Vehicle weight and TC stall rating?

[Sleeper]

How much does the vehicle's weight come into play with the stall of a converter?
I have a hybrid that weighs 2800 lbs, now given the same engine setup and HP in a 3800lb car, would the converter stall and behave the same?
I guess I'm trying to figure out, with less load would you need a higher stall rating?
Much like when rating the stall of a given converter. Less hp =less stall, more hp = higher stall.
Clear as mud?

Paul
1972 Toyota Celica with an 87 GN Engine.
Motor 30 over, 10/10 crank, high vol.oil pump, SpeedPro 194/204 Cam, Comp Cam 980 valve springs, ported and polished heads, PTE 44 turbo, 0.65 Ex housing, Dutweiller Big neck intercooler, Jay Jackson's 62 mm Throttle body, ported and polished plenum with upper part of EGR tower removed, Power Plate, solid MAF pipe, K&N Filter.
Postons headers and 2 pce crossover pipe. Hand made TH style DP, 3" exhaust split to 2 ½ " dual Magnaflows.
52 # Siemens low imp. injectors, Red A's modded ECM, Translator Plus, LT1 MAF (Mounted in the up-pipe) Extender chip, Boost Commander, dual wastegate solenoids, Adj. Fuel Reg, Hot wired Walbro GSS 340 intank fuel pump, Poly Mount.
ATR billet OD H20 pump pulley, FlowKooler water pump, 2 speed Ford Taurus electric fans, RMI 25.
Type II coil pack and module, 8.5 Magnecor's, AC CR42's.
DirectScan, Caspers Knock gauge, Autometer 30/30 boost/vacuum gauge, Autometer tranny temp gauge.
200 4R tranny, B&M 28,000GVW SuperCooler, remote filter, Energy Suspensions Polyurethane mount, stock D5 converter, B&M Megashifter, Chopped Ford 9" @3:25 Trac Lok rear with a 300 ZX disk brake setup. Air bags, 85 Supra 57 mm piston 10" vented rotor front brake setup, Nissan 300 ZX 15/16 master cylinder, Dunlop SP 5000 205/50ZR 15's front SP 8000 245/50/15's rear. Hurst Roll control, Ford power steering rack, Bilstein Rally shocks rear, Tokico race struts front, heavy duty coils.

 

[MeanBuicks]

Yes and No.

The true stall of a converter behind a given powerplant will not change regardless of other vehicle parameters. If your engine was installed in the Titanic the converter would stall exactly the same as is does in the Toyota WHEN USING A TRANS-BRAKE; the ultimate load.

That being said, the actual behaviour of the converter in accelerating the vehicle will vary with different vehicle weights, gear ratios, tire heights, etc. These parameters will provide different loads on the output side of the converter.

Flash stall speed, the split-second tach reading when going to WOT, will tend to vary due to the different loads induced by the above variables. Then you have converter variables such as torque multiplication, rate of acceleration & efficiency.

Your thinking is correct and that's why those vehicle parameters are utilized by converter manufacturers to match a race converter to a customer's application. What's behind the converter is just as important as what's spinning it.

 

[2quiktocare]

Well said Greg. Precisely why you should have your converter built specifically for YOUR aplication, not a shelf model with a set stall. Mark

 

[Sleeper]

Thanks Greg and Mark.
Just for arguments sake, would the stock D5 "behave" differently in my application than in a full weight car?

Thanks,
Paul

 

[2quiktocare]

In a word,,,, YEP

 

[Sleeper]

More words please

I'm asking because with my engine/turbo combo in a TR, most would say the stock D5 would be ok for a 95% street driven car. I'm trying to figure out if I'm making my car under-perform by using it.
I know the PTS Extreme would really make a difference... but I'm really want to understand the functioning of what I have presently.

Thanks
Paul

 

[2quiktocare]

Sleeper, go to our website and fill out a complete converter spec sheet so we can have a look and tell yo more from that. Make sure you fill it out completely so we ca see what you have, and I can better answere your question then. Mark

 

[Sleeper]

Mark,
Tried to fill out the spec sheet, but when I submit it it redirects to " Page not found" ???

See my sig above, for car setup.

Greg, anyone...
I'm still fishing for specific input about the D5 "behaviour" behind different weight vehicles.


