I wonder if there is a way to find out how much (how many degrees) the ignition timing is retarding when using a lower octane fuel? I have a ELM327 bluetooth reader. Is it useful in finding the current timing settings? The car is Subaru BRZ.
Ignition timing and low octane fuel
- Thread starter Ded Mazai
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I have used Torque a little bit , but can not remember id it displays timing .
As you probably know , the computer used the knock sensor to determine the timing .
I have tried running premium gas & it seems to improve MPG , some times . Not sure I am always getting true premium or if the alcohol content ( suppose to be limited to 10% in our state ) varies .
Does not seem to improve MPG enough to make up for the added cost . If a little additional range / miles was critical , might be worthwhile ?
As you probably know , the computer used the knock sensor to determine the timing .
I have tried running premium gas & it seems to improve MPG , some times . Not sure I am always getting true premium or if the alcohol content ( suppose to be limited to 10% in our state ) varies .
Does not seem to improve MPG enough to make up for the added cost . If a little additional range / miles was critical , might be worthwhile ?
For my Ford products, I can monitor the timing using Torque. Check out all the sensors that are availible for your vehicle - it was a stock/built in sensor in Torque for my applications. Note that it doesn't say how much it is retarding, it just reports what the timing is at that moment.
Originally Posted by Ded Mazai
I wonder if there is a way to find out how much (how many degrees) the ignition timing is retarding when using a lower octane fuel? I have a ELM327 bluetooth reader. Is it useful in finding the current timing settings? The car is Subaru BRZ.
Don't know exactly how much timing is retarded using 87 vs 93, but it is retarded some what. Our 2.3 EB Explorer is ok to run 87 but for the best "power" it's recommended to use 91 or higher, which is 93 usually. Last year driving from NJ to Key West we used only premium. It had nice power and the mpg was around 23-25 at high speeds, ie 75-85 mph for hours on end. Did the same trip this year again and used only 87 octane fuel for the entire trip. Acceleration was slower, not bad, but slower none the less. The mpg was in the 22-24 range. With 91-93 octane fuel costing anywhere from $0.60-$1.00 more per gallon than 87 octane it was not worth to me the small benefit in power and mpg. As far as additional fuel dilution using 87 vs 93, my used oil analysis don't show that and wear metals are similar using either fuel. We do try to use only top tier fuel.
Whimsey
I wonder if there is a way to find out how much (how many degrees) the ignition timing is retarding when using a lower octane fuel? I have a ELM327 bluetooth reader. Is it useful in finding the current timing settings? The car is Subaru BRZ.
Don't know exactly how much timing is retarded using 87 vs 93, but it is retarded some what. Our 2.3 EB Explorer is ok to run 87 but for the best "power" it's recommended to use 91 or higher, which is 93 usually. Last year driving from NJ to Key West we used only premium. It had nice power and the mpg was around 23-25 at high speeds, ie 75-85 mph for hours on end. Did the same trip this year again and used only 87 octane fuel for the entire trip. Acceleration was slower, not bad, but slower none the less. The mpg was in the 22-24 range. With 91-93 octane fuel costing anywhere from $0.60-$1.00 more per gallon than 87 octane it was not worth to me the small benefit in power and mpg. As far as additional fuel dilution using 87 vs 93, my used oil analysis don't show that and wear metals are similar using either fuel. We do try to use only top tier fuel.
Whimsey
Subaru recommends 93 octane or 91 if there is no ethanol in the fuel. This is understandable. The reason I am asking is following. I have always used 91 gas and had some pinging when I pressed the gas pedal after cruising with light load. I guess that was normal since the gas was 91, not 93. Recently I have switched to another gas brand and used 91 as always. The occasional pinging was gone. So I decided to go lower in the octane level and diluted half tank with 87. Still no pinging. That surprised me. I don't want to harm the engine but if I can get by using 87 than why not? Now I am guessing that either I cannot hear the pinging because of the retarded ignition or for some reason the car likes this particular gas better. May be checking the actual ignition timing on different types of gas can help?
You may be able to use the lower octane during the cooler months.
Maybe the ping will come back in the summer with warmer air temps.
I am not sure if Russia changes gasoline blends like we do in the US.
The RVP changes here in Indiana 5 or 6 times a year.
Maybe the lack of ping is from a "winter" blend of gasoline.
It does look like Russia changes gas blends-
https://pegasusoil.com/images/pdf/Russian-Gasoline-SPECIFICATIONS-PEGASUS-OIL.pdf
Code
Vapour pressure/kPa
November 1st to April 30th 45～85
May 1st to October 31st 40～65
Maybe the ping will come back in the summer with warmer air temps.
I am not sure if Russia changes gasoline blends like we do in the US.
The RVP changes here in Indiana 5 or 6 times a year.
Maybe the lack of ping is from a "winter" blend of gasoline.
It does look like Russia changes gas blends-
https://pegasusoil.com/images/pdf/Russian-Gasoline-SPECIFICATIONS-PEGASUS-OIL.pdf
Code
Vapour pressure/kPa
November 1st to April 30th 45～85
May 1st to October 31st 40～65
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Always use whatever your car is tuned for is the best recommendation. Some vehicles, like everything with a 5.7 hemi, says "89 recommended, 87 acceptable" while my little 4 cylinder and my v6 say "87 required." Yeah the computer will pull timing to protect itself, but is also reducing horsepower and fuel economy.
I have a Bluetooth reader and Torque (the paid version) on an Android tablet. When I first got Torque, it showed both timing advance and knock retard. After an update some time in the last year, it still shows KR but I can't find timing advance. Admittedly, I don't use it regularly and have not tried very hard to find the timing setting again.
On my Chevy Silverado, there is a definite difference in knock retard depending on the fuel octane.
On my Chevy Silverado, there is a definite difference in knock retard depending on the fuel octane.
Originally Posted by Skippy722
Always use whatever your car is tuned for is the best recommendation. Some vehicles, like everything with a 5.7 hemi, says "89 recommended, 87 acceptable" while my little 4 cylinder and my v6 say "87 required." Yeah the computer will pull timing to protect itself, but is also reducing horsepower and fuel economy.
^^^^
I agree.
My car says recommended 93 but with the caveat you stated here.
Always use whatever your car is tuned for is the best recommendation. Some vehicles, like everything with a 5.7 hemi, says "89 recommended, 87 acceptable" while my little 4 cylinder and my v6 say "87 required." Yeah the computer will pull timing to protect itself, but is also reducing horsepower and fuel economy.
^^^^
I agree.
My car says recommended 93 but with the caveat you stated here.
Intake air temp has a strong effect on spark knock.
It's why an intercooler improves improves turbo performance in two ways.
Even my previous Toyota Matrix would run stronger on 89 or 91 octane in hot weather (over 90F), even though it called for 87.
Back in the '70s knocking was rampant in the summer, but not in the winter.
It's why an intercooler improves improves turbo performance in two ways.
Even my previous Toyota Matrix would run stronger on 89 or 91 octane in hot weather (over 90F), even though it called for 87.
Back in the '70s knocking was rampant in the summer, but not in the winter.
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