11-14-2019, 03:25 AM | #1 |
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Hi,
Thought I'd share my mpg experiences with bootmod3: 1) stock = 23.8 2) stock with charge pipe (cp) = 23.4 3) bootmod3 stage 1 91 = 23.7 (Inc cp) 4) bootmod3 stage 1 93 = 25.2 (Inc cp) These are UK mpg figures and based on approx 80% Highway driving, 10% City, 10% County roads blasting All on 97RON / 92.5AKI |
11-14-2019, 12:43 PM | #2 |
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11-15-2019, 08:19 AM | #3 |
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Ha! My average mpg is 11.5
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11-15-2019, 10:28 AM | #5 |
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11-16-2019, 12:40 PM | #7 |
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11-20-2019, 03:41 PM | #9 |
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UK miles are the same as US miles; see Wikipedia quote:
The international mile is precisely equal to 1.609344 km (or 25146 / 15625 km as a fraction). It was established as part of the 1959 international yard and pound agreement reached by the United States, the United Kingdom, Canada, Australia, New Zealand, and Union of South Africa, which resolved small but measurable differences that had arisen from separate physical standards each country had maintained for the yard....but a UK gallon is 4.54 litres whereas a US gallon is 3.78 liters. This means that if you want to see the OP's numbers equal to US mpg you have to multiply by (3.78 / 4.54) = 0.833. This gives the following results:
The M2 is thirsty for the power it produces and very octane sensitive. Because AKI is an average of RON and MON, there is no direct conversion from RON to AKI; unless you know the MON of your fuel, your AKI is a guess. Many US M2 owners have found that they're unable to run the 93 AKI map on pump gas that is sold as 93 or the 91 AKI map on pump gas sold as 91 here. This is the reason there is a 91 ACN map for crappy US 91 fuel. I captured extensive logs for my car running 91 AKI pump gas here in Silicon Valley and the tuners at PTF that looked at them said that the fuel was performing more like 89 AKI based on the data. There is some logic to think that forced induction engines like ours are more sensitive to MON than RON, and fuel in the US is able to achieve a high AKI rating by having high RON and low MON, averaging out, but being bad for our engines. Logs from UK cars running 'Super Unleaded' there have shown practical octane results far higher than your 92.5 SKI guess. Based on guesswork, I'd have thought that UK fuel octanes work out like this:
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11-20-2019, 05:59 PM | #10 | |
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95 UK = 89 USA 99 UK = 93 USA This is because UK uses RON, and AKI is (RON+MON)/2 99 octane in UK is NOT equivalent to 97 octane in the USA. |
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11-20-2019, 06:23 PM | #11 | |
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You said: AKI is (RON+MON)/2 I said: AKI is an average of RON and MON These are the same statement. I think what you might be objecting to is my point that if MON is a variable and you don't know the value, it's impossible to calculate AKI. Rather than trusting logs of performance etc. It's worth taking a look at some gas where the RON and MON are both quoted. VP Racing has a great table that lists RON, MON and AKI for their race fuels here: https://vpracingfuels.com/master-fuel-table/ Unfortunately we don't have similar data for pump gas, but there is still some important information in the VP Racing data:
To be fair, and in the interest of not starting an argument because I respect you Anthony1s, I don't know what the fuel is like in Pennsylvania. My 1st hand experience is based on CA fuel but I have read on this forum from many M2 owners in other parts of the US having timing issues with the 93 AKI BM3 OTS maps that European owners simply don't have.
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11-20-2019, 06:34 PM | #12 | |
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11-20-2019, 06:40 PM | #13 | |
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I can't comment on Pennsylvania gas, but I grew up in the UK (left at 28) and visit there every year so have first hand experience of California and UK fuel. I think everyone would agree that ACN fuel is pretty awful, despite its AKI of 91, but I'm basing my broader statement on the number of Europeans safely running far more aggressive tunes on their fuel and the number of US owners outside of Arizona California Nevada that struggle to run the OTS 93 maps on 93 AKI fuel here.
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11-20-2019, 06:44 PM | #14 |
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Also Anthony1s, I want to apologise... I'm pretty passionate about this topic because I'm angry about it... Not with you, so I'm sorry if my post seems that way, but with the oil industry.
I've chosen to install a WMI system on my car just to get it to give me the same performance that I would have got stock if I'd lived in the UK, but it's disappointing that I've had to do that.
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11-20-2019, 07:45 PM | #15 | |
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I'm not sure how to convince you otherwise, but it's always been my understanding that USA fuel (outside of ACN) is the same quality as UK fuel. Only difference being the rating system used for it. http://www.etuners.gr/fuel/ http://www.pencilgeek.org/2009/05/oc...nversions.html https://en.wikipedia.org/wiki/Octane_rating At 4:50 in the video he talks about UK vs USA gas. If you believe differently, based on your real world personal tests... I can't really argue against that. Because I will never have a chance to personally experience and test using gas from different continents in my M2. I'm just going by my understanding based on the links above. |
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11-20-2019, 08:11 PM | #16 | |
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Thanks for your understanding.
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I actually think this would make a great Exposé for some site like Jalopnik to investigate. I thought about doing this myself, but I've no idea how or where I could get official RON and MON testing done. If there was some way like Blackstone, enthusiasts like those on forums like this could get results from around the country and highlight the issue to auto makers and the public as a whole. By the way, it was the Wikipedia article you posted that got me started on this topic originally. This section about MON: Another type of octane rating, called Motor Octane Number (MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance.And this section about aviation rich effectively being the only octane rating based on forced induction engines: Aviation gasolines used in piston aircraft engines common in general aviation have a slightly different method of measuring the octane of the fuel. Similar to an AKI, it has two different ratings, although it is referred to only by the lower of the two. One is referred to as the "aviation lean" rating and is the same as the MON of the fuel up to 100. The second is the "aviation rich" rating and corresponds to the octane rating of a test engine under forced induction operation common in high-performance and military piston aircraft. This utilizes a supercharger, and uses a significantly richer fuel/air ratio for improved detonation resistance.
