With only 1500cc torque is not something to expect, not sure how familiar you are with tuning small displacement NA motors, but even a meager 5hp and a couple foot pounds is considered an improvement.


And 2Rismo, mexico reccomends 5w20 because of the much warmer climate, u should see how much thicker oil recommendation gets from the manufacturer the closer you get to the equator, it offers more protection in the hot weather and is probably cheaper than 0w20 wich usually comes from expensive base stock, but their fuel is rated on the same system as ours is. As far as octane goes, do u remember when the 99-00 b16a2 civic si came out? Honda clearly recommended premium gasoline, wich was already at the razors edge of knock on the b16a2, and its compression ratio was lower than the l15b1, yet people STILL ran 87 in them out of sheer cheapness and ignorance, people did the same with the integra gsR, and the rsx type s. Did they blow up? No, but they would prematurely fry piston rings and burn a shitload of oil after 60k miles or so, and developed a host of other annoying issues over time. Like i said the b18c b16a and k20a2 are Lower compression than the l15b1 yet they recommended premium fuel for them, so what does common sense tell you to do? For me, 87 octane is too low for comfort. So yes u can run low octane in a hi comp motor without killing it, but its far from ideal as weve learned over the years with Hondas high compression motors.

 

oh ive had hondas for 30yrs and played with them so i know a thing or two about NA tuning. that green honda you have, i had one brand new in a different color many years ago. which is why im asking why you even bother to do it especially knowing torque is not something to expect as you mentioned from these little honda engines. id go forced induction and run higher octane fuel with purpose, meaning... if that car meant so much to me.

 

My little green car makes 200 crank HP at 9200 rpm dude, runs a 13.8 on street tires. Out of 1.6 litres NA so very little torque, but torque doesnt mean shit at 9k rpm. I built that car to run the touge and circuit (thinder hill, willow springs) and i prefer the NA powerband to the unpredictable nature of boost, especially with how an FF car behaves in the corners. Small NA engines make power by spinning fast at high pressure. Turbo is lazy imo, and especially unreliable in comparison to a finely tuned NA motor. Imo tuning a small engine to make power NA is a lot more meaningful than a bolt on turbo kit.

 

You need to read up on why we advance timing in Spark Ignition gasoline ignitions and why when using higher octane fuels we advance the timing at all. In a nut shell, it is to make up for the slower burning rate of higher octane fuels.

The following quote was copied form Wikipedia. You can read the entire article here but it spends a lot of words on history and older mechanical / vacuum advance systems that may not interest you:
https://en.wikipedia.org/wiki/Ignition_timing

The ignition timing is also dependent on the load of the engine with more load (larger throttle opening and therefore air:fuel ratio) requiring less advance (the mixture burns faster). Also it is dependent on the temperature of the engine with lower temperature allowing for more advance. The speed with which the mixture burns depends also on the octane rating of the fuel and on the air-fuel ratio.

You also need to read up on the Octane measure types. Mexico uses a different system than we do. Read up on RON, MON, and (R+M)/2. The US is (R+M)/2 (also know as AKI) Which is an average of RON and MON and is about 4-6 points lower than the Mexico measurement system. So 91 RON is equivalent to 85-87 (R+M)/2 (AKI).

I found this almost non-technical explanation for you on Wikipedia:
https://en.wikipedia.org/wiki/Octane...ne_Number_(RON)

 

Brace yourself

im going to give you some hands on knowledge, that actually comes from the temporal lobe of my brain, and not Wikipedia.

Higher octane fuels are used in higher compression engines to prevent pre detonation and allow ignition at the highest possible point of the compression stroke, fully utilizing the slower burning fuel to make the most powerful explosion possible near top dead center (some engines slightly before, some slightly after, usually directly dependant on compression ratio), to force the piston downward as hard as possible, at the optimum rod/crankshaft angle, with the least amount of resistance possible.

Timing is advanced, or retarded in modern engines with knock sensors to take advantage of higher octane, slower burning fuel to make more power, or to adjust timing to prevent knock with lower octane, easier burning fuel in a high compression engine. The faster an engine turns, the faster the ignition timing needs to be in order to hit that sweet spot, at higher rpm wot the ignition/injection pulse needs to happen sooner and sooner in comparison with each increase in revolution, wich is why timing advances radically in those conditions compared to holding a constant engine speed/load.

The reason our l15b is advancing timing in response to higher octane during high revs and wide open throttle (the conditions i care about), is because lower octane would combust more readily under those same conditions with the 11.5 to 1 compression ratio and would not require any ignition advancement to combust near tdc, instead the ecu dumps more fuel to cool things down and prevent knock, and to keep from advancing timing to the point where combustion starts so early it actually fights the compression stroke, wich would result in unacceptable loss of power. These ecu are set from the factory to readily accept 87, but the ecu is adjusting to make more power with 91 octane. This isnt comparable to tuning a race engine to a set standard high octane rating, in wich case u may end up needing to pull timing significantly to make more power in the high rpm range, without use of a knock sensor. You are relying on 105+ octane based on a your known compression spec to prevent knock in that kind of situation, not sensors and variable ignition timing.

My old built 12.5 to 1 b16 ITB setup would backfire through the intake on lower octane fuels (used to get to/from race track), the air/fuel mixture would pre detonate before the intake vavles were fully closed during the compression stroke, it was running a chipped p28 tuned for 105 octane, and the knock sensor was disabled obviously.

