By on February 5, 2009

 

The vocabulary used to classify hybrid drivetrains has been lagging considerably behind new developments, as Wikipedia’s article on the matter proves. The old parallel, serial, mild and plug-in hybrid categories do little to illuminate public understanding of the underlying technology, and much to confuse it. Enter the BYD Dual-Mode, VW “Twindrive” and, now, the AVLTurbohybrid”. With cooperation from BMW, Bosch and LuK, AVL has developed a mild-ish hybrid drivetrain. The consortium claims it’s cheaper and more fun to drive than a “full hybrid” while offering nearly the same efficiency. Care to deep dive?

The system is built around a turbocharged, direct-injection 1.6-liter engine (tuned for a flat torque curve) coupled to a long-geared manual transmission and a clever electric drive strategy. Electric power replaces low-end torque lost to tall gearing. AVL also claims that turbo overboost maintains a steady charge. Even if you only have, say )slowly), a 15kW double layer capacitor module instead of a lithium-ion battery, you don’t loose [sic] no juice. 

Still awake?

That’s how the boffins rolled during testing of their Stage One (v1.0?) system. Even without regenerative braking or a high-capacity battery, AVL claims that its BMW 320i mule was 24 percent more efficient (NEDC) than a stop-start equipped, naturally-aspirated 320i– at an estimated 150 percent of the price.

And though that doesn’t sound great, a certain unnamed 1.5 liter power-split hybrid (Prius) offered only 36 percent better efficiency than the NA 320i at (again, estimated) 300 percent of the price (to produce, of course). Those BMW badges are expensive.

Anyway, the kicker (claims AVL): the Turbohybrid 320i is more fun to drive than either a weedy NA four-banger Beemer or a Prius. And that I buy.

Check out their release for graphs of elasticity, tip-in, and other “fun to drive” proving stuff.

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15 Comments on “Turbohybrid Beats The Battery. Sort Of....”


  • avatar

    Wouldn’t anything be more fun to drive than a Prius? At least if you prefer to watch where you are driving instead of the damn dashboard.

    –chuck

  • avatar
    PeteMoran

    Are we returning to the PC/XT PC/AT days of having everything marketed with a “Turbo” label????

  • avatar
    NulloModo

    What I get from this is that automakers are finally getting into rethinking the basic design of powertrains, which has to be a good thing. There are likely to be as many if not more misses than hits, but R&D is never wasted money.

    Pete –

    I thought those ‘turbo’ buttons has to do with certain early applications being designed with the clockspeed or processing power of the CPU almost hard-coded in, and thus the button was necessary so that one could turn off the ‘turbo’ in order to get older apps to run properly.

  • avatar
    Kyle Schellenberg

    I used to drive an Acura Integra that would rev at 3500 rpm at 65 mph. My friend had an mid-80s Jetta (4-speed I think) that would rev at 4200 rpm at the same speed.

    Multi-speed transmissions (6,7,8) provide a gear ratio that gets you off the line and a top gear that gives you a relaxed engine at highway speeds. The concept of adopting taller gear ratio across the range supplemented by battery boost for the loss of power is an interesting way to get fuel economy gains. Probably even better with a CVT.

    I know that Ford has been talking about moving to 4 cylinder turbos as a more fuel efficient option to 6-pots. Maybe turbos will make a comeback.

  • avatar
    westhighgoalie

    **Even if, say, you only have a 15kW double layer capacitor module instead of a lithium-ion battery**

    That sentence just gave me diabetes.

  • avatar
    tedward

    Interesting. I wonder if it could be combined with that steam system that BMW has been working on.

    Either way, keep the manual equipped for eventual production and it might actually be worth driving. Just say no to CVT.

  • avatar
    Eric Bryant

    Boy, if I’m reading things correctly, then the AVL system is a rather straightforward implementation of a parallel hybrid scheme. It’s clever and appears to be fairly simple, and thus probably makes a lot of sense. Simple hybrids (start-stop “micro” hybrids and parallel systems like the above) will likely be mainstream technology in five years; as indicated by AVL’s numbers, the value proposition of these simple systems is hard to beat.

    If we’re going to start dubbing something as a “turbohybrid”, then the Cummins exhaust waste heat recovery system should be first in line. It uses excess exhaust manifold heat to flash a refrigerant from liquid to gas, which then powers a turbine connected to a generator, which in turn passes power to a flywheel-mounted electric motor. Pretty slick, and it can give an extra 20 HP from a 500 HP engine at full snort by employing heat that would otherwise exit the smokestack.

    Honorable mention to Woodward Governor and Detroit Diesel, both of which have mechanical systems that take excess exhaust energy and place it on the crankshaft.

  • avatar
    PeteMoran

    @ tedward and NulloModo

    I wonder if it could be combined with that steam system that BMW has been working on.

    Turbosteamer?

    It’s what I feared; everything will have Turbo in the name even if it’s a button that does nothing or just appears in marketing.

