User #15607 16408 posts
Turbo B
Whirlpool Forums Addict
The way an engine works (one designed for these fuels), is that the engine computer monitors all these different settings, from the AFM/MAF (air intake), to the O2 sensor (exhaust gas), to knock sensors (remember here, we are talking cars DESIGNED FOR use of the higher octane fuels), and numerous other sensors around the engine.
If you fill the car on 91 Ron, the AFM, O2, and Knock will have a certain value.
When the engine is started, the engine computer will advance the timing up to 2 -3 degrees, and monitor knock values, if detected, the ECU will retard the timing back slightly until the values are within acceptable limits. Mainly the Knock sensor in this equation will show that when you step on the go-pedal, the engine will start knocking earlier, so what the engine computer does is 'retard' the timing on the engine slightly more to reduce this knocking effect. This retardation will reduce performance somewhat.
knock: in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise time in the piston's stroke cycle. The peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive.
(Thanks Wiki)
Now, when you run 98 Ron (or higher) fuels, the engine computer does the same thing when started, it advances the timing up to 2 – 3 degrees, this enables the maximum 'factory' limited power to be developed from the vehicle's engine. If, again the knock sensor reports too much knock, the timing will be retarded slightly to reduce pinging.
98 Ron fuels are better formulated to withstand the harsh environments of the cylinders, therefore better avoid this pinging effect, and thus timing on a performance engine will remain further advanced on 98 ron, than it will on 95 or 91 ron fuels.
Remaining further advanced means the engine can develope higher power levels without the potential for damage.
Links:
Here are some links to some of the effects that pinging/knock/detonation have on an engine...
http://w6rec.com/duane/bmw/piston/piston2.jpg
http://www.aa1car.com/library/piston...ion_damage.jpg
Comparison of good vs bad:
http://bedwani.com/turbohonda/crx-bd-pist3.JPG
B.
anchor: whrl.pl/RbXEny
posted 2009-Jul-31, 8am AEST
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