Well, Audi has succumbed to ditching the centre differential full time quattro in favour of clutches and mumbo jumbo. At least I owned two real quattro cars while the going was good.
I couldn't fully understand the new AWD explanation in this article, but Audi Media Centre to the rescue! Here we discover illogic spread thick, speaking from my viewpoint as a mechanical engineer:
https://www.audi-mediacenter.com/en/quattro-with-ultra-technology-the-permanently-available-all-wheel-drive-system-5503and download the .pdf for Audi's explanation written on banana skins.
Yes, this "permanently
available" AWD is not on duty all the time, just "available". Thus it is dubbed "quattro ultra" in marketing doublespeak, elevating a non-descript concept to that of Wowee, Folks! this is the latest and greatest.
All this stuff shoehorned into the new A4 Allroad is apparently an attempt to save 0.3l/100km mileage. Or the square root of a headwind plus leaving the dog at home to save weight divided by blind hope. It is of course presumably cheaper to manufacture and saving all of 10 lbs from a 3671 lb car (as per C/D's weigh-in on the sedan at a portly 1667 kg).
At least Audi do not claim 100% of the power can be sent to either front or rear as needed, because that is Mr Yarkony's remark alone, and is impossible with the series clutch on the end of the transmission. No, you get FWD or AWD with varying torque to the rear depending on how hard that clutch clamps. Yes, Audi has now made a version of the Subaru MPT system first introduced in 1988, yea these 28 years ago! BMW also copied it for the 2005 X-Drives, ditching diffs. And which Subaru's better VTD system with centre differential surpassed easily, although all gone on all regular civilian Subarus now, the 2014 Outback 3.6R having the last one if specs are to be believed. My old Leggy GT has VTD, thank goodness.
Proceeding apace, yes, we find "ultra quattro" is similar to the rear axle and main propeller shaft declutching to the Chrysler 200 AWD. But lo, Audi says those hydraulically actuated systems are no good. No, they need to be electrically actuated. OK, but they keep the hydraulic engagement on the A3/S3 as their .pdf shows. Oh well, why be consistent? That would be no fun.
No, this permanently "available" ultra quattro on the A4 is predictive! As well as being reactive and proactive! It knows when to go to AWD before the need arises apparently, fortune telling on a grand scale by the Audi engineering staff. It takes 200 to 250 milliseconds to engage AWD and to get the propshaft up to speed then a spring bangs in the dog-clutch on the rear axle to engage the half-shafts. Luckily for we mere mortals, Audi has us covered because it knows half-a-second ahead that AWD will be required.
All this cannot really pass the smell test. From the Audi article:
"With reactive activation, which rarely occurs in practice, the system reacts to sudden changes in the coefficient of friction. These occur, for example, when the wheels go from dry asphalt to a sheet of ice."
With these words, typical Canadian driving conditions are chucked out the window, because they "rarely occur in practice". So there. We've all been dreaming four months a year. And a quarter second or more goes by with FWD only. Great.
The Subaru MPT system keeps the rear wheels on duty all the time, throwing away a quite possibly ephemeral 0.3l/100 km in the process. It also avoids a whole lot of fancy electronic fandango and egghead scientific hot air attempting to explain this as a boon to mankind.
This new "ultra quattro" is to be spread far and wide in the longitudinal engine Audi AWD models. What a load of technocratic BS to describe a system less capable than the existing one.
I remain duly unimpressed with ultra quattro. Mere words to justify an unrequired solution, to ease manufacturing costs, and to impress what the Brits call "punters". It is in fact Haldex Ultra. No more.