  • avatar

    What if Toyota switches the Prius to a direct injection turbo engine? Would it gain another 20%?

  • avatar
    menno

    The British diesel engine manufacturer (Gardener, I think it was) produced a compound turbo-supercharged diesel for bus and truck (lorry) use in the 1960’s.

    The belt-driven supercharger was also connected to the hot side of a turbocharger. Under low engine speed conditions, the supercharger and turbocharger didn’t do much, at low-mid-range the supercharger boosted as well as helped to scavenge the exhaust side for more power, and at high engine loads, the turbocharger not only aided the supercharger, but put power back into the engine via the supercharger belts! If you can imagine all of that.

    So take something similar (but on a small diesel or gasoline engine), put it in a car (with emission equipment and an intercooler for the turbo-supercharger), and the turbo-lag would be “gone” just like that.

    Now take the gearbox out, put a small hydraulic hybrid system into place (kind of like hydrostatic drive on a rider lawnmower), plus a nitrogen filled ball which could act as a hybrid system energy reservour, engineer some electronic controls and a computer to run it, program the engine to start/stop, and you’d have Pruis like efficiency from a car costing very little more than a conventional turbocharged gasoline or diesel car.

    It’s all do-able. Plus, it lends itself nicely to “right-wheel-drive” since there would obviously be no driveshaft, but only a couple of high pressure lines between the front drivetrain/hybrid system and the rear combination hydraulic motor/regen pumps.

  • avatar
    PeteMoran

    @ EJ_San_Fran

    What if Toyota switches the Prius to a direct injection turbo engine? Would it gain another 20%?

    I wouldn’t expect so on the turbo front. A turbo engine is useful if you require more torque/power from a smaller displacement. They add complexity, weight and they aren’t fuel efficiency devices.

    I can’t think of a good reason why Toyota wouldn’t use DI in the new 1.8L Gen 3 Prius NZ engine however. It might be because DI has it’s greatest benefit for variable RPM applications. The Prius engine operates in a fairly narrow RPM range for a petrol engine. Maybe “regular” fuel injection is just fine.

  • avatar
    psarhjinian

    Anyway, the kicker (claims AVL): the Turbohybrid 320i is more fun to drive than either a weedy NA four-banger Beemer or a Prius. And that I buy.

    Yes, but that’s not really fair. The Prius is designed for fun in the same way a Maytag is. I other words: not at all. You could drop a three-hundred horse turbo four in the Prius and it still wouldn’t be fun.

    The vocabulary used to classify hybrid drivetrains has been lagging considerably behind new developments, as Wikipedia’s article on the matter proves. The old parallel, serial, mild and plug-in hybrid categories do little to illuminate public understanding of the underlying technology, and much to confuse it

    This is a “mild” system akin to BAS (GM) and IMA (Honda). There’s no wild new paradigm: it’s a motor that sits between the engine and transmission and turns the crank. The “new hotness” comes from a less low-rent ICE, which isn’t really that special at all.

    You have parallel (where the motors and engine run independent of each other), series (where they don’t, and which is what this is) and mild, which is really a form of series that does nothing except act as a big starter. Wikipedia is right and the PR fluffery is wrong.

    Call me when we’re making gas/battery/hydraulic hybrids or somesuch.

  • avatar
    psarhjinian

    Are we returning to the PC/XT PC/AT days of having everything marketed with a “Turbo” label????

    Side note: that “Turbo” button existed to throttle the processor clock down so that badly-written programs that timed themselves via the 4.77Mhz (ouch) clock in the original PC—instead of the RTC clock, as they ought to have—wouldn’t flake out at being run at the breathtaking speed of 8, 12 or 16MHz.

    On later PCs (386s and such) that couldn’t throttle down that far, though, it was a “feel-good” button.

  • avatar
    PeteMoran

    @ psarhjinian

    I recall the term lingered long after the button did nothing. The “turbo” word seemed to make it’s way into everything else at the time too. It was a catch-all replacement for “super”.

    Here another example.

    “I’d even bought a vacuum cleaner because it had the word ‘turbo’ on it!”

    Ah… the memories…

  • avatar
    PeteMoran

    @ menno

    Hydraulic hybrids are interesting up’n’comers. One to watch for sure.

    The pros and cons as I understand it are;

    1. Excellent regenerative recovery compared to electric.

    2. Constant speed drive efficiency still significantly lower than direct drive via CVT from high pressure system heat losses.

    3. Limited alternate power source only range. You can’t store more than a few miles of hydrostatic pressure.

    4. Combined system weight in smaller applications is higher than electric. Looking good for heavy vehicles (Hino have a hydro/hybrid test bed with running gear courtesy of the forklift division probably).

    5. Packaging/drive component arrangement flexibility.

    Obviously all those things are being worked on – somewhere. I’m not aware of any of the major manufacturers pursuing it however.


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