Welcome to the Corvette Forums at the Corvette Action Center!

Stall Speed Converters

F

fasterthanu

Guest
How do these work? I don't mean the specifics, but I do have a 2500rpm stall speed. If I floor it from a stop, the car moves instantly... Shouldn't it wait until 2500rpm to move? *I have a 700R4 trans in my 76 vette* I had a 3500rpm stall speed in a TH350 before this one, and it did the same thing. Before though, I was able to brake torque it, and hold the car to 3500rpm without tires spinning... Before I did the last few upgrades on my vette, I held the brake and floored it, and it went up to 2500rpm, and just held me there. So, to use stall speed converters, you brake torque until stall speed?
 
B

Bullitt

Guest
From the September 2002 issue of Car Craft, when questioning TCI Automotive Marketing Manager Stanley Poff:

Q: What is the least understood aspect of the products your company sells?

A: Convertor stall speed. Stall speed is relative to engine torque. Very few customers understand that the convertor is a torque multiplier. Less torque equals less stall, more torque equals more stall with the same convertor.

From Car Craft issue August 2002, an article titled "What's Up with Stall?"

So what's the talk about stall speed? Stall speed boils down to the rpm at which the convertor effectively locks up the motor to the driveline and multiplies torque at a one-to-one ratio. Since the guts of a convertor consist of a fluid coupling, the two halves of a conventional convertor are never directly locked together like a clutch disk to a flywheel- unless of course it's a modern lockup version with an integral friction clutch. A good convertor should produce less than 10% slippage after the engine rpm has exceeded the stall speed, otherwise the constant, heat building slippage will lead to wasted engine output and an early death for the transmission.

Convertors are related to stall within a certain rpm range. That's not because the convertor companies don't know their product; it's just that your individual engine characteristics and vehicle specs influence stall speed and make a precise number nearly impossible to predict. Even the term "stall speed" itself isn't perfectly defined. Here are the three distinctions you're likely to encounter.

True Stall: The rpm the engine cannot exceed when the driveline is locked. The most accurate way to determine true stall speed is by locking first gear and Reverse with a transbrake and observing engine rpm at wide open throttle (WOT).

Flash Stall: The rpm the engine "flashes" to when launched from rest at WOT. A convertor will often briefly flash to a higher rpm than it's true stall speed.

Brake Stall: The rpm the engine cannot exceed with the brakes locked and the driveshaft not spinning. Brake stall isn't usually an accurate measurement tool since the engine overpowers the wheels before the true stall speed is reached.

The article goes more in-depth with a few sidebars added in. Since this issue is no longer on the shelf, try going to http://www.carcraft.com. If it's not there, I can mail you a photocopy of the article. Let me know.

--Bullitt
 

Evolution1980

Well-known member
Administrator
Joined
Feb 25, 2002
Messages
4,302
Location
Cleveland, Ohio
Corvette
ZZ4, 700R4, Steeroids rack & pinion, VB&P Brakes
Ah-ha! Ya see? Ya see?!?!? I wasn't that far off! :D
 
F

fasterthanu

Guest
as for torque convertors for the 700r4, this is the response they sent me to that question... A 2200 stall speed converter, does that mean if I floor it the car won't move until 2200rpm? Or does that mean I can brake torque it without wheels turning and hold the car firm to 2200rpm?

Joe:



The second statement is basically correct. "Does that mean I can brake torque it without wheels turning and hold the car firm to 2200 rpm?"



We use the brake stall rating not flash stall.



Sincerely



Steve Holmes

Bow Tie Overdrives
 
B

Bullitt

Guest
Do you have a conventional or lock-up convertor?

--Bullitt
 
B

Bullitt

Guest
Are you just trying to establish launch technique? If so, I guess you can get away with brake stalling a few times, but be aware that this will affect the longevity of the parts involved. You don't really want to screw up the brakes, do you? To be safe, get a transbrake if you'll be drag racing often.

--Bullitt
 
F

fasterthanu

Guest
brakes? Cheap enough, easy enough to replace. Trying to get my best launch... Cam goies 3500rpm, stall speed is 2500rpm, would like to launch close to that vs. at 800rpm...
 
P

page62

Guest
Doesn't it put a strain on the whole driveline? Tranny, diff, everything???
 
F

fasterthanu

Guest
sure it will, but.... why get it if you are never going to use it? Its not like you do it all the time. As it is, everytime you put your foot down, it costs money...
 

Evolution1980

Well-known member
Administrator
Joined
Feb 25, 2002
Messages
4,302
Location
Cleveland, Ohio
Corvette
ZZ4, 700R4, Steeroids rack & pinion, VB&P Brakes
Fasterthanu...

I like your thinking....

---------
On an unrelated note...I think having my own mug as my avatar is even a bit too scary for me to handle.... I just don't think I pull it off as good as Ken or 82 Guy.... :D
 

Guy

Proud to Support the Corvette Action Center!
Joined
Apr 12, 2001
Messages
1,342
Location
New England
Corvette
2010 CRMT Grand Sport Coupe
Evolution1980 said:

On an unrelated note...I think having my own mug as my avatar is even a bit too scary for me to handle.... I just don't think I pull it off as good as Ken or 82 Guy.... :D

LMFAO - I think my ugly puss is pretty scary :eek and thought about changing it soon. Maybe we would get more new members then :gap .

I like this one:

maul.jpg


:w
Guy
 
B

Bullitt

Guest
Just remember that you need those brakes at the end of the run! It's your car, so it's up to you. However, you'll never get the consistency that a transbrake can provide. Not to mention reaching the desired stall speed. If you want to get the best launches, you have to buy the appriopiate parts.

--Bullitt
 
F

fasterthanu

Guest
how much does trans brake run? How hard to install? And WILL it hurt to drive the car every day on the street? I mean, it won't use it unless you set the trans brake, right?
 
7

73BB

Guest
Flash Stall is the most fun!

Would a Line-Lock not be more economical and practical for a street driven car? This is the method that I was considering. I have yet to price a trans-brake setup.

TIA
 
C

cmegga

Guest
Just out of couriusity , if you looking for a better launch why dont you consider a different gear ??

I have close to the same set up, a 375hp engine 3500rpm cam and a 2400 stall converter. It is great on the highway, but is still a dog out of the whole. I have pretty much realized there is nothing i can do about that until I get the stock 2:82 gear out of there.

Ill be upgrading to a 3:73 over the winter and Im hoping to see a big diffrence.
 
F

fasterthanu

Guest
you WILL see a BIG difference. I got a 4.10 gear =P OD comes in handy, God Bless the 700R4 trans =)
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom