Why does 98/FRS?BRZ use premium 98 fuel? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

djmm · 03-25-2014, 08:23 AM

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?

Shagaliscious · 03-25-2014, 08:26 AM

12.5:1 compression ratio.

NahumCC · 03-25-2014, 08:59 AM

Quote:

Originally Posted by Shagaliscious

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.

kevman_101 · 03-25-2014, 10:16 AM

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.

GreenMonster · 03-25-2014, 10:18 AM

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.

ZionsWrath · 03-25-2014, 10:21 AM

[ame="http://www.youtube.com/watch?v=ygBP7MtT3Ac"]Jeremy Clarkson POWERRR!!! Top Gear - YouTube[/ame]

TM · 03-25-2014, 10:24 AM

Quote:

Originally Posted by GreenMonster

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.

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

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orlandorealtor · 03-25-2014, 11:01 AM

I think Chevron is 94

humfrz · 03-25-2014, 11:52 AM

Quote:

Originally Posted by Shagaliscious

12.5:1 compression ratio.

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 ....

humfrz

Tromatic · 03-25-2014, 02:44 PM

Quote:

Originally Posted by humfrz

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 ....

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!

Guillaume · 03-25-2014, 02:47 PM

Quote:

Originally Posted by Tromatic

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

The Merlin also had a hugeass supercharger

chrisl · 03-25-2014, 02:55 PM

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.

Tromatic · 03-25-2014, 02:58 PM

Quote:

Originally Posted by Guillaume

The Merlin also had a hugeass supercharger

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

Guillaume · 03-25-2014, 04:53 PM

Quote:

Originally Posted by Tromatic

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

03-25-2014, 08:23 AM	#1
djmm Senior Member Join Date: Sep 2013 Drives: toyota Location: Australia Posts: 358 Thanks: 25 Thanked 163 Times in 81 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	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?

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03-25-2014, 10:16 AM	#4
kevman_101 Senior Member Join Date: Apr 2013 Drives: 2013 Scion FRS Location: Bathurst New-Brunswick Posts: 222 Thanks: 3 Thanked 101 Times in 61 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	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.

03-25-2014, 10:18 AM	#5
GreenMonster Just doing research Join Date: Mar 2014 Drives: 03 Acura CLS 6MT Location: Southeastern MA Posts: 331 Thanks: 91 Thanked 97 Times in 77 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	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.

03-25-2014, 10:21 AM	#6
ZionsWrath Thanks Join Date: Apr 2013 Drives: BRZ Location: NY Posts: 4,163 Thanks: 5,989 Thanked 3,100 Times in 1,498 Posts Mentioned: 38 Post(s) Tagged: 3 Thread(s)	[ame="http://www.youtube.com/watch?v=ygBP7MtT3Ac"]Jeremy Clarkson POWERRR!!! Top Gear - YouTube[/ame]

03-25-2014, 11:01 AM	#8
orlandorealtor Member Join Date: Feb 2014 Drives: 2014 Scion FRS WHITEOUT Location: Orlando,Fl Posts: 43 Thanks: 5 Thanked 7 Times in 7 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	I think Chevron is 94

03-25-2014, 02:55 PM	#12
chrisl Senior Member Join Date: May 2013 Drives: 2006 Cayman S, 2007 Outback 2.5i Location: Colorado Posts: 1,116 Thanks: 116 Thanked 455 Times in 303 Posts Mentioned: 8 Post(s) Tagged: 0 Thread(s)	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.

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