Ehh!!! Can i say that sunoco gas kicks ass!!! Wish i could get some around here...

Marko!!

 

I just want to say that premium gas has about 5 to 6 percent more energy per gallon compared to regular. All cars made will run on regular but wont all get the power and mileage the car was designed to get. Honda has a knock sensor and runs around 14.5 air fuel mixture most of the time 13.5 at full throttle and will run better with premium. Additives in gas are ethonal,toloune,isooctane,triptane,butane,isopenta ne,etc. any single ingredient to bring the octane up to specs. plus detergents etc. There are about 550 hydrocarbons and almost have an infinte way to mix them so every time you get gas it is different form the tank before. The new gasoline on market is better than before but doesnt have good lubrication properties so they use an food grade additive like viscon, that go under different names. People get confused about burn speed the faster your car revs the more advance the timing needs to keep up(less time).

 

**Back from the Dead**

Awesome thread! Just read through most of it and will read some again. Needed some information on what octane to run on the Fit.

I'm looking now because I tested a 2014 1.8ltr LX Accord maf sensor housing on my 2015 Fit. This was with a large cone filter attached. Everything was normal until I did a full throttle run. Normally, my air/fuel ratio is around 11.8:1 with the stock air box. With a cone air filter, it is around 12.2:1. With the larger maf sensor housing, my air/fuel ratio was at 15.0:1 at WOT. I was using Android Torque Pro recording for knock and it detected knock (Said one of 4 samples detected knock).

So, I ran the gas tank as low as I could and refilled with 92 octane. Will re-install and do more testing, with a different (Better) air filter. Looking forward to the results.

 

Curious... are your (Torque app) AFR and knock counts based on sensors, signals... or calculations?

edit: nevermind, it's calculated (guesstimating).

 

Let's say after your modifications, your air/fuel ratio is just lean enough to cause detonation at wide open throttle, on 87 octane. You want to take advantage of this extra air coming in. In which of these two scenarios would you gain the most horsepower while being safe.

1) Adding more 87 octane fuel to bring the air/fuel ratios down until detonation stops or

2) Raising the octane until detonation stops

??

 

Unless you already have a system to adjust AFR... the answer is pretty straightforward... increase octane.

If you have a fic or even manage a reflash of the ECU, then you can attempt more fuel with timing retard. But then again... if all your mods are for power anyway... why wouldn't you want higher octane?

 

Um, 86 because that's regular here. 100.1% stock.

 

You are asking that question to say that higher octane will net more power if used to stop detonation rather than bringing air/fuel ratios down with more fuel. Thanks! This is what I was asking the Fit community.

And even if I did have something to adjust fuel to make it run richer, my question is doing which would net more horsepower while stopping detonation (More fuel or higher octane).

 

2 words: meth injection

I wonder how much more power you would get on a stock NA motor

 

Its really more of... avoiding the loss of potential power. After all, a gallon of 87 octane gas has the same "energy content" as a gallon of 93 octane gas.

When you get knock, you have to retard the timing... that affects the efficiency of the engine in drawing out power from the fuel.

Like I said earlier, there are basically two ways to do that... add fuel or raise octane.

Now, the truth is, adding fuel isn't specific to fuel... as JN2k108 mentioned, you can do meth injection or water... the primary purpose is to cool the air and resulting air/fuel mixture (it creates a place for some of the heat to go).

But either way you look at it, each have their limits... too much fuel (or mist liquid) will eventually "flood" the engine and hamper fuel ignition. And higher octane has limits in efficiency for a given engine (planning on a 180 degree timing advance?!? yeah, don't think so), and not to mention availability/price (as in, while you can find 91/93 at your local gas station, race fuel is typically harder to obtain).

