Stall speed

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ir3333

ir3333

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How do you select your converter stall speed. Do you target rpm below your normal cruise speed
so there is no slip while cruising, or just look for a flash rpm that is close to your maximum lo rpm torque?
Can you get both? Will modern converters be tight at most rpm and still flash to a higher values?
 
Just like a cam, it’s application specific. You racing? Cruising? Mostly highway? Gear ratio? Weight? Call a quality converter company and give them the details, but be brutally honest with yourself on what you want.

In my small town where everything is 25mph, I run short gears, and I aim my stall speed at my 65 mph cruising rpm. Not because I do a lot of highway, but because I don’t want to create excessive heat if I decide to. Loose or tight, long term cruising under the stall speed will create more heat due to slippage.
 
i did have Frank Lupo spec me a 9.5" converter for a 340 that was lazy at lo rpm. It was reasonably tight cruising but i grew to dislike driving through it coming out of corners or resuming speed after going down hills. It would flash to about 3200 rpm from idle and was fun but the novelty wore off and it didn't seem very effective at slower speeds like 30 or 40 mph.
 

ir3333 said:
i did have Frank Lupo spec me a 9.5" converter for a 340 that was lazy at lo rpm. It was reasonably tight cruising but i grew to dislike driving through it coming out of corners or resuming speed after going down hills. It would flash to about 3200 rpm from idle and was fun but the novelty wore off and it didn't seem very effective at slower speeds like 30 or 40 mph.
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Get a PTC and not the cheap one. I’ve got $1200 in my current PTC and it’s a work of art. It will idle up my driveway and flashes to 3600.
 
Find a GOOD performance rebuilder, and there are a number of good ones that have been mentioned. They probably have a website, and usually have a spec sheet that asks a lot of questions. Questions to some that seen silly, but they need to be answered honestly. With that information, the builder can build a converter that is best suited for your application. DON'T let price be your main reason to purchase, as having worked in the converter industry, and have seen a ton of converters apart, you only get what you pay for. Cheap converters are cheap for a reason.
 
ir3333 said:
How do you select your converter stall speed. Do you target rpm below your normal cruise speed
so there is no slip while cruising, or just look for a flash rpm that is close to your maximum lo rpm torque?
Can you get both? Will modern converters be tight at most rpm and still flash to a higher values?
Click to expand...
Send me a message, I have some information that will be a big help to you.
 
ir3333 said:
i did have Frank Lupo spec me a 9.5" converter for a 340 that was lazy at lo rpm. It was reasonably tight cruising but i grew to dislike driving through it coming out of corners or resuming speed after going down hills. It would flash to about 3200 rpm from idle and was fun but the novelty wore off and it didn't seem very effective at slower speeds like 30 or 40 mph.
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weird, i've run a few lupo converters in different cars over the years. all 9.5". they always nailed the converters for me..
 
abodyjoe said:
weird, i've run a few lupo converters in different cars over the years. all 9.5". they always nailed the converters for me..
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Im not putting words in the OP’s mouth but it sounds like he asked for more converter than he really wanted, which is common. Most converter companies and going to give you exactly what you ask for, regardless of if it’s what you actually need/want.
 
UCC did mine. Love it

CONTACT UCC​

Ready for the​

High Performance Custom Torque Converters - Ultimate Converter Concepts

Detail Specs​

Name
Email
Phone
Transmission Type Manual Automatic
Transmission Make
Low Gear
Input Shaft
Converter Bolt Pattern
Transmission Brake
Full or Pro Tree
Two Step RPM
RPM @ Shift Point
Expected Stall RPM
Ft Brake or Transmission
What Size and Stall?
Mid Plate Thickness
1/4 Mile or 1/8 Mile or Other
Altitude of Track
Make of Car
Weight of Car
Type of Rear Suspension
Engine Size
Bore
Stroke
Rod Length
Cylinder Heads
Compression
Intake Manifold
Carburetor CFM
Fuel
Nitrous
Supercharged/Turbocharged
Camshaft
Lift
Adv Duration
Duration @ .050
Rear End Ratio
Tire Height or Rollout
Tire Width
Average 60' Time
Avg 1/4 Mi ET & MPH
Other Instructions / Comments
 
Question...did you select a converter based on your cruise speed or a specific flash stall
..They nailed it for me.. Op asked for wrong converter.. spend $1200 bucks... find a good builder...give them the details... be honest
all good advice guys but i was wondering what you based your decision on?
 
