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Test drive of the Torotrak IVT (4)


by François Dovat

DRIVING

Engine at 1200 rpm the big Ford Expedition moves forward or backwards at will, cm by cm on the 25 % grade. It could make it until it runs out of fuel without overheating or wearing its transmission. Full throttle: it rushes forward, the revs quickly rising to 3600 before stabilizing gradually at 4200, speed at which the big V8 already pumps out all his power.

On the other hillside, the descent is as slow as wished, without brakes, shifter on R, the Ford even willingly and gradually restarting in reverse on demand. Then, on the oval of the Leyland Technical Center test track it accelerates as a plane taking off, its 265 hp not weakening until the wished speed is reached. When lifting the foot a 130 kph, the revs falls to 1100. They rise immediately again according to the required power, but without the slightest feel of delay in the pulling force.

Torotrak do not intend to re-teach the driving to the drivers. The tested prototype has a single program only, which simulate the behavior of an hydrodynamic converter. A creep identical to that of the production Ford AOD is programmed. However the passage of D to R or conversely doesn't produce any jerk… of course! The shift lever under the steering wheel remains that of the production vehicle with the P-R-N-D-2-1 positions. The last two provide an effective engine brake, the deceleration occurring with a perfect progressiveness. Whether it's in the traffic or on the track, the Torotrak transmission is extremely pleasant. The engine winds up in revs only if the driver asks for real power. Most of the times it revs at less than 1500 rpm and becomes virtually inaudible, but stays ready to pounce like an eager cat if necessary. The computer constantly chooses the optimal ratio and the driver is freed of any concern about what the transmission does or is going to do. In brief: sensational!

SOON IN PRODUCTION?

9 OEMs and transmission manufacturers acquired licenses, among which quite recently ZF Friedrichshafen AG and the Japanese tractor maker Iseki. It is said that several prototypes equipped with Torotrak transmissions are being tested on the road and the rumor runs that BMW might be the first car manufacturer to market the Torotrak IVT. The British firm equipped in 2001 some Chevrolet Suburban/Tahoe and Ford Expedition for evaluation by their OEMs, amongst them the one the author had the privilege to test drive. Those impressive SUV of 2.3 T are propelled by 5 to 5,4 liters V8s; their trials were satisfactory in every respects. GM declared the concept production ready, but prefers to leave the manufacture to specialized Tier 1s like Aisin AW. At least Getrag and probably ZF might also produce the transmission under license. Ford and ZF seem convinced of the advantages of the Torotrak IVT as it sprang out of recent official declarations.

The efficiency of this pre-production type would exceed the 91 % with a slip in the order of 1 %. If the ratio span of the variator itself reaches 5, it is widened up to the infinite (vehicle stopped) and inversion by the regrouping epicyclical gear set.

TOROTRAK

Founded in 1988 as a BTG department, the firm employs at present a hundred highly qualified persons and holds more than 250 patents. It took up the technology developed separately by different teams – notably Leyland Trucks – brought together the engineers and the competent executives, invested in a building and brand new installations involving notably a workshop equipped to assemble simultaneously 10 transmissions, 7 transmission test benches, 2 rollers test benches for vehicles, 4 vehicles lifts and an assembly hall. Its funds results mainly from the £ 50 million obtained in 1998 at a stock exchange flotation during its demerger from BTG.

Since the beginning of 2002 more than 300 engineers and executives of different OEMs and transmission manufacturers test-drove the prototypes during demonstrations in Germany, in Japan and at the factory itself. Torotrak engineers presented their latest developments at the CVT 2002 Congress in Munich and at the SAE 2003 Transmission & Driveline Systems Symposium in March 2003 at Detroit. They stated that the power recirculation in low regime had been greatly reduced toghether with a largely improved acceleration from standing still.

See : http://www.torotrak.com/technical_papers.html

ADVANTAGES

- Absolute progressiveness

- Outstanding creeping ability up and downhill

- Lightning fast transient response

- Relaxed driving

- Low revs in cruising

- Optimal engine use

- Mileage improved by 20%

DRAWBACKS

- Not yet in production

- Lack of a direct drive

- Power recirculation in low regime

(© François Dovat)
#110

Technical files

Idée & conception © 1999-2011 van Damme Stéphane.


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