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

http://ecomodder.com/forum/attachmen...1&d=1383318583

Admin note --

this discussion originally came from here: http://ecomodder.com/forum/showthrea...age-27384.html

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If you've eco-driven / hypermiled a range cars and have compared the ability of manuals vs. automatics to beat their EPA ratings, then you have probably seen that manuals typically trounce the EPA city ratings by a much bigger margin than automatics, even without using advanced hypermiling techniques like pulse & glide or engine-off coasting.

Why is that?

That's what this thread is about.

(Note: we're talking about city/combined driving here, not highway driving. Don't think because you can trounce a manual's EPA rating in the city that you can necessarily beat the equivalent automatic car in real world driving (cruising) on the open highway. On the highway, it all comes down to gearing, and if the automatic is geared significantly "taller" than the manual, it might win.)

I've done a bit of searching on this...

Not surprisingly, test drivers performing an EPA certified fuel economy/emissions on a dynamometer must accelerate & decelerate the vehicle at precisely defined rates.

They essentially stare at a compter screen hanging in front of the windshield and follow a trace, trying not to "colour outside the lines". It's a big video game. (Deviate from the prescribed speed by over 2 mph, and the test is thrown out.)

This is easy with an automatic: Put it in "D" and work the pedals.

When testing a manual, though, the driver is instructed on the computer screen exacty when to upshift or downshift.

Source: The Truth About EPA City / Highway MPG Estimates
Car & Driver, August 2009, by DAVE VANDERWERP

So there's our answer in a nut shell. And it explains why there's a much bigger opportunity to trounce the EPA in sub/urban or combined driving with a manual than with an automatic.

But what I didn't find (and I'm not going to keep searching right now), is just how the shift points are determined.

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UPDATE, Nov 13 -- Found the answer. In current EPA testing, shift points are provided by the manufacturer. See post #17 for description & link to source.

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I've found references that at various times in the past, the EPA used:

(A) Pre-1976 ... exclusive use of universal shift points for all vehicles based on speed thresholds: 1st to 2nd @ 15 mph; 2nd to 3rd @ 25 mph; 3rd to 4th at 40 mph (source)

(B) Vehicle-specific shift points as provided by the manufacturer (which, predictably, led to MPG boosting shenanigans like skip-shifting and/or lugging the engine);

(C) Vehicle-specific shift points that were based on a percentage of max engine RPM or bracketed the engine's torque peak (maybe... that one was part of an old comparison study on the subject);

(D) Shift points based on a vehicle's dashboard shift light/indicator;

(E) Shift points based on research of how actual drivers shifted;

(F) Some combination of the above.

But I didn't find anything definitive for current testing.

http://ecomodder.com/forum/attachmen...1&d=1383244832

Source: EPA-AA-SDSB 81-8
A Summary and Analysis of Comments Received in Response to the EPA/NHTSA Information Request Regarding the Effects of Test Procedure Changes on Fuel Economy
By: James Hourihane, Glenn D. Thompson and Edward LeBaron
November 1980

I wonder how much variation there is from test to test, and how many runs they do.

The C&D article said there's little variation, even with hybrids: "the EPA claims the results are repeatable within one to two percent."

Don't know how many runs they have to do, though.

From what I know, it's a set shift point (like you said... we don't know if it's set by the EPA, calculated per vehicle or set by the manufacturer). If the vehicle has a shift indicator light, the tester follows that. If it has skip shift, then the tester is forced to skip shift, so the tester follows that.

I would think shift points should be matched to the automatic. Of course, the CVT could cause some difficulty in precision, and if there is a difference in gears, it could also make an issue (4 speed auto vs 5 speed standard).

I am uneasy on the statement "the EPA claims the results are repeatable within one to two percent." because of the posts on the sticker.http://blog.truecar.com/wp-content/u...-monroney1.jpg

It had the estimates as the average between the high and low results for the sections. So if they ran the EPA tests, wouldn't it be more like 17-19 City, showing 18, rather than 14-22 showing 18? This is under the impression there is one test, not 10 tests with different variables, and the results all mixed up and used to calculate it.

"expected range for most drivers = 14 to 22 mpg"

That's the standard "Your mileage may vary" disclaimer, not the test results.

Edit: I pulled out my calculator and both the city and highway ranges are +-20% from the epa number.

Think I'll split the EPA/shifting discussion into a new thread. It's interesting in its own right, and I can see people searching for this topic...

So they should all be uniform, I would guess.

