Octane And You

[Kodeen]

So if I have a stock a3 and am running premium (93 here), and there is nothing about my setup that would otherwise introduce knock, will my stock ecu advance timing as much as is done with the hondata reflash or high-octane map on kpro? Or do those go beyond what the stock ecu wil do?

[Lucid Moments]

So if I have a stock a3 and am running premium (93 here), and there is nothing about my setup that would otherwise introduce knock, will my stock ecu advance timing as much as is done with the hondata reflash or high-octane map on kpro? Or do those go beyond what the stock ecu wil do?

I honestly do not know. There are people that say the ECU will advance timing until knock is detected, but they have not introduced any evidence to support that claim. Of course I have no evidence to support my suspicion that it will advance timing up to a certain point set in the programming. Of course there is only so far you can advance timing and still make power and that may be a limiting factor also.

[Twisted-X]

Mythbusters should do a comparison between different octane's mileage and HP.

[VividSI]

When i went to 93 I was getting better mpg but then it dropped off to normal after about 15 fill ups. Now that I have the Hondata Reflash I cant tell a difference in performance using 87, 89, 93. With the Reflash I get about 310 on the tank with my foot in the motor.

[k20z1]

Mythbusters should do a comparison between different octane's mileage and HP.

i'm intersted, email them LOL

[slurp812]

If the stock engine retards the ignition alot to deal with knock then the octane is insufficient.

The Kseries ECU advances the ignition till it hears knock and it retards the timing and then slowly advances it till knock is heard again, a higher octane fuel will allow more ignition advance before that knock occurs, thusly raising power. So a STOCK engine will most definetely see some improvements.

This is a common misconception left over from the NON-ELECTRONIC age and technologically deprived engine and engine management systems.

You cannot divorce the engine and engine management when talking about octane requirements.

Though the gains may not be much, there will be a measureable difference on a dyno.

I log my mileage. Every drop I burn. But I'v recently did some other changes to my car to increase mileage. Once I get in a grove again, I may switch to 89 and see if how it works out $$$ vs miles traveled. I want to know if the increase in mileage will offset the extra cost. At the current higher prices, an extra dime is a little over a buck for a full tank of 89 vs 87. so like $2 bucks for 92 (or 91). 2 bucks, to me is 17 to 18 miles. So if I could go 390 on 10 gallons, instead of the ~370 Iv been getting, I would break even with 92. From what I understand, the more $$$ gas also has more detergents, which will at least in theory help keep injectors cleaner...

[TheKone]

If the stock engine retards the ignition alot to deal with knock then the octane is insufficient.

The Kseries ECU advances the ignition till it hears knock and it retards the timing and then slowly advances it till knock is heard again, a higher octane fuel will allow more ignition advance before that knock occurs, thusly raising power. So a STOCK engine will most definetely see some improvements.

This is a common misconception left over from the NON-ELECTRONIC age and technologically deprived engine and engine management systems.

You cannot divorce the engine and engine management when talking about octane requirements.

Though the gains may not be much, there will be a measureable difference on a dyno.

This is very interesting. Could you post the source information saying our k series ecu's do this? Thanks.

[Deadphishy]

This is very interesting. Could you post the source information saying our k series ecu's do this? Thanks.

From what i've gathered using the less then recent but still newer K-pro addition of the Stock Knock logic system. The ECU does not Advance until it hears knock. It advances until a set ceiling based on the OEM MAP. If at any time while driving the motor detects knock it will retard the ignition. Once no knock is heard it will try to re-advance the timing back to the stock ceiling. If the fuel you are using is junk then the computer will hate you because it will consitant be retarding the ignition to keep the motor from knocking. (An Engine saftey feature not a getting maxium performance/economy out of the fuel you are using)

If you put in fuel that is of a high octane then 87, the chance that your car will knock will be reduced, and your car will stay at it's pre-set ignition timing ceiling more often.

Having a motor advance the timing above what the manufacture decided was safe for the standard fuel used does not sound like a feature that would promote long engine bearing life.

That is just my un-educated 2 cents. I've never read anything about the ECU actually raising the ignition ceiling. The only ECU learning that i am aware of is the short term fuel correction (which i guess isn't learning more like a feed back loop), and Idle air control valve.

[TheKone]

From what i've gathered using the less then recent but still newer K-pro addition of the Stock Knock logic system. The ECU does not Advance until it hears knock. It advances until a set ceiling based on the OEM MAP. If at any time while driving the motor detects knock it will retard the ignition. Once no knock is heard it will try to re-advance the timing back to the stock ceiling. If the fuel you are using is junk then the computer will hate you because it will consitant be retarding the ignition to keep the motor from knocking. (An Engine saftey feature not a getting maxium performance/economy out of the fuel you are using)

If you put in fuel that is of a high octane then 87, the chance that your car will knock will be reduced, and your car will stay at it's pre-set ignition timing ceiling more often.

Having a motor advance the timing above what the manufacture decided was safe for the standard fuel used does not sound like a feature that would promote long engine bearing life.

That is just my un-educated 2 cents. I've never read anything about the ECU actually raising the ignition ceiling. The only ECU learning that i am aware of is the short term fuel correction (which i guess isn't learning more like a feed back loop), and Idle air control valve.

What you are saying is what I am used to seeing and hearing. As long as I don't get knock on 87 octane then i should not see any improvement in power going to 91 or better. I live at about 3500ft above sea level which would make my need for higher octane even less as my manifold pressure will never be as high as the same engine at sea level. If someone can confirm what Doug says though that would be greatly appreciated.