I'm trying to do some research and think I have
a method for finding what your torque converter
is stalling at from a 1/4-mile ALDL scan.

If anyone has ALDL data from their 1/4-mile
runs and have a good idea what their converter
stall should be, I was hoping you could post
your results to see if the data supports the
hypothesis?

I need:
1) RPM reading when your VSS (speed)
first goes non-zero at the launch
2) What your converter stall should be
3) What kind of VSS your car has (or what
year car if the VSS is original) The
VSS should be magnetic in '90-'92
cars, and mechanical in the '82-'89
cars..

What I think will show is that the RPM of the
magnetic VSS cars will be exactly at the non-zero
VSS point. On mechanical VSS cars, the
stall will be 400-500 rpms less than the
non-zero VSS point...

Data from my two recent motors and different
converters are shown below. {ZZ4 w/3400
stall shown stalling at 3900 and the 383
w/2900 converter shown stalling at 3400.
My VSS is circa 1985..}

(I posted this on the transmission board but I
guess it wasn't the proper forum..)

Thanks for any help..
mike

 

If you have your transmission gears, rear gear, tire height, and engine speed you can derive an engine speed as if there were no slip in the TC. Compare that to your actual engine speed and you can find the stall of that combo.
The only thing you need to be able to find is which gear you're in, but that shouldn't be hard unless you have a high stall. Even then you can just look at the MAP to see a shift.

 

?????

Your sidebar says you have a '12" 2800stall'
converter. How do you know it stalls at 2800?

Can you give me an example from what you're
describing above that shows that your conv.
is actually stalling at 2800? (flash stall)

thanks
mike

 

Look at a data log, and from a standstill, at 100% TPS, look at how high the rpms go to before you see a VSS input. That will be the flash speed of the converter. Your stall speed with be very close to that unless you have a high slippage converter.

One very, very important and often totally ignored characteristic of conveters is how the stall/flash stall speed on the converter allows the engine to recover after a shift. depending on the tranny and shift rpm of the engine determines from what rpm an engine has to pull from after a shift and that relationship to the converter stall is important. While the intial leave from the lights is critical, the shifts further down track are too.

 

One point is that the older mechanical
VSS systems have to see several pulses
before they go non-zero, and so the
stall point appears 400-500rpm higher...

I've verified 2 mechanical and one digital
VSS, but looking for some more data to
coraborate it...

thanks
mike

 

One thing, I've thought of doing along these lines is using a Anti-lock tone ring and sensor, that'd have to give some excellent resolution.