Four Wheel Drive Drag Race Cars

Post by **TyreFryer** » Sat Jan 19, 08 4:19 pm

Does anybody know of any four wheel drive drag race cars that have been built? In theory it would help to distribute the power to twice as many tyres but I guess there must be some reason why it isn't done?

I seem to remember when Duncan was going to race his Challenger against that Evo/Subaru/can't remember what it was now, for the magazine article, the guy who owned it was talking about problems with the four wheel drive when drag racing it?

Jon · Post by **Jon** » Sat Jan 19, 08 4:24 pm

this thing that my workmate helped build is one...(I made a couple of billet bits for it) I think a lot of the drag skylines, subarus and evos are still 4 wheel drive

http://www.keithcowie.com/index.php?page=about

and of course there was the hurst hairy olds

Post by **TyreFryer** » Sat Jan 19, 08 4:36 pm

Interesting stuff, thanks Jon. Just been reading up on the Hairy Hurst though and it was an exhibition car like the Hemi Under Glass Barracuda. What about serious race cars other than modern Japanese, anybody know of any others?

AllKiller · Post by **AllKiller** » Sat Jan 19, 08 4:41 pm

Its because you need more power to make up for the drivetrain losses through 2 sets, not one.

Skyline GTR's are 2wd until the engine torque gets up and then switches to 4wd....this helps,
hence the GTR's famous snaking and snatching as they accelerate, as the 4WD kicks in transfering more power or less to the wheels gripping most.
But come off the gas fast in a bend and your back to 2wd

just when you need it most.

Alot of GTR's are made rear wheel drive only for serious drag stuff

Then theres TV Tommy Ivo

http://www.buicks.net/misc/tommy_ivo.html

Post by **TyreFryer** » Sat Jan 19, 08 4:57 pm

AllKiller wrote:Then theres TV Tommy Ivo
http://www.buicks.net/misc/tommy_ivo.html

Superb!

I hear what you're saying, but do you really lose more power than you can lose traction, surely you would be able to get more power through the wheels (if you can make it)?

Anonymous · Post by **Anonymous** » Sat Jan 19, 08 4:58 pm

i guess the main reason is , imagine you have a perfect launch on your car, the front wheels will have next to no weight on them, so pointless trying to get any power transmitted to them, and any power is likely to be negated by the extra weight.

but maybe if you had 4wd setup with most of the weight at the front so that the weight transfer would make the power go evenly though all wheels on launch, that could work

Post by **TyreFryer** » Sat Jan 19, 08 5:02 pm

That's where the engine is!

AllKiller · Post by **AllKiller** » Sat Jan 19, 08 5:43 pm

Its a fine balance Martin, the extra weight is a problem as Will said, and loss through the drive train as i said,

But if you increase power to overcome this, you normally needs a bigger motor....as most 4WD derivatives have over a stock 2WD version.

Then your back to square one big power, to move more weight and smoking all 4 tyres off the line .... zero benefit

Post by **TyreFryer** » Sat Jan 19, 08 6:56 pm

Hmmm, a regular SWB Landrover weighs 2,953lbs with fuel (just used this as an example as I have a load of Landy books for reference). That's with the transfer box and front axle and prop. It should be possible to shed some weight from that but of course a bigger engine would add some more. So even with an truck type, heavy duty running gear it's 'weigh' lighter than a B body. So weight may not be a problem on something with less agricultural engineering, what about parasitic drag of all the extra running gear?

AllKiller · Post by **AllKiller** » Sat Jan 19, 08 7:21 pm

Parasitic loss is about 25-27 % on a 4wd vehicle with a manual box, about 30 % on a auto.

A good comparison... would be a Jensen FF 440 with 6 Pak and 4WD, and a E or B body with a 440 6....bet the E/B would win everytime.

Pete · Post by **Pete** » Sat Jan 19, 08 8:09 pm

Discussed this with Mr Hauser recently, his view was that a 4WD could not live with a well set up purpose built AMERICAN style drag car. The cost to achive a similar performance is huge.

However, it is a different matter on the road.

Anonymous · Post by **Anonymous** » Sun Jan 20, 08 12:27 am

Thats really only a handling issue though, heard a good saying lately,

If it can go around corners its not going fast enough!!!!

Post by **TyreFryer** » Sun Jan 20, 08 10:40 am

AllKiller wrote:Parasitic loss is about 25-27 % on a 4wd vehicle with a manual box, about 30 % on a auto.

That's interesting, where did you get these figures from? What's the parasitic loss on a 2wd vehicle for comparison?

Now I'm going to show my ignorance. How much traction can you expect to lose at best on a 2wd A,B or E body mopar at full throttle on launch running a fairly standard setup? Maybe super stock springs, Suregrip, slicks, standard axle, pinion snubber, with or without tubbed arches? Say for arguments sake if you are making 600bhp? What percentage would you be able to use without braking traction?

Pete · Post by **Pete** » Sun Jan 20, 08 11:05 am

Dave's maths speadsheet details the approx bhp getting to the track.

I found that putting in the times and speeds I had, plus the known weight (4 post weighing facility at Shakey) it has loosing very little.

I think the key thing when working on a drag car is to know the ACTUAL weight, not a figure out of a book.

For example, Nick Woods '70 Roadrunner was found to be 200lbs heavier than my '69 Barracuda. You would not have answered that out of a book or in a pub quiz.

Post by **TyreFryer** » Sun Jan 20, 08 11:11 am

My Satellite weighs 3,400lbs Pete (including fuel and me), with everything stripped out. In theory if I stuck the same engine in a SWB Landrover with all wheels driven (would have to change to Rangerover transfer box) I'd save around 400lbs and have all wheels driven.