Mexican 91 octane is the same as californian 91 octane energy content wise, and mexico actually rates their 87 and 92 pemex based on the AKI (anti knock index) wich is actually more stringent than standard RON rating system. the whole R+M/2 rating method still relies on RON primarily, and is an adjustable variable that allows them to adjust octane rating numbers to be the same between winter/summer gasoline differences so they can justify prices easier without us americans freaking out. You can get high quality gas in all the bigger mexican cities, like i said, u can even get 92 octane wich is unavailable in california for the most part. Pemex gasoline is of decent quality and the mexican lower octane gas myth has been debunked many times before as you can see with a quick search on the subject, there are a few articles where they compare american/mexican gasoline chemically showing ppm values very similar to eachothers respective octane rating.

I do appreciate your insight and useful information on the subject, im fully aware of how these systems work, and well versed in patroleum byproducts and their functions in modern and classic, cylindrical and rotary combustion engines.

 

I agree with everything you stated but the next to last paragraph.

I do not get on here trying to impress people, or flaunt my degrees or experience in the international petrol-chemical industry. I try to keep my postings as non-technical as possible to help people rather than try impress them. I used Wikipedia because the referenced entries were primarily non-technical and easily accessible.

Oh yes, energy content has nothing to do with AKI. There is some indirect relationship between energy content and RVP. That is primarily because refiners are adding additional butane in the winter when the EPA is not on their rear end to keep RVP numbers lower.

None of this applies to California where they follow their own rules. (CARB) That along with taxes is why your fuel is more expensive there. The other 49 states and territories fall under the EPA. I have no experience with the CARB controlled markets. My background is the USA, Canada, and several other international markets.

Enough of this. I supplied the information. People can use it or forget it. Free advice is usually worth what you pay for it.

 

Thanks, except i never said i had, or touted any degree whatsoever. Im a self taught, 30 year old, mechanical, electrical, and biochemical engineering enthusiast with alot of hands on experience that is totally and purely driven on passion and maybe a little bit of OCD. That is all. I seek knowledge every chance possible and comprehend/retain it well.

 

I need to apologize. It has been about 35 years since I have been south of the border (Mexico) for business. I looked it up and you are correct. Mexico uses the AKI octane measurement system, not RON. I was wrong.

Your memory is the first thing to go when you get old.

 

Its ok man, you are still very knowledgeable despite having Alzheimers 😂 lol im kiddn. No hard feelings at all, u know more than most here, im just a crazy guy with OCD who likes machines and chemicles too much.

 

In the UK I'm using shell 99ron
Question though
Why does America use the lower octane rating

 

I thought it was the SECOND thing to go....but I can't remember what the FIRST thing is!

 

You are probably correct. I can not remember that far back. I had to look for my car keys for 1/2 hour today. I left them in their usual place (in the car), but not in the ignition. They were on the dash. We usually leave the keys in the cars around here for that very reason, but it did not work this time.

 

That is an interesting question. I do not know the history. I suspect it was just like a lot of other measurements. They were developed by different organizations or countries that choose not to talk to each other. NTSC vs.PAl television, Centigrade vs. Kelvin, vs Fahrenheit, inches vs. Centimeters, 120 vs. 240 volt , 50 vs. 60 cycles.

Part of it probably is the N.I.H. (not invented here) syndrome and no one, including me, wants to change what they are most familiar with.

Here is a good one. Aviation in the North America uses MON not AKI and a dual system of lean and rich octane numbers. 100 used to be advertised as 100/115 and 100/130 which are lean and rich numbers. Now it is 100 LL. Aviation also uses Centigrade temperatures, with feet for altitudes, nautical miles for distance, and inches for barometric pressure. There is a real mixture of systems.

If it hasn't changed, Russia use to have their lowest octane fuel in MON so it was around 75-77, while it's higher grades were RON with octane numbers in the 91 - 96 range. I'll have to research that and see if it is still that way.

Sorry for the long non-answer. I'm pretty sure it is more than you wanted to know.

 

If you want to learn why the American octane ratings are a lower number, here's a good article:

https://en.wikipedia.org/wiki/Octane_rating

Skip down to Measurement Methods.

 

I used to run the cheapest top tier available; never had issues. But with the fit, I noticed that the power delivery is not always consistent. Sometimes it punches good torque, and other times it feels rather lethargic. I was wondering why. I always blamed it on the variable intake cam/weather/ambient temperature/engine too hot etc.

I tried 91 for the first time last week, and BOY OH BOY what a difference! Amazing consistency in power delivery and the engine feels like it wants to run hard all day long.

So... I tried 94 octane, and I did not feel any difference from 91. So I will be sticking with 91 from canadian tire since they have the best price for 91.

And also, did I mention? My fuel economy improved. From 7.5 L/100kms to a touch under 7. Probably no ethanol in 91 since the "may contain up to 10% ethanol" sticker is affixed only on the 87 and 89 flavors.

Just my .... 2 cents.

 

 

regular is good enough isn't it?

 

 

Yes, it's good enough, 87 octane gets the job done. But I regret not putting premium (91 octane) from the very beginning (bought my gk new). I am not sure how I will deal with carbon deposits [not a fan of catch cans]. So I have switched to 91. But to deal with intake carbon deposits, I rely on the 'italian tuenup'. Seems to be working just fine ... for now.

For the record, I ran 87 for a good 80k miles and had no issues with it, besides inconsistent power delivery. But if you have the CVT (I have the manual 6 speed), then you probably won't feel any changes in power delivery (my guess); but you may get better fuel economy with 91.

 

Fuel in California is VERY expensive due to taxation and blend I know all too well. I just paid 3.75 for Premium today.

Glad that I have a FIT.

91 is not required, Regular 87 is all that is required for a FIT engine.
I just like 91.

I am even hearing that some folks that I work with that have high end European cars that say 91 required are putting 87 in to save money, especially the ones that lease since they will not be holding on much past 36K miles.