Car running way better on 100 octane, should I be concerned?
#16
By the way, altitude reduces the octane requirement. The 93 octane that our cars need only applies to sea level. In Denver, the octanes offered are 85/87/91. The 91 is appropriate for the 997 at this altitude, and is roughly equal to 93 at sea level.
#17
Quite correct. Premium octane has but one purpose - to reduce or eliminate predetonation. You can also solve the problem by reducing the ignition advance if you are forced to run on anything less than 93 octane. The 928 had a circuit that you could switch on for this purpose. Of course, you sacrifice a bit of horsepower by doing so. The only cars that can take advantage of 100 octane fuel are race cars (hence the name "race fuel") or highly modified street cars, with more extreme advance curves that are prone to predetonation. Any octane that exceeds what your owner's manual calls for is a complete waste of money.
By the way, altitude reduces the octane requirement. The 93 octane that our cars need only applies to sea level. In Denver, the octanes offered are 85/87/91. The 91 is appropriate for the 997 at this altitude, and is roughly equal to 93 at sea level.
By the way, altitude reduces the octane requirement. The 93 octane that our cars need only applies to sea level. In Denver, the octanes offered are 85/87/91. The 91 is appropriate for the 997 at this altitude, and is roughly equal to 93 at sea level.
Dave
#18
With stock computer, the M3 runs as best it can with 93 octane. There is NO improvement in performance using any higher octane. The M3's stock computer will not adjust any engine setting different from factory determined levels with any octane higher than is necessary to keep engine from knocking.
#19
I'll search the citation down; I know I captured it somewhere.
-d
#20
The ONLY way that any engine will benefit from a higher octane is if the engine is currently knocking due to the fuel igniting from compression and not spark. Without knock detected on an otherwise properly running engine, the predetermined timing is set at its maximum and you have all the power you are going to get. Octane does not provide power, it reduces compression ignition.
Those of you who claim that there are computers out there that can somehow determine your octane level and will automatically increase power if you use a higher octane than your engine requires, are misguided (to be polite). There is a maximum timing setting on your engine for various engine speeds, temperature, etc. Everything else being equal, the only time your timing will be pulled will be when knock is detected.
If knock is not detected using an 85 octane fuel, then using a 90 octane will provide absolutely no increase in performance. The required octane rating of the fuel for your engine is not to provide power but to eliminate knock. Octane can only recapture lost power. It cannot create more power.
Those of you who claim that there are computers out there that can somehow determine your octane level and will automatically increase power if you use a higher octane than your engine requires, are misguided (to be polite). There is a maximum timing setting on your engine for various engine speeds, temperature, etc. Everything else being equal, the only time your timing will be pulled will be when knock is detected.
If knock is not detected using an 85 octane fuel, then using a 90 octane will provide absolutely no increase in performance. The required octane rating of the fuel for your engine is not to provide power but to eliminate knock. Octane can only recapture lost power. It cannot create more power.
#21
If knock is not detected using an 85 octane fuel, then using a 90 octane will provide absolutely no increase in performance. The required octane rating of the fuel for your engine is not to provide power but to eliminate knock. Octane can only recapture lost power. It cannot create more power.
If the engine knocks, with any octane-rated fuel, Motronic will retard the timing. If this occurs, you can benefit from a higher octane. The optimum environment is to provide a fuel with sufficient pre-detonation resistance (octane) to prevent the ignition timing curve from being retarded / "de-advanced" under any circumstances.
Cool? That being said, I think that octane ratings in the 93-95 octane range will help the 997 run in its design range. Anything over that is wasted.
Thanks for the clarification.
#22
I have a 2006C4s. I drive the poop out of it. Has 23000 miles at least 20000 of them very hard. My friend and I were at a gas station with 100 octane gas. So, I figured, what the heck. The engine reves smoother, is way less apt to stall without the perfect launch, pulls harder, like a lot harder, has way less exhaust filth on the tail pipes and I went from 16.4mpg to 20.3mpg while driving harder because it was fun.
...
Joe
...
Joe
That being said, I generally just step off the clutch around 1-1.2k and use the throttle liberally. <g>
-d
#23
With stock computer, the M3 runs as best it can with 93 octane. There is NO improvement in performance using any higher octane. The M3's stock computer will not adjust any engine setting different from factory determined levels with any octane higher than is necessary to keep engine from knocking.
Sorry disagree with you on this....
Dave
#24
So, if what your say is true, then a stock engine is always knocking when running 93 octane gas and therefore pulling the timing?
Other than that, there are no other possabilities.
If you insist on disagreeing with me (which makes you wrong) , why not enlighten us to exactly what in the engine changes when you go from a 93 octane (which prevents knock) to a 95 octane. There must be some specific changes in the engine to increase performance.
