jatmonn997tt

Needed some technical advice regarding 91 octane fuel. Currently own a 2007 997 Turbo with about 26,000 miles (Upsolute ECU mod and NHP exhaust) that was purchased and used in Southeast Michigan where 93 octane is plentiful, and only fuel used in my car. Currently using my car in Sacramento for business. Is it harmful to the engine to be running 91 octane now ? MY concern is that the Upsolute ECU is not programmed to handle the lower octane fuel. Currently have had no problems in normal driving, however have avoided WOT so far (but would love to open it up!) Also, would it be better to add those "Octane Boosters" (eg 104+ or NOS brand) to the fuel tank to correct the issue ?

Thanks in advance for your help guys !

Macster

To be safe perhaps you should ask the company that supplied the Ecu mod what octane of fuel it advises you run in the car.

Perhaps the mod'd Ecu can adapt to 91 octane gasoline ok and there's no real problem.

At WOT the engine's octane requirements can go down. The Ecu suspends emissions monitoring under hard acceleration, high loads, high engine speeds, and supplies the engine with more fuel (a richer fuel mixture) that combats detonation.

It is the part throttle slow rpm high load situations where the higher octane gasoline helps, if the engine is designed to use it.

Most engines spend the majority of their time at 30% throttle or less which is why part throttle ignition advance with better economy, engine responsiveness, etc. is so critical.

Sincerely,

Macster.

gradyex

I have the same problem as you (2007 TT with 26k miles also). I live in SF and 91 is all I can get my hands on unless I make a 40 min trip to infinion raceway to purchase 100 unleaded at a hefty price of about $7 bucks per gallon. My car is stock but I notice a difference when I add 6 gallons of 100 to my tank mixed with the 91. After 93 octane my car will not gain from anything higher so basically its just a waste. Your car might be entirely different with the CPU mod.

Now, what I do is every other tankfull or so is I add Lucas octane boost. This pushes the 91 to 92 octane. For some reason these stock turbos really respond to just 1 or 2 points (if under 93). It takes about 15 minutes for the computer to adjust. So long story short is we are not as lucky as the rest of the country when it comes to fuel and octane ratings. We just have to put up with what we have. The best advice is find out what sort of CPU flash you got and talk to the company about your options. Good luck.