A&Q about 350Z
Q:
the truth about gasoline is for ca people it has mtv-e in it and its going to give us all cancer becuase of lame-*** nafta. sick!
A:
The factory computer sets an optimum ignition curve. It leaves it fully advanced to that point unless it senses detonation. So, if your owner's manual recommends 87 and you put 93 in, it won't continue to advance, it will just use the default map in the memory.
So, no more power or economy will come from more octane unless something is out of whack with the engine. As a normal operational thing, a stock engine will rarely retard ignition on the recommended fuel.
A:
Advancing the timing past optimal lead for your combination will hurt power and most likely economy with it. If your car makes best power on a dyno at 35* total advance with 87 octane, switching it to 37* and 93 octane will lower power. The key there is flame front. Since you haven't changed the flame front speed, you build too much pressure 2 degrees sooner in the chamber, meaning the rising piston has to fight more pressure. The result is lower power.
Proper advance doesn't change with octane, its fixed given the mechanical operating parameters of the engine. This is the exact reason why you need ENOUGH octane and adding more won't make more power.
Adding more octane won't "let" the computer do anything. It won't go past optimum lead. You have to physically program the computer for more timing, which, like I said, will most likely hurt power and economy. The right combo is the best combo. More is not better.
A:
Curious.
My VW GTI required premium fuel. The manual said it would run on regular, but at reduced power.
An old car with breaker points, I could manually advance the timing with premium, and get better mileage, but that timing would would cause knocking if I put regular in it. And that really hurt performance.
My present car, the manula suggests premium if I'm towing, or using the car in very hot weather.
A:
Exactly what I was saying with the VW... its timing curve, compression, and other properties are optimized for premium. Reducing octane kicked in the knock sensors, retarded ignition, and reduced power.
Conversely, my 73 454 is optimized for 87. If I advance the timing and run 93 it just knocks and pings because the flame front is smacking the top of the piston way too early. Power and economy suffers greatly. I'm using more of the crank's rotation fighting the early ignition.
All I can suggest on the points car is that it was timed conservatively in order to prevent overheating, reduce NOx, or it was an HD application where detonation was a potential problem
And your present car... they're just covering their butts on warranty repairs in case you're one of those tow drivers that just puts their foot to the floor and hopes