Airbag suspension systems can absolutely transform
your vehicle for towing heavy loads or, alternatively, they can be used to
create that eye-catching ‘low rider’ stance. In the first part of this series
(see
Airbag Suspension Systems - Part One)
we looked at the different types of airbag systems, their
advantages and pricing. Well, now it’s time to put airbag suspension to the
test.
Let’s take a close-up look at Airbag Man’s Holden
VYII Commodore SS ute and hit the road!
Airbag Man Development Ute
This VYII SS ute is Airbag Man’s R&D mule and,
when we sampled it, it was using a Firestone airbag at each corner and in-cabin
control with two preset ride heights. We spoke with Airbag Man’s General
Manager, Brett Curtis, on the details of the system...
Under the nose, the ute uses an aftermarket
replacement strut assembly which has its coil spring and spring platform
removed. The new platform for the triple bellow airbag unit is a custom cast
alloy item which is attached to the strut using grub screws. Mr Curtis points
out there’s no need to weld to the strut body (which can be a dangerous
exercise).
At the top of the revised strut you’ll find
another custom cast alloy mount which accepts the top plate of the airbag. Note
there are no dedicated bump-stops because, when fully compressed, the airbag
acts like a bump-stop.
“Maximum suspension travel is usually determined
by the stroke of the damper and movement of suspension links rather than the
airbags,” Mr Curtis says.
At the rear, the Holden ute comes fitted with a
separate spring and damper setup which makes airbag installation relatively
straightforward. A double bellow airbag unit is mounted over the standard spring
platforms and is attached only at the top using heavy-duty stainless clips. The
airbag remains captive in the same way as the standard rear spring.
Air pressure for the airbags is generated by a 12V
piston compressor which is mounted under the rear. This particular compressor
draws up to 17.5 amps and can generate up to 150 psi. Air pressure is stored in
an 8.5-litre reinforced vessel which is mounted under the rear alongside the
fuel tank. Mr Curtis says a large volume pressure vessel helps improve the
inflation response time of the airbags.
Air pressure is supplied to the airbags via 150
psi rated hose (as used in air-brake systems) together with brass fittings and
solenoids. There are six solenoids in the system. One pair of solenoids controls
air entry/escape of the rear airbags and the two remaining pairs control air
entry/escape of the individual front wheels. In this configuration, the front
wheels are individually adjustable but the rear airbags operate in unison.
The solenoids are controlled by in-cabin switches
wired to a ride height control module with two presets. The ride height presets
are programmed via laptop.
On the Road
The Airbag Man R&D ute is the focus
of on-going efforts but is indicative of what can be achieved with a stand-alone
airbag system.
With the car set to just over the standard ride
height, the ride is very compliant and feels well damped. However, it feely wallowy through corners and the handling isn’t aided by the alignment specs well outside of the front-end’s ‘sweet spot’.
“To get the most out of the system you
really need to have the wheel alignment set to suit your most common ride
height,” Mr Curtis says.
The car can be raised further but this isn’t
advised for normal driving – it’s only for negotiating steep driveways and
clearing obstacles.
With the car dumped to its lowest setting - about
40mm lower than standard - the ride is much harsher over bumps. Mr Curtis says,
at this ride height, it’s possible the airbags are reaching the limit of their
compression and are functioning as bump-stops. This isn’t a specific problem
except for the deterioration in ride quality. Take a close look at this photo
and, again, you’ll see wheel alignment angles are clearly different to the
elevated ride height. Some experimentation with alignment specs would certainly
be beneficial.
The only other downsides are slightly increased
NVH transmitted through the new strut top-mounts and an occasional popping noise
from the airbags when lowering the vehicle. Brett also points out that this
system uses relatively small 1/8 inch solenoids which don’t give the rapid ride
height change achieved with larger diameter solenoids.
Interestingly, the system is also configured so -
in the case of an automatic transmission vehicle - you can’t lower the car when
in Park. This causes driveline windup which can damage the transmission. The
solution is to adjust ride height only in Neutral and with the handbrake lightly
applied.
Since our photo shoot, Mr Curtis says they’ve
revised the front upper airbag mounts for a neater appearance and are currently
installing a more sophisticated control system. As we said, it’s an R&D
vehicle...
Price and Availability
Airbag Man’s complete On-Air airbag system for the
Holden costs around AUD$4500 plus installation (which takes about a day). That’s
not too bad when compared to some adjustable coil-over suspension which, of
course, can’t be adjusted from the cabin.
At present, Airbag Man offers stand-alone
suspension systems to suit Holden Commodore, Subaru Impreza WRX, Honda Civic and
Integra. A system for Ford Falcons is also being developed. Each system comes
backed with a 12 month warranty.
With some fine tuning in the area of
wheel alignment, we reckon an airbag system would be a great addition to any car
that’s receiving ‘the works’. No longer do you need to put up with a permanently
slammed ride height and a jarring ride to impress your mates.
At last – there’s a real alternative to a coiled up
piece of steel!
Contact:
Airbag Man +61 7 3889 6556
www.airbagman.com.au
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