BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
M2 Technical Topics > N55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > mpg experience with bootmod3

Post Reply
 
Thread Tools Search this Thread
      11-14-2019, 03:25 AM   #1
widetyres
Lieutenant
United Kingdom
279
Rep
488
Posts

Drives: M3 E92 DCT, 2012
Join Date: Oct 2018
Location: UK

iTrader: (0)

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
Appreciate 1
Bee Pee1737.50
      11-14-2019, 12:43 PM   #2
mike@x-ph.com
BimmerPost Supporting Vendor
mike@x-ph.com's Avatar
United_States
23785
Rep
190,128
Posts


Drives: 07-335/12-328/18-M4/21-M4CP
Join Date: Sep 2013
Location: Las Vegas

iTrader: (23)

__________________
Check out our current sale by clicking on this link!
https://x-ph.com/sale/

Phone number 702-494-9435
Appreciate 0
      11-15-2019, 08:19 AM   #3
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Ha! My average mpg is 11.5
Appreciate 2
      11-15-2019, 08:41 AM   #4
cecaa850
Captain
United_States
259
Rep
699
Posts

Drives: 2018 M2
Join Date: May 2018
Location: South East TX.

iTrader: (0)

Quote:
Originally Posted by Anthony1s View Post
Ha! My average mpg is 11.5
He's probably on kilometers per liter or something like that. LOL.
Appreciate 0
      11-15-2019, 10:28 AM   #5
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Quote:
Originally Posted by cecaa850 View Post
He's probably on kilometers per liter or something like that. LOL.
I think mine so bad cause I drive only in the city, in DSC off mode, with big wide tires, and rarely shift below 4k
Appreciate 0
      11-15-2019, 01:56 PM   #6
akkando
Major General
akkando's Avatar
5860
Rep
6,631
Posts

Drives: 17 M2 DCT LBB,11 e90 M3 ZCP IB
Join Date: Jan 2017
Location: Bay Area

iTrader: (1)

I'm not seeing a difference in MPG.
Appreciate 0
      11-16-2019, 12:40 PM   #7
widetyres
Lieutenant
United Kingdom
279
Rep
488
Posts

Drives: M3 E92 DCT, 2012
Join Date: Oct 2018
Location: UK

iTrader: (0)

Quote:
Originally Posted by cecaa850 View Post
Quote:
Originally Posted by Anthony1s View Post
Ha! My average mpg is 11.5
He's probably on kilometers per liter or something like that. LOL.
Lol!

Definitely miles, but UK miles so a bit higher.

It's the long highway commute I do which makes the figures quite good.
Appreciate 0
      11-16-2019, 04:54 PM   #8
MZWIE
Lieutenant Colonel
386
Rep
1,660
Posts

Drives: M2
Join Date: Jun 2007
Location: GEORGIA

iTrader: (0)

No way. Mine is 22+ and always drive in the city.
Appreciate 0
      11-20-2019, 03:41 PM   #9
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

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:
  1. stock = 23.8 UK mpg = 19.8 US mpg
  2. stock with charge pipe (cp) = 23.4 UK mpg = 19.5 US mpg
  3. bootmod3 stage 1 91 = 23.7 UK mpg (Inc cp) = 19.7 US mpg
  4. bootmod3 stage 1 93 = 25.2 UK mpg (Inc cp) = 21.0 US mpg
This are great figures, and better than I get, but not by that much.

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:
  • 95 RON ≈ 93 AKI - (Regular Unleaded Fuel; lowest RON available at the pump)
  • 97 RON ≈ 95 AKI }
  • 98 RON ≈ 96 AKI } (Super Unleaded Fuel)
  • 99 RON ≈ 97 AKI }
I realise that this looks like I've just subtracted 2 to get from RON to AKI, but that seems to be what the evidence suggests.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 1
Poochie9099.00
      11-20-2019, 05:59 PM   #10
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Quote:
Originally Posted by Nezil View Post
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:
  1. stock = 23.8 UK mpg = 19.8 US mpg
  2. stock with charge pipe (cp) = 23.4 UK mpg = 19.5 US mpg
  3. bootmod3 stage 1 91 = 23.7 UK mpg (Inc cp) = 19.7 US mpg
  4. bootmod3 stage 1 93 = 25.2 UK mpg (Inc cp) = 21.0 US mpg
This are great figures, and better than I get, but not by that much.

