100 octane
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100 octane
passing through L.A. i stopped for gas and found 100 octane at the pump. a guy in an sl500 suggested mixing half-and-half to try it out, so i did. (only after starting to pump the new stuff did i realize that it's $4.69 per gallon!)
my D2 seems to like the new juice. any chance i'm doing damage with the higher octane?
my D2 seems to like the new juice. any chance i'm doing damage with the higher octane?
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It depends on the car ...
Some cars, like our Audis, actively control the ignition timing to adapt to fuel grades. If you are a cheapskate dope, and put 84 octane in your ~$70k car, then it will detect this, and change the ignition timing to compensate .. lowering the power output in the process.
I honestly do not know how high the A8's computer senses and compensates in the OTHER direction (for high octane gas) so I can't comment definitively.
One thing is for certain tho; the A8 knows what you put in the tank and changes the power output of the car via ignition timing to compensate.
I would be curious to know how paying $5 a gallon for 100 Octane fuel from the pump compares to adding Octane Booster to normal gas, when you want to get the same 100 Octane number.
I honestly do not know how high the A8's computer senses and compensates in the OTHER direction (for high octane gas) so I can't comment definitively.
One thing is for certain tho; the A8 knows what you put in the tank and changes the power output of the car via ignition timing to compensate.
I would be curious to know how paying $5 a gallon for 100 Octane fuel from the pump compares to adding Octane Booster to normal gas, when you want to get the same 100 Octane number.
AudiWorld Senior Member
Joined: Mar 2003
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it will improve the performance
audi's have had knock sensors for ages. the motronic doesn't "know" about the octane of the gas, but it dynamically alters timing based on ignition performance. hence the higher octane the better. in my old turbo rs2, once 98-ron gas came out, the effect was immediate wiht no backing off boost half-way through wot runs.
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Should be easy to determine with ...
VAG-COM or <A HREF="https://forums.audiworld.com/a8/msgs/49791.phtml">CarChip</a>, just monitor ignition timing versus load with a tank of 92 octane and a tank of 100.
My ignition timing runs at 26 deg of advance cruising at 65 mph; but at full throttle, ignition timing is only 2 deg of advance. If the timing is retarded less than 24 deg with 100 octane fuel, you're getting more power, and I could plug the numbers into my computer model of the 4.2L motor to calculate the gain.
The 11:1 compression ratio motor is certainly prone to pre-ignition/detonation. The computer model says max power is with 18 deg of advance at full throttle, and 16 deg of retard from this is a lot. The only question is how much of this retard is due to knock sensors.
My ignition timing runs at 26 deg of advance cruising at 65 mph; but at full throttle, ignition timing is only 2 deg of advance. If the timing is retarded less than 24 deg with 100 octane fuel, you're getting more power, and I could plug the numbers into my computer model of the 4.2L motor to calculate the gain.
The 11:1 compression ratio motor is certainly prone to pre-ignition/detonation. The computer model says max power is with 18 deg of advance at full throttle, and 16 deg of retard from this is a lot. The only question is how much of this retard is due to knock sensors.
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Re: 2 degrees can't be right...
The exhaust temp would be very high and you wouldn't see much power with 2degrees advance.
Even if the 5valve S8 engine is probably burning faster then the old ABz 4valve it may be of interest to know that I run 28degrees advance at WOT on my Autronic controlled ABZ. This is without knock sensors.
This may have been a bit more timing then needed, the 'carbon ring' on the center ceramic is to far down to be seen). But I haven't had any detonation problems with it (also verified by reading the plugs).
Even if the 5valve S8 engine is probably burning faster then the old ABz 4valve it may be of interest to know that I run 28degrees advance at WOT on my Autronic controlled ABZ. This is without knock sensors.
This may have been a bit more timing then needed, the 'carbon ring' on the center ceramic is to far down to be seen). But I haven't had any detonation problems with it (also verified by reading the plugs).
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Re: 100 octane
BMWho,
My 2000 A8 pinged from day 1 on Washington's 92 octane. Octane booster only burned out the 02 sensors. The car was happiest when I was in Canada and could buy 95 octane, or mix unleaded racing into the tank. My '04 seems to have a better map, and adjusts better to lower octane fuel.
Robin
My 2000 A8 pinged from day 1 on Washington's 92 octane. Octane booster only burned out the 02 sensors. The car was happiest when I was in Canada and could buy 95 octane, or mix unleaded racing into the tank. My '04 seems to have a better map, and adjusts better to lower octane fuel.
Robin
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