And that's why, eventually, even with one method... you'll eventually use BOTH methods to get the most power from the engine (as you allow more and more air in, one method isn't quite enough). It's just, using higher octane doesn't require rewiring/reflashing/installing stuff.

~~~~~

Now, I know that in reality, knock (detonation) is different from pre-ignition... but for the most part, either option of more fuel/meth/water or higher octane is a solution to both... so I treat them as the same.

 

Why add more fuel when you can increase octane to avoid knock? Goal is to keep AFR as stoic as possible while keeping knock at bay? You're not going to do that dumping a bunch of fuel unless you have the air and spark to match right?

There's a a point of diminishing returns I think with the stock ECU, running 100+ for instance I don't think will gain you any more than running 93, I have no data but I assume the timing advance probably maxes out before you could take advantage of any of that. Maybe someone can expand on that.

Besides, blowing out your cats would suck and race gas is expensive.

I would assume the same for water/meth as far as diminishing returns on stock ECU and ignition timing.

 

Goobers, after reading your post I started to wonder how does this works in the new direct injection engines (like the GK has).
I'm completely ignorant on this subject, but just thinking about it, there are a lot of new factors involved like air compressed and already hot before fuel injection, mixture ratio not even in all the chamber but higher near the spark plug, the posibility to change spark timing but the moment of the fuel injection also and so on.

 

You're right in that the effect is a little different if you're only adding fuel via software.

However, if you go the meth/water route... you have to put in a separate injector in the intake anyway. Of course, you have the option of adding a fuel injector in the intake too.

That being said, I personally am weary of 5th injectors nowadays... because you can't control exactly how much fuel gets into a specific port... unless you put one injector PER port (or have it constantly spraying!). Which I am guessing starts to defeat the purpose of direct injection.

On the flipside... DI should generally avoid pre-ignition, since it only sprays in the fuel at the point it's supposed to ignite in the cycle anyway.

As for the knock (detonation after the fuel/air mix starts burning)... extra fuel, even with extended DI duty cycles (ie, spraying longer) should help by having cool fuel absorbing the heat so that's there's less chance of heat induced detonation. It also helps keep the chamber cooler (slightly?), since it's not just heat from compressing air that is a potential issue.

Anyway it's sliced, the "adding fuel" option requires quite a bit of work.

Overall, making going with higher octane an easier choice.

Of course, this is purely conjecture by a newbie too.

 

Goobers,

Thanks for your explanations! I've been watching video after video of runs I have done with the 92 octane vs 87. Timing advance seems to be maxed out at 15.5. It will go over this temporarily but settle at it at between 6000-6500rpm at wide open throttle now....with 92 octane. On 87 octane, timing advance would hover in the 11.5-12.5 range with the same intake setup.

I need to find that sweet spot compromise with a larger 2014 maf I've been testing and the tweaking the intake diameter. I have a few more tests to do at the track with just the right intake diameter to bring air fuel ratios between 13.5-14.0 with the larger civic maf sensor at wide open throttle.

BTW: Still riding on 92 octane but horsepower does not seem to be more than what I ran previously. All my numbers are coming out to be the same, on the same streets under the same weather conditions. Just that timing is more advances on 92 vs 87. In this case, 89 octane may be just the right compromise with this. I need to do one or more tests with the larger civic maf though. This car loves to breath. It just needs to measure the air in properly.

 

nanny ecu?

 

Ok so what does the argument mean if you do the cooler spad0r0k plug and run 93 only? My good friend is a Acura tech and he doesnt follow this making more power but adding to knocking.


Please some one explain what this mod does as im going to have Honda do this on my 1st oil change. s2000m spark plugs and run 93 exclusive but not until I understand this mod. I do know in DM markets per my reading VTEC.net Japan than the 1.5 I-VTEC was made to run on 95 octane but it would knock on 87 so Honda runs a hotter plug on usd motors to stop the knocking on 87. Honda didn't want to sell an economy car in the US that needed 91+. THANK YOU FOR THE INSIGHT.


Here is the ink to the vtec.net japan article.

New FIT/JAZZ L-Series i-VTEC Engines

The new (2nd generation) Honda Fit was just launched in Japan for the JDM in October during the Tokyo Motor Show. This amazing little car will now be making its way outside of Japan and to the rest of the world from next month onwards. For Asia, it will continue to be called the Honda Jazz and will be launched starting in Thailand and thereafter across the rest of Asia next year.
This new Fit comes with either of two 'new' engines, actually a development of the engines that powers the outgoing 1st generation model. They are the 1.3l L13A SOHC i-VTEC and the 1.5l L15A SOHC i-VTEC. The new L13A has discarded the i-DSI technology in favour of i-VTEC and delivers the superior low-rpm torque of its predecessor along with a lot more power in the high rpm range, as well as enhanced fuel economy in everyday driving. It is now 16-valves in configuration, still SOHC but features enhanced intake performance and DBW (drive-by-wire) and delivers a max power of 73kW (100ps), 14ps or 16% more power than the outgoing L13A i-DSI. Using the 12V/16V VTEC implementaion and new ECU tuning helps it deliver this max power along with a class-leading 24km/l in fuel economy (Japan 10.15 rating).
