toocoolpash wrote
Are you serious? How come? I was told putting higher octane in would increase power "/
Because if he's mapped it to run on 95 RON then the engine has been detuned to run on lower octane fuel without knocking. This is sometimes done for countries where 98 RON is difficult to come by.
The effect of putting 98 RON in would now be just the same as putting 98 RON in a 1 litre Saxo - no effect on power output, the engine isn't tuned for it.
On the other hand, if what he's done is leave the set of backoff maps in the ECU so that it can adapt to 95 but still use 98, then you can still obtain advantages from super unleaded. But this is NOT the same as "mapping for 95". I'd guess that he's made the full power map more aggressive but left the "95RON map" as it is and maybe done something to the way it changes between them.
The octane rating of the fuel has nothing to do with its "power". It's a measure of how difficult it is to set fire to. 98 RON is harder to set alight than 95 RON, so that it can be used in higher compression engines without detonating.
Detonating is where pockets of the fuel-air mixture explode simply from the heat of compression. The explosion creates much higher cylinder pressures and shockwaves through the combustion chamber, overstressing the cylinder head, piston, conrod and crank. The fuel-air mixture is meant to burn in a smooth and predictable way after ignition by the spark plug, producing a relatively gradual pressure rise. The explosions produced by detonation cause sharp pressure rises and occur earlier in the power cycle than those produced by proper ignition - detonation is faster than burning. It is very destructive and will trash your engine in seconds if left unchecked.
(98 RON is harder to set fire to than 95 RON but you don't measure that by waving a match over a pool of it. Both will go whoof and burn your eyebrows off).
The standard map expects 98 RON and the ignition timing is set to take advantage of that. If you fill a standard car with 95 RON, the knock sensors (two solid-state sensors bolted to the crankcase that detect the vibration that is characteristic of detonation) will immediately detect knock and the ECU will move to a different map, with a richer mixture and less ignition advance, ensuring the fuel is ignited by the spark plug before it detonates.
Trouble with this is you're relying on the knock sensors to work every time you switch on the engine. As far as I know, as soon as it detects knock the ECU goes to a different map - but it has to detect the knock first, so the engine has to start to knock - which is not good for it.
I'm not sure what process it uses to regain best power if you put 98 RON back in. I assume it shifts to a more aggressive map by stages at each startup until it detects knock again, or reaches the preset "98-RON standard" map. Advancing by small increments will minimise engine damage - which accumulates every time you get knock.
)
Vince defiantly knows his stuff down at stealth racing 
