Quick Drive: Honda Turbo Engines and Future Powertrain Tech
Replacing Displacement: The Power of Turbocharging
Honda recently invited us to its research center and test track at Tochigi, Japan, to preview a number of powertrain technologies the company is working on and which will likely see production in the future.
While we can only offer limited evaluations based on our one- or two-lap track test drives, we can give you an idea of what to expect from Honda’s future cars. Test drives included Honda’s new line of turbocharged three- and four-cylinder engines, a new eight-speed dual-clutch transmission with torque converter, a steer-by-wire system and a prototype vehicle built from lightweight carbon-fiber composites rather than aluminum and steel. All of these technologies are prototypes and are not production-ready.
1.0-liter Turbocharged Inline Three-Cylinder Engine
Envisioned as a replacement for small, naturally aspirated four-cylinder engines, this turbocharged I-3 makes 127 hp and 148 lb-ft of torque. That’s more than the 117 hp and 106 lb-ft from the 1.5-liter I-4 of the outgoing U.S.-spec Honda Fit. The difference is, the turbocharger gives this engine a better torque curve with more mid-range punch, so drivers won’t have to absolutely wring it out to get good acceleration.
We sampled this engine in a European-spec Civic hatchback, where it performed comparably to any other Civic-sized car currently on the market. Overall acceleration was about the same, but accelerating in gear, such as to pass, was improved thanks to the turbo torque. Top-gear acceleration, such as passing on the highway, was pretty good, though you needed to floor it to really move. The engine was generally quite smooth with very linear power delivery.
On the down side, this particular engine was in need of some more fine-tuning, as it would occasionally surge rather than accelerate linearly. A Honda engineer assured me, naturally, that this issue would be eliminated before the engine goes into production.
1.5-liter Turbocharged Inline Four-Cylinder Engine
Like the three-cylinder, this turbocharged four is meant to replace a larger four-cylinder engine, say something in the 2.0-2.5-liter range. With 201 hp and 192 lb-ft of torque onboard, it’s well-positioned to do that. Like the three-cylinder, this engine feels comparable in total performance to the engine it’s trying to replace but offers more punch in the mid-range. It also delivers very smooth, linear power. Go all the way to the floor and it’s even reasonably quick in a midsize sedan like our Accord tester.
On the not-ready-for-production side, we noticed the engine was rather loud under acceleration and could be coarse at low RPM, just off idle. We also noticed that our CVT-equipped tester was cruising at 70 mph at 2200 RPM, which seemed at least 500 RPM high. Honda again assures us these issues will be addressed.
2.0-liter Turbocharged Inline Four-Cylinder Engine
This engine is a different story. While it may be called in the future to replace a V-6 engine, our test vehicle was a European-spec Civic Type R and it was tuned for performance, full-stop. And what an engine it is!
With “275+ horsepower” and 295 lb-ft of torque onboard, this car was a riot. Hit the “R” button on the dash and at any RPM you get an impressively strong push back into the seat. That a turbo-four could feel this strong makes you giddy, and you keep flooring it just to get that rush again. The engine revs very quickly and pulls evenly all the way up the dial. In-gear acceleration is strong, but you’ll want to downshift just for that extra pull.
If we had complaints, they would be that it torque-steers a bit when you launch hard. Another is that the throttle is too sensitive in R mode. We also noticed the exhaust was a bit dark, meaning the engine will require more tuning to meet emissions regulations, which we hope won’t spoil the power delivery. We very much hope to see this engine just as it is in a U.S.-spec performance model as soon as possible.
8-Speed Dual-Clutch Transmission with Torque Converter
This sounds odd, so let us explain first. This transmission uses both a torque converter and a dual-clutch system. A typical dual-clutch transmission replaces the torque converter with twin wet or dry clutches. Honda’s transmission instead leaves the torque converter where it is and places the clutches on the two gear shafts, each controlling half the gears. Honda says this was actually quite easy to do because its automatic transmissions never used planetary gears but were more similar to automated manual transmissions, but with torque converters instead of dry clutches. This new unit actually weighs about the same as Honda’s old five-speed.
The reason for all this complexity is to get best-of-both-worlds driveability. While DCTs shift faster than conventional automatics and tend to be more efficient, they struggle with vibrations and smooth clutch engagement when starting from a stop. Honda therefore kept the torque converter and uses it to move the car smoothly away from a stop like an automatic would. The torque converter then quickly locks up and the dual clutches take over and do all the shifting. Thus, you get smooth launches and super quick shifts, as well as better efficiency.
