Shift points: EPA testing of manual transmissions (why beating MT ratings is easier)

[serialk11r]

Originally Posted by kennybobby

3500 rpm at 70 mph => 2750 rpm at 55 mph. Would the load be so much better at 3500 rpm as to overcome the additional aero drag power and still beat the 2750 rpm BSFC?

Nope, the only time going faster saves gas is around idle, where engine efficiency starts getting really poor. Efficiency increases kind of linearly (then falls) with load, but the torque required to go faster increases as a quadratic function of speed.

[Mustang Dave]

Originally Posted by serialk11r

Nope, the only time going faster saves gas is around idle, where engine efficiency starts getting really poor. Efficiency increases kind of linearly (then falls) with load, but the torque required to go faster increases as a quadratic function of speed.

I proved last weekend that a 4-Liter Ford Mustang can get better than 34 MPG just by limiting freeway speed to 65 MPH. Most (non ecomodder) people are incapable of such results.

[jcp123]

My conversion van was the only vehicle which has ever given evidence that higher speed may be helpful...best tank ever was a stretch doing 70mph. Unscientific but...that's all I got.

[MetroMPG]

In a study by the AAA of how closely drivers' real world fuel economy matches vehicle EPA estimates...

Owners with cars equipped with manual transmissions enjoyed 17-percent higher real-world results.

...

AAA culled its data from an analysis of 37,000 records submitted to the EPA, and those records contained more than 8,400 vehicle make, model, and model-year combinations.

In the real world, fuel economy diverges widely from EPA estimates

[jedi_sol]

Originally Posted by ;483812

Owners with turbocharged engines, on the other hand, were the biggest losers. Owners of turbocharged V6 engines reported fuel economy 9-percent lower than estimates, and owners of turbocharged four-cylinder engines reported fuel economy that was 4-percent lower than expected.

I don't seem to suffer from this problem

City driving - stay out of boost, duh.

Highway driving - at 65mph is right at the cusp of boost. Therefore, drive 60mph to stay out of boost. Then for P&G I use shorts amounts of boost to get to speed a lot quicker = longer glides = increased average mpg.

3 Seconds of short boost acceleration only lowers my trip mpg by 0.1mpg vs 6 seconds of nonboosting acceleration can lower my trip mpg by 0.5mpg

[Hyperaboutmpg]

With manuals down to 8-10% of the U.S. Fleet, only the fleet epa mpg performance of the automatics matter! I never ran epa mpg tests, the auto cos. do it themselves. Only ran octane requirement increase data, and emissions dynamometer test. Of course u.s. Fleet economy matters, if it's not too late!

[MetroMPG]

I thought of this thread this week when I read a Canadian review of the new Nissan Versa sedan.

https://www.theglobeandmail.com/driv...eatures-in-an/ (might be behind paywall)

A reader responded to the reviewer's statement about how much more efficient the CVT rating is than the 5-speed manual. Reader noted that his/her real-world experience is that a manual transmission is still the way to go for best real world fuel economy.

RIGHT ON, buddy!! Was my response.

One of my biggest peeves in car reviews is how often they say something along the lines of:

"the CVT is terrible to drive, but at least it gets better fuel economy than the manual".

Nope! In the real world, it probably doesn't.

[MetroMPG]

As of today, Mirage owners have logged 6576 fill-ups over 3,279,170 km /
2,037,582 miles on the Mirage Forum fuel log.

• CVT drivers (97) are reporting: 40.2 MPG (US) = 5.8 L/100 km
• 5-speed drivers (103) are reporting: 44.5 MPG (US) = 5.3 L/100 KM

Going by the car's 2015 EPA ratings:

• CVT: 37 city / 44 hwy / 40 combined
• 5-speed: 34 city / 42 hwy / 37 combined

We see CVT owners on average are achieving the car's EPA rating, while 5-speed owners are beating the rating by 20% on average. That's a bit higher than the 17% advantage reported for manual transmission drivers in the wider AAA study.

[cRiPpLe_rOoStEr]

Originally Posted by MetroMPG

Pre-1976 ... exclusive use of universal shift points for all vehicles based on speed thresholds

Quite similar to what we're told to do at the driving schools in my country

[B440]

Originally Posted by jedi_sol

I don't seem to suffer from this problem

City driving - stay out of boost, duh.

Highway driving - at 65mph is right at the cusp of boost. Therefore, drive 60mph to stay out of boost. Then for P&G I use shorts amounts of boost to get to speed a lot quicker = longer glides = increased average mpg.

3 Seconds of short boost acceleration only lowers my trip mpg by 0.1mpg vs 6 seconds of nonboosting acceleration can lower my trip mpg by 0.5mpg

I see the "stay out of boost" statement often from Subaru owners, and while it seems to apply in your case, it's not universal. I owned a Jeep Renegade with the 1.4L Fiat turbo engine and it was nearly impossible to stay out of boost in any real world driving.

The Subarus have 2.0-2.4L engines that could be NA and still motivate the car (no boost). The Renegade would be a turd if the 1.4L was NA (no boost).