Stickers
2011 Toyota RAV4- 22 (18-26)/28 (23-33)
2011 Subaru Outback- 18 (14-22)/25 (20-30)
2012 Subaru Outback- 22 (18-26)/29 (24-34)
2012 Ford Mustang- 19 (15-23)/31 (25-37)
2012 Chevrolet Cruze Eco- 28 (23-33)/ 42 (34-50)

At first it seemed uniform, but it seems like there are other variables than just giving a +/-4 range for city, +/-5 for highway.

I edited my post above, but it's +- 20%. A couple of your examples are off by a rounding error, so I'm guessing they start with the unrounded number.

Ah, that would explain the deviation. I see, that is rather disappointing- I always assumed there was some basis other than just a percentile, it seems pointless this way.

Some interesting points:

"The EPA has a specialized company manufacture small batches of consistent fuel, which is 93 octane (cars running 50-state certifications get a slightly different, 91-octane “California” blend)." <--and no mention of 10% ethanol

"The EPA tested the M5 in both 400- and 500-hp modes and found no difference in the amount of fuel used. The demands of the test cycles never call upon all the M5’s horses anyway. And the Honda Insight’s econ mode—activated by a dash button and claimed to improve fuel economy—registered no effect, either. It relaxes throttle response, so the test driver simply compensates with additional throttle to achieve the required speeds. However, GM’s skip-shift device, found in the Corvette among others, irritates by forcing the driver to shift the manual transmission from first gear to fourth at low speeds and was developed precisely to improve fuel economy on the test cycles. It was approved by the EPA, i.e., not considered cheating."

"In 1998, all the major players in heavy-duty diesels (Caterpillar, Cummins, Detroit Diesel, Mack Trucks, Navistar, Renault, and Volvo) were cited for an engine-control strategy that leaned out the air-fuel ratio at steady highway speeds, which boosted fuel economy at the expense of NOx emissions. The EPA slapped those seven manufacturers with what it called the “largest civil penalty in environmental enforcement history,” a total of $83.4 million in fines." <--So this and other posts I've read on here basically lead me to believe that "lean-burning" is an easy and excellent way to save fuel, but raises NOx emissions, so automakers barely implement it?

"Don’t even think of comparing EPA figures with stand*ardized fuel-economy tests from other countries because the test cycles are very different. For example, the European highway rating, called “extra urban,” is higher than the EPA’s by about 30 percent, so a rating on that cycle of, say, 60 mpg, would be closer to 40 in this country. The mainstream press, not realizing the difference, often complains that automakers refuse to bring efficient models here when, in fact, they may not be all that efficient when measured by U.S. standards." <--Euro cars can get 75+mpg. Even dropping that down to U.S. mpgs would still be better than most cars sold in the USA.

I'm quite certain they just use the 15-25-40 shift points. My car weighs under 1 ton and has a puzzling 22mpg city rating. The Lotus Elise I think is rated 21 and that thing is another 200 pounds lighter and has a 6 speed transmission with 5% higher revs in 1st gear. Same with the Celica GT-S, which has the same drivetrain more or less (lower mpg rating all around despite more gears and an engine that's within 2% of the same efficiency).

One day I had Torque up on my phone while in heavy traffic and noticed that rolling in 1st gear my fuel economy was typically a bit under 20 mpg, and decreases substantially past 3000rpm. In 2nd, it's in the high 20s, and in 3rd it's in the low 30s. Seeing that the whole city test happens essentially in gears 1-3, basically what's going on is that they're getting maybe mid 20s steady state and then lose some gas mileage to decelerating and accelerating, and you arrive at your low 20s.

If they just shifted at 2500rpm instead (that would be like, 12-20-27) there would be no way to get under 25mpg in this car.

Note that that is for diesel trucks, not gasoline engine automobiles. Only Renault & Volvo even make cars.

The action was in 1998, yet the 2000-2006 Honda Insight implemented lean burn in a gasoline engine, and quite successfully.

This is because the Insight is equipped with a special NOx catalyst.

I'm going to drop a line to my buddies at Transport Canada and see if they can find anything on the topic. I never thought to ask about this while I was in the dyno cell at NRCan but I remember wondering about it as there was a Cobalt SS Turbo in line to get tested and it had a 6 speed manual.

Thanks! I submitted a message via the "Contact Us" form on the NRCan site as well. We'll see what happens.

It would be nice to get some current information on this topic.

