Why does 98/FRS?BRZ use premium 98 fuel?
 

I don't mean to troll, but I've always wondered why this car has to use premium/98 type of fuel when the matter of fact is the engine is not a performance car engine?
Anything special in the boxer engine which requires it to have only premium?

Pardon my ignorance if it seems like a stupid question.

PS - Having read the manual, it says you can use 95 unleaded quality fuel without giving giving adverse effect in driveability/durability... now I'm confused... Then what's the point of giving it 98, apart from the marginally better miles per gallon?

12.5:1 compression ratio.

This right here is your reason. The higher octane is needed to increase the resistance to knock/pre-detonation in the combustion chamber.

For reference as to why the compression ratio of this motor is unique most factory FI cars run around a 9.0:1 from the manufacurer and for N/A motors around 10:1 or just slightly above that.

Direct injection has allowed compression ratios to be bumped up. The FA20 with a 12.5:1 is a first to me.

It might not sound like a performance engine to you, but it kind of is. It pushes 100hp per liter. Take a Corvette ZO6 with 505hp. Devide 505 by 7L and you get 72hp/L. I`m pretty sure a Civic Si needs premium and most hot hatches as well.

With the ECU systems these days, you should be able to run regular and not do damage to the engine, unless you push it hard as it should sense detonation and work with the ignition, cams and fuel parameters to get rid of detonation. You will hurt the performance and fuel usage with regular, but if you`re stuck, regular should not kill the car in one single tank. Just don`t hit a racetrack with a tank full of regular.

Hmm... didn't realize Australia had 98 and 95. Here in the states, our highest is 93 with 91 and 89 being the other choices.

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Why does 98/FRS?BRZ use premium 98 fuel?
 

Australia used a RON rating while the US uses AKI for octane. 98 RON is equivalent to 94 AKI.


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I think Chevron is 94

Yes, I remember it well, it all started back in the 40s when the military wanted more powerful, thus faster fighter planes ....... ohhhh ..... sorry ..... carry on .... :bonk:


humfrz

A quick google shows the RR Merlin to have a 6:1 and a Wasp Major to be 6.7:1. ETA:

Interesting! High Compression!

The Merlin also had a hugeass supercharger :)

It's already been mentioned, but it absolutely is a performance engine. 100hp/L naturally aspirated with a 7400rpm redline and a 12.5:1 compression ratio puts it solidly in that category.

With a 6:1 compression ratio. The FA20 makes almost twice the power per liter as a Merlin.

2030hp for the ultimate version of the Merlin, 75hp/l. That's LS territory 70 years earlier :)

It's not comparable. Different method of measuring.

I wonder if a four-cylinder chunk of a Merlin would fin in the FR-S?

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I want the V-8 Hyabusa engine used in the Ariel Atom 500.

It's also making that power at 3000RPM, along with a mountain of torque. HP/L isn't necessarily a good measure when talking about engines that big, since they're limited in their power output by the fact that they can't spin as fast (due to size). The top Merlins were making around 3600 ft-lb from 27 liters, which is 133 ft-lb/L. This is extremely good even for a modern forced-induction engine - it beats the GT-R and the MP4-12C, and it's comparable to the 911 turbo with overboost. Those turbo/supercharged WWII aircraft engines really were impressive in their output.

(Admittedly, it was running 130-145 octane, heavily leaded fuel)

A Napier Sabre powered FR-S would be cool. For a few minutes.

Essentially what everyone else said.... the compression ratio in this car is insane (in regards to the norm), and despite it's "lack" of power it still makes 100hp/L which is a VERY performance orientated engine. If you want to play you gotta pay

Come to think of it... almost all of the looney hot hatches now a days make well over 100hp/L, the 15' Golf R for example makes 296hp from a 2.0 for example, that almost 150hp per liter.... which is utterly ludicras :bow:

You can`t mix NA with turbo in this kind of measure. Plus most hot hatches now have a turbo and make the 100hp\L the lazy way really. Having 100hp\L, while having enough torque to be drivable and being good on gas with no forced induction is a good accomplishment, especially in today's CO2 rules and all those regulations.

Yep, many turbo engines will surpass 100 hp/L easily. Different ballgame.

BTW the upcoming CLA AMG makes 355 hp out of a 2.0L turbo. That's 178 hp/L. From what I hear, it's the classic big turbo, small engine setup. Laggy, peaky, etc.