If we compare the Impreza 2.0 non-turbo (125bhp, designated GX around here) to a similarly powered (lets take a 2.0 Focus), how much of a safety benefit will the AWD be?

I reckon that in such cars you don't have the necessary torque to get yourself into dangerous understeer, especially in gears higher than second. So unless the driver is extremely stupid, and goes into a wet corner with throttle all the way to the metal, in a low gear, it's unlikely that the AWD will be much of an advantage (of course, when comparing 200bhp+ cars, AWD does come into play). And even then there's no real danger as a slight decrease in throttle will immediately cancel the understeer.

And what about going into the road shoulder unintentionally at high speed? or going over an oil spill at high speed? (lets assume cruising at 70mph). Will then AWD be safer than FWD?

I know that AWD *is* superior to FWD, the question is how relevant is that for lower powered cars, or in short, if the Subaru Impreza GX has some kind of an active safety advantage over other cars in it's group.

thanks!

 

I suspect that many of the sport owners will reply to this, but all I can say is that I used to have an Audi Coupe Quattro which had the 2.2ltr engine but no turbo. I am guessing it had less than 150bhp

The way it went round corners was a revelation to me it was just so utterly stable at any speed. When it slid it was a gentle progression sideways rather than the front just washing wide.

I think there is a limit to lack of power and usefulness of 4x4 (justy) but I think with most cars 4x4 is a benefit over FWD.

 

It rather depends on how you're driving... I guess we're all familiar with traction circles.

If you're cornering on a neutral throttle with all your grip, no matter how little the power, accelerating *will* make the car understeer a lot - you're asking the fronts to provide traction. AWD will be more balanced. In both cases, there will be rearward weight transfer, which will cause the rears to pick up grip, so some understeer is likely to result; depending on drive bias f/r, and suchlike.

Also, don't underestimate how little power is required to compromise fwd - I used to drive a Saab @ circa 130 Bhp. Wheelspin / power understeer was a regular problem / feature.

 

If you drive beyond the limits (yours or the cars) you will crash, AWD,RWD,FWD, it doesn't matter.

A good RWD,FWD or AWD will all be pretty close, its how you drive them.

 

Not if there is more power than grip they won't, that's why all the rally cars are 4WD.

 

I can comment on this one as before the Scoob Turbo I had a Focus 2.0 Zetec ESP . My boss used to have a classic shape Impreza Sport (Now has a bugeye WRX).
We often followed/chased each other from our place of work to our HQ and often travelled in each other cars (Around 20 mile run of mixed roads).

There is no doubt that in 85% of driving conditions the Focus was faster and handled better, the steering feel on the Focus is in a different league. Even in the wet the Focus would pull away from the Sport and I'm talking country lanes and B roads although the ESP was working overtime.
Suspect it would be different in the wet without ESP with average drivers.

The only place the sport had the edge on the Focus was pulling out of a side road onto a main road in the wet when the traction control would just kill the power on the Focus and the traction of the sports AWD system would let it pull away cleanly. In anything above 1st gear a 2.0l Focus ESP doesn't have the power to spin the 205/60 X 16 tyres anyway so its traction once moving isn't a problem.

People may say I'm mad but the Focus understeered less than the Impreza sport with ESP off and with it on the Focus turns in as sweet as anything and you've got to be driving like a complete idiot to get understeer with ESP on.

Lee

 

DavidRB: yeah all the top teams are 4WD, and the 2wd F2 teams kick their @rse on the tarmac stages, its only the gravel stuff that they really win on, but I don't drive on gravel too much going to work, so I stick by my point.

 

Erm..

The 'limit' of a car is a grey area, not a line - the big difference between the three is how they handle *on and around* those limits (on the limit might be as simple as too much right hoof leaving the lights, causing you to reach the limit of traction)

If none of the tires is at it's limit of traction, then it matters not which, if any of the wheels are driving.

 

The GX seems to feel more settled on the twisty roads than other 2ltr equivilent cars that I've driven, focus included. It may not be as quick, but it feels a hell of lot more planted.

Rgds, Alex

 

Not true, the only times they managed it was big news (and I'm not even talking what would happen without the power limitation...)

but the Q is what happens when hitting standing water, going off to the shoulder... which will be safer the AWD car or the same?

 

Gravel / tarmac is irrelevant. What matters is the torque-to-grip ratio. You need less torque to break traction on gravel than tarmac, but the laws of physics are still the same.

The point about FWD, RWD and AWD being the same might be true if you restrict the range of cars to sub 200bhp and road conditions to dry tarmac, but not if you consider more powerful cars or less grippy surfaces.

Absolute cornering speed and braking ability is (relatively) unaffected, but the ability to accelerate and particularly the ability to accelerate while cornering is greatly affected by the drive train layout.

 

I thought we were talking about cars with less than 130bhp.

Lee

 

We indeed are

So would you say that the AWD is an advantage or disadvantage when used in a 125bhp Impreza? It raises the fuel consumption, lowers the max speed and makes it slow and heavy. (Assume living on something other than ice). In fact, judging by formal specs, the 125bhp Impreza is slower than a 1.6 Focus!

(again, given very slippery surface or a very powerful car - like the GT, WRX - there's no doubt AWD is handy)

 

Lets start by saying the Sport and GX are very good cars both stable, sure footed and reliable.

FWD technology has moved on vastly over the last 5 years, put the Sport up against a Escort GTi or a 2.0l Astra and it would walk all over them. We wont even mention Nova's

The best of the latest FWD chassis can handle 130bhp with ease though, I'm currently running around in a 155bhp 156 Veloce and its just about imposible to get the 205 section 16" tyres spinning in anything other than 1st gear even in the wet, traction and understeer are never a problem, turn in is very crisp and direct the passive rear wheel steering pitching the car in.

The Zetec spec Focus have a more sporty suspension setup than the rest of the range and the 2.0l ESP has 16" rims and all the electronic aids to eliminate understeer almost completley. I hadn't driven an ESP for around 18months but had one as a hire car a few weeks back, enjoyed every minute of driving it very entertaining.

If I wanted a safe, reliable, stable car that wasn't boring to drive then a sport/GX would probably fit the bill. Downside being the poor fuel economy to performance ratio and relatively high purchase price (Paying for AWD in both instances).

If I wanted a more sporty faster alternative for the same money there are plenty of choices. The Focus 2.0l ESP, Focus ST170 or even the 180bhp Octavia RS spring to mind.

You pays your money.. etc.. etc..

Lee

 

BTTT, because that's imporant

 

Having driven a Forseter GLS for a year or so and various low powered FWD things before that I can honestly say that the forester was way more stable at speed. A lot of my driving is below 35mph and the AWD does stop you wearing through your front tyres every 10k miles. I did find understeer in wet 1st gear junctions a problem as on my current forester S-turbo, but that's just the tyres and weight of the car I think. I only drive an AWD car as I have to drive around fields quite often, otherwise I'd go FWD to save me lots on petrol (and I only pay 45p per litre for SUL )

 

The Forester does indeed seem to be stable, the question is how much of that can be attributed to the AWD and how much is simply because of good chassis design, especially at speed, when the torque transferred to the wheels in neglible.

Where is SDB when you need him?

 

Which do you prefer???

bit of coffee time light reading

What wheel drive???