[Max Well]

Originally Posted by schmitzna

My wife's M40i came with Bridgestone Dueler H/P Sport AS 245/50R19 -- didn't see those on your list.

I wasn't able to find any distinction between the weight of the Dueler H/P Sport AS and the Alenza (in the same size). All of the links I posted in this thread on 27 Nov at 10:54AM mention the main differences as 'improved wet handling and longer tread life'. So for the purpose of this study would assume nearly same weight unless new data comes to light.

If you get a chance to share your HWY numbers for the chart we can see how they fare vs the Yokohamas. At this point we still have way too few data points to make any comparisons, so hoping folks can provide stats when/if they get a chance.

[kozzi]

Short stretch as traffic kept me from cruising steady too long:

M40i, 699M , Pirelli PZero RFTs
35.2 miles traveled close to sea level
74.9 mph average speed
24.9 mpg in Sport+ mode
36 psi front 39 psi rear
Cruise set to 75 mph
RPMs @2200

[Max Well]

Originally Posted by kozzi

Short stretch as traffic kept me from cruising steady too long: ...

Very interesting, kozzi - many thanks for sharing! Chart updated. And as we get more sampling we should be able to start separating which variables make the most difference, especially if we make individual (single) changes on different runs as ando and sor have done. Next up for us will be Sport mode to see what drop we get with the higher RPMs as well (just haven't had time for a trip as we hosted folks for the Holidays). I'll have to think up an excuse for a day trip!

Thanks again, kozzi!

[sor]

I discovered a quirk of the trip computer today that I think threw off some of my numbers. In short, the two entries I previously provided have no known accurate average speed.

This is obviously user error, but it turns out that holding down "BC" to reset the trip computer doesn't seem to reset the average speed unless you're actually on the display that has average speed and average MPG. This seems obvious in retrospect, but also weird in that you can reset just the MPG on this screen and not the average speed, by switching to the MPG meter display and holding BC.

I know for a fact that the average speed numbers are off, and honestly they seemed weirdly low to me knowing what my cruise was set to and how often I was at cruising speed. If I were to guess, they should both be in the 72-75 mph range, but if you want the data to be accurate you may want to remove the entries altogether or at least blank out the speed and just leave them for rough perspective.

All this said, I ran the same route today with a correct reset (which is part of how I discovered the error) and back home. The run there is partial because I reset the computer part way through. These are good numbers as I watched the values zero out this time:

Run to destination:43.2 miles, 75 MPH, 1850 RPM, 32.9 MPG, comfort
Run back home: 99.7 miles, 77.9 MPH, 2000 RPM, 30.3 MPG, eco pro

[Max Well]

Originally Posted by sor

I discovered a quirk of the trip computer today that I think threw off some of my numbers. In short, the two entries I previously provided have no known accurate average speed. ... All this said, I ran the same route today with a correct reset (which is part of how I discovered the error) and back home. The run there is partial because I reset the computer part way through. These are good numbers as I watched the values zero out this time...

Excellent, thanks sor - data updated. It just takes a moment to update and repost the chart so not a problem.

[bwcooper]

Just got back from 200 mi trip (each way) to San Antonio. Most of the trip is on US highways instead of the interstate, so I had to slow down going thru all the towns, which are about 30 to 40 miles apart. Speed limit varies between 55 and 75 mph, and I averaged around 60 mph. Since I got nearly identical mileage for each direction, I'll post the overall as one trip, getting right at 26.0 mpg. I also checked after a 45 mile stretch on the interstate, going a more constant speed, averaging 66.8 mph (2000 rpm) and getting 27.6 mpg. I took the readings from my Trip Computer as shown below.

I have the standard 698M wheels with Yokohama tires (same as Maxwell) on my M40i.

Summarizing:
Leg 1 410 miles, 1800 rpm, 62.0 mph, 26.0 mpg, Comfort Mode
Leg 2 45 miles, 2000 rpm, 66.8 mph, 27.5 mpg, Comfort Mode

Suggestion: Add type of road to the chart. Travelling on the US Highways vs Interstates definitely hurt my mileage a lot given all the slow downs, despite going a tad faster.

[Max Well]

Thanks for contributing, bwcooper! I've added the notation about thru-town HWYs, as I agree that will definitely skew the data and probably can't be used to assess tire contributions in this study. I'm not sure if you recall your tire pressures, but if you can share I'll complete your data lines.

