When you are about to spend some serious money on your car , or as is normally the case even more ! don't make the converter the weakest link. Matching a stall converter to your engine is one of the best performance enhancements that you can make. So often we recieve converters for inspection,report and assessment and upon reciept of the vehicle specs the converter is mismatched to their specific combination. All good things take a little bit of extra effort and in the case of Hi stall converters filling in a spec sheet can be a great investment by getting it right first up. You can send us an enquiry form by clicking the enquire on line tab under the diamond logo or give us a call during business hours. Want to deal with someone closer to home ? ,we can put you in touch with a number of selected local and interstate resellers who are able to talk you through your coverter , transmission and engine combination.

If you have the time we have compiled some FAQ about stall and stall speeds and tried to put them into some easy to understand language !

STALL SPEED

Torque converter stall is a commonly used term and is commonly misunderstood.  Stall is the speed at which the converter will hold the engine speed and not allow further gain, i.e. the engine “stalls”. The key word here is engine. The speed at which stall occurs with a given converter is a function of engine peak torque. It is clear that the stall speed on a given converter will not be the same when coupled to a tame small block engine as it is when coupled to a high performance big block engine.
When comparing stall speeds it is very important to account for the engine that drives it.  True converter stall can best be determined when a Transbrake is used.  Testing for stall value by locking the wheel brakes generally does not produce a true stall value because the engine power can often cause wheels to turn overpowering the brakes.  Stall speed determined by this method should be identified as such when discussing stall speed determination.  Flash stall is determined by launching at full throttle and observing the peak RPM attained at launch.
Selection of the right stall speed for your vehicle should be matched to the engine peak torque, engine torque curve shape and vehicle weight. In general the stall speed selected for your converter would be 500/700 rpm below the peak torque.  This speed allows the margin for application of the torque reserve on takeoff.  When selecting stall speed without having prior experience to go by, it is better to conservatively estimate the engine torque than it is to over estimate it.  If you over estimate the torque output, you will have a converter with a stall speed too low making your car slow off the line and a slow ET.  A properly selected stall speed will give you better launch and a better ET.  You can see why it is important to consult with professionals prior to making a stall speed selection.  Within the converter, stall speed is balanced off against inefficiency after launch. Getting desired stall at the expense of performance after launch is just as costly as improper stall speed to begin.  The optimum converter has careful selection and design of changes to the impeller, turbine and stator.

HOW CAN I DETERMINE STALL SPEED OF MY CONVERTER?

Stall speed is very difficult to determine unless your car is equipped with a Transbrake to lock your drive train.  Testing stall speed by holding the wheel brakes and running the engine against the locked brakes will usually result in wheel rotation before true stall speed is reached.  The engine simply overpowers the ability of the brakes to hold the car.  When rotation starts you are no longer at stall.  For this reason people talk about brake stall, which is not a true stall at all.  An alternative method of measurement is to launch at wide open throttle and observe the engine RPM reached at launch.  This is flash stall.

WHY IS PROPER STALL SPEED IMPORTANT?

Stall speed should be matched to engine performance, the car weight, tire size and gear ratio.  Proper selection of stall spec will make for quicker launch, better 60 ft. time and a better ET.  It is very important that these parameters be specified when ordering a converter to assure satisfaction.

WHY IS STALL SPEED DIFFERENT WITH THE SAME CONVERTER ON DIFFERENT ENGINES?

Engine output is what really determines stall speed for a given converter.  For this reason the converter you have been using may not be adequate when you improve performance of your engine.  This is particularly true when using an improved camshaft.  Improving heads, carburetion, installing turbos and manifolds can all affect stall speed.  Remember that you want to have stall speed matched to your particular car combination.

WHAT IS FLASH STALL, BRAKE STALL AND TRUE STALL?

The truest definition of stall speed can only reliably be determined in conjunction with a Transbrake. Wheel brake stall is determined by locking wheel brakes and running the engine against the locked brakes.  As discussed above, the engine will usually overpower the brakes and wheel rotation will begin before the true stall speed is encountered.  Flash stall is observed by launch at full throttle and observation of peak RPM at launch.

IS STALL SPEED THE ONLY CONSIDERATION IN SELECTING A CONVERTER?

While stall speed is very important it is by no means the only consideration when selecting a converter.  Torque multiplication at launch and high end efficiency are equally important.  Stall speed can be attained in many ways that cripple the converter in other ways.  Stall speed can be obtained at the expense of looseness at low speeds and loss of performance at higher speeds after launch.  You want a converter that produces the right stall without sacrificing performance down the street or down the strip.

DOES STALL SPEED AFFECT NORMAL STREET DRIVING?

Normal driving is not affected by stall speeds up to approximately 3000 rpm, particularly with a good converter.  A car will begin to roll normally when a high stall speed converter is used.  Quick acceleration will be favourably influenced by stall speed. A very high stall speed (above 3000) would not be satisfactory for street use.

We hope this helps your understanding of what stall is about. If you still have questions then give us a call on 07 3320 1366