There is a small degree of increased performance in modern standard manufacturer's vehicles when it comes to using premium fuel. Not to the extent that I would say it is significant but enough to notice a little more pep. Reason being, the higher octane means more resistance to detonation as you said. As a result, the knock sensor factory-standard ECU's utilise picks up less knocking which means less retard of the ignition timing which means more efficient burn and therefore a bit more bang for the buck.
Retarding does prevent pre-detonation to a point. If it didn't, the manufacturers wouldn't go to all the trouble of spending so many dollars on research to pick the right sound for the knock sensor to depend on to minimise the pinging. Of course, there's only so much you can do before you retard is so much that you end up fouling the spark plugs and worse yet, the EGO sensor. So to say that it does not result in more horsepower is wrong. To say that it only results in a small and almost insignificant amount of horsepower due to a more advanced ignition timing is true. I strictly use premium because I drive a turbocharged Maxima at 8.5:1 compression so I need a turbo-friendly fuel for the task otherwise I would have to retard the ignition timing and dump more fuel in my MoTeC mapping which would definitely rob me of horsepower and waste fuel. Adios, Tony --------------- TAMA - The Strongest Name in Drums --------------- -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Gary Udstrand Sent: Thursday, 18 August 2005 3:52 To: The Hardware List Subject: Re: [H] Gas prices Higher octane needs usually result from higher compression in performance engines. This higher compression can result in the fuel igniting (in the absence of a spark from the plug) before the piston reaches TDC (well, actually the engine should fire prior to TDC. It is just firing earlier than it should in the process). Retarding the timing will do nothing to prevent pre-detonation (pinging) in that case. Also, higher octane does *not* result in more horsepower. Octane represents the resistance of the gas to detonation, the higher the octane the more resistant the fuel is to detonation. It does not have more stored energy.
