Volvo S60 KERS Hybrid Prototype: Brief First Drive

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Volvo S60 KERS Engineering Prototype

Volvo S60 KERS Engineering Prototype

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Can you really improve fuel economy and performance just by taking a production car with a turbocharged 5-cylinder engine and adding Formula 1 race technology? 

To find out, we headed to Volvo headquarters in Gothenburg, Sweden to test-drive a top-secret prototype Volvo has been testing for the past year.

It's an ordinary-looking 2013 Volvo S60 sedan with an 80-horsepower Kinetic Energy Recovery System (KERS) bolted to the rear axle. 

The Basics

Unlike the regenerative braking found on cars with start-stop, hybrid or all-electric drivetrains, KERS is an entirely mechanical system which bleeds off the car’s kinetic energy under braking, transferring it through a continuously variable transmission and storing it as mechanical energy in a vacuum-encased carbon-fiber flywheel.

As a consequence, a car with a KERS system does not require a heavy-duty alternator or motor, complex power electronics or additional batteries.

Instead, the flywheel stores the mechanical energy for up to 30 minutes, releasing it when required to aid in acceleration. 

Behind the wheel

Approaching Volvo’s one-of-a-kind prototype, there’s a noticeable whine from the S60’s trunk as its flywheel spins with energy from the previous test drive.

That’s due to a lack of sound insulation, says Volvo. Being an engineering prototype and proof-of-concept vehicle, it’s a little rough and ready around the edges. 

Inside the cockpit, too, some obvious giveaways remind us we’re sitting in an engineering mule. Alongside the standard S60 dash, there’s a tablet PC mounted to the dash, displaying KERS status information, and the obligatory red emergency disconnect switch required of all prototype vehicles. 

To start with, our chaperone disengages KERS completely, so as to remind us of the stock performance of Volvo’s usual 2.5-liter Turbocharged five-cylinder engine. Accelerating quickly onto the test track thanks to 254 horsepower and 266 foot-pounds of torque at the front wheels, there’s nothing strange or unusual about driving this car. 

Volvo S60 KERS Engineering Prototype

Volvo S60 KERS Engineering Prototype

Enlarge Photo

Then KERS is switched on and placed into ‘hybrid’ mode, we enter head for a tight corner, and start slowing down. 

Somewhere behind the rear seat, we hear the sound of a jet engine crossed with a laser rifle and quickly realize KERS is spinning its flywheel up to an electronically-limited 60,000 rpm top speed. The sound is intoxicating, and a quick glance at the KERS system display tells us we’re recapturing somewhere around 30 kW of instantaneous power.

Exiting the curve and heading for a reasonably steep incline, we accelerate and notice the S60’s engine doesn’t roar as much as it did on entering the track. This time, KERS is doing some of the work and the gasoline engine is noticeably less strained. 

Cresting the hill and passing down the other side, we notice the T5 engine has completely switched off, coasting down toward the next corner. At low speeds, and when there’s enough stored energy, the prototype creeps along using just the flywheel-stored energy to move it along, starting the engine when more power is needed. 

Switch into ‘Sport’ mode, and KERS acts a little like a boost function, storing energy when the car is cruising as well as braking to release it under heavy acceleration. 

The result, Volvo says, is a 0-62mph time of 5.5 seconds, 1.5 seconds faster than the stock S60 T5. While Volvo’s tiny test track didn’t afford us much chance to test this, we can say the extra 80 horsepower boost from the KERS system gave the well-built Swede a sportier feel.

Meanwhile, the high-pitched whine as the KERS system charged up, combined with the way it pushed us into our seats every time it discharged encouraged us to squeeze the throttle to the floor at every apex, however short the straight.

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Comments (15)
  1. Any thoughts on how this considerable angular momentum affected handling when it was at full spin?

  2. done properly it should have counter-rotating drums to neutralize that.

  3. Wonder if the KERS vacuum fly wheel could be fitted to the front end of a Fiero using the GM X car steering, independent suspension, differential and constant velocity joints connected to the KERS storage unit. While the rear engine and transmission would remain independently operating. Has Volvo or anyone tried that? What else would be needed.

  4. Great to see you back at GCR

  5. The problem wtih KERS system is that you can't spin it up without driving/braking first. Then once you pull into your garage that spinning wheel is just a waste at that point. Not to mention the gyro effect on the turns or over the bump.

    However, it is more compact and lighter than the typical hybrid system. I am NOT sure this 60,000 rpm high speed wheel will last as long or cost less to service after some signficant miles.

  6. it may be better for delivery vans.

  7. So the first take off in a trip has no energy and the last stop is wasted., doesn't seem like a big deal to me. The only way that would make a big difference is if you literally make a trip with no stops and little speed variation. In which case you picked the wrong technology to save fuel with. Regarding the gyro effect, would it be any worse than the spinning crankshaft, gearbox and drive shafts?

  8. I don't think any of the powertrain parts that you mentioned spin at 60,000rpm. Assuming that KERS system actually holds some power, it will be a lot of momentum that spinning disk holds...

  9. True, but they do have a lot of mass. The article doesn't make mention of the weight of the flywheel, but it does give rpm and power so assume one of the engineers on here can deduce the weight from the other info. Would be interesting to know.

  10. LOL never mind, info was on page 2

  11. As a layman this would appear to be well suited for pickup trucks, capturing energy during braking and helping to get that heavy truck moving again at stop lights? Yes/No?

  12. Actually, it was hinted that a larger system could be used in Busses, where the duty cycle requires lots of heavy stop/start driving. Of course, it could also be used with any existing drivetrain: gasoline, diesel, electric, hybrid...

  13. Since it's fairly light, scale it down a bit and combine it with a regular electric hybrid system. Some components could be shared. Hard braking spins up the KERS, light braking charges the battery (and any ratio in between). Same goes for acceleration. Turn off the car and any remaining KERS motion charges the battery.
    For bonus points: let me plug the car in to an outlet for 30 seconds to spin up the KERS system to 100% before I leave.

  14. Rich, you're right. It could work that way. But in all honesty, I think any smaller and the system would cost more than the benefits it gives...

  15. For full hybrids, I'd reckon that instead of adding a whole new system (and lots of parts, plus soundproofing), it's probably simpler to beef up the electric motor(s) and complement the batteries with supercapacitors for whatever extra instantaneous power is desired.

    A typical bank of supercaps capable of supplying or absorbing 60kW (~80hp) weights only ~20kg (e.g.

    Re pre-charging this KERS: it'd take an ordinary 120V outlet ~5 minutes to deliver 150W*h, which then may be good for roughly 1/2 mile, saving like 5~10 cents in gas.
    I don't think many people would bother to either wait that long, or get some higher-power circuit installed (30s would require 240V 80A), for so little benefit.

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