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Best Gas For FL5?

ayau

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I can promise you with every fibre of my body that there is NOT knock on a factory stock FK8 when using the fuel octane it is specifically designed for (91). How knock works on the FK8 is documented over at the Civicx forums.

Essentially the Bosch ECU will retard timing from knock and forget everything when you take your foot of the gas and repeat. The factory tune is ready for ethanol. Honda would not sell a car that cannot be fuelled in the continent in 99% of stations. I don't have the exact laws but I'm 100% positive is federally mandated to accept ethanol.
How can you validate it’s not knocking on 91? Did you run the Hondata factory map and log knock and timing?

I’m aware of how the Bosch ECU works. I have experience tuning my own FK8.

Never said factory tune doesn’t work with ethanol. I was implying that the Bosch ECU more than likely is using a universal map because it’s tuned on no ethanol. Other countries don’t use ethanol as much as the US. The ECU runs full time closed loop AF. Any change in fuel will be automatically adjusted by the fuel trims.

The speculation is that the fk8 is rated higher in other countries is because they have access to higher octane. The US rating is based on 91, which is what’s commonly available. So if you use 93, you’ll get the last few HP because the engine isn’t knocking.
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Tickle

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This is hilarious. I'll pump 93 from BJs in that bitch because... That is what I put in my Accord and it hasn't blown up. It'll be my daily driver.
 

TheCanadian

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The speculation is that the fk8 is rated higher in other countries is because they have access to higher octane. The US rating is based on 91, which is what’s commonly available. So if you use 93, you’ll get the last few HP because the engine isn’t knocking.
So your logic is that, again, the car is knocking on its factory tune when it's using the fuel (91) that's recommended in the owners manual? So your argument is that the car is hurting itself by knocking (over a long period of time) when using the Honda recommended fuel?
 

ayau

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So your logic is that, again, the car is knocking on its factory tune when it's using the fuel (91) that's recommended in the owners manual? So your argument is that the car is hurting itself by knocking (over a long period of time) when using the Honda recommended fuel?
Im saying car knocks on 91 factory tune, yes.

I’m not implying there’s long term negative effects if you’re using 91. Honda recommends at least 91 and some knock is acceptable.

I bet you could run 87 because Honda knows people will do it. The ECU will quickly detect the knock and aggressively retard the timing.

Im saying running 91 on factory tune and having 0 knock is untrue.

There’s 0 harm running 93 if you have access to it, and a reasonable person isn’t going to calculating the cost difference between 91 and 93. This is a 40k car, not a 5k beater.
 

toastyJ

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Let's clear a few misconceptions.

Ethanol is great for cars. Even the owners manual approves of using ethanol gas. Up to 15% I believe. Ethanol increases knock resistance. This is a good thing. No knock means more power.

Go to a busy gas station. The idea is less chance of getting stale gas.

Get the highest octane you can get in your area, e.g., 93

So from best to worst:
93 with 10% ethanol
91 with 10% ethanol
91 with 0% ethanol
87 with 10% ethanol

Super Agree on going to a busy station. I used to go to Shell only but because of the cost premium the gas sat around longer than other stations, my k.con was up in the .65-.7 range or something crazy after pulls in the summer. Once I switched to a busier top tier rated station my k.con never increased over .55 in the hottest and mustiest weather. If I added a gallon of E85 it wouldn't really budge from .49 (default value) and sometimes I saw a mystical .48 lmaoo.
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