Q active Question

[louiegz]

I'm sure this has been asked, but what are the main diferences between the active suspension of the G50 Q and the active damping of the current Q? I've noticed for 05, it will be offered standard on all Qs.

[Q45tech]

Dynamically changing the stiffness of a shock absorber vs actually maintaining the car body level. The early active system actually changed the effective spring rate on each corner simultaneously and provided ~~300-400 pounds per corner of lift.....roughly 30% of body weight was supported via active system all the time!

[elwesso]

Dennis, so are you saying this new thing isnt as effective as the new setup??

It seems that if infiniti offered their old setup (it can be the original setup with all the same main parts), they would compete much better.....

[1992Q45A]

Of course it isn't

Active damping has been around for ever. Selective damping has been around for ever to

It's just a chinsy way to say you have an advanced suspension

[fxjackso]

The new Cadillac has active shocks. The BMW has active sway bars. But only the Q45a, the Mercedes ABC, and the Citroen Zantia have real pump pressure driven active suspensions.

[Jesda]

And the Infiniti system likely wont leave you stranded.

[texasoil]

A number of mfg's have offered versions of variable stiffness shocks over the years. This is TOTALLY DIFFERENT than true 'active suspension' like the Q45a has. ACTIVE SUSPENSION (actually semi active since it still uses conventional springs for 60% of the curb weight support) utilizes stored high pressure oil to force the wheels down into holes, adds pressure to the outside wheels when cornering,etc. Adjustable dampening can emulate a lot of the Q45a feel without the weight and mechanical complexity of hydraulics, and can even improve on some areas like high frequency response (short bumps) The difficulty with adjustable dampeing is the lack of enough energy to drive the wheels down into a hole. Thus the car body will drop considerably more tha a Q45a type system. If the road presents 'bumps' more than 'holes' or droops, then adjustable shocks can/may do a good job. Its a compromise system--lighter weight, lower power consumption, but lower benefits too.

[Jesda]

I'm looking forward to when delphi magneride technology will be available on non-GM vehicles.

[IvoryJ30t]

i noticed the mercedes ABC had a very high failure rate.

when i was towing for mercedes, i would pick up new S430's and S500's with malfuntioning ABC systems all the time.

its a pain in the *** to get a big mercedes that is practically touching the ground up on a flat bed. took many 2x4's.

one of the failed S430's i picked up was black on black with black tints and 18" giovanni wheels. the extreme drop caused by the ABC failure made the car look awesome. too bad you arent going anywhere with the frame dragging on the ground.

[rover3l]

isn't the case that the Q45a also reduces the pressure of stut over a raise bump as well as forcing the strut down into a depression or hole type of bump.

[rover3l]

related to this I don't understand why replacing the 4 strut accumulators provides 90% of the ride quality whereas the very complex additional 5 only adds a further 10% improvement. Does the active effect actually operate with replacing only the strut accumulators?

[texasoil]

Replacing only the strut accumulators gets you perhaps 70% of the bump absorbtion and hole following(smooth ride). It does not give you any more 'active' than the main accumulators have capacity left (usually not much if any) , The Pump DOES provide some active on long duration events--like sweeping turns or hard braking.

[rover3l]

so with the fully active working should I see a difference over pot holes and raised bumps.

I still have this unresolved knocking sound over multiple medium size bumps like you get on a crudely patched road. I do not see any leakage of silicone fluid from the subframe mounts and the suspension bushings seem in good shape. All the piping and exhaust etc seem solidly fixed so I am suspecting water hammer noise. Do you have experience of what this sounds like and does it occur on an active if not fully recharged. Note it was there prior to the replacement of the strut accumulators and is still there afterwards.

The only other thing I can think of is the strut mounts themselves at the top. Can these be accessed from within the trunk?

[texasoil]

You can get 'water hammer' noise resonating through the oil piping if the valve accumulators are flat, or if there is gas trapped in the piping. Also check exhaust hangers carefully. Rear muffler is heavy and WILL bang against body if not properly secured in place.

[rover3l]

Checked the exhaust and it is rock solid. Changed the sway bar bushings and as far as I can checked the subframe mounts (no sign of fluid leaking). Noise is still present but strangly not over large bumps. It only seems to occur on a certain pattern of bumps. Typically a series of medium size bumps and it sounds like something hitting the underside on the drivers side rear. There is nothing to be felt but just the noise. At first I thought it was the spare wheel cover or the jack rattling around but I removed everything from the trunk and no improvement.

Other than reading about water hammer noise I have no idea what this actually sounds like in an active Q