Detonation on 91 Octane

[White05X3]

I was driving today and it sounded like I was getting some detonation under heavy throttle. I have never used <91 octane (the best available here in LA). Just to check, I put about 9 gallons of 100 octane into it (at $8/gallon, thank you very much).

Is anybody else getting detonation? Is that just a normal k20 sound? I am still very new to this car and maybe it was just how it sounds...

Thanks in advance!

[honda06si]

yea. the injectors are pretty loud on this car. i mean if you say your not used to it, that might be it. how many miles are on your car?

[White05X3]

I have about 850 miles so far. I would be really surprised if it WAS detonating, but it still caught me off guard.

Thanks for the quick reply!

[honda06si]

yea. if your are worried about it take it to the dealer and ask them what the noise is. they cant say no or charge you anything so it wouldnt hurt

[wing_gundam]

Originally Posted by White05X3

...(at $8/gallon, thank you very much)....

WTF? That's bloody expensive! A civic shouldn't cost $88 US to fill up. That's the first sign you may be using the wrong fuel.

[projectprelude]

F**K that...ahaha

[honda06si]

he put "race" fuel in it because he thought it was knocking due to a low octane

[White05X3]

Yeah, that 100 Octane race gas is extremely expensive. I have no intention of using it all the time. It was just an experiment. If there was some bad gas in there the 100 octane would deal with it...

[Gamble]

Filling up with 100 octane is pretty rediculous. If you really think you are knocking go to the dealer (or someone else with a Si) and ask them to take a listen.

[iVTECpower]

Pfft... That's not rediculous. I wish somewhere around here sold 100 octane.

[subee13]

Race fuel made for race cars... You are well on your way to the 200 club with the civic. I think you are rediculous for putting 100 octane in. Teh engines are made to use 91-93 gas not 100. the 88 you spend to fill up is a months worth of gas. I am curious to see your gas milage with it though. Hopefully you get decent milage at least. I also hear that if you put sugar in the gas tank it will stop detonation and oil in your coolant.

[dextor]

Originally Posted by subee13

Race fuel made for race cars... You are well on your way to the 200 club with the civic. I think you are rediculous for putting 100 octane in. Teh engines are made to use 91-93 gas not 100. the 88 you spend to fill up is a months worth of gas. I am curious to see your gas milage with it though. Hopefully you get decent milage at least. I also hear that if you put sugar in the gas tank it will stop detonation and oil in your coolant.

Like he said, he did it once to see if the problem was bad fuel, he doesn't do it regularly, stop calling people ridiculous.

[iVTECpower]

Subee is rediculous for calling people rediculous.

Rediculous.

[honda06si]

Originally Posted by iVTECpower

Pfft... That's not rediculous. I wish somewhere around here sold 100 octane.

100 octane doesnt help you. search around the forum there is a post about it

[redsi06]

you could always just add a little bit of 0ctane booster to the tank. that might solve your problem, for about $4/ bottle.

[BubzSI]

Maybe bad gas?

[White05X3]

Originally Posted by redsi06

you could always just add a little bit of 0ctane booster to the tank. that might solve your problem, for about $4/ bottle.

I had a really bad experience with octane booster fouling plugs so I avoid that junk like the plague.

As to whether or not 100 helps, I realize that it will not add power. What it did was raise the average octane in the tank if in fact I had gotten some bad gas. Remember, "octane" is the measure of the gasoline's ability to resist detonation. By raising the overall octane in my tank, I eliminated that as a possible cause of the noise.

And believe me...the $88 I spent on gas is far cheaper than the cost to me of taking the car in.

As for subee...if you disagree with my analysis, that is great. I appreciate the debate which is why I bother posting on this forum. However, calling people names will never lead to a solution to a car problem. In the future, if you elect to launch a personal attack, may I respectfully suggest that you spell check first? Also, I humbly recommend that the facts you use in your attack be correct, or else you run the risk of looking like a fool. Just some friendly advice.

[Jayhawker]

I didn't think the Si had a "learning" ecu. I know my S2K didn't and it was a waste of money to run 100 ocatane since the computer would not advance any timing.

[White05X3]

Originally Posted by Jayhawker

I didn't think the Si had a "learning" ecu. I know my S2K didn't and it was a waste of money to run 100 ocatane since the computer would not advance any timing.

I don't know what a "learning" ecu is...I don't think that the ecu on the Si will advance the timing beyond what it would do on good 91. However, wont the ecu retard timing if there is less than 91 and it senses detonation? Assuming so, wouldn't it then theoretically re-advance the timing to max as soon as there was good gas and hence no detonation? I suspect the ecu tries to run at max lean and advance whenever possible, right?

There is one situation where 100 is not a waste of money IMHO...that is at the track. While it will not make me go any faster, it should serve as a form of "insurance" against detonation and hence expensive engine damage. In that respect it might not be a waste.

In any event I am not hearing the same noise anymore so perhaps I just had some bad gas in there. My next fill-up will be with 91 and I will see what happens.