87,91,93 tune
01-27-2008, 09:39 AM
#1
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87,91,93 tune
I just purchased a SCT tuner from Brenpeed. The question that I have is there a big differnce from getting a 91 or 93 octane tune. I am living in Fort Leonard Wood Mo and cannot find a gas station that sells 93 octane fuel.
01-27-2008, 01:09 PM
#3
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Location: Jackson, Oh
Posts: 897
RE: 87,91,93 tune
Ourengines are designed (compression ratio) and the PCM (engine computer) are programmed to adjust the spark firing angle for a certain range of fuel octane. The engine has what is called a predetonation sensor to signal the computer to advance the timing or retard the timing to correct for preignition (known as knocking or pinging)..But it has a limited range from retard to advance. So the fuel has to be of the correct octane for the timing to fall within this range. If you use a slower burning HIGH octane fuel, the spark control must adjust itself to it's full Advanced end of the spectrum...But it will not go far enough to compensate for the High octane fuel (usual above 90 or more)..What ends up happening is that, since the fuel burns slower and incompletely, a lot of left over unburned fuel remains and carbons up the combustion chambers. Resulting in higher compression eventually and then you are force to use the higher octane fuel by fault...So the faster burning 87 octane is optimum for proper combustion efficiency as these engines are set up for. Using any higher octane is a waste of money too...89 octane is a blend of the 87 and the 92+ at the pump's mixing valve. I would suggest you should havehad4.10 gears installed. You would have had a lot more fun, and enjoyed your purchase more. I use 92 in my car though. It is setup for it(dyno tuned), andI amrunning boostso its a must to prevent detonation.
01-27-2008, 10:56 PM
#4
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RE: 87,91,93 tune
ORIGINAL: dennis_112
Ourengines are designed (compression ratio) and the PCM (engine computer) are programmed to adjust the spark firing angle for a certain range of fuel octane. The engine has what is called a predetonation sensor to signal the computer to advance the timing or retard the timing to correct for preignition (known as knocking or pinging)..But it has a limited range from retard to advance. So the fuel has to be of the correct octane for the timing to fall within this range. If you use a slower burning HIGH octane fuel, the spark control must adjust itself to it's full Advanced end of the spectrum...But it will not go far enough to compensate for the High octane fuel (usual above 90 or more)..What ends up happening is that, since the fuel burns slower and incompletely, a lot of left over unburned fuel remains and carbons up the combustion chambers. Resulting in higher compression eventually and then you are force to use the higher octane fuel by fault...So the faster burning 87 octane is optimum for proper combustion efficiency as these engines are set up for. Using any higher octane is a waste of money too...89 octane is a blend of the 87 and the 92+ at the pump's mixing valve. I would suggest you should havehad4.10 gears installed. You would have had a lot more fun, and enjoyed your purchase more. I use 92 in my car though. It is setup for it(dyno tuned), andI amrunning boostso its a must to prevent detonation.
Ourengines are designed (compression ratio) and the PCM (engine computer) are programmed to adjust the spark firing angle for a certain range of fuel octane. The engine has what is called a predetonation sensor to signal the computer to advance the timing or retard the timing to correct for preignition (known as knocking or pinging)..But it has a limited range from retard to advance. So the fuel has to be of the correct octane for the timing to fall within this range. If you use a slower burning HIGH octane fuel, the spark control must adjust itself to it's full Advanced end of the spectrum...But it will not go far enough to compensate for the High octane fuel (usual above 90 or more)..What ends up happening is that, since the fuel burns slower and incompletely, a lot of left over unburned fuel remains and carbons up the combustion chambers. Resulting in higher compression eventually and then you are force to use the higher octane fuel by fault...So the faster burning 87 octane is optimum for proper combustion efficiency as these engines are set up for. Using any higher octane is a waste of money too...89 octane is a blend of the 87 and the 92+ at the pump's mixing valve. I would suggest you should havehad4.10 gears installed. You would have had a lot more fun, and enjoyed your purchase more. I use 92 in my car though. It is setup for it(dyno tuned), andI amrunning boostso its a must to prevent detonation.
01-28-2008, 05:17 PM
#5
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Location: Jackson, Oh
Posts: 897
RE: 87,91,93 tune
I understand that, butis he really willing to pay high fuel prices for such a low increase in HP. I understand running 93+ octane in a car with F/I, or HIGH compression. But for a stock to mild N/A car. Its not worth it. Most bolts on's the HP you net is so slow and/or out of the power band for a N/A car, you are better off saving up for a centri/turbo/heads+cams/etc. Thats what I was getting at with my post above.
01-28-2008, 05:53 PM
#6
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RE: 87,91,93 tune
His post is a simple question that doesn't need debating. No you will not see much difference between the 2. If you're willing to pay for the fuel, which you must be if you're asking this question, then tune your ECU for 91 octane and run that. I noticed when I was in Toledo, OH and Detroit, MI last week that they sell 94 octane at the pump. But then again it's right by a Sunoco refinery.
01-28-2008, 06:16 PM
#8
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RE: 87,91,93 tune
ORIGINAL: dennis_112
The engine has what is called a predetonation sensor to signal the computer to advance the timing or retard the timing to correct for preignition (known as knocking or pinging).
The engine has what is called a predetonation sensor to signal the computer to advance the timing or retard the timing to correct for preignition (known as knocking or pinging).
01-28-2008, 06:51 PM
#10
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RE: 87,91,93 tune
ORIGINAL: dennis_112
I was refering to the system that prevents detonation as a sensor. Since whats controls pre-detonation is sensor(s) i.e. MAF, o2 sensors. I think I was windy enough as it stands.
I was refering to the system that prevents detonation as a sensor. Since whats controls pre-detonation is sensor(s) i.e. MAF, o2 sensors. I think I was windy enough as it stands.
