High Stall Torque Convertors!

[1viadrft]

Hello... this is my first time venturing in the Racing Tech Forum... I have an NA 300zx with AT. At the moment I'm planning on beefing up the engine and running nitrous... along with various bolt-ons. I am also planning on beefing up the tranny... this would only make sense, right? Anyhow... looking for parts to beef up the AT... I ran across a 300-800RPM stall TC. LINK I'm not sure how these work exactly. Stall? Could someone explain this to me? Is this application okay for me? I'm building up my Z... but it's not gonna be an all out race car... I want to be able to drive it on the streets too! Can someone help me out here?

[-Josh-]

If you plan on doing a lot of racing in this car then a stall converter would be a good choice for you A/T. 800 RPM seems awfully low though.

[Volvord 784VC]

Actually the information about the converter on the link states that the converter's stall is 300-800 rpm above stock. A higher stall converter allows the engine to rev higher before the converter couples, at higher rpm's the engine is producing more HP so acceleration is quicker.

[1viadrft]

So my redline will be higher?

[Volvord 784VC]

No it has nothing to do with the redline. As an example if you take your left foot and press hard on the brake, now take your right foot and press the throttle to the floor (make sure you do this in a safe place!!) the tach will rise to probably around 1500-1800 rpm and stay there, this is an indication on the stall speed of your current torque converter. With a higher stall converter if you did the same thing the rpms would be around the 2200-2800 rpm range. One caution, what I explained to you halding the brake and applying maximum throttle will create a tremendous amount of heat in the transmission and can, or will, cause damage if doen for long periods of time. Only apply full throttle for a short period and then let the engine idle to allow the trany to cool.

[1viadrft]

Thanks a million...

[CBFryman]

lol if the engine has enough torque holding the brake and flooring it will power brake it....keeping it in park will give you best indication...but even still my dads trailblazer will hit 3300 in park and 6500 in neutral...but it has a 1800 stall converter (stock converter)....

[ec437]

ay... doing it in park could seize the converter, couldn't it?

[Zgringo]

Ivia, My race Zed has a 4,500 stall TC. Which means I come off the line it 4,500, shift at 9,000, and thru the lights at 9,500.
Stall is the point at which your engine cannot rev any higher without releasing my line lock.

[AllGo'n'Show]

Ok, Sorry if im reviving a old post but I still don't get the purpose of a stall. I put my brake on full, rev up and it will hold my revs at the tree? Then when it hits green i just release the brake and gun it or am I missing something? Links would be good to if u don't feel liek explaining.

[benchtest]

(simplified version, so don't get too critical please) Stall speed is the rpm your engine will reach at full throttle if in gear and the trans. output shaft is not allowed to turn. It's effectively slippage built into the convertor. If it didn't slip at low speeds, it would act like a manual with the clutch engaged all the time. The higher the rpm, the more power it tries to send to the transmission. Once you exceed the stall speed, the convertor transmits power to the transmission input shaft with very little slippage (there is always some slippage unless it has a lock-up clutch). A higher stall convertor is used to allow the engine to reach higher rpms before it is loaded by the drivetrain. Yes, it will be streetable with only a few hundred rpm more stall, but your mileage will likely decrease.

[500]

Higher stall torque convertors were initially created for use in engines with radical cams. A typical convertor for an older { 60's } V8 might have a stall speed of 800 to 1200 rpm. If you put in a radical cam your engine may idle at 1200 to 1500 rpm { or higher }. With the stock convertor when you put the tranny in gear the motor would go dead.

Also the radical cam would cause the engine to have no lowend torque so a convertor just loose enough to allow the engine to idle would severely limit the cars performance because the engine would struggle to get the car moving. Once the rpm reached the bottom of the cams torque curve then the car would start to pull hard.

There are two basic ways to raise the stall speed; #1 is to make the convertor have more internal slippage and #2 is to decrease the diameter of the convertor.

Method 1 is often used on cheaper convertors when just a small increase in stall sp is desired. If you try to make the large dia conv have too high a stall sp you end up with a very inefficient conv. that slips a great deal even at high rpm. This generates a ton of heat and doesn't effectively use your engines hp.

Method 2 is the correct way to create very high stall speed convs. By selecting the appropriate dia for the application you have the stall sp that matches the power characteristics of your engine along with very little slippage at high rpm.

And PULEEZE don't call them "stall convertors". They are "high stall convertors ".

Lunch is ready !!
500