Hey everyone,

I知 curious of everyone痴 opinion when it comes to having a cold air intake and performance exhaust installed if I should upgrade to a higher octane gas. I知 running a AEM intake and a HKS silent hi power.

Thanks

 

I have no mechanic background nor i worked on cars.

but as far as i am concerns, unless you are adding forced induction (eg, turbo), or change pistons,i dun think putting premium fuel helps.

my understanding is that the reason you need higher octane gas is for higher compression ratio, and i dun think CAI nor exhaust(non-catback i am assuming) has much effect on compression ratio..

I am probably wrong so dun quote on me.



ps. you should check out a lot of videos on CAI (Cold Air Intake). I was gonna do one but i feel that its not worth the price, especially when it comes to power increase. i figured i rather spend money on shifter cable bushing, better tires and short throw shifter (no one is making one right now.. hopefully someone will start mass-produce it soon..)

 

The benefits of premium are only really seen on higher power engines. I did feel like my Fit was peppier on Premium but not worth the extra cost. MPG went down too. Save your money.

 

Octane is a measurement of how resistant gasoline is to detonation, which can be caused by excess heat in the combustion chamber causing the fuel/air to ignite before the spark plug fires. Since you're not going forced induction and you can't change your compression ratio, the only thing that would affect detonation is spark timing.

The engine mapping is set from the factory within a range of advancing or retarding the spark based on if the engine sensors find signs of detonation, but they'll usually be on the conservative side for a economy car. So, going to a higher octane fuel might cause the ECU to advance the timing somewhat, but not enough to see a huge boost in power. It may be that going to a ktuner will let you remap the engine for more spark advance, but without this, you won't see the full effects of higher octane fuel.

 

Yes! I measured my ignition advance while doing dragstrip runs, going wide open throttle. All my old videos I did (Between 170-210 Torque Pro Videos) are gone since they were on an old hard drive that crashed (I didn't back it up). What I noticed was that my ignition advance would drop down lower than it did when I used higher octane. I'm talking 87 octane as the low and 92 octane as the high.

Also, on top of this, with the intake/exhaust combo, I did add a larger maf housing from a 2014 Honda Civic (Butchered, it's not a direct replacement) and had the car tuned to support that maf diameter. Along with that tune, the air/fuel ratios were modified as well as ignition timing, meaning the ignition timing was made to be even more aggressive than the stock ignition advance table.

So...in a nutshell, your ignition timing will become more advanced. No, you don't need to use premium but if you do, this is something you could expect. Premium fuel would help more in hotter climate. I posted somewhere the details about how much of a difference the advance was but it's been so long ago. Don't feel like looking. Good luck!

 

TOP TIER is recommended in the owners manual , https://toptiergas.com/licensed-brands/ . Use 88 or 89 with E5 . 90 or 91 w/o E around 4 weeks . VALERO is our preference . SUNOCO on occasion . TOP TIER gas brands are few and far for the area . Many gas stations are switching to unknown gas .

 

Top tier is a must. But regarding octane - theoretically in a high compression engine the ecu is often "pulling timing" to save the engine. You know how some cars, usually premium euro ones in the 90s, had premium "recommended" and then they'd make more power? Yeah well basically all engines are designed like that today, they have to be to make economy and emissions standards. But at some point OEMs realized Americans are kind of simple and they really hate the decision making that the two power levels forces on them. So because the engines can safely run low octane due to modern knock control, they just say regular unleaded is good enough and leave it at that.

So. Some cars will make more power with less fuel at higher octane. Some it won't make much difference. Check out recent motor trend article. FWIW gd owners were claiming more power out of premium; I've been running premium in my GE to help track down some power issues and I cannot say I feel any faster. That article included a new crv where it made zero difference. Ford bmw and Chrysler, big changes. Your mileage... Puts on sunglasses .. May vary 😎

 

Typo 10char