Barry, I understand your justification based on the compression. But you've got to take into account that there's more to the engine's function than just compression. Ignition tuning and air/fuel ratios play a bigger part in the octane requirements.

The L15A was tuned to be efficient, so it's likely lean burning in most aspects of the tune, with probably somewhat safe ignition timing.

If you notice knock with low octane, definitely up the octane. But, I don't myself, so 87 I'll use.

FWIW, most cars produced now use 9.5:1 or 10:1 compression stock. Higher compression motors are generally more efficient, but that doesn't always necessitate high octane fuel.

 

The higher gas octane make the exhaust even quieter, not louder, so how can I even "THINK" the engine is more powerful?! I'm not that stupid!

It doesn't matter how many hp the CAI gives, only the fact that it draws in a lot more air than the stock air box. The imbalance in the fuel/air mixture makes the on-board ECU compensate for it, but it can only do so much with low octane gas. The reason turbocharged and supercharged cars can burn high octane gas, even though higher octanes resist combustion, is the fact that these cars draws in massive amounts of air. Air (e.g. oxygen) is an essential part to any sort of combustion. That's why I would need 89 octane gas!

You think I'm going to believe some guy on the internet over the power I feel under my own pedal?! NOW YOU"RE KIDDING YOURSELF!! A guy on another thread felt the same power increase when he switched from 87 to 89 octane gas, and he had an SRI.

Don't bother to reply to my message, chimmike. I won't see it anyways.

 

Now I know you're not naive, just an idiot. You're comparing a 5bhp intake on an 80whp car to a turbo or supercharged car that has gained as much as 50-75% more hp over stock via the forced induction?

FYI: Octane doesn't compensate for added airflow. Larger flow injectors and wider injector duration does. But the miniscule adjustments a CAI would require don't need larger injectors, and the wider duration for the additional airflow is probably negligible.....which is why the stock ECU can compensate for it.

Tell me. What limits how much air an engine can take in? Oh, wait. You won't see this question.

You don't have to believe me. I provided links with factual evidence from people who know far more about cars, chemistry, and engineering than you or I ever will.

Have fun in your delusion!

 

Japan has 100 ron that it tunes all car too. They put a knock sensor on so it will run on regular to be sold in USA. Premium gas is made from Alykates (92 to 100octane)the have 10 percent more energy but cost alot more (main ingredient in racing fuel) 50 percent of all gasolines is the same as regular (Parafins -18 to 67octane) but octane boosters are different. Tolulene(114 to 118octane) burn faster but a lower energy (BTU) per pound. Ethonal up to 10 percent (130 ron) lower btu, ETBE(111 pump octane canbe use up to 17 pecent higher btu), then there season changes so right know there is more isobutanes less tolulene in gas, wont get good gas mileage lose 15 percent at least. You wont make more than 20 horsepower with out nos or supercharging and engine rebuilt with bigger and better parts. If there is a problem with your ecm Dealer mechanics replace it at send it back to Japan they dont reprogram just read codes and add new updates from factory but cant explain how it works. There is a reflash program that tuners can update but the ecm will go back to stock, then is a piggy back that can be reprogram with laptop that tricks ecm to add power (fuel), That is in open loop full throttle, close loop the ecm adjust the fuel and timing for a complete burn at 14.5 air fuel ratio with upto 10percent adjustment lean to rich. At full throttle the max brake torque air fuel is 13.2 to 13.7. closer to 13.7 because hondas are more effiecent.

 

Racing Fuel Characteristics Good read about ethanol.

 

Just remember that 100ron is more equivalent to our 93 octane, as our octane ratings are based on MON+RON/2.

They do have a lower octane fuel there, I think it's 91 RON, which is like our 87 octane, or actually a little lower.

But you did prove my point. Thanks

 

It more like 95 octane and in England Bp came out with 102 ron (96 octane). The main reason people use premium because it keeps there cars running the way it was susposed too. My dad has a 98 Toyota 3.0 engine that Toyota had problems with sludge, My dad always used premium gas and didnt have that problem, the car engine is like new inside with 95000 miles. Gasoline is alot cleaner now but still can cause problems.

 

i remember the sludging issues the toyota motors had. However, that was unrelated to engine octane, rather, it was an oil circulation/oil overheating issue.

Toyota tried to run their motors very hot around that time for emissions purposes. Unfortunately their methodology in the motors wreaked havoc with the oiling system and oil would sludge over and build up in the pan, destroying crank bearings, etc.

 

Was surfing the net and found this link Octane Rating - Thor Racing (Japanese Performance Car Tuning) .

 

Octane rating - Wikipedia, the free encyclopedia

Pretty interesting. the U.S. octane is based on the anti-knock index.
Also, that article says "It is possible for fuel to have a RON greater than 100, because iso-octane is not the most knock-resistant substance available)"