• Dec 28, 2009
Are there any among us that wouldn't prefer a meaningful boost in fuel mileage from our current car or truck, all other things being equal? Sure. And the good news is that there are a couple of easy ways to achieve that laudable goal, starting with adding stop/start technology to the car's powerplant.

In case you're not familiar with the fuel-saving tech, we're basically just talking about automatically shutting off the engine when it's not needed, which requires little more than some computer controls along with a slightly more powerful battery and starter motor (though some systems are admittedly more complex). Not exactly rocket science, but at an estimated cost of $500 per vehicle, it does cost a rather substantial amount. Either way, it does sound pretty intriguing, right? So, why don't we see more of these cars in the States?

You can add head Mazda engineer Robert Davis to the list of those who think stop/start should spread throughout the States and according to Automotive News, and he's got a theory as to why it hasn't: the Environmental Protection Agency's fuel economy testing procedures. Naturally, an engine needs a chance to idle for the stop/start-equipped car's computer to switch it off, and the EPA's current test cycle only allows that to happen one single time.

We don't know about you... but our city driving patterns usually include way more than one single stop. By way of comparison, the Japanese city cycle is programmed to allow the engine to idle much more and cars with stop/start technology boast a significant mileage improvement – from seven to nine percent, according to Davis. Besides, most of the start/stop systems we've sampled on foreign-market cars include an override button for those who find the technology objectionable.

So, if there's a problem with the way the technology jibes with the government's testing methodology, what's the solution? The EPA is currently accepting public comment and is seeking input on how to modify its fuel mileage testing procedures. Davis is calling for an "industry wide" agreement on a procedure that would help highlight the benefits of stop/start technology. Is that the right direction to go? Feel free to sound off in the comments.

[Source: Automotive News - sub. req.]


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  • 58 Comments
      • 5 Years Ago
      It should be optional. I wouldn't pay $500, or even $100 for it, because it would never save me that much fuel. In my 13mi commute, it would never shut off. The only place this saves fuel is stop/go traffic, in extremely congested urban areas. The majority of us who don't drive in those conditions won't benefit from this niche technology.

      • 5 Years Ago
      Hrm, I'd like to see the EPA's rebuttal. Anywho, what a shame. the A4 with this tech (tdi of course) is putting out better numbers than the prius (by 1mpg). Pretty much every automaker seems to be employing it in europe and i've heard numbers from 10 to 15% savings in fuel economy, not bad for a simple revamped alternator... and I'm guessing that's why millions of cars have it now, ranging from econoboxes to performance models.
        • 5 Years Ago
        @zamafir:

        I'm with you 100%. The EPA testing cycle was updated not too long ago, but it's just not appropriate for some of the new(er) tech. Failing to account for EVs, series hybrids, stop-start, etc. isn't laziness or oversight, it's just the EPA being behind.

        If a manufacturer has the technology and has a decent pricepoint for deployment, then they should offer start-stop anyway. The EPA is going to revamp their testing cycle anyway, so what does it hurt to get ahead of the curve?

        • 5 Years Ago
        *starter motor
        • 5 Years Ago
        Yeah, I too would like to hear their response. Seems a bit ridiculous to me if this really is the case.
        • 5 Years Ago
        In all honesty it could be like the VOLT scenario, said tech has never been tested before, the EPA is a bit bureaucracy, it'll take a moment or two to adjust. But really, last i heard these thins cost automakers $60-300 per car which isn't that bad... I don't get why the better off luxury brands don't just include it right now... even if testing doesn't report the advantage. People buy TDI's knowing they'll get close to 50 on the highway even if the EPA testing cycle says 40.
      • 5 Years Ago
      What is interesting is that I found information about this on fueleconomy.gov:

      http://www.fueleconomy.gov/Feg/tech_engine_more.shtml#isg

      Integrated Starter/Generator (ISG)

      These systems automatically turn the engine off when the vehicle comes to a stop and restart it instantaneously when the accelerator is pressed so that fuel isn't wasted for idling. In addition, regenerative braking is often used to convert mechanical energy lost in braking into electricity, which is stored in a battery and used to power the automatic starter.
      Potential Efficiency Improvement:
      8%
      Savings Over Vehicle Lifetime:
      $1,800*

      LouisJ @ http://www.providagroup.com
        • 5 Years Ago
        This is the same as GM's "mild hybrid" system.
        • 5 Years Ago
        @Guevara

        This thing your calling efficient dynamics by BMW looks like a recent development. The GM PHT (Parallel Hybrid Truck) was released 5 - 6 years ago. Check YOUR facts.
      • 5 Years Ago
      I don't understand....In the "city cycle", the reason traditional cars get lower MPG's is because of all the "stopping" and starting at lights etc. How can EPA simulate that, and get the results they do, if the car only "stops and starts" once?. If that were true, city mpg's would be higher, as most hybrids do. fuel efficiency at a constant 25-45 mpg is much better than at a constant 60 or 65, with 45 to 50 being the best.
        • 5 Years Ago
        Lower speeds with numerous deceleration and acceleration events. The EPA city cycle isn't a constant 25-45mph as you claim.

        Even if you only stop and start once that doesn't mean you are going to achieve higher mileage when you are running a test that has you moving up and down the speedometer several times over the given course. Purely starting and stopping isn't what gets you lower mileage in the city, it's the accelerating that does it. It's all physics, once the car is in motion (i.e. on the highway), it is easier to keep it moving, getting that same car up to speed though takes much more power (and burns more fuel).