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:
  • 95 RON ≈ 93 AKI - (Regular Unleaded Fuel; lowest RON available at the pump)
  • 97 RON ≈ 95 AKI }
  • 98 RON ≈ 96 AKI } (Super Unleaded Fuel)
  • 99 RON ≈ 97 AKI }
I realise that this looks like I've just subtracted 2 to get from RON to AKI, but that seems to be what the evidence suggests.
Are you suggesting that UK gas is better quality than USA gas? Because that's not true. UK gas is basically the same quality as USA gas (outside of Arizona/California/Nevada). UK just use a different rating system.

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.
Appreciate 1
Poochie9099.00
      11-20-2019, 06:23 PM   #11
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Quote:
Originally Posted by Anthony1s View Post
Are you suggesting that UK gas is better quality than USA gas? Because that's not true. UK gas is basically the same quality as USA gas (outside of Arizona/California/Nevada). UK just use a different rating system.

95 UK = 89 USA
99 UK = 93 USA

This is because UK uses RON, and AKI is (RON+MON)/2
I don't think you're necessarily disagreeing with me...

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:
  • C9 has a RON of 98.5 and an AKI of 96.8
  • C50 REG has a high RON of 102, but a low MON of 87.5 resulting in an AKI of 94.8
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.

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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings

Last edited by Nezil; 11-20-2019 at 06:33 PM..
Appreciate 1
Poochie9099.00
      11-20-2019, 06:34 PM   #12
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Quote:
Originally Posted by Nezil View Post
I don't think you're necessarily disagreeing with me...

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:
  • C9 has a RON of 98.5 and an AKI of 96.8
  • C50 REG has a high RON of 102, but a low MON of 87.5 resulting in an AKI of 94.8
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.

To be fair, and in the interest of now 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.
I just don't understand your point is all. Disregarding race gas... are you saying that USA pump gas (outside of ACN) is worse than UK pump gas at preventing detonation? It seems like you are... and that's what I'm disagreeing with.
Appreciate 0
      11-20-2019, 06:40 PM   #13
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Quote:
Originally Posted by Anthony1s View Post
I just don't understand your point is all. Disregarding race gas... are you saying that USA pump gas (outside of ACN) is worse than UK pump gas at preventing detonation? It seems like you are... and that's what I'm disagreeing with.
Yes, that is absolutely what I'm saying.

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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      11-20-2019, 06:44 PM   #14
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      11-20-2019, 07:45 PM   #15
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Quote:
Originally Posted by Nezil View Post
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.
It's cool. I see no problem with how you're speaking to me.

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.
Appreciate 1
widetyres279.00
      11-20-2019, 08:11 PM   #16
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Quote:
Originally Posted by Anthony1s View Post
It's cool. I see no problem with how you're speaking to me.
Thanks for your understanding.
Quote:
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.
Understood. I do believe differently, but I don't have solid proof, just a fair amount of evidence.

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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 1
Poochie9099.00
      11-20-2019, 08:51 PM   #17
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Quote:
Originally Posted by Nezil View Post

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.
Well, I guess that section should give you some insight. When you said above...

"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...
Appreciate 0
      11-20-2019, 11:40 PM   #18
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Quote:
Originally Posted by Anthony1s View Post
Well, I guess that section should give you some insight. When you said above...

"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...
I think I understand the mis-understanding if that even makes sense!

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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      11-21-2019, 10:08 AM   #19
Anthony1s
Banned
756
Rep
2,149
Posts

Drives: 2018 Mineral Grey M2
Join Date: Oct 2017
Location: Pennsylvania

iTrader: (0)

Quote:
Originally Posted by Nezil View Post
I think I understand the mis-understanding if that even makes sense!

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.
"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%."

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..
Appreciate 0
      11-21-2019, 12:07 PM   #20
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Quote:
Originally Posted by Anthony1s View Post
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.
First off... how then do you explain that ACN 91 AKI doesn't perform as well as other US 91 AKI?

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:
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.
It's not simply a non-linear scaling. Take a look at this way to represent the data:


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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      11-21-2019, 12:35 PM   #21
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

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.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      11-22-2019, 06:45 AM   #22
widetyres
Lieutenant
United Kingdom
279
Rep
488
Posts

Drives: M3 E92 DCT, 2012
Join Date: Oct 2018
Location: UK

iTrader: (0)

Quote:
Originally Posted by Nezil View Post
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.
Your absolutely right Nezil - that's what I meant to say!!!
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 02:37 PM.




m2
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST