FWD vs AWD

[redlightningsvx]

Mine was FWD then I got it converted to AWD. Thew FWD was definatly a little quicker to go from a start being lighter and all but the AWD corners better still fast off the line with the 4.44 and can handle the snow/rough terrain. If you go AWD you'll need pretty much the entire rear half of an AWD SVX like struts/hubs/rear end, some wiring, etc.

[mikecg]

I let someone drive my FWD before all the Modds. They told me that it felt alot more responcive then theirs. They could be just the result of the lighter wieght. The FWD is several hundred pounds lighter. Lighter tranny, no rear diff, no center shaft, or rear shafts.

[oab_au]

Originally Posted by mikecg

I let someone drive my FWD before all the Modds. They told me that it felt alot more responcive then theirs. They could be just the result of the lighter wieght. The FWD is several hundred pounds lighter. Lighter tranny, no rear diff, no center shaft, or rear shafts.

Plus the lower diff ratio. 3.7:1 against 3.5:1.

Harvey.

[svxistentialist]

Originally Posted by redlightningsvx

Mine was FWD then I got it converted to AWD. Thew FWD was definatly a little quicker to go from a start being lighter and all but the AWD corners better still fast off the line with the 4.44 and can handle the snow/rough terrain. If you go AWD you'll need pretty much the entire rear half of an AWD SVX like struts/hubs/rear end, some wiring, etc.

I could accept that Seth. It would probably be fairer to compare a 4.444 FWD with a 4.444 AWD, just to even up the odds.

The FWD will still be lighter and faster, the AWD will be more stable and grippy in poor traction conditions.

[svxistentialist]

Originally Posted by oab_au

Plus the lower diff ratio. 3.7:1 against 3.5:1.

Harvey.

Harvey are you saying the FWD final drive ratio is 3.700? I was not too sure on that.

Joe

[Wikedjuggalo]

Joe,

The FWD ratio was 3.70 for all fwd from what I understand.


As far as the handling not sure, I'll let you know once I put up my newly converted one. There is a difference, and a big one, in the types of steering. That being between the RPM and speed sensitive.

[oab_au]

Originally Posted by svxistentialist

Harvey are you saying the FWD final drive ratio is 3.700? I was not too sure on that.

Joe

Yes Joe, thats as far as I know from the reports that I have read.

I think you can sum up the differences between the three types of drive, by looking at the way they handle a tight corner.

The FWD has to supply all the drive force, and all the change of direction force, so the front tyres reach their slip angle earlier, to under-steer.

The 4EAT depends on how much rear drive is applied. If the pedal is down, there is more rear drive, but if it is lifted, under-steer happens.

The VTD has most of the drive from the rear, but it also has the drive to the front to pull the wheels in the direction of change, the torque split will never drop below 36/64.
This amount of drive to the front wheels varies with the amount of steering, the tighter the turn, the more drive. The practical difference is with tight turns under throttle. The car just goes around with maximum drive, and steering grip.

Though, I might be biased.
Harvey.

[92 SVX]

Originally Posted by redlightningsvx

Mine was FWD then I got it converted to AWD. Thew FWD was definatly a little quicker to go from a start being lighter and all but the AWD corners better still fast off the line with the 4.44 and can handle the snow/rough terrain. If you go AWD you'll need pretty much the entire rear half of an AWD SVX like struts/hubs/rear end, some wiring, etc.

Good information however his problem is not converting from a FWD, he was thinking of converting a awd to fwd well not really but that would have been the end result.

His auto trans is or has failed he was looking at a jdm trans on ebay cheap but not having the rear gear ratio to match the front he knew he would have a problem. Thought he could have only the front pull him around.

[oab_au]

Originally Posted by 92 SVX

Good information however his problem is not converting from a FWD, he was thinking of converting a awd to fwd well not really but that would have been the end result.

His auto trans is or has failed he was looking at a jdm trans on ebay cheap but not having the rear gear ratio to match the front he knew he would have a problem. Thought he could have only the front pull him around.

Yes there is no way you can have only the front wheels driving, on a VTD.

Harvey.

[trueblue]

I have been in an autocross only once in my life, and that was in a 1970 stock Opel GT. It was a fun experience in a good looking but badly underpowered car, that was a dog on the track.

If the SVX was a lighter car with more power, I think it would blow the doors off a WRX in a autocross because of the lower profile.

[svxistentialist]

Originally Posted by oab_au

Yes Joe, thats as far as I know from the reports that I have read.

I think you can sum up the differences between the three types of drive, by looking at the way they handle a tight corner.

The FWD has to supply all the drive force, and all the change of direction force, so the front tyres reach their slip angle earlier, to under-steer.

The 4EAT depends on how much rear drive is applied. If the pedal is down, there is more rear drive, but if it is lifted, under-steer happens.

The VTD has most of the drive from the rear, but it also has the drive to the front to pull the wheels in the direction of change, the torque split will never drop below 36/64.
This amount of drive to the front wheels varies with the amount of steering, the tighter the turn, the more drive. The practical difference is with tight turns under throttle. The car just goes around with maximum drive, and steering grip.

Though, I might be biased.
Harvey.

Thanks Harvey. I was outlining the general characteristics of the three available types for True Blue because his first and second post showed he had a less than perfect understanding of what could be involved.

