Octane selector / switch?

[jalucerol]

Hi.
Is there an octane selector or switch? in my old Chevrolet Corsa there was an switch called "A/B switch", it was a way to telling to ECM wich RON were you using, A for 90 RON gasoline and B for 95 RON gasoline.
I'm wondering if there is something like that in my Aveo LT 1.6 and where it is located...

[ontarian_frog]

Hi.
Is there an octane selector or switch? in my old Chevrolet Corsa there was an switch called "A/B switch", it was a way to telling to ECM wich RON were you using, A for 90 RON gasoline and B for 95 RON gasoline.
I'm wondering if there is something like that in my Aveo LT 1.6 and where it is located...

No there is none. The car is equipped with a knock sensor and can somewhat adapt by itself. You're pretty much wasting money by putting a higher octane gas in.

[jalucerol]

I use a 95 RON gasoline, because my aveo engine has a 9.5:1 compression ratio.
My old corsa had a RON switch, with two positions, A for 90 RON gasoline, and B for 95 RON gasoline. Here, in Argentina, there are two gasolines, 95 nad 97 RON.
My corsa came by default with that switch in A, I switched it into B, ECM modifies it's inyection map advancing ingition time, thus gaining reaction.

[petrified.rabbit]

how do you convert those numbers to (R+M)/2 so we can see how they compare?

i'm not looking it up..

[ontarian_frog]

how do you convert those numbers to (R+M)/2 so we can see how they compare?

i'm not looking it up..

Ron is the R in the equation.... I believe 91 Ron is 87 octane here.

[byron84]

Some people say they get better mileage when putting in higher octane. I think the final answer for any individual case would depend on a number of things, such as whether or not there is ethanol in the 87 octane.

Someone, I think on this forum mentioned getting better mileage on 91 octane. I tried it for a tank, and I got 7.0L/100KM instead of 7.5L/100KM. The problem is, that variation could easily be attributed to doing slightly more highway on that tank or whatever. Even wind and traffic conditions affect your mileage significantly, so it's pretty hard to say "oh yeah, sure... it's definitely cause I put in 91 octane!".

Although, now that I have the ScanGauge it is easier and a lot more fun to track my mileage. It's interesting to see it fluctuate as you drive.

[jalucerol]

Mileage not depend of RON / MON, it depend (apart from driving conditions) of fuel's Heat of Combustion [Hc] and Density [rho].
Hc is the amount of heta released when you burn an amount of mass of fuel.
Rho is the amount of mass per volumen unit (mean Gallon, Liter, cubic feet, etc)
I just want to know if there is a way to tell to ECM what fuel are the engine using, modifying inyection map...
I must say sorry by my english, please remember that I'm in Argentina...

[ontarian_frog]

Mileage not depend of RON / MON, it depend (apart from driving conditions) of fuel's Heat of Combustion [Hc] and Density [rho].
Hc is the amount of heta released when you burn an amount of mass of fuel.
Rho is the amount of mass per volumen unit (mean Gallon, Liter, cubic feet, etc)
I just want to know if there is a way to tell to ECM what fuel are the engine using, modifying inyection map...
I must say sorry by my english, please remember that I'm in Argentina...

There is a way to advance timing, which I will not explain... I don't want to be responsible for breaking your engine.

This guys however explains it pretty good:
http://www.autospeed.com.au/cms/A_110896/article.html

[dragonwarrior2016]

A mechanic told me unless the valves are clattering you shouldn't put a higher grade in Take for example my old car used to run on regular until last year when it shot a sparkplug out the engine block I rebored the hole and switched to plus and it never did it again. Even after I sold it I went up to the couple who bought it and they showed me that it never happened again and they've Been putting Plus 90 Octane in the car. I tried plus in the Aveo it doesn't do so well the gas mileage suffered i got 23 MPG switched back to regular and it gets in upwards of 34 MPG.

[Daox]

Valve clatter has nothing to do with octane content. Octane simply effects ignition timing and the possibility of pinging/detonation. I've also never seen octane rating significantly alter gas mileage. I'm not saying it can't, but dropping your mileage by 30% is gigantic and wouldn't come from putting in a higher octane fuel.

Run what octane your car is designed for. If its not programmed for higher octane you'll see absolutely no benefit to running it.