whats the deal with 93 octain gas
01-03-2010, 09:59 PM
#1
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whats the deal with 93 octain gas
herd many oppinions on the topic of gas octain levels.
after gathering the facts it seems like half the world thinks it improves fuel eco, performance, and other stuff. the other half disagrees
i personaly have no idea but i have an edge evo and it says to use 93 for lv 3 so i do. but if i know im going to run lv 1 or 2 for a while i switch back to 87.
someone set the record strait.........whats the deal with 93 octain gas?
after gathering the facts it seems like half the world thinks it improves fuel eco, performance, and other stuff. the other half disagrees
i personaly have no idea but i have an edge evo and it says to use 93 for lv 3 so i do. but if i know im going to run lv 1 or 2 for a while i switch back to 87.
someone set the record strait.........whats the deal with 93 octain gas?
01-03-2010, 11:43 PM
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hi there,
i come from a background of turbocharged 4 cylinder vehicles and just bought myself an 07 stx 4x4. saw your question and figured id let u know what the deal is. octane ratings are a measure of a fuels ability to resist detonation. meaning its easier to light sertain fuels on fire than others. 87 octane being easier to combust and 93 being harder. race gases like c116 is octane 110 i beleive making it hard to light on fire. the benefit of higher octanes is that they ensure you are only lighting your air and gas mixture in the combustion chamber with your spark plug. in performance applications like forced induction or high compression natrually aspirated motors you get a lot of extra heat. this extra heat alone isnt too harmful for short amounts of time but the extra heat can cause the gas to ignite before your spark plug fires which is very damaging to the engine over long periods of time or in high detonation situations. aswell when the factory tunes the maps in your trucks ECU(computer) they are using whatever gas they recommend you use. this is important that you follow what they suggest becuase not only are higher octane gases harder to ignite but they burn a slower rate. so when a factory suggests you use 87 and you put 93 in your tank your ignition timing will be a little off. hope that clears some stuff up for you. dont ever let people tell you that theres no difference between 87 and 93 lol becuase their is a big difference. your programmer is a reflash tool. the guys that built it put the truck on the dyno and ran it on 93 octane to eliminate detonation while they adjusted the air fuel ratio and ignition timing. while adjusting these factors they got more power out of the motor but it would have cuased extra heat. hense them using and suggesting for you to used the 93.
feel free to ask if u have any questions
Darryl
i come from a background of turbocharged 4 cylinder vehicles and just bought myself an 07 stx 4x4. saw your question and figured id let u know what the deal is. octane ratings are a measure of a fuels ability to resist detonation. meaning its easier to light sertain fuels on fire than others. 87 octane being easier to combust and 93 being harder. race gases like c116 is octane 110 i beleive making it hard to light on fire. the benefit of higher octanes is that they ensure you are only lighting your air and gas mixture in the combustion chamber with your spark plug. in performance applications like forced induction or high compression natrually aspirated motors you get a lot of extra heat. this extra heat alone isnt too harmful for short amounts of time but the extra heat can cause the gas to ignite before your spark plug fires which is very damaging to the engine over long periods of time or in high detonation situations. aswell when the factory tunes the maps in your trucks ECU(computer) they are using whatever gas they recommend you use. this is important that you follow what they suggest becuase not only are higher octane gases harder to ignite but they burn a slower rate. so when a factory suggests you use 87 and you put 93 in your tank your ignition timing will be a little off. hope that clears some stuff up for you. dont ever let people tell you that theres no difference between 87 and 93 lol becuase their is a big difference. your programmer is a reflash tool. the guys that built it put the truck on the dyno and ran it on 93 octane to eliminate detonation while they adjusted the air fuel ratio and ignition timing. while adjusting these factors they got more power out of the motor but it would have cuased extra heat. hense them using and suggesting for you to used the 93.
feel free to ask if u have any questions
Darryl
01-04-2010, 12:15 AM
#3
12 Second Truck
X2 on that. If your vehicle manufacture, performance parts manufacture, flash tool, or tuner specifies a certain octane then run it. Thats what its designed to run on. Running higher octane dosen't give you better mpg's nor does it clean out your fuel system.
01-04-2010, 01:19 AM
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To add to what these guys said, regarding a normally aspirated engine:
Higher octane is beneficial in higher compression applications as it is more stable, but, it does physically burn slower. It usually hurts the performance of a lower compression motor.
Simplistically, compression ratio is measured by how much room the detonion has to explode in. More room means less bang. A loose example: if you place an amount of gunpowder in the open and light it, it will flash and burn, but aside from a freak accident, not much else happens. If you pack the same amount tightly into a sealed container, you get a big boom.
Using hypothetical numbers, an ECU in a car with say 8.5:1 compression ratio, may run the timing at 32° Before Top Dead Center ( BTDC ). That means 32° before the piston gets to the very top of its cycle, and the valves are seated fully, the spark plug is fired and the fuel is starting to ignite. If you are using high octane fuel in this engine, there is a very good chance the fuel is not burned completely before the combustion cycle is completed...... meaning a possible loss of power and a waste of fuel.
On a higher compression engine, say 10.2:1 using 93 octane, the ECU advances the timing to compensate for the slower burn rate, say to 27° BTDC. <edit as I forgot this portion ...it was late and I was tired> Now higher octane fuel burns slowers, so why would you ever delay the ignition? Because, the higher compression helps speed up the burn process. This is to ensure all the fuel is being burned and it is getting as much power as it can from each explosion.
