Well not exactly 93 because remember California's and I believe some other states premium is 91. Also I'm pretty sure regular is rated at 87 R+M/2, where do you see 86 regular available? Is that what is there in NC?

So, that means the L15A will have zero benefit to running a slightly higher octane, can you prove this without any doubt? Again, just because the owner manual states use at least 87, it also doesn't mean that's the end all be all.

You seem to blindly just believe everything you read as fact, so why are you not believing this. I'm joking with you of course. I am not factually stating the motor will run better with higher than 87, but for myself, I can only get 93 on base, 89 or 96 off base and with the prices of gas about $6~7/gallon off base, I'll just keep using the 93 for $2.86/gal.

Until somebody fully cracks the ECU and see if it has learning ability to increase/retard ignition, which in fact it will retard if knock is detected, nobody can really say what's best one way or the other. 1 thing to do, hook up a scanner and check what the knock threshold values and ignition timing is at high load/high rpm and compare the data between regular, midgrade and premium. That right there would give the answer.

 

Higher octane does not mean more power. There is actually less energy in a gallon of higher octane fuel. The problem comes when you use a lower octane than needed... it releases more energy but at the wrong time in the engine. Octane is designed for types of vehicles for the prevention of detonation. As far a production of gasoline, it is not any cleaner. It just has stuff in it to prevent it from burning too quickly. I suggest you use what has been tested by Honda in hundreds of thousands of miles of testing... use what they recommend. If octane ratings are different in different countries, that's another matter.

 

oops my bad i keep saying 86 because thats the year i was born lol

yeah i ment to say 87...

but yeah... lets think.. we don't wanna misslead anyone with our assumptions. for right now we just know that Honda Fit uses regular gas (87 octane) and Honda Civic SI's use Premium 91 or 93 octane.. that we know for sure... because it is actually in writing.

iam sure we will have the same argument if we went over to the Civic SI forums and say "Oh the civic si can't utilize 87 octane correctly..." everyone will be enraged because the user manual actually states to use premium gasoline, but why can't the civic si use 87 octane?

 

I do... a lot...



I have beat on my car near the redline in very hot conditions, it has never knocked.

I pretty much try everything to give my car any advantage, I have put in a premium fuel for an event to see if it would make a difference... no increased performance results at all.

To try and quantify that, I tend to be very in tune with my car when it comes to squeezing out performance; as an example I can easily pick out which tire is more than a 1/2 psi out of the optimum range when I run my car.

Believe me of all people... if there was any kind of advantage to running a premium fuel, I would be all over it in a second.

 

That's cool, but you haven't scientifically quantified that there is not an even slight improvement in the engine's running, just your seat of the pants. Also we know already there is a difference between both the engine and ECU between the 2 model Fits.

I know if I do get the J's reflash (might have to if a self-tuning application doesn't evolve) I have to use Premium because of the advanced timing implemented, if not, KNOCK KNOCK, who's there is what I will be hearing if I used non-premium. They altered the stock ECU's timing, so it just might be possible that the GE8 ECU is smart enough to advance timing if it senses the conditions to do so. Again, nobody should quote me on this, but one also can't just blindly say it doesn't happen without actually doing testing in at least the nature I described.

Also, it might just be that the L15A in the GE8 doesn't see any benefit from a higher octane fuel in stock form.

 

I could probably haul out my data-logger to see for certain what is going on. Driving around on the road I wouldn't be able to tell, but when I runned timed events against other cars it becomes very apparent what helps and hurts me.

Also I would agree if you are changing the timing for more compression you need to make the switch to premium!

I don't know about the GE8, but the GD3 ECU is very invasive and will fight any piggy back systems, very frusterating. If you look closely at the old AJR fit pictures you wil actually see an LFC unit (Learning Function Canceller) to prevent the ECU from screwing around with settings on turbo kits.

 

Exactly. I'm with you.

If the mechanical device, based on heat dissipation, compression, metallic strength, timing requires a certain octane, use it. If the octane is not appropriate based on untimely ignition, switch to the higher octane. An engine designed for a high octane can not operate on low octane properly, because, even though the lower octane will generate more energy during burn, it will not generate it at the proper time... the engine lowers it's efficiency and actual HP to the wheels is decreased.

Thanks for your personal accounting of actual trials testing out higher octane.

 

I'm new to the FIT - 2.5K. The drive is just beginning to become fun - not that it hasn't been all a long, it has - it's just opening up more.

Interested in your high rev techniques. I'm still learning the engine and really haven't found those other cams. What range should I be working for would you think?? Tell me a bit about this engine.

I'm also learning about the weight distribution/breaking/cornering/stopping stuff. Nice to have a bit of over/steer again.

thanks_K_C_

 

I've always driven my cars hard the Fit has no problem at 6500 pulling uphill with 87 octane. Knock in modern cars is pretty noticable because they pull a lot of timing; when it hits you'll know it.