In the real world, the prototype delivered on its promises. Leaving a stop was no different than any traditional torque converter automatic, with smooth acceleration and no hint of chatter or balkiness from the transmission. Once under way, the transmission changed gears lightening quick and so smoothly that we almost couldn’t feel them happen. Response to the paddle shifters was nearly instantaneous as well.
This prototype struggled, though, with some downshifts. While some were smooth, others were harsh and abrupt. Engineers grimaced and admitted the software needed more work to eliminate those instances. Absent that problem, this transmission seems almost ready for prime time and could offer a compelling alternative to balky DCTs and slow-shifting automatics.
With the advent of electric power-steering racks, steer-by-wire is the next logical step as cars incorporate more safety systems and we advance towards autonomous driving. Disconnecting the steering wheel from the steering rack allows automakers to reduce vibration transmitted into the cabin as well as correct for crowned roads and crosswinds, or simply steer autonomously, all without the driver knowing it.
Honda’s solution is a very good one. It’s first time out the door and still a prototype, but based on our time in the test car, Honda’s unit is hands-down better than Infiniti’s much-maligned (but recently updated) production system in the new Q50. Driving around a tight winding track in an otherwise stock Accord sedan, it feels barely any different than any of the regular electric power-steering systems found in production cars today. The only really noticeable difference is the complete lack of steering feedback and feel, as Honda hasn’t tried yet to simulate road vibrations in the steering wheel.
Steering response, even when driving hard, was very linear and it always felt like we were getting exactly the amount of steering at the wheels as we were commanding at the steering wheel. The steering wheel felt nicely weighted for a family sedan and the weight built naturally with steering input. In short, it felt like driving any other family sedan.
Aside from the lack of feel, the only other drawback was a lack of reaction during understeer. Normally, steering wheels tend to get light when a car understeers and you can feel the lack of grip. When pushing this prototype to the point of understeer, there was no change in the steering weight to signal that the front tires weren’t gripping. We hope Honda decides to simulate that effect in the future so that drivers will be more aware that they’ve exceeded the limits of grip.
Super Light Structure
Like all automakers, Honda is aggressively researching weight-saving technologies, as weight is the enemy of performance and efficiency. Naturally, that means the company is researching carbon-fiber and carbon-fiber reinforced plastics (CFRPs) as ways to bring down weight without sacrificing strength and, ultimately, crashworthiness.
To illustrate what they’ve learned so far, Honda built a CR-Z hybrid on an all-new carbon-fiber monocoque tub with aluminum sub-frames for the engine and front and rear suspension. Though not a drop-in replacement for the standard metal frame, the new carbon-fiber tub weighs just 176 pounds. Replacing the metal body panels with carbon-fiber and glass-fiber-reinforced thermoplastic pieces cut the weight of the body in half. The lighter-weight body and frame then allowed Honda to reduce the size of the wheel hubs, brakes, wheels and steering system as well, and further savings could be found in smaller tires and a smaller drivetrain. In total, Honda took 661 pounds off this CR-Z, a 30-percent reduction compared to stock. The engineers say that’s good for a 30-percent improvement in zero-to-60 mph acceleration and a 20-percent improvement in fuel economy, jumping it to a combined 40 mpg on the U.S. test, up from 34-37 in production cars today. We've tested manual-transmission U.S.-spec CR-Zs accelerating from 0-60 mph in 8.3 and 8.4 seconds.
Of course, this test car is a long way from production. The massive side rails of the tub make the door sills very high, so Honda installed what amount to power-operated T-tops in the roof to make more room for entry and egress. The seat is a racing bucket and the interior is only half-present. But, Honda says, it has a bone-stock drivetrain. That’s impressive, because it feels a whole lot quicker than stock.
Not only is straight-line acceleration improved, but throttle response is better across the board. Whether making a pass or powering out of a corner, the car feels like it has much more power and a more linear delivery. Upon entering those corners, the car feels more nimble and balanced, changing directions very quickly and in total control. We were able to place the car exactly where we wanted it on the road thanks to our confidence in its super predictable handling and response. It’s a shame this exact car won’t ever be for sale, as it’s a very fun little sports car very much in the vein of the vaunted Subaru BRZ.
While we may not get this exact car, don’t bet against seeing carbon-fiber technology in future Hondas. The engineers say they’re working on ways to speed-up and automate the construction process to make it viable for mass production. Currently, carbon-fiber must be laid by hand in a time- and labor-intensive process.