Effects of a TOO HIGH STALL converter

[tomard]

I think I got myself a stall converter that is too high, but before I go there, can you experts tell me what the typical symptoms are, if that is the case

On a positive note, I think all my leaks are gone, and my pressures are up, temps are always under 200* ..... will put my lockup switch back in when it cools down. Does anyone have the P/N for the normally open switch for 4th gear, so I don't have to get the whole "kit" ?

 

[Dusty Bradford]

Car has to build a lot of rpm before it moves. At WOT it will sound like it never changes gears. With a data logger of some sort the rpm will only drop 200 rpm or less. Even 400 rpm drop is not enough.

 

[tomard]

Are you referring to when the converter hits its stall speed or when it locks up?

Tell me if I am on right track?
A lower stall rpm, will get it moving quicker from stop?
A higher stall rpm, will produce more heat

How would one decide what is the right level for ones motor?

 

[Grimster]

So could you estimate your stall speed by looking at log files and how much rpms drop with a shift?

 

[TurboDave]

So could you estimate your stall speed by looking at log files and how much rpms drop with a shift?

It's very difficult to define in forced induction cars. But a good rule of thumb is to get the car up against the converter and see what rpm is reached with "0" vacuum/boost (aprox. 100kpa). This value probably wont match what the converter manufacturer advertises, but it's a good place to start.
If your footbrake can hold the boost, try it at 5#, then 10# and compare the numbers to advertised stall.

 

[tomard]

How about in an older carburated unit, like mine?

 

[Dusty Bradford]

Are you referring to when the converter hits its stall speed or when it locks up?

Stall speed has nothing to do with lock-up. I am speaking about rpm as in pulling away from a stop sign or when power braking. A tight converter will see 2000 rpm at 0# of boost, a loose one will see 4000 rpm at 0# of boost.

A lower stall rpm, will get it moving quicker from stop?
A higher stall rpm, will produce more heat?

Yes

How would one decide what is the right level for ones motor?

Turbo converters have to match a lot of components. Engine size, turbo size, rpm range, rear gear and tire size will get you very close. One thing that can throw a combo out the window is too much turbo for the motor. A large turbo with a low shift rpm will kill a combo.

 

[87NAT]

I had a 10" 3200 in my car and it resulted in my best 60 foot ever(1.58). BUT I was in third gear way before the 1/8 mile and the rpms climbed to 6000-6200 and only dropped 200-300 between 1-2 and only 200 rpms between the 2-3 shift. My RPM datalog looked like a straight line. Thats how you know you have a tight converter. Went with a 2800 and all is good. Havent went to the track yet though.......

 

[HeatleyRacing]

I had a 10" 3200 in my car and it resulted in my best 60 foot ever(1.58). BUT I was in third gear way before the 1/8 mile and the rpms climbed to 6000-6200 and only dropped 200-300 between 1-2 and only 200 rpms between the 2-3 shift. My RPM datalog looked like a straight line. Thats how you know you have a tight converter. Went with a 2800 and all is good. Havent went to the track yet though.......

Sounds like your converter was LOOSE, not tight, Is that what you meant ?

 

[Dusty Bradford]

HAHA. Yes, Ed meant to say loose

 

[87NAT]

Hey, Im a public school graduate from south Louisiana. Your lucky I capitalize the first letters of my sentences.

My bad....yeah way LOOSE....

 

[HeatleyRacing]

Ive gotta get off my butt and go use a few of these methods to see where my stall is. I spoke with Dusty earlier and he told me to do the RPM check at 0 boost and 5 boost like was mentioned in this thread. Ive learned more about these GNs in the past week on this board than I would have learned in years at the school of hard knocks.. Isnt this place great ???

 

[challengermike]

Converters that are made well will not slip alot when normaly driving.Alittle more than the stock one.However some companys will make converters that are very loose and have poor street manners.So dont confuse a poorly made converter with having to much stall.Usually the really cheap ones.I had a 3,800 stall in my car and it would spool super fast,drive like normal but inbetween full throttle shifts it would sit at 3,800 rpm untill it would match the rpm in whatever gear and then it would pull hard again.

 

[bison]

Yes that is correct. A quality converter like the PTC i have is very efficient in all aspects. Cruising (about 5% slip), top end (under 5% ), but when the converter is loaded the stall is increased dramatically. I see about 3100 with zero boost/vacuum. Flashes to 4700 at 24psi. The converter works so well its like magic. Its without a doubt the biggest improvement ive seen from a single part in years of playing with these cars.

 

[John Wilde]

Yes that is correct. A quality converter like the PTC i have is very efficient in all aspects. Cruising (about 5% slip), top end (under 5% ), but when the converter is loaded the stall is increased dramatically. I see about 3100 with zero boost/vacuum. Flashes to 4700 at 24psi. The converter works so well its like magic. Its without a doubt the biggest improvement ive seen from a single part in years of playing with these cars.

SNAP!!!

 

[Boost231]

good info

 

[Chevota]

Dusty - What about an AC 4000 stall with 1000 hp, 231 ci at 3000lbs? 5.33@130mph. Details will be PM'd. If there is anything to gain I'll open the checkbook


scott wile

 

[Boost231]

what is ideal for rpm drop. im looking at around 7-800rpm

 

[GNVYUS 1]

Tomard you haven't given us much to go off of but since you're a 350 with a 200-4R behind it the scenario is slightly different since you're probably not making the kind of torque we are while brake boosting the car. If you were to dyno the car and see where the torque band is you can get a better idea of what the converters stall should be so you can launch there on an N/A car.

Get that lock up switch back in as that's where the MPG and cooler fluid temps kick in when you're cruising around.

Chevota, sounds like a bolt together PTC is in your future, I think someone on here said there's was around 2% up top, damn.

 

[Dusty Bradford]

Dusty - What about an AC 4000 stall with 1000 hp, 231 ci at 3000lbs? 5.33@130mph. Details will be PM'd. If there is anything to gain I'll open the checkbook


scott wile

Got any FAST logs you can send me of a good clean pass?

With the weight of your ride I bet the converter is working very well. Obviously by the e.t's it's hauling ass The 9" doesn't work so well in the heavier cars with a limited rpm range. That's why's it's so easy to blow the a/c's away with this 9.5. If you turn over 6k at that weight, there may not be much to gain. If I can look at some logs I'll let you know though.