From my own autocross experience (over 5 years) I can tell you right now that Sugarphreak is running his engine hard and its getting hot. If that isn't not causing knock on 87 nothing will. Autocross can be harder on an engine than your average race track run your for a short period your running your engine hard and high moving up and down the rev range and even at times laying on the rev limiter for more than what some people would call saine.

If you feel the need to put more expensive gas in your tank the oil companies will gladly take your money. Engineers tune the engine with a good safe tolerances for the octane they choose.

 

i actually redline my fit on a daily bases lol.

 

The Fit engine knock sensor will retard the timing an average of 2 degrees when changing to the lower octane fuel.

 

???? lower that what - 87. I follow the book on gas, but I am going to start seeing the revs. Shift @ 3500-4500 on the way up and bang it down when I feel the need. K_C_

 

I checked the user's manual and it said that I should use RON 91 gasoline. Now I haven't been able to find a straightforward answer as to what octanage that measure represents. Anybody have any ideas?

 

RON 91 is the same as the 87 Octane in US fuel grade.

 

For octane info look HERE. RON 91 is Regular gas.

Things gets complicated in the US because octane is listed as an averaged number [RON MON] meant to represent an AKI or anti-knock index.
K_C_

 

Typically just driving the city, even when I accelerate to merge I tend to keep it under 4500rpms.

For autocross though I keep the revs easily between 4200rpms and 6000rpms, that is where all the power is.

Actually I have a dyno I did a few years ago; it was done on a stock Fit on a Mustang dyno (which reads lower than a dynojet btw)

HP Notes:
Max power is achieved at 5800rpm, on this dyno it measured 86.7whp. It tapers off to about 80whp at 6500rpm, but at 4000rpm it only is putting down 62whp.

Torque Notes:
The max Torque comes in around 4900rpm, it measured 83.9ft/lbs on this dyno. After that torque peaks @ 4900rpm it drops off dramatically to only 62ft/lbs @ 6500rpm. One cool think about the L15 is from about 2500rpm onward you almost have a flat torque line to 4900rpm, so it makes the fit much more "torquey" than a lot of other small economy cars.

 

So I'm thinking the variable cams are what flatten the torque range??? Trying to understand this i-vtech engine/cam thing.

I now see that under 4500RPM in and around makes sense. I've been edging towards that and it does feel like there's a sweet spot. I've got a 69Alfa Spyder. That car loves the RPM's - 1750cc mechanical fuel injection - your ass sits 8" off the tarmac. The FIT is a whole different thing, but it's feeling nice to be back in a car that love the revs.

Now what's this I hear about the ECM and high revs and shifting patterns. That only for the AT's, or what?
K_C_

 

Go here for some interesting reading on RON and MON and AKI.

Octane rating - Wikipedia, the free encyclopedia

As interest, in Great Britain a Research Octane Number (RON) of their "super plus premium" appears to be a whopping 98 but in the USA this would only show on the pumps approximately a 91 octane. Is this confusing enough?????

 

1) U.S. has Corporate Average Fuel Economy (CAFE) regulations.

2A) From the 02-05 Jazz ESM:I suspect the KE, KG, KB are either the GD's 1.5L i-DSI or 1.5L VTEC. So I'll say 95 ROM (minimum) for the 1.5L.

2B) 95 RON ~= 90/91 (R+M)*0.5 AKA U.S Premium in many areas.

3) Honda specs 5W30 outside of the U.S. with at least one oil manufacturer (Castrol) recommending multi-grades oils from 0 upto 40.

A quick check of halfords.com (uk) for the Jazz 1.4L shows 5W30 oils.

Here's some one from Australia mentioning 10W30 for their GD.
https://www.fitfreak.net/forums/fit-...html#post18426

4) U.S. "drivers" seem to not follow lane discipline, which makes overtaking difficult, and at least reduces the amount of overtaking. Speed limits are low and average speeds reduced by people in vehicles following too close to fully stop without hitting the vehicle in front of them.

5) The U.S. has significant corn subsidies. Corn can be made into Ethanol and is promoted as being green.

6) Lower priced fuel tends to oxygenate with higher volumes of Ethanol. Besides being cheaper for U.S. refineries to purchase, the lower heats of combustion of Ethanol guarantee customers needing to buy more fuel due to lower fuel economy.

7) It's harder to confirm that lower octane have higher percent volumes of Ethanol than high octanes. However, there is some indication by either industry insiders or good liars that premium uses higher quality (mass) oxygenates than lower octane fuels.



A less protective grade of oil, e.g. 5W20, is possibly a concern for Honda. If so, Honda might have detuned the 1.5L VTEC for 5W20/CAFE/U.S. Or perhaps they assume U.S. drivers do not know how to drive above 3000 RPM or don't care--A/T >> M/T.

So if Honda has not detuned for U.S. drivers, CAFE/5W20, etc, and if a driver requires maximum power (after confirming tune of the stock engine/ECU or tuning), then there only one reason I can think of to use premium octane--lower ethanol.

Lower ethanol --> less likelihood of water damage (EtOH = hygroscopic) & better fuel economy (MPG, L/100km, etc).