Infiniti QX30 Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
107 Posts
Discussion Starter #1
Can we make an assumption that since this car is built on the Mercedes GLA platform, the all wheel drive transmissions of this car are Mercedes' 4matic transmission and not Infiniti's AWD? If so, what generation 4matic is it? And is it true AWD or only when it detects that AWD is needed?
 

·
Super Moderator
Joined
·
403 Posts
It is my understanding that the QX30 uses the 4Matic system, yes.

I found these tid-bits on the Mercedes website:

https://www.mbusa.com/mercedes/benz/performance/4matic said:
INTEGRATED IN AN INNOVATIVE WAY.

The most innovative components of the new 4MATIC for compact models include the output shaft to the rear axle integrated into the seven-stage automated 7G-DCT dual clutch transmission, and the differential with an integrated, electrohydraulically controlled multi-disc clutch. This enables fully variable drive torque distribution between the front and the rear axle. The performance flow to the rear powertrain is carried out by a compact power take-off unit (PTU), which is fully integrated into the main gearbox and is lubricated via its oil system. Additional benefits of this design are a lower system weight than is available from the competition, and high efficiency. All 4MATIC models are outstanding, as are the front-wheel-drive versions with good energy efficiency.

The 4MATIC all-wheel drive is a completely new development and was designed specifically to coordinate with the new front-wheel drive models.

FULLY VARIABLE DRIVE.

Fully variable torque distribution is ensured by the electrohydraulically operated multi-disc clutch integrated into the differential. The basic principle is that if the multiple-disc clutch is disengaged, the front axle drives the vehicle almost entirely. If the multi-disc clutch is engaged, the rear axle comes into play. However, drive torque distribution can be variably shifted between the front and rear axles depending on the situation (torque on demand). The rotor-type pump integrated into the differential provides the operating pressure to activate the rear axle within milliseconds. The pump is automatically activated by slight rotational speed differences between the front and rear axles, and a proportioning valve adjusts the pressure.

INTELLIGENTLY SOLVED.

The actuation of the new 4MATIC follows the basic principle of "as often as necessary, as seldom as possible". If circumstances allow, the all-wheel models are driven almost entirely in the highly economical front-wheel drive mode. If the driving situation demands, drive torque is rapidly adjusted at the rear axle. However, as soon as additional torque on the rear axle is no longer required, for example in the case of strong braking where the ABS comes into play, the rear drive train is deactivated and the torque reduced to zero. If there is a risk of understeering or oversteering under load, the torque is first distributed so that the vehicle is stabilised again. If this is not enough to stabilise the vehicle, the ESP® or 4ETS control systems, which are adapted to 4MATIC operation, help to keep the vehicle on course.

With this strategy, the developers have combined optimum efficiency with top vehicle dynamics and driving safety.

INDIVIDUALLY ADJUSTED – MADE FOR PERFORMANCE.The powerful AMG versions for compact models fulfil the highest standards of engine technology and power transmission. Whilst the performance-oriented AMG 4MATIC all-wheel drive was being developed, the focus was on the concepts of "performance" and "dynamics". The adaptation of the 4MATIC control system for the AMG versions is based on 3-stage ESP®. The torque distribution depends on the activated gearshift program of the 7G-DCT dual clutch transmission. In the ECO program, the rear axle is provided with less torque, so that the handling seems gentler and supports an economic driving style with lower revs.

In the SPORT or MANUAL modes, the activation times are shorter and more torque is transferred to the rear axle to help provide for a dynamic and sporty driving style. In this way, the individual drive programs support the driver's personal style of driving.s personal style of driving.

 

·
Registered
Joined
·
107 Posts
Discussion Starter #4
Thanks for the info, both of you! Super handy. I had to google Haldex-Clutch. They seem... okay, but maybe earlier models a bit unreliable.

It's interesting how the AWD version of QX30 gets less gas mileage, but according to this, the AWD is only used on-demand, so you'd think most of the time it would just be standard front wheel drive and thus a closer range in mileage to the 2WD version of the car.
 

·
Super Moderator
Joined
·
403 Posts
It's interesting how the AWD version of QX30 gets less gas mileage, but according to this, the AWD is only used on-demand, so you'd think most of the time it would just be standard front wheel drive and thus a closer range in mileage to the 2WD version of the car.
A few reasons for slightly decreased fuel economy with the AWD:

  1. Weight - The DCT housing is larger and has additional components (such as bevel gears). There is also the drive shaft to connect the DCT to the rear differential. Then the weight of the rear differential. Then the rear drive shafts. Weight takes fuel to carry around.
  2. Rotating Mass - The rear wheels require CV joints in the AWD drivetrain. There is also the driveshaft that connects the DCT to the rear differential. This increases the rotating mass in addition to increasing friction -- all taking more power and thus lower efficiency.. Even when the clutch is disengaged -- meaning the engine isn't powering the rear wheels -- all of the parts are still spinning (CVs being driven by wheels rotating on the road, and driveshaft spinning by PTU on DCT.
The AWD only affects mileage slightly... The difference would be larger in a full-time system. But it's hard to get around the additional weight/rotating mass.
 

·
Registered
Joined
·
107 Posts
Discussion Starter #6
Yep. Still seems that a stated 10% decrease in gas mileage is a lot for the additional stated curb weight difference on the 4wd (3,409) vs 2wd (3,320) Luxury versions is under a 100 pounds.
 
1 - 6 of 6 Posts
Top