Transman..your inbox is full. I think that i would just target a stall a couple of hundred rpm below my normal cruise rpm.
Not interested in high rpm flash stall. your thoughts...pros / cons?
 
The general rule of thumb is that you want the stall speed to be "around" the same RPM that the engine makes the most torque on an engine Dyno.

This is why a Dyno sheet from an engine (not chassis) Dyno is also a very important piece of information to give to your converter builder.
 
ir3333 said:
i think that is good advice for a racing application and the cam duration factors big too for racing.
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Converters are still a bit of a mystery to me but seems to me for the streets you need at least enough stall to coverup cam overlap and above that how much performance you want (compromise/uncompromise) and "UN" seems around peak torque.
 
For those that know got a question somewhat related.

Say you shift at 6,400 rpm peak hp is at 5,800 rpm but you got a long flat torque curve of at least 450 lbs-ft from 3,500-4,500 rpms but technically peaks 455 lbs-ft at 3,500 rpm.

Wouldn't something around a 4,500 rpm stall generally/potentially be better since it's practically the same the same torque but obviously more power to launch especially if traction is no problem ?
 
273 said:
For those that know got a question somewhat related.

Say you shift at 6,400 rpm peak hp is at 5,800 rpm but you got a long flat torque curve of at least 450 lbs-ft from 3,500-4,500 rpms but technically peaks 455 lbs-ft at 3,500 rpm.

Wouldn't something around a 4,500 rpm stall generally/potentially be better since it's practically the same the same torque but obviously more power to launch especially if traction is no problem ?
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I think this is true. I was always under the assumption that the stall speed matched to the rpm where the torque peaked (or thereabouts) would give the greatest acceleration. But then I read an article in which an engine builder said that a real race car never operates down at peak torque. It should always be above that point. Since then, I have heard several racers say that their cars were faster with much more stall speed than they would have anticipated. Obviously , with a street car, there will be some compromises. As far as stall speed vs cruise rpm, my 318 Duster with a 9.5 PTC flashes to about 3500 and cruises about 3000 at 70 mph with a 3.23 gear. My 440 Satellite has a 9.5 Dynamic that flashes closer to 4000. Also 3.23 gears. No issues with either. The Sat feels a little more "slippery".
 
I run a 3 plate, carbon fiber lock-up converter in my ride. I read on these forums to spend the money for a higher end converter, which I sourced at Precision of New Hampton. It stalls at 3800 rpm, and locking and unlocking the converter in 4th gear on the highway at a steady state cruising speed only changes engine speed by 350 rpm.

It feels like a normal converter at low throttle settings and is otherwise hard to tell it has a medium stall built into it. At high and full throttle settings, it allows the engine to get into the power band instantly. One of the best places to spend the bucks in my experience.

200R4 3 (Medium).jpg
 
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ir3333 said:
How do you select your converter stall speed. Do you target rpm below your normal cruise speed
so there is no slip while cruising, or just look for a flash rpm that is close to your maximum lo rpm torque?
Can you get both? Will modern converters be tight at most rpm and still flash to a higher values?
Click to expand...

For some reason or an other, by message box is full, and I'm having a problem deleting them. Send me an email.. gshortre@telus.net
 
But there are 2 stall speeds? normal when the converter engages the driveline under regular driving and flash during wide open throttle from idle. Should a converter with a flash stall of 3200 jump to 3200 rpm while cruising at 2500 if you go to WOT?
My dynamic 9.5" wouldn't.
 
It depends on your gear,driving habits, among other things.
If you have a football field sized torque curve stall is less important unless you are drag racing. Then shift recovery plays a role.
A small engine with lower torque at lower rpms will want/need more stall to keep the cam from falling below its operating range.
There are compromises to everything. Big block torque makes the wrong converter a little more forgiving IMO.
You can also have too much stall but that is another topic.
 
ir3333 said:
i did have Frank Lupo spec me a 9.5" converter for a 340 that was lazy at lo rpm. It was reasonably tight cruising but i grew to dislike driving through it coming out of corners or resuming speed after going down hills. It would flash to about 3200 rpm from idle and was fun but the novelty wore off and it didn't seem very effective at slower speeds like 30 or 40 mph.
Click to expand...

Depending on the details of you car, and your personal expectations, what you describe might be unavoidable.

A performance oriented street converter is a compromise.
 
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