The new 1.5l L15A SOHC i-VTEC delivers superior fuel economy combined with good torque throughout the rpm range. Using the 'power SOHC VTEC' technology first used on the D15B engines of the 5th generation (1991-1995) Honda Civics, it now delivers a max power of 88kW or 120ps, 10ps or 9% more power than the outgoing L15A SOHC VTEC. Along with this, it still delivers a fuel economy of 19.6km/l !
The CVT gearbox too have received important enhancements. It now features the use of a torque converter and offers better off-the-line acceleration. It is yet unknown whether it still retains the use of the infamous 'start-up clutch'. The CVT gearbox have revised gear ratios for better performance and also improved fuel economy during cruising. A new low-friction, high efficiency oil pump and CVT pulleys plus a new creep control system (implemented via ECU programming) provide optimized 'creep control' at low speeds and during idling for improved fuel economy.
This short technical overview is written using the materials found in both the Honda Fit page on the Honda website for the Japan Domestic Market (Honda?????????????????) as well as materials from the Honda Motor Co. Ltd resource page for media. The translation from the japanese languaged materials have been done on a best effort basis. As with the new format for our technical overview articles, the actual technical materials in this article will be published in watermarked JPG formt, to enforce copyright on this review.


heres the huge break down of our motors 01-13


http://asia.vtec.net/Series/FitJazz/lseries/index.html

 

Use the recommended octane, there is no point of using more expensive gas. Octane is the length of burn time (to be veryyyyyyy basic), the higher octane the longer burn time and it's not meant for the Fit.

 

The actual recommendation specifically says:
It doesn't specifically recommend only 87 as they would've added something like "Usage of higher octane fuel is not necessary." And if you had read the thread, you would've seen how the Fit does that.

Octane isn't the length of burn... it's the resistance to burning (and self-igniting), that creates an effect of longer burning with higher octane. However, this resistance to burning is what is needed in high compression engines. And @10.4:1, the Fit is somewhat at the higher end, only able to use 87 with knock "control" (knock sensor with timing retard along VTEC, cam timing, etc).

And like I said, if you had read the thread, you would see that, with 87 gas, there's plenty of retard (in both occurrence and degree, or less pompous speak: how often retard happens and how far back it retards timing)... but with higher octane, not as much. Won't matter much if you're sticking to low RPM (and have functioning coolant system)... but if you are consistently in the high RPM range... the engine will continuously get hotter and hotter, creating more chances to knock/pre-ignite, then requiring even more retard. The Fit's ECU only has a limited range to advance or retard timing... and while running out of room to advance timing isn't an issue, when you run out of room to retard... the engine limps to save itself and you're out of power (and a potential traffic hazard on the highway).

That being said, not counting the "butt dyno." I can positively say the Fit can make use of higher octane gas. There are certain things that the Fit has a HARD time doing... like wheel spin (hard on dry pavement, easier on wet). It's not impossible with 87 gas... but when you get used to doing it... you'll notice it's (a little) easier to do with higher octane gas. When it rains, I absolutely have trouble trying start from stop. Too gentle and it threatens to stall... any more and at least one front wheel, if not both front wheels, will spin.

But if all you are doing is using the Fit as a purely "point A to point B" vehicle, never pushing the RPM beyond 3k-4k RPM, then by all means stick to 87. As any gains you might get from higher octane is wiped out by the higher cost of it.

It would take a miracle (or disaster?) for me to limit myself to only 4k RPM or less for a whole day/evening.

So, what octane should a person use? The correct answer is... that depends on how you drive.

 

As of tonight, I'm absolutely convinced that 92 octane with mild/moderate modifications is the way to go for more horsepower. I have tested between 87 and 92 over and Over and OVER again. Tonight, I've done my final test. I was actually running on 89 octane to try to reach a happy compromise. At full throttle, instead of my timing advance being in the 11-12 range like it was on 87 octane, it hovered in the 13-14 range on 89. On 92 octane, the timing advance stick at 15.5 or start at 15.0 then start ramping up to 15.5 before the run was over.

Android Torque pro horsepower on the same road, in both directions, same outside temperatures have been consistently anywhere from 4-8whp more than on 87 octane. I'm not saying your results will be the same. I'm not even saying that this is 'TRUE' hp readings and all that. I really don't care to be honest. I do know that the car has been consistently faster and making more hp/tq on 92 with visibly higher timing advance than on 87. I'm sold! After this final tank of 89 octane is empty (Almost done now), I'll probably never put less than 92 octane in the car again. I really didn't expect this to happen but it's what it is.

BTW: I wasn't really testing octane tonight. Was trying to get this Torque Pro app add-on to work so I can graph horsepower and torque curves between modifications. Uggh.....can't get it to work just yet. Just want to see power differences and curve. I don't care for the actual numbers.


One other bit of information that is fairly important to remember. When on 87 octane, off idle acceleration always started with the timing advance in the single digits (7-9). A couple rare instances it would start at 11, taper down to 8-9 then back up to 11 at wide open throttle. On 92, off idle acceleration always started out at 15-18, then taper down to 15.5 or stays at 15. Just my observation!