91 vs 94 Octane

[Reaper]

Originally Posted by Decay107

I'll see if I can dig up one of my old logs from the stock tune. Right now I only have tuned logs on this computer.

by the way im not trying to be a **** im just going off of experience from reading stock tunes from the motorcycle world.


I find it hard to believe a worldwide manufacturer would make the oem ecu calibrations primarily setup for 93 when it would be a better case scenario to calibrate for 91 with the potential to run 93 than vice versa.


If you have a stock tune that shows consistent knock correction on 91 and its not a bagillion degrees out towing a trailer up a mountain I will retrack my previous statement.

[steve99]

Originally Posted by Reaper

by the way im not trying to be a **** im just going off of experience from reading stock tunes from the motorcycle world.


I find it hard to believe a worldwide manufacturer would make the oem ecu calibrations primarily setup for 93 when it would be a better case scenario to calibrate for 91 with the potential to run 93 than vice versa.


If you have a stock tune that shows consistent knock correction on 91 and its not a bagillion degrees out towing a trailer up a mountain I will retrack my previous statement.

Have not read a USA maunal but the OZ ones state 98 ron to be used ie 93 usa stuff but it can be run on 95 ron or 91 usa fuel.

It knocks like crazy on 95 ron ie your 91 , resulting in the ECU reducing the IAM (ignition advance multiplier) from the optium value of 1 to about 0.6 or less if you drive agressivly. Seen stock tunes pull 4 degrees of timing even on 98 ron in warm weather.

Yep it will run on less than 93 usa fuel, but it will not produce optium power and it will knock , not seriously enough to damage engine as the ecu will reduce timing advance each time it detects knock.

[Reaper]

do you have any stock tune logs to show that? That means this car is basically crippled when sold in areas that don't have 93/98ron. That's embarrassing from a manufacturing standpoint.

[Kodename47]

Originally Posted by Reaper

do you have any stock tune logs to show that? That means this car is basically crippled when sold in areas that don't have 93/98ron. That's embarrassing from a manufacturing standpoint.

Why? High compression will mean that the car is more knock prone and require the extra knock resistance of higher octane fuels. At least in most areas you can run the full advertised power with decent fuel. This was the compromise that they did to get the power levels they were looking for. The car isn't crippled running on less than optimal fuel, it just isn't running at full potential.

[xwd]

Originally Posted by Reaper

do you have any stock tune logs to show that? That means this car is basically crippled when sold in areas that don't have 93/98ron. That's embarrassing from a manufacturing standpoint.

Subaru has a history with the WRX/STi and other cars of tuning them to run on 93 and then letting them knock to run on 91, to the detriment of engines. I wouldn't really be surprised if this car was the same way. Getting a tune on those cars was safer than letting it run the way it was stock.

[nocwage]

So there isn't any evidence of a difference yet? What about people with OFTs etc that can log?
If no one has done it then I'm going to test when I finally get my OFT.

[Jrdad]

Im running OFT stage 1 on 91 (E0) right now. Ive watched the IAM drop to .9 but its always comes right back up. Its only happened twice and I dont have any logs, but I think it was from sitting in traffic then knocks a bit on throttle tip in. When I was on 94 it never dropped, but I had worse gas mileage due to the ethanol.

[hmong337]

I only use 94 and nothing else. Shell still gives chirps. The power difference is noticeable. My car will never see 91 unless I really had no choice but to pump it. The car calls for 93 anyways.

[Apoc]

Originally Posted by nocwage

So there isn't any evidence of a difference yet? What about people with OFTs etc that can log?
If no one has done it then I'm going to test when I finally get my OFT.

The evidence is everywhere. I'm just not motivated to gather it up for you because your need for it is based off of your lack of effort to find it yourself.

[steve99]

Originally Posted by nocwage

So there isn't any evidence of a difference yet? What about people with OFTs etc that can log?
If no one has done it then I'm going to test when I finally get my OFT.

fill tank with 91 leave stock tune in ecu, log IAM FLKC FBKC Knock correction and KC LEARNED.

OFT tunes knock much less than stock tune , the new oft 2.0 tunes will offer specific 91 and 93 tunes due to fuel differences.

read thread i did on KNOCK FIX FOR AUSTRALIAN FUELS and ECU LOGGING FOR BRZ 86

You will then have the evidence

[Kodename47]

Power differences:
Dyno day here in the UK, Dynapack hub dyno:
98/99 RON stock cars ran ~ 160bhp
95 RON stock cars ran ~ 150bhp

[nocwage]

Originally Posted by Apoc

The evidence is everywhere. I'm just not motivated to gather it up for you because your need for it is based off of your lack of effort to find it yourself.

I could only find people saying there was a difference without any actual proof (logs, dyno charts etc), if there isn't any hard data then it's not evidence it's conjecture.

And we're not talking custom maps that actually take advantage of the fuel, we're talking the stock one size fits all maps.

I ran 94 in my 2010 WRX until I got a Cobb Accessport and could actually see that there was no difference in the knock adjustment on either fuel with the stock map.

[s2d4]

Originally Posted by nocwage

I could only find people saying there was a difference without any actual proof (logs, dyno charts etc), if there isn't any hard data then it's not evidence it's conjecture.

And we're not talking custom maps that actually take advantage of the fuel, we're talking the stock one size fits all maps.

I ran 94 in my 2010 WRX until I got a Cobb Accessport and could actually see that there was no difference in the knock adjustment on either fuel with the stock map.

Science bro.

[Boxer486]

Originally Posted by Reaper

by the way im not trying to be a **** im just going off of experience from reading stock tunes from the motorcycle world.


I find it hard to believe a worldwide manufacturer would make the oem ecu calibrations primarily setup for 93 when it would be a better case scenario to calibrate for 91 with the potential to run 93 than vice versa.

Believe it, because that's exactly how it is. I remember Edmunds and others doing tests comparing rated HP/TQ from different vehicles using CA 91 versus 93/94 available elsewhere. In each case, the 91 was down from the rated SAE values that the 93 delivered which was in line with the marketing and actual ratings.


Your thinking is backwards based on what I've read. It's easier and better to maximize timing and power delivery using higher octane available in the rest of the world and let Californians deal with piss water by letting the ECU compensate.


Now you would be correct that if the car was designed around 91 optimally, it would produce more power than 94, same for designing around 87. This is because the lower the octane the higher the BTU content = more power potential. However, lower BTU with higher know resistance + greater compression will always outweigh this miniscule difference IF the car is designed to take advantage of it.