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I've read that you have to be careful to put the correct octane in your car depending on what tune you use. Such as, if you use a 93 Tune you will need to have at least 93 octane in your vehicle. They say if you don't you may damage your engine. I am curious to know exactly what can be damaged in the engine? I have yet to do any mods but would like to educate myself as to all of the risks. My concern would be that the gas station quality of gas. So would it be better to look for 94 octane if you use a 93 tune or 92 if you use a 91 tune? Or am I just overreacting?
 

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Basically a tune modifys fuel and timing. If the octane is not sufficiant then you can get ping or knock which is caused by the air fuel mixture igniting too early. This can lead to burnt valves and holes in pistons. The good news is that these smart cars sense the knock and retard timing and fuel. The result is what feels like less performace.

From my experiance I would run one of the better fuels like Sunoco or BP. Dont push the car till the second full tank as the first will be diluted with what is in the tank to begin with, yes a 1/8 tank may cause slight problems.

Once you find a brand/ station that suits your needs try to stay with that one as station to station may have different suppliers.

It is also fine to use say 93 with a 91 tune but not the other way around.
 

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If your running the predator canned tune most run better with the 91 tune using 91 or 93 gas. If you get a cmr dyno or e mail tune just make sure the a/f at the tail pipe is between 12.2/12.5 and you will be ok. Theres a saying a a/f that is 13.0 is lean and mean but watch out lol. You can make any octane you want buy mixing vp109 or sunoco 104 OR 100 OCTANE AT THE PUMPS to get any octane and oxygen increases you want. The 100 at the pumps in CA is low 1.8% oxygen any where else its 3.3%. Because we in CA are restrited to low 1.8% oxygenated 91 gas i have made octanes of 93,95,96,98,101 and 105 with my cmr dyno tune and never changed the tune at all. The increases are based on my tests from my best 91 octane times to all the diff octanes and they were all 1/8 mile. The min increase was .10 and the max .22 AND THIS WAS WITH A RACE WT OF 5190 LBS.
 

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Loading the correct tune based on fuel is key to performance and longevity when it comes to your Engine, the problem is detonation or more commonly known as pinging. Pinging or detonation occurs when your piston is at the end of its compression stroke and rather than the Spark Plug igniting the F/A mixture, it's ignited by other means. There are a few ways in which this occurs one of which is due to poor quality fuel. Other causes include ignition timing is advanced too much, carbon buildup in the combustion chamber, engine running to hot to name a few. Whatever octane fuel you can get in your area, that's the tune you need to dump in you ECU. If you can't get 93 than stay away from the 93 tune unless you can do some logging and make certain you don't have a detonation issue. I don't know if you're overreacting, you're just being cautious and when it comes to pinging you should be. If you can get 93 then tune it to 93. I can't get 93 in my area, there are some stations that do carry it but I'm not going to out of my way to use it. The car runs great with 91 and a 91 tune with no pinging issues. You should also note that all brands of fuel are not the same. My car runs very good on Mobil and Chevron, it runs like crap on Shell. I haven't really tried any other fuel so I can't give an opinion on the others.

BTW, due to the noise levels of our power plants, it's very difficult to pick up any pinging noises if you are experiencing this. Also keep in mind that if you dumped a 93 tune in a Engine that uses 91 fuel you may feel some slight increase in power, but the downside is way too risky IMHO.
 

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Load the tune and go to town!


 

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Detonation from a lower octane fuel 87 (fast), which ignites sooner than a higher octane rating 93 (slower), with a given a timing advance value will make the rods shudder making the piston slap in the cyl bore. Thats why with a higher octane we can add timing to create more power. Power is increased when the combustion is timed to an optimum rod/piston position nearest the top dead center as possible w/o the rod/piston wanting to go backwards instead on continuing to rotate CW. The greater the leverage the greater the power. Think of a longer pry bar being able to do more work. Work capability = torque. Delay the timing event and the leverage is less. Gotta find the sweet spot.

You can beat up your pistons, rings, rods, bearings, oil pump if crank driven etc if everything is spazing out inside.

The engines have a fail safe to detect the slapping and banging and retard timing by a few degrees of rotation until it stops. Sometimes it cannot do this if the problem is too great and then you put a hole in the block!

Boosted cars are particularly susceptable to this.

Marion
 

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the knock sensors are so fast to pick up knock computer will retard timing. just watch your live data stream. the only way you could hurt a hemi is with a supercharger and too much boost and timing, nos ect. or disconect knock sensor. these knock sensors are very sensitive.
 
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