Other than that, there are no other possabilities.
If you insist on disagreeing with me (which makes you wrong) , why not enlighten us to exactly what in the engine changes when you go from a 93 octane (which prevents knock) to a 95 octane. There must be some specific changes in the engine to increase performance.
#25
Well,
I've learned this board is as bad as any. So far only the fella from Chicago was nice and helpful People could use a reading comprehension class or two. It wasn't a maybe it's faster question. It was a fact. The dealer checked my car. In fact, the O2 sensor is retarding my timing on 91 octance more then any car they have seen. The O2 sensor is used to detect knocking. I figured if you read my first couple of posts, you would understand I know about timing, knocking, advance and what not. I may be getting a new motor per the dealer.
I wish I could just filter out people based in New Jersey. I didn't learn to drive in a Camero.
Joe
I've learned this board is as bad as any. So far only the fella from Chicago was nice and helpful People could use a reading comprehension class or two. It wasn't a maybe it's faster question. It was a fact. The dealer checked my car. In fact, the O2 sensor is retarding my timing on 91 octance more then any car they have seen. The O2 sensor is used to detect knocking. I figured if you read my first couple of posts, you would understand I know about timing, knocking, advance and what not. I may be getting a new motor per the dealer.
I wish I could just filter out people based in New Jersey. I didn't learn to drive in a Camero.
Joe
#26
Guest
Posts: n/a
Well,
I've learned this board is as bad as any. So far only the fella from Chicago was nice and helpful People could use a reading comprehension class or two. It wasn't a maybe it's faster question. It was a fact. The dealer checked my car. In fact, the O2 sensor is retarding my timing on 91 octance more then any car they have seen. The O2 sensor is used to detect knocking. I figured if you read my first couple of posts, you would understand I know about timing, knocking, advance and what not. I may be getting a new motor per the dealer.
I wish I could just filter out people based in New Jersey. I didn't learn to drive in a Camero.
Joe
I've learned this board is as bad as any. So far only the fella from Chicago was nice and helpful People could use a reading comprehension class or two. It wasn't a maybe it's faster question. It was a fact. The dealer checked my car. In fact, the O2 sensor is retarding my timing on 91 octance more then any car they have seen. The O2 sensor is used to detect knocking. I figured if you read my first couple of posts, you would understand I know about timing, knocking, advance and what not. I may be getting a new motor per the dealer.
I wish I could just filter out people based in New Jersey. I didn't learn to drive in a Camero.
Joe
#27
Well,
I've learned this board is as bad as any. So far only the fella from Chicago was nice and helpful People could use a reading comprehension class or two. It wasn't a maybe it's faster question. It was a fact. The dealer checked my car. In fact, the O2 sensor is retarding my timing on 91 octance more then any car they have seen. The O2 sensor is used to detect knocking. I figured if you read my first couple of posts, you would understand I know about timing, knocking, advance and what not. I may be getting a new motor per the dealer.
I wish I could just filter out people based in New Jersey. I didn't learn to drive in a Camero.
Joe
I've learned this board is as bad as any. So far only the fella from Chicago was nice and helpful People could use a reading comprehension class or two. It wasn't a maybe it's faster question. It was a fact. The dealer checked my car. In fact, the O2 sensor is retarding my timing on 91 octance more then any car they have seen. The O2 sensor is used to detect knocking. I figured if you read my first couple of posts, you would understand I know about timing, knocking, advance and what not. I may be getting a new motor per the dealer.
I wish I could just filter out people based in New Jersey. I didn't learn to drive in a Camero.
Joe
#28
See you in class. The reason you experienced better performance with higher octane is exactly what we've been saying - running too low an octane caused your car's computer to retard the timing to avoid knock. When you ran higher octane it allowed the computer to use the normal timing map, which increased power ouput. Personally I thought everyone was helpful. There are other forums if you don't like this one.
#29
See you in class. The reason you experienced better performance with higher octane is exactly what we've been saying - running too low an octane caused your car's computer to retard the timing to avoid knock. When you ran higher octane it allowed the computer to use the normal timing map, which increased power ouput. Personally I thought everyone was helpful. There are other forums if you don't like this one.
As others have correctly pointed out, too much octane is a waste of money and can actually reduce combustion efficiency unless the engine management is tweaked to exploit it. Since octane provides slower and/or better controlled flame travel, 100 octane fuel in a 997S is too much. A blend of pump premium and 100 octane unleaded that results in a 93-94 octane mix should provide the best result.
Here is an excellent article that provides a wealth of information on this subject:
http://www.europeancarweb.com/tech/0...ted/index.html
MC
#30