الموضوع: تقرير دقيق عن إمبريزا 1.5

ده يا جماعة تقييم جميل أوى عن سوبارو إمبريزا بالموتور البوكسر ال 1.5 لقيته على الموقع
The New Subaru Impreza 1.5 Litre Engine In Detail
للأسف هو إنجليزى ومافيش وقت أترجمه بس هو بيظهر ببساطة مميزات الموتور البوكسر مقابل المواتير العادية وخصوصاً مع الدفع الرباعى لسوبارو عشان طريقة نقل الحركة تبقا فى خط مستقيم ، وحتى مقابل الموتور البوكسر القديم (تقريباً ال 1.6) بيظهر تفوق أيضاً للعزم على السرعات المنخفضة
وكمان بيتكلم عن الفتيس ال 10 نقلات (5×2 للمانيوال) وبعض الكلام عن الأمان والتصميم
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Subaru has built an enviable reputation for reliability, long engine life and accessible performance through the design of its horizontally-opposed, all aluminium ‘boxer’ engines. This ‘flat-four’ layout gives a lower centre-of-gravity for enhanced cornering grip.
It is also ideal when mated to Subaru’s standard symmetrical all-wheel drive system because of the engine’s compactness, light weight and ability to connect with the AWD transmission in a straight line.

Now, the new 1.5 litre ‘boxer’ engine has been designed to offer strong low to mid-range pulling power, known as torque, while also having the ability to rev to high speeds for brisk overtaking. So despite being the least powerful Subaru, the new Impreza 1.5R makes the most of its power and torque, providing comparable performance to most similar-engined lower-medium hatchbacks.

For example, top speed is 109 mph for the manual, with a 0-60 mph time of 13.7 seconds. Fuel economy is also respectable with 29.4 mpg on the Urban Cycle, 44.8 mpg on the Extra Urban Cycle and 37.7 mpg Combined – 2 mpg better than before. Exhaust emissions are also competitive at 176 g/km.

Power is now 107 PS (2 PS more) at 6,000 rpm and torque is 104.7 lb.ft at a low 3,200 rpm while the compression ratio is 10.1:1. However, the torque is greater at lower engine speeds than with the previous model, improving throttle response and flexibility.

As with all Impreza engines, the new 1.5 litre features twin overhead camshafts per cylinder bank (DOHC) plus an Active Valve Control System (AVCS) which is a form of variable valve timing. This enhances both low-speed pulling power and high-rev response.

Also shared is an electronic throttle for more responsive acceleration plus centrally-located spark plugs, pent-roof combustion chambers and multi-point fuel-injection with an ignition coil for each cylinder.

Of special interest is the 1.5 litre’s bore and stroke dimensions, selected to optimise combustion efficiency for low emissions and fuel consumption while providing strong power and torque.

In fact, the new 1.5 litre shares its 79 mm stroke with Subaru’s four-cylinder 2.5 litre turbo engine. Naturally, its bore dimension is a much narrower 77.7 mm.

Other efficiency measures include low-friction, lighter valve springs and a 4-2-1 equal length, ‘constant-pulsation’ exhaust system which avoids gas flow interference and speeds up the warm-up of the catalytic converter.

Ten-Speed Transmission/Symmetrical All-Wheel Drive

For the new model, the Impreza 1.5R has revised, slightly higher 2nd, 3rd, 4th and 5th ratios for improved high-speed refinement and enhanced fuel economy.

The symmetrical all-wheel drive system features a nominal 50/50 front to rear torque split. However, a centre viscous-coupling senses which axle has the best grip and varies this ratio in milliseconds according to the road surface.

This maximises tyre grip and handling accuracy, instilling confidence in the driver – especially on rain-soaked motorways or snowy country lanes.

All new Imprezas receive slicker-shifting five-speed manual transmissions, while the optional four-speed automatic gearbox is more fuel-efficient and offers the driver the opportunity to change gear manually during sportier driving.
The Impreza 1.5R now has a double-cone synchroniser for second gear giving a lighter change while a hydraulic clutch replaces the cable arrangement for smoother, quieter operation. In addition, the 1.5R has revised 2nd 3rd, 4th and 5th gear ratios while the WRX has revised 1st, 2nd and 3rd ratios. A four-speed automatic transmission provides smoother changes with greater sensitivity to the driver’s wishes. As with the new Impreza 2.0R and RX, the 1.5R has a five-speed manual gearbox with a low-ratio, dual-range transfer gearbox, effectively providing 10 speeds. Owners find this particularly useful when towing or covering difficult road surfaces as it provides extra engine-braking for greater control.

It is more efficient, saving fuel, because a slip lock-up device reduces wasted engine revs. In addition, advanced electronics – linked to an electronic throttle – match engine speed with the best gear for any given situation.The standard low-ratio transfer ’box on manual Imprezas effectively provides 10 speeds. This is useful when towing or covering difficult road surfaces, providing extra engine braking – and therefore greater control – at low speeds.

As with previous models, the full-time all-wheel drive transmission features a 50/50 front to rear torque split on manual models and 60/40 on the automatic. However, the split varies according to changing conditions.

The manual Impreza has a centre differential with viscous coupling which senses which axle has the better grip and distributes torque accordingly to minimise the risk of wheelspin.

The Impreza 2.0R and RX plus the WRX benefit from Subaru Vehicle Dynamics Control as standard. This has previously only been available on certain automatic versions of the Forester and Legacy/Outback.

Subaru Vehicle Dynamics Control uses sophisticated sensors to detect side to side and front to rear slip plus sudden steering movements. It controls oversteer /understeer and potential loss of control by braking individual wheels and cutting engine revs – all in milliseconds.

On automatic models, a similar function to the viscous coupling is carried out by Subaru’s sophisticated Active Torque Split system. This employs electronics,
sensors and a multi-plate hydraulic transfer clutch. Again, on 2.0 litre models, SVDC is standard.

Finally, the Impeza WRX changes its previous viscous rear limited-slip differential to a mechanical one which reduces weight and improves fuel consumption.

Passenger And Pedestrian Safety Boost

Both occupants and pedestrians are well protected by the latest Impreza thanks to a whole series of safety measures aimed at achieving the highest standards of both occupant and pedestrian safety.

Curtain and side airbags are now fitted to all models together with driver and passenger airbags. Front seatbelts have pre-tensioners, most models have anti-whiplash head restraints and all front seats have energy-absorbing backs.

The brake pedal is energy-absorbing, being designed to snap away under severe impact, protecting the driver’s lower limbs. In the rear seat are two ISOFIX-compatible child seat mountings.

The passenger airbag is dual-stage which provides progressive protection matched to the severity of the impact and the standard anti-lock brakes (ABS) come with electronic brakeforce distribution (EBD). This juggles the braking force between front and rear wheels according to load shifts during deceleration. All Imprezas have front ventilated disc brakes and solid rear discs.

Outside, pedestrian injury is reduced thanks to a more rounded contour to the top of the front bumper, a gently curved bonnet and windscreen wipers which collapse, softening any impact.

High tensile steel of varying thickness is used extensively throughout the body, providing good crushability where needed while protecting the passenger area.

Not only does the elimination of the previous Impreza’s front subframe reduce body weight by 20 kg but the new structure better dissipates front impact forces.