93 Octane vs 91 Octane
 

I read in the owners manual that the fr-s requires 93 octane gas. In the States the best we have is 91 octane. How much does that effect the performance of the car and does it damage the engine in anyway?

In YOUR state lol. 93 is readily available where I live. E85 too

I'm pretty sure 93oct is available in most places outside Cali. 91oct won't damage anything although this is lowest octane you should run in a 12.5:1 compression engine like the FA20. The ECU will adapt to 91oct but will obviously not perform as well.

Firstly, other states do have 93 octane. Perhaps not at all gas stations but I have no trouble finding 93 in NY.

Secondly, the difference between 91 and 93 is very small. Using 91 will not cause any problems unless you have an incredibly aggressive custom 93 tune. Theoretically there is a performance difference but you'd need a dyno to really tell. I doubt most people could accurately tell which is faster in a blind test.

If 93 was really necessary over 91 the car wouldn't be sold in California.

Or in parts of Canada. I've never seen 93 in New Brunswick or Nova Scotia.

I'm sure the owner's manual says something like, "Use 93 octane if available, otherwise 91 octane* is perfectly acceptible."

93 is recommended. 91 is minimum. The engine runs safely on 87 as I understand it, just not well.

Elevation affects octane requirements. 91 is the most common up here in Calgary at 1,000 meters elevation (3400 ft). I've used 94 with no noticeable effect, probably because the thinner air up here can't use more octane.

If you are in coastal areas you should be able to get 93 or 94 easily.

Yea I grabbed a tank of the petro 94 when I was down in the city. Didn't really notice anything from the usual 91 shell.

Petro 94 is simply 91 with 10% ethanol.

sorry confused myself, not petro 94, ultra 94 octane at petro.

and if thats still the one your thinking about, link to info?

I can't give you a link right now, but a quick Google search should give you some results. It's even written on the pumps when you go at the station IIRC

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He's correct. I put 94 from Petro in, and my crickets started instantly.

Yea he said the octane is still 91 though? I know it's got ethonal but it doesn't bother me.

Technically, it is 94. BUT not 94 pure gas. It's a blend with ethanol in it. =)

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I see some turbo numbers on 93 up as high as 330whp.

If I have WMI on 91, would that be equivalent to 93 at least?

I bought the WMI along with the FB turbo kit system hoping to get some better numbers than just 91 could offer.

This time of year, I don't notice much of a difference between 91 and the 94 we have here. In the heat and humidity of summer, the car runs noticeably different on the 94. So much so, that I put up with the crickets to run it. I wouldn't describe it so much as more power, it just runs better... Throttle response is better, there is less hesitation on initial tip-in, and an occasional ping that I get when rev matching is less apparent on the 94. My elevation (~300 feet) on the shores of Lake Ontario may play into that a bit.

93 Octane vs 91 Octane
 

Will petro or husky 94 in canada be more beneficial on a turbo setup over shell 91 with no ethanol?

Ethanol is high octane. There's no reason to avoid using it other than fuel economy suffers a bit since ethanol has less energy per litre.

Pretty much all North American gas has ethanol in it, more in winter, except for Shell V Power which uses a different (and supposedly secret) octane booster.

The stories about ethanol being a bad thing are just stories, not based on any fact.

Octane rating is a performance rating. 93 is higher octane rating than 91, regardless of what is put in the fuel to achieve the rating. 91 is European regular gas.

^^ European octane ratings are also calculated differently... european 91 octane is the same effective octane as north american 87 octane. RON vs AKI (RON + MON / 2).

http://forums.rennlist.com/rennforum...explained.html

Octane is also not a performance rating, it's a rating of knock resistance. A side effect is that it lets you run more c/r and/or timing for better volumetric efficiency (and power).

Higher octane fuels actually burn a bit slower, so unless your engine is designed/tuned for higher octane you actually get worse performance from incomplete combustion. If you're not getting knock or timing pulled on 91 octane, running 93 or 94 octane isn't going to generate more power without a new tune.

I've not seen 91 in Europe. They don't sell it as far as I know, at least not in Western Europe.