Thanks again!

[bwcooper]

Originally Posted by Max Well

I'm not sure if you recall your tire pressures, but if you can share I'll complete your data lines.

Ooops... forgot that. I believe they were running 34 in the front and 36 in the back.

[Max Well]

Thanks, bwcooper - spreadsheet updated. Interesting the mpg difference between my run and your 45 mile run. Maybe the tire pressure difference? Just an N=2 on the Yokohamas so will be interesting to see if that pans out. I hope to get a chance to run in Sport, but haven't had time with Holidays/family and staying in town.

[bwcooper]

Originally Posted by Max Well

Thanks, bwcooper - spreadsheet updated. Interesting the mpg difference between my run and your 45 mile run. Maybe the tire pressure difference? Just an N=2 on the Yokohamas so will be interesting to see if that pans out. I hope to get a chance to run in Sport, but haven't had time with Holidays/family and staying in town.

While I didn't have to slow down to 55 or anything, the traffic was heavy on my 45 mile run, so the adaptive cruise control (which is really awesome!) kept having to slow me down. Could probably have gotten better mileage if traffic was less and if I had pumped up air in tires after the cold front. I'll try to do another test soon to add another data point.

[Keweenawbee]

Originally Posted by bwcooper

While I didn't have to slow down to 55 or anything, the traffic was heavy on my 45 mile run, so the adaptive cruise control (which is really awesome!) kept having to slow me down.

Love the tech too and it works great, but I find it annoys other drivers behind me when using it to approach the faster pacing cars in the left lane (passing lane here in the USA) I am assuming it is flashing the brake lights to announce it's deceleration too, at a distance that is somewhat abnormal. Going further off thread but of interest, the winter storms and plowing here in MN leave salt remnants that tend to diffuse the usefulness of the lane keeping, but I am going to love it during the warmer seasons on our frequent 1/2 day road trips.

[Max Well]

I still have been unable to find the highlighted wheel weights, and if anything, the ETK site seems to have removed some of the weights I had previously found. Can colleagues up North provide any of the missing wheel weights if they have been removed for your winter set-up? Apologies in advance for having to request such...

[voyagergab]

Sorry it took me so long.
The weight of the 20" winter set including a 699M rim, 20"x8", Pirelli Scorpion 245/45/R20, TPMS, valve and logo cap is 27.7kg or 61 lbs

Looks like the tire itself weighs 12.7 kg or 28 lbs
Which makes the rim 15 kg or 33 lbs give or take the sensor and valve

https://www.kaltire.com/en/tires/sco...er/170745.html

[Max Well]

Thanks for contributing, voyagergab. Still on the lookout for the missing wheel weights as well, and am hoping the lack of data is just due to the G01's infancy. We'll be doing some travelling in a few weeks so I hope to run at least a few hundred miles in Sport and then EcoPro to round out our G01's data.

[Max Well]

Yesterday we left for a 300 mile trip on lightly traveled Interstate roads which allowed a perfect chance for obtaining uninterrupted data. Before leaving I once again insured tire pressures cold were similar to November's numbers.

As we're out of town I just have my laptop so don't have access to edit the spreadsheets, but the results I obtained are confusing. I made sure to clear the trip computer once I was at cruise speed and not before entering the Hwy.

The first segment was about 110 miles with avg speed 78.8 mph in Sport mode, with outside temperature range under clear skies of 22-25 deg F. Tire pressures via on-board monitoring were just a few psi higher, and tire temp indicated 68 deg. The mpg was only 23.6... RPM stayed around 1900.

I tried to consider what I might be missing because of the profound difference in mpg c/w the value of roughly 29mpg I obtained in Comfort mode back in November, but nothing came to mind. So after a brief stop I changed to EcoPro and once back on the Interstate I reset the trip computer when back at cruise speed. Outside ambient temp range was now about 25-28 deg F for ~80 miles, tire psi reported the same and tire temp was about 70 degrees. Avg speed 79.0 mph, and once again, only 23.8 mpg... Couldn't find a way to get the RPM to display while in Eco Pro.

One more stop, this time to refuel, and back on the road in Comfort mode with outside temp now 28-30 deg F, tire data reported about the same, and RPM 1950. After about 70 miles or so, once again, only 23.7 mpg... To insure the trip computer was being cleared correctly, once we got off the Interstate I then checked data at slower Federal Hwy cruise at 50 mph for about 10 miles and it was appropriately improved at around 35 mpg.

