Hogwash. 1) An uncontrolled flame front causes knock. Which can occur during or after spark plug ignition- not the diesel cycle you’ve described. 2) Higher performing turbo-charged vehicles typically have a lower compression ratios augmented by forced induction. 3) There are many high compression, naturally aspirated, engines designed to run on 87 octane. The compression ratio doesn’t dictate octane. 4) All modern engines can dynamically monitor for pre-ignition (knock) and adjust timing, fuel, etc. for the best engine performance. which comes with advanced timing. If knock is detected, the ECU will pull timing and add fuel which is less optimal in regards to performance, mileage, etc. 5) Using a higher octane fuel with more resistance to knock will allow more optimal engine parameters resulting in performance benefits in most turbocharged engines.The octane rating of gasoline essentially tells you how much the air-fuel mixture can be compressed before it will spontaneously ignite. Gasoline with an optimal octane rating performs best in an engine designed to run on that octane level. Refiners aim to produce gasoline that has this optimal octane rating so it will meet the specifications for the most kinds of engines.
Inside an engine, you have the piston moving up and down, with the injectors metering a given amount of fuel into the combustion chamber as the piston travels up toward top-dead-center position. As it moves up, it compresses the fuel-air mix already in the cylinder. When the air fuel mixture ignites by the heat of compression rather than because of the spark from the spark plug, it causes knocking in the engine and a loss of power. The knocking sound is caused by two exploding "flame fronts" - one explosion from the pre-ignition of the fuel-air mix caused by compression and the other from the rest of the fuel-air being ignited at a slightly different time by the spark plug. The two flame front explode and send shock waves through the air of the cylinder, which meet in the combustion chamber and give you that annoying knock effect.
Lower octane gasoline like "regular" 87-octane gasoline can handle the least amount of compression before igniting. The compression ratio of your engine determines the octane rating of the gas you must use in the car. This is the same as saying your engine is designed to perform its best with a specific octane rating of gasoline. A "high-performance engine" has a higher compression ratio and requires higher-octane fuel to prevent it from prematurely igniting fuel before the spark plug does it.
So, octane does not enhance the explosion in the cylinder like most people think. What does octane do? It just prevents the air-fuel mixture from igniting before the spark plug does it. Firing the air-fuel mixture at the proper time gives you the maximum power your engine was designed to get. Using higher-octane gasoline than your engine is designed to utilize is only wasting your money.
ECU’s are what?Let me correct the record in case the debate has not been decided regarding putting premium fuel into a car that takes 87....
It is true that prior to fancy ECUs and mapped timings on older cars, using premium will not provide or unlock more horsepower, it will though provide a slight MPG boost.
It is also true that - (using the HK 2013 to current 2.0T engine) - putting 93 into this engine WILL provide more power, but not for the reason you think....
1. When using 87, these engines will ping at low RPM/high load scenarios AND under boost.
2. This knock is detected realtime by the ecu and each cylinder is retarded between 0.5 degrees up to 6 degrees. (Each cylinder monitored individually)
3. Using 91 or 89 or 93 will virtually eliminate this knock, thus, the ecu will not retard the timing.
I've observed Knock retard (using live OBD2 data) on my 2.0T with 87oct @ sea level and at least one cylinder is always being slightly retarded under almost all driving conditions. Especially so in high heat.
On several ococcasions I used 93oct and noted that virtually no knock was detected in any cylinder under any driving condition. Thus, no retarded timing.
Upon switching back to 87 the knock retard was immediately visible on my scan tool.
Further there was a very noticeable difference between the performance of the car under 93 and 87 with 93 providing drastic improvements 3rd,4th,5th,6th gears from 1600 to 3000rpm.
So, yes, using premium is not a 'sucker's play' in certain cars.
Also take a look at the 1998 Grand Cherokee 5.9L....it ran only on 93oct due to Jeep programming it with advanced timing (to make it the world's fastest SUV)...If you put 87 in it it was a ping machine...this in itself is proof that -even as far back as 1998 - manufacturers were using octane and timing to squeeze every drop of power out.
The 2013+ 2.0T is a VERY well designed stock engine and there are no easy ways to squeeze tons of free power.....They did a great job front to back....
That being said, it is easy to guess that ECUs are