Thanks,
Paul

 

[Sleeper]

ttt

 

[chris718]

SORRY TO TAKE THIS STANCE BUT I DONT AGREE WITH ANYONE HERE ON THIS ONE.IF THE VEHICLE IN QUESTION IS NOT USING A TRANSBRAKE THE SAME ENGINE ,CONVERTOR ,REAR END RATIO WILL GENERATE LESS STALL SPEED IF THE WEIGHT OF THE OTHER VEHICLE IT IS TO BE INSTALLED IN IS 1000 LBS LIGHTER .THIS IS SIMPLY BECAUSE THE ENGINE WILL NOT HAVE TO WORK AS HARD TO GENERATE ENOUGH LEVERAGE TO OVERPOWER THE TIRES.THIS IS PROVIDING THE ENGINE REACHES THE POINT OF OVERPOWERING THE BRAKE SYSTEM,WHICH IS A VERY REAL SCENARIO .IF THE CONVERTOR IS NOT MATCHED TO THE ENGINE IT WILL NOT INCREASE MUCH BECAUSE THE ENGINE WONT BE ABLE TO ENTER THE TORQUE CURVE WHEN UPLOADED AGAINST THE RING AND PINION,THE BRAKE SYSTEM AND THE VEHICLE WEIGHT.FLASH STALL SPEED WILL INCREASE IN THE LIGHTER CHASSIS BECAUSE OF THE REDUCED PRESSURE /VACCUM DROP ACROSS THE ENGINES INTAKE SYSTEM ALLOWING THE ENGINE MORE FREE RPM RUNUP AGAINST THE LOAD IT MUST OVERCOME TO INGEST AIR AND FUEL NEEDED TO PROPELL THE VEHICLE FORWARD,MUCH IN THE WAY A VEHICLE REVS LIKEV A F#$% IN NEUTRAL OR PARK.HOPE YOU ALL CAN SWALLOW THIS AS I HAVE SEEN THIS SCENARIO BEFORE AND IT IS CERTAINLY A REALITY.

 

[Sleeper]

Thanks for the reply Chris.
I seemed to have opened a can of worms here.

So if I understand this... Because my engine has to work less to move my car, it doesn't need to produce as much torque, and that will cause the converter to stall less. If I'm stalling less it may not be in the optimum part of the torque curve???

Now the confusion... If I run too much stall, I'm just going to break the tires loose and go up in smoke. (I'm talking about street tires here)

What is the optimum stall for my combo?

Paul

 

[Sleeper]

Just doing some more thinking.
Tighter higher stall, or looser lower stall? Or is this animal possible? (Working with street setup 2200-2800 stall)

Paul

 

[chris718]

going to bed ill answer tomorrow after work .

 

[Taffy]

It will still not matter the weight of the car if he is overpowering the tires. It is true that a heavier car will be able to hold the tires better, but since we are talking about 2 different cars, that does not count.

If the 2 different cars had the same exact ability to hold the tires from spinning eg very good brakes, the converter will still stall at the same place.

I could never get more than 5 psig boost out of my GN and it was in the 3600 lbs range with me in it. But that is not to say that the Toyota will only be able to hold 3 psig because it is lighter.

Greg is right, but Chris brought up a VERY good point. So sleeper, how good are your brakes on your Toyota??

 

[Sleeper]

Taffy,
Brakes are very good.
I'm more concerned about daily driving, when I punch it. I'm not always going to be leaving every stoplight building boost on the brake, and am wondering how my light weight effects the stall.

P.S. Greg, Mark, Chris, etc.
I'm going to be away for a few days, and I might not have access to a computer, so If I don't respond to this post right away, please bear with me.

Paul

 

[Sleeper]

I'm back.
I would love to get some more input on this.

Paul

 

[Taffy]

The stall rating usually is rated when the car is not moving, with the tires not spinning. With the turbo cars, more boost gives more stall, generally.

If think that your question is: How high will the converter flash on the street when I stab the accelerator. The heavier cars will load the turbo harder, thus higher flash. On your lighter car, you might not flash the converter as high as a car that weighs 3600 lbs like my car.

I do not know how to change flash in the converters, so hopefully one of the trans guys will let ya know.

 

[chris718]

the toyota definately wont be able to hold the brakes if a 3650 gn cant at 6 to 8 psi.that is my point and if it does itll stall the same but flash higher in the lighter car.been there done that and if you havent then you dont really know do you?my post should be read again so you can see that i clearly stated the point about overcoming the brake system.without a transbrake or big tire your motor will overpower the tires at wot stall with the vehicle stationary.

 

[Sleeper]

Thanks for the replies.
I understand what you are saying about the brakes Chris. FWIW I have a Ford 9" with a disk brake setup under the car, but I'm really not as concerned about launching the car for drag racing purposes. I would definitely go with a trans brake then.
I'm more interested in the get up and go of daily driving street driving.
So, what is recommended?
Still trying to figure out the stall/flash issue. Can they be mixed and matched?

Paul

 

[Sleeper]

ttt
Greg, Mark, Bruce ???