So I am at a loss to explain the ~5 mpg difference with our M40i at exactly same tire pressures, cabin load, and pure Interstate cruise at 79 mph through all 3 modes when c/w our Nov data? The only variable really different is the cold weather (it was in the 70s as I recall then). Although it was a completely different route it was light Interstate traffic at relatively level grade with almost no braking or need for acceleration phases. Unfortunately I did not look at reported tire pressures and temperatures while driving back in November, but I'm wondering if that could be the reason? Or does something change about the aerodynamics/grill vents in cold weather (if anything I would think the vents would be open with less aerodynamic flow in hot weather)? Or is it just the cold road and tires?

Hopefully it'll warm up before our return trip home on Sunday so I'll repeat the measurements in reverse. Am curious what others may think. And wondering if our colleagues in the Southern hemisphere might have a chance to share some data from their hwy travel, to also indicate on-board monitor-recorded tire temp and pressure after driving a while at speed in hot weather (and compared to starting cold tire pressure and temp).

And is there a way to identify RPM while in Eco Pro?

[Slalom]

Max Well,
Thank you for the very thorough analysis.
Do you recall the ambient air temperatures from November? I am wondering if the temperature has anything to do with the numbers. As I recall, turbocharged engines in particular develop peak power at about 32F. It could be that with the denser cold air you are getting more fuel in the mix and thus lower economy numbers (and more power too).

Just a wild guess.

[schmitzna]

How are these variables being controlled?

• Wind direction and speed
• Elevation change / grade

[Max Well]

Originally Posted by schmitzna

How are these variables being controlled?

• Wind direction and speed
• Elevation change / grade

Good points, schmitzna as these definitely affect performance. In the first post of this thread I alluded to the difficulty of encompassing all variables in this rough observational study. But the hope was for everyone to try to obtain data from relatively level HWY over longer (rather than shorter) distances to offset short peaks and valleys which should average out, especially if starting/ending elevations are similar. GoogleEarth can provide a rough idea as one follows a cursor over a Hwy's path. FWIW, our route's paths start/end points were within ~25 feet or so of each other, with max change of about +/-75 feet along the routes.

Wind direction and speed are more difficult to assess over a long journey given the potential for directional changes as highways meander about the compass even when heading in a generalized North-South or East-West, and the ability for tree lines and/or buildings to block wind flow, etc. For an accurate study, such as on a drag strip - that can be controlled (and usually is). But for the purposes of this project it was hoped if a fair number of Forum Members can contribute that some trends might become apparent as the 'n' increases.

Originally Posted by Slalom

Max Well,
Thank you for the very thorough analysis.
Do you recall the ambient air temperatures from November? I am wondering if the temperature has anything to do with the numbers. As I recall, turbocharged engines in particular develop peak power at about 32F. It could be that with the denser cold air you are getting more fuel in the mix and thus lower economy numbers (and more power too). Just a wild guess.

Thank you, Slalom - I think the outside ambient temperature was in the 70s back in November. I hadn't thought about what you indicate, so I did some searching online and am including a number of links. Indeed, it appears air temperature and density have a significant role in a vehicle's efficiency -far, far greater than I had previously thought. I'll definitely add a column for temperature when I get home, and to be honest, I'm surprised about my lack of knowledge on this topic... And if you do the math, my mpg is about 82% in this 20-30 degree weather as it was in the 70+ weather, so guess it is at least consistent.

Given the importance of this added variable, it seems my goal of identifying the effect of tire/wheel size and weight on vehicle efficiency at highway speeds has become more difficult.

https://www.fueleconomy.gov/feg/coldweather.shtml - “Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds; Tire pressure decreases in colder temperatures, increasing rolling resistance.”

https://www.greencarreports.com/news...ther-heres-why - “one property of air, like many substances, is that it expands when it warms. This makes it less dense--molecules of the various gases are spread further apart. This means that every gulp of air your car is taking during combustion has less oxygen in it at warmer temperatures, and if there's less oxygen, the engine compensates by using less fuel. This is bad from a power perspective, but good for economy. The engine is combusting less fuel due to the warm air, improving fuel economy. During winter, the reverse is true--denser air encourages the engine to chuck in more fuel, boosting performance and harming economy.”

