The HUMMER H3 | Part Three

HUMMER H3

HUMMER H3

Power, torque and Maximum Drivability

The 2008 HUMMER H3 is powered by GM’s inline five-cylinder Vortec 3.7-litre petrol engine.  This all-aluminium ‘smart engine’ is both high-tech and lightweight and is fitted with dual overhead camshafts, electronic throttle control and variable valve timing.  Specifically designed for this type of vehicle, it delivers 245 ps at 5600 rpm and 328 Nm of torque at 4600 rpm.  For superb drivability both on- and off-road, 90% of the engine’s torque is available across a broad rev-range, from 2000-to-6000 rpm.

The Vortec engine provides the H3 with excellent performance combined with good controllability for easy off-roading.  On the road, the comfortable ride is matched to lively acceleration that equals the V8 powered H2 in most driving conditions.  The Vortec engine’s advanced technologies, including counter-rotating balance shafts, which help to minimize noise, vibration and harshness.

Electronic Throttle Control (ETC) with Sequential Electronic Fuel Injection (SEFI) eliminate the throttle cable and provide outstanding throttle response both on- and off-road.  Coil-on-Plug ignition does away with spark plug leads, delivers high energy and cuts exhaust emissions while stretching fuel economy - up to 20.4 mpg (combined cycle).

H3 was the first HUMMER to offer the choice of a manual or automatic transmission.  In addition to the standard five-speed manual transmission, which is a fun option for the serious off-road performance enthusiast, offering the ultimate driver control, customers can opt for the Hydra-Matic 4L60-E electronically controlled four-speed automatic.

Immensely capable 4x4 Drivetrain

At the heart of the HUMMER H3’s immense capability is an electronically controlled four-wheel-drive system with an advanced traction control system (TCS), an incredible 45.1:1 crawl ratio (as standard) and lockable front and (optional) rear differentials.  The TCS ensures that even with three wheels spinning, the H3 can still move forwards, even up a 10% incline.

The Borg-Warner two-speed electrically controlled transfer case has a robust 2.64:1 low-range gear reduction for highly controlled, off-road obstacle climbing.  The Adventure model has as standard, an ultra-low 4.03:1 ratio for ultimate obstacle-climbing control.  This is the most aggressive transfer ratio that GM has ever offered on a regular production vehicle.

The four-wheel drive system gives drivers a choice of four operating modes:

1.  ‘4High-range Open’ is used for optimum highway performance and comfort under normal every day road conditions.

2.  ‘4High-range Locked’ allows torque to be transferred to the front or rear wheels as needed.

3.  ‘4Low-range Locked’ is for severe off-road use, such as crawling over large rocks or logs, or deep sand or snow.

4.  ‘Neutral’ is a setting used for flat-towing vehicle recovery, if required.

As an option (standard on Adventure), a fifth operating mode is available with electronic, driver-selectable full-locking rear differential.  With the rear differential locked, and the optional 4.03:1 low-range transfer case gearing, the H3 is as capable of crawling and climbing as the legendary HUMMER H1 and H2.

Standard fit on the Adventure model is a crawl ratio that is raised to 68.9:1 (manual transmission) and 56.2:1 (automatic) to give drivers a heightened level of control that makes the H3 one of GM’s most capable off-road vehicles.

Robust chassis, delivers Smooth ride and Responsive handling

While functionality and off-road performance are key features of the HUMMER H3, it also provides a surprisingly smooth and comfortable ride on-road, along with responsive handling and braking control for everyday driving.

Key features contributing to this rare combination of attributes include a fully welded ladder-type steel chassis frame, with a modular, three-piece design that incorporates fully boxed components for outstanding strength and torsional stiffness.  Special high-strength steel is used to manufacture the side rails and cross members for extra durability and impact-resistance.

This frame is combined with an independent double-wishbone front suspension with torsion bars and, at the rear, a ‘Hotchkiss’ design multi-leaf, semi-elliptic, dual stage leaf spring suspension.  Large diameter, 46 mm gas-filled shock absorbers are used all round, with 36 mm (front) and 25 mm (rear) anti-roll stabiliser bars.  The two suspension systems, which are equipped with microcellular urethane bump-stops which act as secondary springs, provide both excellent on-highway comfort and outstanding off-road capability.

A highly sophisticated, power assisted rack-and-pinion steering system, with a three-bushing mount design and a 17.0:1 ratio, contributes to a manoeuvrable 11.3-metre kerb-to-kerb turning circle, similar to many D-segment cars.

The H3 is equipped with four large disc brakes and an electro-hydraulic four-wheel ABS anti-lock system, plus a Dynamic Rear Proportioning valve, so that quick, controlled stopping power is assured.

To protect the H3 chassis under the most arduous of off-road conditions, underbody protection incorporates four protective shields as standard.  These include a front skid plate; a sump guard skid plate that also protects the front axle; a transfer case shield and a fuel tank shield.

HUMMER H3 | Part Four
31 March 2008 Staff
 

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