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11-20-2019, 08:51 PM | #17 | |
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"There is some logic to think that forced induction engines like ours are more sensitive to MON than RON" The difference being how fuels are tested and not anything to do with the fuels themselves being different, I don't see that statement to be true. "There are more examples in the list, but suffice to say that it's very possible to have the two fuels with the same RON having different AKI, and to have a fuel with a low MON and high RON equalling the same AKI as a fuel with higher MON and lower RON." Also this statement I don't believe to be true, because of what I mentioned above (how the fuel is tested being the only difference). Two of the same fuels will never behave differently, nor will two fuels with the same AKI rating. But also, a MON rating will NEVER be higher than a RON rating due to the testing procedure. The MON test is more stressful, meaning the MON rating will always be lower than the RON rating. Does that make sense? I feel like I can do a better job at explaining... |
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11-20-2019, 11:40 PM | #18 | |
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It's true that the only difference between MON and RON is how it's tested, and that in gasoline, RON will always be higher than MON because the MON test is more stressful. But... how much lower RON will be than MON can and does vary between fuels. Some fuels behave better under the higher load MON test than others, it's all about the blending of different hydrocarbons and alcohols. According to Wikipedia, pure Ethanol has a nice high RON of 108.6, and a low MON of 89.7; a MON to RON ratio of 83%. 2,2,3-trimethylpentane has a similar RON of 109.6, but a MON of 99.9; this time a ratio of 91%. I don't dis-believe that US fuel companies are lying about the octane rating. That would be a very serious fraud case. What I do believe though, is that US fuel contains more of the chemicals with a lower MON to RON ratio which nets out to the AKI stamped on the pump. Let's assume for a minute that 97 RON does truly equal 93 AKI. We know the RON so MON can be calculated to be 91. Giving it a MON to RON ratio of 94%. Do you agree that it's totally possible that US E10 93 AKI (non ACN) fuel could have a RON of 99 and a MON of 87 giving a MON to RON ratio of 88%? This is the crux of my theory, than the US hydrocarbon / ethanol blend results in a lower MON to RON ratio and is a poor fuel compared to Europe when used in forced induction engines. The move to 10% Ethanol in the US is relatively new, and may very well be the major contributing factor in all of this. The other trend that is fairly recent is the move to smaller forced induction engines. It wasn't that long ago that US cars had massive low compression naturally aspirated engines with pitiful power outputs. Most articles and the established thought about octane US vs UK pre-date these two changes.
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11-21-2019, 10:08 AM | #19 | |
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So that puts ethanol at 99.15 AKI, and the trimethylpentane at 104.75 AKI. Which is why I presume we use AKI, because it gives a better picture of how resistant a fuel is to knock detonation. All the AKI rating is is the fuel's resistance to knock. It doesn't matter how the fuel gets to that rating. Any and every fuel with a 93 AKI rating is going to perform the same, as far as preventing knock. I think you are putting in more variables when you say "UK gas is better" or that the ingredients matter. Yes, not all 93 AKI fuels will give the same gas mileage, or have the same engine cleaning properties, or be harmful to your gaskets/seals, etc. But they will all prevent knock the same. Edit: I do see what you're saying though. About how one fuel performs better in the MON tests than the RON tests. Definitely got me thinking a little bit more. I wonder if it's a scaling anomaly. Like how -40C and -40F are the same temperature. Last edited by Anthony1s; 11-21-2019 at 10:16 AM.. |
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11-21-2019, 12:07 PM | #20 | ||
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I think this is where we're disagreeing... In an extremely broad sense, all 93 AKI fuels will have the same resistance to knock, and before the days of high compression forced induction engines that may even have actually been close to the case in practice. RON is a light load test, MON is a heavier load test. Wikipedia even details an even heavier forced induction load test for aviation fuels. It's totally possible for a fuel to have a good resistance to knock at low load (RON), and a poor resistance to knock at higher load (MON), just as the data from wikipedia and VP racing show. It's also possible for two 93 AKI fuels to have different ratios of MON to RON, also shown in wikipedia and VP racing data. Both MON and RON aren't particularly good approximations of a modern forced induction engine if you read the details. MON is higher load than RON, but it's still pretty weak load compared to forced induction. Quote:
As you can see, the relationship between AKI and MON to RON ratio is all over the place. I added a linear trend line that does show there is a sort of trend, but clearly there is a spread around this trend line. Based on the assumption that European 95 = 91 AKI and 97 = 93 AKI I added those two points as well. You can see that they're way high above the trend line because they have a MON to RON ratio of 92%. One caveat... I know that there are other characteristics of fuel that affect their performance in forced induction engines. Ethanol has a low MON but performs well because as it changes state from liquid to gas it absorbs a lot of heat, cooling the hot compressed intake air and thereby the combustion itself, reducing the potential for knock. This wouldn't be reflected in the MON or RON values at all because the intake air would be at atmospheric temperature.
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11-21-2019, 12:35 PM | #21 |
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Another much simpler way to look at this, is that if European Super unleaded 97 RON fuel has a MON of 89 (93 [AKI] * 2 - 97 [RON] = 89 [MON]), if you wanted to select a fuel with the same MON from VP Racing's line of Unleaded fuels, you'd be looking at an AKI of 95.5 (VP RX102).
For European Regular 95 RON fuel (87 MON) you'd be looking at 92.75 AKI (VP Moto) You have to go to really high octane fuels in the US (97 AKI+) to get MON levels above 89.
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11-22-2019, 06:45 AM | #22 | |
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