https://www.scientificamerican.com/a...uel-economy-o/ - the amount of drag between tires and the road is about 20 percent greater at 0 degrees F than it is at 80 degrees F.

https://www.cnbc.com/2014/02/14/cold...s-mileage.html - “New research from the Oak Ridge National Laboratory found that some models can lose as much as a third of their fuel economy when the mercury drops to 20 degrees.”

http://www.aet-turbos.co.uk/blog/sto...er-performance

http://stratifiedauto.com/blog/the-e...rged-vehicles/

https://mechanics.stackexchange.com/...ect-horsepower

https://www.reddit.com/r/cars/commen...ts_horsepower/

[Max Well]

Spreadsheet in first post updated with data from our recent trip and columns added for ambient air temp, wheel PSI and temp from tire pressure monitoring, and altitude. I also attached the G01's recommended cold tire pressures from the owner's manual there as reference.

Before this trip I had no idea how much ambient temp can affect a vehicle's efficiency. And these effects are multifactorial - colder temps increase air density which worsens aerodynamic drag, increases rolling resistance of the tires, and increases amount of oxygen available to the engine hence increased fuel consumption (but also increased power output). I added altitude after seeing sor's data and researching the effects of altitude on vehicle performance and efficiency. At higher altitude the air becomes less dense and contains less oxygen which simulates what happens at higher sea level temperatures in comparison to cold temperatures (improved efficiency but less power).

Interesting to see the front tires consistently ran higher temps by at least a few degrees - makes sense, as one wishes for improved traction (friction) on those. And given the increase in tire temp of the lower PSI fronts (especially at higher speed), I have a better understanding of the reasoning for increasing the tire pressure from baseline cold 32/35 PSI to 38/45 PSI for high speed travel. Logical to see how the risk of tire failure rises in under-inflated tires at high speed. It makes me wonder what those tire pressures and temperatures will be on 95 degree Summer days.

[sor]

Interesting that I got my results in ~30 degrees Fahrenheit. I'm at 5000 feet though so that's another factor.

I've never really noticed such a big swing between hot and cold weather as described, and I've paid attention to MPG. I have a hunch as well that turbo cars should not be affected nearly as much, as they also aren't as affected by altitude/air pressure. The turbo helps regulate the air density and temperature going into the engine.

Did you keep an eye on your instantaneous MPG at any time? That's what led me to my own discrepancy and error in resetting the trip computer properly. If your instant readings look good but the trip is off there may be other data factored into the trip that shouldn't be.

[Max Well]

Originally Posted by sor

Interesting that I got my results in ~30 degrees Fahrenheit. I'm at 5000 feet though so that's another factor.

I've never really noticed such a big swing between hot and cold weather as described, and I've paid attention to MPG. I have a hunch as well that turbo cars should not be affected nearly as much, as they also aren't as affected by altitude/air pressure. The turbo helps regulate the air density and temperature going into the engine.

Did you keep an eye on your instantaneous MPG at any time? That's what led me to my own discrepancy and error in resetting the trip computer properly. If your instant readings look good but the trip is off there may be other data factored into the trip that shouldn't be.

Thanks, sor - your data updated in the spreadsheet as well.

Yes - I actually followed the instantaneous mpg like a hawk and everything I saw was consistent with the end result. I was especially concerned early on with your prevous post hanging in the back of my mind, so I repeated zeroing early on in the journey to be sure. And when I got off the Hwy and did the Federal Hwy test at 50mph it captured roughly 35 mpg and was consistent with the instantaneous reads as well. And that the mpg improved on the return trip, even despite being in Sport+ at 2500 RPM (which I though would surely have less efficiency), with the weather warming and the tire pressures increasing - I think this is real.

The more contributions we get from others the better we should be able to start seeing trends and ascertain what is more important as independent variables - tire pressure, temperatures, etc. We just don't have near enough sample size now.

[Max Well]

Oh, and I meant to ask, sor, how are you finding the RPM when in EcoPro? I scrolled through the lower instrument panel options, and I tried looking at the dash monitor Sports gauges but they only showed torque and HP. I see ando had RPM as well, so I must be missing something somewhere.

And next up, I want to simulate kozzi's settings of 74.9 mph and Sport+ to see what kind of mpg I get, to at least try to make the known variables as close as possible.