04-29-2016, 11:07 AM | #23 |
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All the higher octane does on a stock car is maintain what you have. The ECU has preset parameters and does not learn higher octane values. Now if you are tuned and playing with timing, etc, then is a different ball game.
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04-29-2016, 09:31 PM | #24 | |
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04-29-2016, 11:28 PM | #25 | |
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When an engine detects knocking, it's going to do something to compensate. Generally pull boost or timing. This might provide useful information: https://en.wikipedia.org/wiki/Octane_rating#Effects and https://en.wikipedia.org/wiki/Octane...nal_variations Scroll down to the bullet item about the US, and pay particular attention to the sentence about turbo cars being forced to run 91 instead of 93. |
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04-30-2016, 02:43 AM | #27 | |
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We're already very familiar with octane and how it impacts knocking, timing, and horsepower. This is the M2 forum, after all. I asked if you had any specifics about this particular BMW engine. Seems like aside from a generic "most turbocharged vehicles are unable to produce full power, even when using the "premium" 91 AKI fuel" Wikipedia answer, we don't yet. As a practical example, I'd like to know if a bone stock M2 in California running 91 is going to be measurably slower than the same car in Washington State running 93. I somehow doubt it. Last edited by ried; 04-30-2016 at 02:59 AM.. Reason: Grammar. |
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04-30-2016, 09:54 PM | #28 | |
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04-30-2016, 10:30 PM | #29 | |
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You seem to know the answer, so let's hear the details |
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04-30-2016, 10:57 PM | #30 |
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Yes, it should definitely be measurably slower, and possibly noticeably slower. We can see on the instrumented dyno runs (bone stock) that the top end suffers timing pull on 91. And that's simply what you'd expect from an aggressive tune - be it from factory or aftermarket.
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05-01-2016, 02:16 PM | #32 |
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Great video, Nine Lives. Everyone else, jump to 5:20 for the raw data from the dyno. Total is 1-2% difference in whp for premium fuels in the UK. Note that they were comparing the cheapest with the most expensive pump fuels.
I wonder how much BMW's turbocharging will affect the results? It may widen the delta as ajvdh pointed out. Another factor to consider is how much the ethanol content of our American fuels might impact performance. |
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05-01-2016, 03:27 PM | #33 | |
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05-01-2016, 06:07 PM | #34 |
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Adding higher octane fuel will not increase power. When BMW says their cars adjust to the fuel they aren't saying power will increase with better fuel. All they are saying is that the car will begin to pull timing once knock/pre-detonation is detected. Typically this is due to lower quality fuel. If BMW says the car makes 265 hp on 91 octane, it's going to make 265 hp on 93 octane, 265 hp on 100 octane, etc.
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05-01-2016, 07:20 PM | #35 | |
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05-01-2016, 09:13 PM | #36 |
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Disagree, but you are entitled to your opinion.
There are numerous articles, in the hundreds, that show you won't get more performance using higher octane gas on stock motors. Dyno tests back this up. Furthermore BMW rates and designs their motors at 91 AKI. Stock motors aren't scalable to the octane rating you put in the tank. Otherwise dumping C16 into your tank would give you a substantial HP increase. |
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05-01-2016, 09:29 PM | #37 |
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Just like the GTI, the M2 will make more power going from 91 to 93 octane. Since the M2 has a more aggressive tune, with already known N55 boost levels, I'm guessing at least 5hp more. Believe what you want, but try doing a little research next time.
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05-01-2016, 10:30 PM | #38 |
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I've done my research. My advice to you is the same.
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05-01-2016, 10:40 PM | #39 | |
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05-02-2016, 01:53 AM | #40 |
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At this point we're all just pissing in the wind. At the end of the day, we're talking 1 or 2% whp difference, if any at all. Ethanol might even play a bigger role than that.
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05-02-2016, 03:51 AM | #41 |
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I'm not sure why anyone would spent a tidy sum on a high performance car and then fill it with a low grade fuel but each to their own.
V-Power all the way for me!
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05-02-2016, 10:31 AM | #42 | |
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I wonder what the HP tolerance from the factory is? Probably around 5hp...... |
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05-02-2016, 10:35 AM | #43 |
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