Three simple questions - pls point me

[jl222]

Makes one wonder why rally cars have 4 wheel drive

No wonder needed, it is because when Jeep ran the rally circuit in 1972-73 with their new Quadratrac full time all wheel drive they totally ran off from the other competitors. They won the FIA rally champion ship that year. They beat the European cars that normally dominated the sport so resoundingly that the FIA outlawed All wheel drive until Audi and Subaru developed commercial all wheel drive systems.

It was a case of no competition and total dominance. In loose traction conditions like rally (salt) all wheel drive is the drive of choice if you want to get power to the ground reliably.

It also gives you a secondary advantage over the absolute increase in traction. It provides "terrain advantage", by using multiple drive wheels you reduce the chance that all wheels lose significant traction at the same time. The only down side of all wheel drive is drive train losses and complexity/packaging issues. If those can be managed it will out perform 2 wheel drive in almost every case.


Of course that is why it is also outlawed in land speed racing except in special construction and production even though it comes standard on a good number of production performance cars. Adjust the rules to accommodate the lowest common denominator, rather than deal with all wheel drive classes in other than production and special construction.

Larry

Yea Larry I really don't wonder.

  Hey does anyone know what became of Jim fuelings coupe with the dually rear tires?

  Seems like Larry [cant't think of his name right know] bought it and he belonged to the High Desert Racers.

        JL222

 

[Interested Observer]

The horse was not dead.  It was still out there proffering a misleading and confusing concept, at least to those not conversant with the mechanics of the situation.  Now it is.

[lsrengineer]

  Makes one wonder why rally cars have 4 wheel drive

   JL222

  have to look in my Carroll Smith Tune To Win book were it explains adding weigh detracts from tire performance.

  But later have company.

Good example - I'll bet the rally car people know a thing or two re. traction on various surfaces and what happens at different slip rates. 

[lsrengineer]

If someone wants to post info. on their vehicle I would like to run it through my current simple estimator.
Low HP cars or motorcycles that you think are not noticeably spinning the tires at full throttle in any gear only.
High HP cars that require pedaling are probably almost impossible to attempt an estimate in a simple manner. 


Need:
- engine torque or hp as a function of rpm (dyno chart preferred)
- gearing and trans. ratios
- rolling radius of driver tire(s)
- timing slip info - or point to online records I can look it up.
- push vehicle detach point and speed, rpm at that speed.