is 4wd not a better alternative to 2wd in the front or back. 4wd has more traction so it would make acceleration faster would it not? if so why do nascars, drag cars, etc not use it as opposed to rear/front wheel drive?
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It’s a weight issue. To make a vehicle AWD it takes added components. The weight decreases fuel rates and only adds traction in corners and acceleration from a stop. The added traction is not significant and current traction systems are more than adequate for racing needs. AWD would be a net lose for the vehicle.
more traction from using all four wheels only really helps if that is the limit like on gravel or snow. On a drag car the front wheels are barely touching the ground when accelerating so four wheel drive would only add weight.
Car enthusiast here. TLDR – 4WD helps with traction, not with raw speed. It actually makes you slower and often less nimble than FWD/RWD once you’re moving due to added weight.
Detailed explanation –
4 wheel drive means power is sent to all four wheels (obviously). On a prepared drag surface where the front/rear tires get traction anyway, 4wd actually makes the vehicle SLOWER because of the added weight of the drive system.
4wd also makes the vehicle slower once it’s moving, again, because of the added weight. I had a front wheel drive VW Jetta GLI with 228 horsepower that would beat AWD Subaru WRXs (258hp) in a roll race (both cars start at 40mph and floor it) because the WRX’s AWD system made it heavier.
There’s also the issue of engine packaging. In drag cars, the engine is behind the driver and the chassis is long and narrow. Power would have to be sent to the front wheels somehow, and it can’t be done wirelessly. There is nowhere to stick the driveshaft to make it happen, and the front wheels of top fuel dragsters are too narrow to get traction anyway.
Where 4wd shines is off road and in adverse conditions.
Distributing the power to all 4 wheels requires a lot more metal in the parts that do the work. Those are some strong pieces of metal since they have to withstand the power of the engine and the roughness or the roads. Also keep in mind that wheels don’t all turn at the same speed, so a differential or equivalent is required to allow their speeds to vary. Now you’ll need a couple of those, and they typically have their own oil for lubricant, etc. Point is, your car is becoming much heavier.
And if you’re racing, weight is a huge concern. 2WD seems like a bargain. But even on the regular roads, saving that weight and material is a good thing, ultimately reducing cost.
There are other interesting technical hurdles, but this is probably the most serious one.
There’s a couple different ways to make all 4 wheels go.
Well, way more than a couple. Let’s stick with 4wd (not awd) vs 2wd, and placement.
Old cars were mostly rear wheel drive, live axle. That’s the car backend with the pumpkin, when you’re driving behind a truck.
That pumpkin has gears to put power to at least one of the tires, coming from a driveshaft from the transmission. Pretty rugged, not very flexible and heavy.
4wd is two of those pumpkin axles, one in front and one in back. Theres a thing stuck to the back of the transmission called a transfer case that sends power to the front wheels in vehicles with 4wd.
Heavy, clumsy, but strong. Not good for speed racing.
Rear vs front wheel drive in racing:
If youre drag racing, all the weight of the car pulls the front up when you take off. If your power wheels are in the front, they lift up. If your power wheels are in the back, they push down, giving more traction. 1 point to rwd.
If you’re turning a lot, having your turning tires be able to drag you out of corners versus push you through them from the rear is great! 1 point for fwd… Sort of.
Powerful fwd cars end up with problems steering because of engine torque. Half a point deduction!
The transmissions that are able to take the most power are big long things that work well sending power to the back. Another point for rwd.
Rwd = strong transmission and big engine sending power to the wheels that don’t do turning and are located where all the weight transfers to. Turning isn’t great, but good drivers make up for that.
Fwd = more agile and makes more sense but when weight transfer and torque steer get figured in, sort of loses its edge.
That doesn’t stop fwd 1500hp Honda CRX racecars from existing. Lots of the old ways of thinking for race vehicles is falling apart, as fwd and awd are becoming better and better. Big, dumb rwd still is the top dog in high end speed though.
But what about awd? It’s a really cool way to make all wheel spin that either use electronic, mechanical or fluid dynamics to make the back wheels go. The whole thing is a little more delicate than full on race applications need, and can be heavy. They’re getting stronger and stronger though, and more cars have good awd systems.
Also a note on Nascar.
It’s a sort of formula race. that being that all the cars have to be built very very similar to each other. It’s a tube chassis, a big v8 from a couple different builders, a strong transmission and a beefy rear wheel drive. It has been this way for decades and will probably never change. There are European and Australian racing leagues that use more realistically built cars, but Nascars are very purpose built.
Depends upon the circumstances. It’s far more expensive in terms of cost of equipment and fuel economy. It also doesn’t make much sense on paved roads in good weather.
Your average vehicle doesn’t need neck breaking acceleration and cornering. As a matter of fact nearly all “4WD” or “AWD” systems are hardly used at all or maintained appropriately.
All-Wheel Drive is different than 4WD and mostly used in the Cars or Midsize SUVs that could use some sort of 4 wheel power. (Like a Subaru on a snowy mountain road) while going at a normal speed on pavement.
4WD is more for low speed off-road use.
Most importantly these systems increase the weight of the vehicle and therefore reduce the performance of the rest of the powertrain.
TLDR: in most applications they reduce performance for little gain. Sometimes they help in specific temporary circumstances.
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