Project 718 Cayman T: Part 2 – Oil Change Mod, GT4 Scoop Install, and Increased Octane - Page 5 of 6

Remember this 93 octane label?

I used the Launch X431 to datalog the ignition retard and this ‘Ignition map RON dependent’ parameter. My guess is when the ECU detects lots of instances of knock, such as here, it does a global map ignition adjustment to account for the lower octane fuel. I had Shell 91 octane in the tank at the time and I was doing repeated wide-open-throttles (WOTs) on the highway in third gear. Each cylinder had upwards of 5 degrees of timing retard. As the RON dependent value increased, the amount of ignition retard decreased with each WOT. As Porsche seems to have calibrated the car for 93 octane, I started looking for a way to increase our crap Cali 91 octane up to 93.

Back in the day when I had the Evo, I would dump in a few gallons of 100 octane to bring the 91 octane up to 93 whenever I was at the track. The Evo was tuned for 93 octane from Mitsubishi too. There is a VP gas station that sells race gas not too far from my office, but it would be a pain to go splash a few gallons of race gas every tank. So, after some Googling, I found this stuff, Race-Gas – Race Fuel Concentrate. The person who started it lost an engine after buying old contaminated race gas at a track. Coincidentally, I was chatting with a neighbor who is a motorcycle track day junkie. He got a bad tank of race gas from a VP station which cost him a whole track day. I looked at other products like VP Octanium, BOOSTane, and Torco Accelerator. Whatever is in those, they are even more concentrated than the Race-Gas stuff. The way I figure, the higher concentration of whatever is in those, is potentially not quite as safe for the engine. Also, I figured super concentrated stuff would be more difficult to get consistent octane levels and an even solution in the whole tank. I bought a measuring glass to meter out 1 ounce of the Race-Gas concentrate per gallon of 91 octane gasoline to bring it up to 93 octane. A full tank of gas is just over 14 gallons, so I poured in 14 ounces. For future octane bring-ups, I will just add an ounce of concentrate for every gallon of gas I pump in. I bought that little stainless steel funnel to use to dump in the concentrate, but its too short to use easily. I guess I can just use the spout that comes on the can.

I was ripping on the car for about twenty minutes. For the most part, I didn’t see ignition retard more than 3 degrees. Once in a while, there was a 5 degree retard. However, the RON dependent value never budged from zero. The car also definitely felt peppier. Notice prior to adding the Race-Gas concentrate, all four cylinders almost always had timing retardation at the same time. In this screen grab, you can see cylinder 3 had no timing retardation at all while the other three cylinders had varying levels. Race-Gas concentrate is roughly a dollar an ounce. Cylinder 4 did see more frequent instances of ignition retard. I will have to check which cylinder is number 4, but I would bet it is the closest to hot exhaust bits.

Lots of WOTs leads to a lot of brake dust. One little mod I added, some decent valve stem covers. The ones that came with the car are some ultra-cheap, thin plastic ones. My bicycle valve stem covers are beefier.