I don't know where you got your strange idea about high octane gas burning slower. The reason you get slightly less power if you use higher octane fuel in an engine that doesn't need it is it contains less fuel per litre. That's because it has more anti knock additives.

It does "burn" slower in the sense that it doesn't explode prematurely before the full stroke of the piston has been reached. 91 is "harder" to combust versus 87. That's the reason why if you put 87 in a twin the ECU has to pull back the timing and not be so aggressive.

In Australia our Shell V-Power is rated as 98RON, but IIRC it's comparable to 93 is the US....is that correct?

Edit: Just found something interesting here. So it appears that 98RON is Australia is comparable to 93 in the US since American stations use PON rather than RON.
http://honda-tech.com/showthread.php?t=284380

The real difference between both of those is that 91 contains more lead. Therefore, lead is a metal and takes longer to burn. Since it's a fine metal, however it will not affect much since 93 do contain traces. What you can do is when you travel outside your area. Add better gas, you can use whichever you want.

Seems legit.

Science and facts, not sure where you get your magical ideas from. Talk to people that tune engines for a living and see what they say about 87 vs 91 octane or 91 vs 94 octane.

The power potential with a new tune is higher with higher octane, but just running higher octane than the tune is built for will do exactly what I said. That alone disproves your theory about the anti knock additives.

You won't harm an engine running it on higher octane, but you're just throwing away money unless it's tuned for the higher octane. That said, I only run 94 for autox and lapping because I get some tip in knock on 91 and 94 is cheap insurance for harsher driving, but daily I run only 91 through mine. I haven't dynoed it with both fuels, but the butt dyno says there is little or no difference in output. Once I get my OFT I'll log some pulls and throw them into virtual dyno to show the differences if there are any.

We did the test at QuebecFRS.com... Difference between 87, 91 and 94 octane on an FR-S...

Results: 87: 155hp, 91: 160hp, 94: 166hp

Source (french) : http://www.quebecfrs.com/forums/index.php?topic=2222.0

^^ I'm not going to go off on that article again, but without doing multiple runs for consistency and comparing logs of what was happening I don't trust the numbers. You could easily do two runs back to back with nothing changed and get a 5hp difference.

The only way you're getting more power form 94 is if the ecu is pulling timing on 91 because of knock.

No one is more blind than the one who does not want to see.

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94 PON (AKI to some).

Flame front speed is the same. Combustion chamber pressure rise is slower. Anti knock additives don't produce as much combustion chamber pressure as gasoline, because the additives have less chemical energy per litre. That's why you can run higher compression ratios and more ignition advance. The extra power comes from the compression ratio and ignition timing changes.

Toyota recommends 93 and expressly rates their engine at 200 bhp only if 93 octane is used. I'ts in the handbook. So, for this engine you can get full power only with 93 (94 in Canada, I've not seen 93). At higher elevations it can make no difference because the engine can't breath enough air. At my locale my engine is down by around 10% from rated hp due to elevation.

This is consistent with Toyotas own information which is in your handbook. At least it is in my BRZ handbook. Not the figures but the statement that rated power is only achieved while using 93 octane fuel.

Lead? That was phased out completely in the early 90's.

"Lead" is taken to mean tetra ethyl lead, grinding up pencils and adding it to your tank won't help.

(Joke: pencils aren't lead either, calm down).

In the 1930's a clever American discovered that adding tetra ethyl lead to gasoline improved knock resistance markedly. The fact that this compound was also highly toxic was swept under the carpet. Tetra ethyl lead won the Battle of Britain. As soon as US avgas arrived in Britain in 1940 Rolls Royce turned up the supercharger pressure in the Merlin engines which then out powered the Daimler V12 in the Me 109 by over 10%.

By the time it became well known that tetra ethyl lead was so toxic the entire motor fleet required it, especially non-jet aircraft. It took over 40 years to ban the stuff. In fact, only the advent of catalytic converters that would be destroyed by lead contamination finally secured its ban.

Mind you, one of the replacements is also known to be toxic....