Even with the VTD if you brake into a tight bend [as you must in autocross] the rear end will rise up and roll as the turn is made by the SVX. Although the AWD does assert grip when power is re-applied it still makes the SVX a ponderous handler in these situations as the roll centre is higher than ideal. Nevin's bigger rear antisway bar corrects that problem.

Does anybody know what is the rear antisway bar diameter on a WRX or an Sti? That would be an interesting comparison and I suspect I know the answer.

Originally Posted by trueblue

I have been in an autocross only once in my life, and that was in a 1970 stock Opel GT. It was a fun experience in a good looking but badly underpowered car, that was a dog on the track.

If the SVX was a lighter car with more power, I think it would blow the doors off a WRX in a autocross because of the lower profile.

You could actually buy a gearbox from Japan that was front drive only which would work if you also installed the JDM TCU that matched it. Electrically it would still be a difficult modification, so I'm not advising that, go for the 4.444.

It brings back my earlier comment about a FWD model SVX with the larger rear sway bar being the ultimate autocross SVX.

Joe

[Trevor]

Kia ora Joe,

In respect of ordinary front biased road cars, with normal roll centres, the cornering situation you describe, calls for increased roll resistance at the front, rather than the rear. Under hard braking, there is sudden additional weight transfer to the front, turn in then throws this extra weight quite violently to the outside front wheel. N.B. In this situation, the car rolls around a corner to corner axis, inside front to outside rear, rather than around a longitudinal centre line.

With added front stiffness the car becomes more responsive to steering, and this allows the driver to do what he will with the rear end, which he will have cast loose when weight transfers. This is how a real driver likes a car set up, regardless of any theory. Photos of aggressive drivers cornering, always show the inside front wheel slightly off the deck. This is evidence which can no be denied.

As the rear becomes unloaded, rear roll stiffness across the car has little stabilising effect in hard cornering and can be detrimental. If the front is allowed to roll, added stiffness will cause the inside rear wheel to unload and lose traction, when power is applied to control the back end. This is due to the roll occurring on a corner to corner axis.

In your part of the world, many are hooked on the fun available driving a classic three wheeled Morgan, for the good reason that they roll on three corners.

Cheers, Trevor.

[huck369]

Ken, I've owned both FWD and AWD (and even a RWD) SVX...
I think the only reason the FWD was a tick faster in the quarter mile was due more to the lower gearing than the small weight difference..

And as for handling the AWD is definitely better in the twistys

[svxistentialist]

Originally Posted by Trevor

Kia ora Joe,

In respect of ordinary front biased road cars, with normal roll centres, the cornering situation you describe, calls for increased roll resistance at the front, rather than the rear. Under hard braking, there is sudden additional weight transfer to the front, turn in then throws this extra weight quite violently to the outside front wheel. N.B. In this situation, the car rolls around a corner to corner axis, inside front to outside rear, rather than around a longitudinal centre line.

With added front stiffness the car becomes more responsive to steering, and this allows the driver to do what he will with the rear end, which he will have cast loose when weight transfers. This is how a real driver likes a car set up, regardless of any theory. Photos of aggressive drivers cornering, always show the inside front wheel slightly off the deck. This is evidence which can no be denied.

As the rear becomes unloaded, rear roll stiffness across the car has little stabilising effect in hard cornering and can be detrimental. If the front is allowed to roll, added stiffness will cause the inside rear wheel to unload and lose traction, when power is applied to control the back end. This is due to the roll occurring on a corner to corner axis.

In your part of the world, many are hooked on the fun available driving a classic three wheeled Morgan, for the good reason that they roll on three corners.

Cheers, Trevor.

Good points Trevor and evidence which I don't intend to deny. The points you make though have more relevance for FWD dynamics than they do for the SVX AWD chassis.

Faster Golf GTi driving classically shows this stiffer front anti-roll bar effect off very well. Aggressive drivers can have the inside rear wheel pawing the air all the time on tight bends. The roll axis is definitely front inner to rear outer. You can accept I'm sure that in the SVX having the inner rear driven wheel up in the air in tight bends is not necessarily going to be good for getting power to the road in a AWD vehicle. So the SVX chassis and suspension is not really set up to FWD parameters I know you will agree.

Harry sent me some links to videos of his SVX autocrossing. He is obviously a useful man behind the wheel as shown by his times, but the rear of the SVX is doing some serious rocking and rolling on the circuits. Graham who used to fettle and race Imprezas [before he discovered the SVX] remarked on this to me many, many moons ago. The rear of the SVX is set up for comfort, not tied down for sporty cornering.

My point is tightening up the rear of the SVX is an automatic given improvement to handling. The front end does not roll much as standard. I feel a thicker anti roll bar than standard on the front could well disimprove the handling.

Joe

[svxistentialist]

Originally Posted by huck369

Ken, I've owned both FWD and AWD (and even a RWD) SVX...
I think the only reason the FWD was a tick faster in the quarter mile was due more to the lower gearing than the small weight difference..

And as for handling the AWD is definitely better in the twistys

I'll agree totally on the AWD handling better Huck.

Are you absolutely sure that is the only reason for the FWD improvement though? For most racing heads, losing weight takes on a god-like significance . Plus take into account also that the FWD is unable to take advantage of rear weight transfer on launch, with the front end scrabbling for grip.

It would be an interesting comparison to run a head to head test between a US AWD with 3.545 final drive and a European AWD one with 3.700 final drive. That might settle the issue.

Joe