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02-11-2018, 02:40 PM | #1 |
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MHD tuning fuel
Hey guys,
I'm looking at putting an MHD tune on my N54. However, I live in Portland, Oregon and the only gas that seems to be available is 87, 89, and 92 octane. If I recall correctly all the MHD stage 1 tunes require 91 or 93 octane. Any ideas here? Thanks for the help. |
02-11-2018, 03:25 PM | #2 | |
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02-11-2018, 03:30 PM | #3 |
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02-11-2018, 03:31 PM | #4 |
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Yeah that's what I do. It's arguably even safer for the car
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02-11-2018, 05:14 PM | #5 |
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02-11-2018, 10:06 PM | #6 |
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A point or 2 will make no appreciable difference.
They are not full on race, extract the most power at all cost, tunes. They are fun and pretty safe. And what they don't catch the DME will adjust for pretty quickly. That does not mean you want to push it hard right away. Work up to it and take logs each time to verify the car is acting correct. |
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02-12-2018, 03:50 PM | #7 |
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Octane is a measure of a fuel's resistance to autoignition, commonly known as knock. A higher octane means the fuel can withstand higher temperatures and pressures before knocking. This allows a custom tuner to advance the ignition timing to increase power. Running a tune designed for a lower octane rating means that the tune has been designed not to knock (for the most part) with the low octane, so a higher octane will be even less likely to cause knocking.
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02-12-2018, 08:17 PM | #8 | |
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02-12-2018, 09:47 PM | #9 | |
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Autoignition is the temperature at which the fuel self ignites. This is how a diesel engine works. Knock is unstable or unpredicted burn rate, much faster than expected. This is generally due to improper fuel to air mixture, not necessarily quantity or equivalency ratio, in combination to ignition advance. They are separate conditions and should never be confused. I challenge anyone to find reliable data about Gasoline Octane ratings and different autoignition temps. If you find them post them. *hint, you'll have a hard time if you do good research |
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02-13-2018, 04:01 PM | #10 | |
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University of Washington study of autoignition temperature of different octane gasoline: Fluid sprayed on a recessed stainless steel plate. 87 octane: 1135-1225°F 89 octane: 1240-1445°F http://depts.washington.edu/vehfire/...sults.html#gas That being said, octane is not always a great measure of a fuel's anti-knock properties. Much research has been done on the Low Speed Pre-Ignition (LSPI) phenomenon that can occur in high compression, boosted engines, and has found that in testing multiple fuels with the exact same octane rating, some may knock and others may not. The test for octane rating is likely a bit outdated, as it is performed on a carbureted, low compression engine designed in the 1920s.
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02-13-2018, 09:23 PM | #11 |
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Looking at the same table, Gasoline of any grade can be from 1,100*F to 1,520*F. Which is what I was saying. It's just not a good measure because there isn't uniform results. That is a very broad range. And on top of that it could vary cycle o cycle.
AND it does not take into account dilution by residual gasses or crank case vapors. Perhaps the most interesting is that E85 has a lower temp than the high end of Gasoline. But in real world we know this to not be completely true. But that's due in part to the Latent heating value. |
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07-02-2019, 05:48 AM | #12 | |
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07-02-2019, 05:04 PM | #13 |
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This type of question belongs on the MHD Facebook Group. It's too embarrassing for this forum.
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