<VV> PG stall & musings on speed

[Padgett]

>Frequently mentioned are the "stall" characteristics of the converters. 
>The idiot question is just what is it that's happening when the torque 
>converter stalls?

First the stall speed (sometimes called "flash") is the rpm an engine will 
reach with a transmission having a torque converter when the accelerator is 
floored in gear with all brakes set hard (see "line-lock")

A "tight" converter will reach around 1700 rpm. This is typical of 
automatics before lockup was common such as the Corvair. A "loose" 
converter will rev higher. My 88 3800 with a lockup transmission will flash 
to 2600 rpm.

For drag racing you want the stall speed to be near the torque peak of the 
engine and may be well over 3000 rpm. Back in the day it was common to see 
9" (very small) Vega torque converters behind big inch engines to reach a 
high stall speed.

It is not good to hold an engine at stall as all of the energy of the 
floored engine is going to be absorbed by the torque converter and turned 
into heat. Racing transmissions will have big coolers to help keep the 
temperature within limits during staging.

As the benefits of automatics in drag racing became evident there were 
several attempts to meld the best characteristics of both a manual and an 
automatic transmission and things like slider clutches and "clutch-flytes" 
became common.

The best thing about the automatics was that the eye/hand/foot (really 
*ss/hand/foot) coordination required to get a big-inch car off the line 
without "going up in smoke" was greatly simplified and the demand for 
people with three feet was reduced. Someone who was good with a Muncie 
could launch balancing the need for weight transfer to the back with 
holding the engine at it peak by burning the clutch for the first 20 feet 
and never touch the clutch for the rest of the run (grinding every other 
tooth off the synchro rings helped).

Something that is hard to imagine in these days of Barrett-Jackson cars is 
just what it took to be a successful racer. Things broke. Often. 
Explosion-proof bellhousings had to be a rule because clutches exploded but 
the protection added weight. Driveshaft loops were needed because a car 
could pole vault if the front universal broke (and was not good for the 
pavement either). To win required a certain element of brutality 
particularly since the tire technology was so bad that delicacy (except for 
small sports cars) meant going slow.

Someone *really* good could make a Muncie or even a Saginaw "sound like an 
automatic" and get a jump from flywheel inertia from every shift. The shift 
rods used by an aftermarket Hurst shifter were considerably larger diameter 
than those from the factory for one very good reason: the factory rods bent 
under drag racing pressure (accepted technique for shifting from first to 
second was as the engine neared the shift point (see *ss above) you pulled 
back as hard as you could on the T-handle (you could exert more force with 
a T-handle than a ball knob) and either (racer's choice) bat the clutch 
(and hope it did not stay on the floor) or pop back once on the gas and get 
right back on it hard. (Warren used to get on me about "rattling the 
floorboards").

Brutal but worth a fraction of a second on every shift at a time when 
fractions decided races.

Nowadays I have become kindlier/gentler partly because back then a clutch 
change was no further away that a tree with a big root or a tall curb. 
Today I prefer to avoid "getting out and getting under" so take that extra 
fraction of a second but once upon a time...

Padgett