levels were for ROW.

 

Sure

 

I believe I saw Scott's car live and in person at Mid-Ohio earlier this season when I stopped over at his garage to say hello.

To say that this car is spectacular would be an understatement. One of the most beautiful cars and liveries I've ever seen in person on a CS, or really any car for that matter.

A work of art to say the least......

 

Yes, it would. They do recommend it though. I think there are temp and humidity factors that don’t make blowing off the factory recommendations, but I don’t think there is a difference in what most people care about, lap times...

 

Here's some sample motec data that shows this ignition advance as recorded by the ECU. The black line is running straight 93 octane and the colored lines are running straight 100. Temps were 76-78 those two day. I dont have data (yet) from a really hot 90+ degree day.

Btw, Porsche says 98 in their documents. This has historically always been a RON only number vs the RON + MON / 2 number we use in the US. If you look at the Sunoco website, they say their 93 Ultra has a RON of 98. So in my view, running 93 in the US is what Porsche is actually recommending.

https://www.sunocoracefuels.com/tech.../beyond-octane

 

Good looking car.

 

I think we all know that all octane does is prevent pre-ignition (knock). That said, I would be super surprised if Porsche released into the wild a car programmed to defensively retard timing at their recommended octane rating. The cars have been smart enough about defensive timing for a whole bunch of years. Given that horsepower sells, it would be baffling as to why Porsche would sandbag. I guess they could start selling cars with three wheels, make the fourth an (expensive) option.

Colin, thanks for the data. Peter, do you have data you could share? Cheers,