Some higher mileage engines do benefit from higher octane fuel simply due to carbon deposits on the piston and combustion chamber. The deposit build up decreases the space the explosion happens in...therefor, raising the compression ratio.
A programmer does not raise your mechanical ratio. It advances the timing so the spark happens sooner at TDC. Mechanically, most vehicle engines have a higher compression ratio, but, the timing is backed off electronically to simulate a lower one. This is why a programmer works. This is also why it is wise to follow the programmers instructions and use high octane with their tunings.
As another of many examples, lets say my engine has a mechanical ratio of 10.5:1. That ratio is a little high and for some reason I want to bring it down. I can retard the timing a few degrees so the explosion happens after the piston has already started descending. Because the apex of this explosion has happened after the piston has descended, say 1/8", it has dropped the ratio to approximately 9.8:1.
I know its alot, and I could go into tons more detail, but, this is what I heard from a guy.....that knows a guy..... that knows another guy. So we know its good info.
Actually , as I read this...... I realize there are some errors in this......I was really tired and trying to write it quickly before I went to bed. Will try to clean it up this evening.
Higher octane is beneficial in higher compression applications as it is more stable, but, it does physically burn slower. It usually hurts the performance of a lower compression motor.
Simplistically, compression ratio is measured by how much room the detonion has to explode in. More room means less bang. A loose example: if you place an amount of gunpowder in the open and light it, it will flash and burn, but aside from a freak accident, not much else happens. If you pack the same amount tightly into a sealed container, you get a big boom.
Using hypothetical numbers, an ECU in a car with say 8.5:1 compression ratio, may run the timing at 32° Before Top Dead Center ( BTDC ). That means 32° before the piston gets to the very top of its cycle, and the valves are seated fully, the spark plug is fired and the fuel is starting to ignite. If you are using high octane fuel in this engine, there is a very good chance the fuel is not burned completely before the combustion cycle is completed...... meaning a possible loss of power and a waste of fuel.
On a higher compression engine, say 10.2:1 using 93 octane, the ECU advances the timing to compensate for the slower burn rate, say to 27° BTDC. <edit as I forgot this portion ...it was late and I was tired> Now higher octane fuel burns slowers, so why would you ever delay the ignition? Because, the higher compression helps speed up the burn process. This is to ensure all the fuel is being burned and it is getting as much power as it can from each explosion.
Some higher mileage engines do benefit from higher octane fuel simply due to carbon deposits on the piston and combustion chamber. The deposit build up decreases the space the explosion happens in...therefor, raising the compression ratio.
A programmer does not raise your mechanical ratio. It advances the timing so the spark happens sooner at TDC. Mechanically, most vehicle engines have a higher compression ratio, but, the timing is backed off electronically to simulate a lower one. This is why a programmer works. This is also why it is wise to follow the programmers instructions and use high octane with their tunings.
As another of many examples, lets say my engine has a mechanical ratio of 10.5:1. That ratio is a little high and for some reason I want to bring it down. I can retard the timing a few degrees so the explosion happens after the piston has already started descending. Because the apex of this explosion has happened after the piston has descended, say 1/8", it has dropped the ratio to approximately 9.8:1.
I know its alot, and I could go into tons more detail, but, this is what I heard from a guy.....that knows a guy..... that knows another guy. So we know its good info.
Actually , as I read this...... I realize there are some errors in this......I was really tired and trying to write it quickly before I went to bed. Will try to clean it up this evening.
Last edited by TwiztdWun; 01-04-2010 at 08:28 AM. Reason: Misinformation
01-04-2010, 07:48 AM
#7
Senior Member
I personally run 87 in my f150. But in my 84 s-10 if I run anything except 93 octane, I get a pinging noise at low rpms. That is the only difference I can see with the two.
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01-04-2010, 08:13 AM
#8
12 Second Truck
To add to what these guys said, regarding a normally aspirated engine:
Some higher mileage engines do benefit from higher octane fuel simply due to carbon deposits on the piston and combustion chamber. The deposit build up decreases the space the explosion happens in...therefor, raising the compression ratio.
Some higher mileage engines do benefit from higher octane fuel simply due to carbon deposits on the piston and combustion chamber. The deposit build up decreases the space the explosion happens in...therefor, raising the compression ratio.
Great examples and nicely explained TwiztdWun.
Last edited by Blown Ford; 01-04-2010 at 08:16 AM.
01-04-2010, 08:20 AM
#9
12 Second Truck
This is normal. Older motor with some carbon build up, a little wear on the timing chain, a little wear on the distributor and so on. You could back some timing out by adjusting the distributor if you wanted to run 87 again.
01-04-2010, 12:01 PM
#10
Moderator (Ret.)
Great writeups on the octane issue. Simply put for me, If I were to run a more aggressive advance on my engine (such as a "tune" on a programmer), I'd be bumping up on the octane. Since I'm running the stock configuration, I use 87 as recommended by Ford. I do however use a good "name brand" fuel, as they have cleaners in them that keep the injectors clean. A common "myth" has been that only the high octane fuels have fuel cleaners added to them; not true. Shell, Mobile, and Exxon all have fuel cleaners in all grades of their gas.