        Here's a quote from C&D magazine which describes the city cycle,
        - "The first test cycle, which sought to mimic rush-hour traffic in downtown Los Angeles with an average speed of 21 mph, is called the FTP, or city cycle, and is still in use today. This dyno test is 11 miles long, takes just over 31 minutes to complete, involves 23 stops, reaches a top speed of 56 mph, and has maximum acceleration equivalent to a lazy, 18-second 0-to-60-mph run." -
        http://www.caranddriver.com/features/09q3/the_truth_about_epa_city_highway_mpg_estimates-feature/measuring_fuel_economy_page_2

        According to that, there are multiple stops, however, I'd guess they are simple starts and stops with little to no idle time for a start-stop system to be effective.
      • 5 Years Ago
      how about actually driving in a real live city like New York to test its city numbers which are never accurate.
      • 5 Years Ago
      The EPA rules are made by those who will benefit from them. The technology itself doesn't matter to the EPA, laws do. GM brands like Chevy rely on having that 1 mpg advantage in their ads so they can say they are the best at something because when real cars with actual advances in technology that actually perform better and waste less is so hard for little old GM to compete with.
      • 5 Years Ago
      We do have start/stop, I know because I read it on AB.

      http://green.autoblog.com/2009/03/21/u-s-porsche-panamera-will-get-start-stop-active-aero/

      Start-stop sucks. Period. It's okay on a hybrid where you have an electric motor to start the car moving while the engine cranks, but for regular gas cars it's terrible, it ads a hesitation at a light that no one finds helpful.

      I do think it's bad that cars are idling at lights, fast food drive throughs, whatever. But that doesn't mean we should make the driving experience suck. If we can't make start-stop work well, essentially seamlessly, then we don't need it at all.
        • 5 Years Ago
        I didn't believe in the tech till I drove a BMW 120d and well... hesitation, what hesitation? In normal driving the car is quick and fast, frugal and I couldn't even tell that the engine would turn off at the lights.

        It's a great system for normal cars. For a Ferrari, I doubt it'll be useful but then again, I don't think they give the option for StartStop do they?
        • 5 Years Ago
        "it ads a hesitation at a light that no one finds helpful."


        A 0.3 sec hesitation? Big deal! Really...what a burden, you're slowed down by .3 seconds on your way to the supermarket *whine*.

        And next, you'll say that a car needs at least 300hp to be helpful?
        • 5 Years Ago
        I've never driven a car with this system, but I already don't like it. Driving a non hybrid car with stop/start would make me uncomfortable at best, especially when I'm at a red light and my engine is turned off for some reason. Hope it turns back on when I touch the gas... I will be clicking the disable button for the system.
      • 5 Years Ago
      And this is just one of many reasons why laboratory tests (and mathematical formulas) isn't as realistic as real-world numbers.

      But I do have to agree with the comment above that if the manufacturers made a stink about this technology, the EPA would in fact find a day to account for it in their testing. Of course that brings me back to my original point is that they would probably add in some kind of "fudge factor" - like say, add 5% to the city number and 1% to the highway number - rather than do real-world testing.

      I also think that the few car makers that do have stop-start technology here in the US, should be applauded for bringing over something that won't "officially" help their EPA numbers, but does help their customers.
      • 5 Years Ago
      I'm still not totally sure how stop/start would work on a gas only vehicle, especially one equipped with a proper manual transmission. I stop at a red light and my engine idles then turns off, the light turns green, then what? Does the engine re-engage as I touch the gas pedal, or as I start letting off the clutch? All to gain an extra mile per gallon in a car that already gets over 30mpg, doesn't sound worth it to me.
        • 5 Years Ago
        Actually, in a stick it works pretty well. At a light you put it in neutral and let out the clutch. Then the engine stops. When you depress the clutch so you can put it back in gear it starts the engine again.

        It's on automatics that it doesn't work as well.
      • 5 Years Ago
      Adopt UNECE regulations.
      • 5 Years Ago
      The main problem for the US is, that it does NOT work with automatic (no pressure or the transmission). Now BMW has a new system which keeps the pressure on even with the engine off, but I think just with the 8 speed auto.
      • 5 Years Ago
      I would like the stop/start function as an option, and even then, have it so the owner can enable/disable it when he desires to do so.

      A) I'm not sure this tech is good for the engine in cold weather states where the engine will be turned on and off before the engine and engine oil can reach operating temp.

      B)Again, cold weather hurts the battery. In an urban enviroment with a lot of stop and go starts, will the alternator charge the battery enough while it is running to make up for contant engine start and stop durring extreme cold.

      C) Great for new cars, probably not great for when the car is 10 or 15 years old. I can see this causing stalled cars in traffic that the computer cannot re-start easily or quickly because the engine is worn and tired (again amplified by cold weather).

      I'm sure the computer will monitor battery condition and might even disable the feature if a check engine light is present, but again there are a lot of ifs with this and I would like the option of having the system, not standard.
        • 5 Years Ago
        And current EPA regulations discount any device that can be readily disabled/removed by the consumer. Any allowance for being able to turn off the feature would eliminate any benefit under the existing guidelines. More evidence that the current rules are flawed. 95% would just leave it be, but because some might turn it off, we'll just eliminate the benefit for everyone.
        • 5 Years Ago
        @Jimbo: So basically this tech will be useless in the southern states, where it is normal to run A/C for 95% of the year?

        I also wouldn't want it to be turning off my AC when it's 115 degrees out, or even 85 for that matter.
        • 5 Years Ago
        Just like hybrids, the start/stop technology would likely be disabled by the engine computer until the engine reaches operating temperature. The bigger question mark to acceptance would be engine-driven accessories like air conditioning would perform. Of course, the computer could also disable the start/stop if the A/C is compressor is in use.
        • 5 Years Ago
        the start/stop technology is more of the mild hybrid kind from what I understand. There are no alternators. Instead you have an electric motor. The battery is heftier to handle the power demand (maybe an alternative to the acid battery is used)

        Atleast this is what I understand it. Maybe I'm wrong.
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