Found: manual transmission testing rules; it's not "blanket" rule based on speed
 

Re: the question to NRCAN, the Canadian department responsible for fuel economy testing here. I just got a reply with a link to the answer in the U.S. as well:

Here's the text from that link, current as of November 8, 2013, with the manual transmission bits highlighted:

Whilst all of this research is great, it might also be worth noting the effect of oil etc. - makers have been known to submit cars with lighter engine and gearbox oil for test in the ECE (aka EU EPA) ratings. I would find it hard to accept that US makers / importers do not do the same thing.

My last car an Aygo was in the £20 car tax bracket for CO2 emissions, cars registered 6 months later were £0. The only difference was 0w20 vs 5w20 oil and perhaps several submissions for test until one made it.

Manual Shift Mileage
 

I'd like to hear more manual shift strategies that work to beat EPA numbers. I have a 2000 Miata 6 speed that pretty easily beats the EPA numbers, at least in city/suburban driving in the 30-45mph range. Miatas are not optimized for mileage. The don't pull well at low RPM, they have hair trigger throttles, and they have very low gearing and in particular no long highway gear even in the 6 speed. I use a Scan Guage II and in town what helps me a lot is the ability to run along in a very high gear for the speed and periodically lift the trottle in gear to get the fuel to shut off. I can get 33-36MPG in suburban driving doing this and short shifting. EPA is 24 city/29hwy. At higher speeds with the low gearing the rapid deceleration from the low gearing makes this less useful because you lose too much speed compared to coasting.
A peculiar thing I notice at highway speed is that it gets better mileage around 70MPH than in the 55-65MPH range and this is despite turning 3,500 rpm at 70MPH. Long trips at 70 yield 32-35MPG while trips at 55-65 are typically in the 29-31MPG range. I had an earlier manual shift 626 that behaved the same way at highway speeds.

Pulse and glide. Its work, but it... works.

Hi, David - welcome to the forum.

As far as shifting strategies, get into the highest gear you can, as soon as you can. Next: coast in neutral rather than engine braking or using the friction brakes depending on how much deceleration you need. Those are the two major differences between how the transmission is used in the EPA tests, and how you can use it.

Sounds like you've got a decent handle on things in town driving already.

You could of course also investigate pulse & glide (engine on or off on the glide), but that's an advanced technique that is arguably mechanically harder on the car, bothersome to the driver/passenger, potentially dangerous (depending on your skill) or illegal (depending on jurisdiction), and may not be appropriate when driving in traffic. But there's no doubt it would raise fuel economy even more.

Colour me respectfully skeptical on that claim. I suspect other factors were affecting your results than cruising speed. This thread shows repeatedly for all types of cars that the slower you can cruise in top gear, the better. I doubt there's anything special about the Miata that makes it an exception to the rule:

http://ecomodder.com/forum/showthrea...you-15182.html

cheers-
Darin

Yep - pulse and glide is the best way to deal with high-revving gears. I'm at 3300 rpm at 70, similar to your 3500. Is it possible to change the rear-end gears on a Miata?

Manual Shift Strategies
 

Darin, on the last point it's the 55-65 mph mileage that has always seemed low to me - not so much that the higher speed numbers seem high. Scan Guage shows more spark advance in the higher ranges, but not much - that's pretty load sensitive, too.

Other (non-Miata) Mazda owners have claimed the same. Has something to do with engine programming, I suppose.

Wait you get 60mpg with stock gearing??? :O holy ****. How long are your glides? I feel like I can never glide very much since I lose speed super fast and my gears are even shorter (3800 at 70) resulting in ultra short pulses so I gave up on P&G, I just glide when there's a significant downhill grade. Also my brake booster runs out of vacuum after 1 application of the brake pedal so I usually don't engine off down a hill in any situation.

Maybe it's time to try engine off...I was going to regrind my intake cam to lower idle and low rpm pumping loss but I decided not to after realizing it would cost almost 2000 dollars after installination.

Interesting. Bears investigating!

David - I know a guy who has a Miata - not sure which year it is, though. Is this something that applies to certain years/engines?

Serial, I think you need to reread the earlier threads.
I have no experience with other year Miatas though looking on Fuelly at people who report their Miata mileage, I'm doing better than most.

Miata BSFC?
 

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?

Others who report it are owners with FSDE engines (FWD 2.0... completely different engine series)... who claim 65 is better than 55... though I personally get good economy doing merely 50... so take it with a grain of salt.

Re- MX-5 economy at speed - MPG displays become less accurate with increases in speed.

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.:)

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.

widespread manual transmission advantage
 

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

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

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

Interesting!
 

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!:)

Car review pet peeves
 

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:

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

Mirage CVT vs. 5-speed MPG real world
 

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.

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

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).