First RWD Impala spy pics?
OpEd by MonaroSS
This may well be the LaCrosse prototype being used as a mule for Impala underpinnings.
Or perhaps it's a secret Alpha Platform mule - see post 48.
Or perhaps it's a secret Alpha Platform mule - see post 48.
http://www.leftlanenews.com/gm-four-cylinder-prototype.html
At the above link at leftlanenews.com is a story entitled; "GM begins testing turbo four-cylinder engine in large cars". But is there more to this story?
They suggest, "According to a check of the prototype's license plate information, the car is registered to Saab and was built by Holden. The car is also listed as having a 260 hp engine four-cylinder — the type GM officials have hinted might show up in the Pontiac G8 and other large cars."
However I have a different speculative opinion. I gave an undertaking to Bob Lutz not to divulge any secrets he my let slip to me in emails we exchange, but this does not cover my suggestions to him. Six months ago, when the whole "will Impala be RWD or FWD" was being discussed widely I sent Bob a suggestion. I said that if I were him I would challenge my engineers that if Zeta and EPII are so flexible then why can't Impala be offered both as a FWD/AWD transverse engined vehicle AND a longitudinal engined RWD vehicle.
He never commented on the idea, which was not unusual, as I had asked him not to tell me any secrets. But the above story made me wonder, when I saw this prototype was built by Holden who are responsible for GM's RWD car programs. If Bob took my suggestion and asked Holden if they could blend some Zeta RWD into the EPII platform then Holden would be the one to build it from an EPII LWB FWD prototype sent to them, which would happen to be the Buick Invicta/LaCrosse platform (being clearly longer than the Opel Insignia sedan) and likely the closest thing GM has to a running Impala prototype mule at the moment.
So besides my suggestion to Lutz, the spy info that Holden built this prototype when they only really do RWD and do test in Sweden (note that a Buick running around Holden would look REALLY odd), what else is there to tell us more.
Well we have photographs of the car at speed, which can help show us if it is FWD or RWD by its dynamic attitude in cornering, accelerating etc. So let’s look:
(You can see larger pics at the link above)
Pic 1. Here the car is under heavy acceleration, as the track is flat without bumps to cause the front lift. Now, while the nose can rise on a FWD car, the clear gap between the fender opening and top of the front tire shows the front rise that normally is the response found in a RWD under heavy acceleration. Furthermore, a close look at the large picture shows that the driver’s left hand with a watch on it is over top dead centre of the steering wheel, which means he is applying opposite lock. And the angle of the front wheels confirms that this car is powering around a left hand corner with the tail hanging out in typical RWD fashion. Yes you can do this with a FWD car too if you simply go fast into the corner and give it a Scandinavian flick. But test drivers seeking real world feedback would be more likely to be conducting conventional driving styles and that means understeer on FWD and oversteer on RWD.
Pic 2. In this pic we see the car in a fast corner and generating sufficient forces to cause body roll, yet one would expect the turn angle of the front wheel to be greater than shown, as FWD cars tend to scrub or understeer in such situations. In stance this car looks more like a Holden Commodore powering through a corner.
Pic 3 & 4. But the real odd picture is this. FWD cars hard charging through a corner can unload the inside front wheel and spin away power, but they more often lift the inside rear wheel off the ground. Here we see clearly that the inside rear wheel is firmly planted and it is the front wheel that is off the deck. This is common with a RWD car powering through a corner but almost unheard of with FWD. These traits are even more clear on the large pics. Have a look and judge for yourself.
There is precedent for offering both transverse FWD and longitudinal RWD in the same car. MG Rover did it with the I4 and V6 FWD Rover 75 that was also sold as a RWD fitted with a Ford 4.6 V8 in the MG ZT 260. See pics below. But they did it ad-hoc as an afterthought. It would be much easier and cheaper to build in the capability from the get-go so you have one set of stampings across the platform range.
See story here with TopGear Video: http://www.zt260.co.uk/main.htm
So if the Impala will be offered with both FWD/AWD and RWD, then the turbo 2.0 I4 makes sense as the first engine to test given CAFE and a manual box should be a given when you go to the trouble of changing the drive train for a sporting character - why be half hearted. But will there also be a V8? There would be no reason why not, except that GM may want to discourage this for CAFE reasons. I would expect a RWD DI 3.6 V6 as the top RWD engine for a while with perhaps a V8 in very limited numbers later on a range topping Chevy Impala Coupe.
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