[Scott Stoneburg]

Ive been trying to research information about the best stall speed recomendations for torque converters. I have always thought that a flash rpm of just under peak torque would be best. Example...my motor made peak torque @ 5000 rpm. (697 tq.) But is 690 or above from 4800 to 5300. So in my thinking im would be shooting for 4800"ish" in flash rpm. That way it takes avantage of the highest torque numbers for more time. I have heard from a couple respected converter companies that they recommend " just above" peak torque for a flash rpm. It was never made clear what just above is, 100 or 200 rpm? With the cost of quality converters, its not something I can really afford to experiment with. My current converter is a TranSpecialties 9" unit. It may work very well with this new motor. It flashed to 4400 behind my 474. The 535 will probably push it farther but that remains to be seen. Anyone care to weigh in with their thought and or experiences?

[Stan Weiss]

Scott,
What was peak torque for your 474?

Stan

[Scott Stoneburg]

Originally Posted by Stan Weiss

Scott,
What was peak torque for your 474?

Stan

I never had the 474 on a dyno. I wish i would have.

[Stan Weiss]

Scott,
If we say that the 474 made the same peak torque per ci (617.53) as the 535 then a rough estimate is the stall will move from 4400 RPM to 4675 RPM.

Stan

[Scott Stoneburg]

Originally Posted by Stan Weiss

Scott,
If we say that the 474 made the same peak torque per ci (617.53) as the 535 then a rough estimate is the stall will move from 4400 RPM to 4675 RPM.

Stan

Thanks Stan. Any insights as to where I would want the converter to stall to based on the peak torque RPM?

[pastry_chef]

ptcrace.com

[Scott Stoneburg]

I went to PTC site and filled out the spec sheet. I was surprised that they didnt ask about HP/TQ. levels of the motor. When TS built my current converter the asked for that info as well as other specs. The current converter was built for a previous 461. That motor made 472 lb/ft @5200 rpm on a chassis dyno. No idea how much "flywheel" torque it made.

[blaktopr]

You will be fine with PTC whatever they give you from the spec form. From my experience from running indexes, you are not going to find a magical half second unless you are swapping between a 10" "Saturday night special" to a PTC unit. My old combo made peak hp at 6600/6800. Started at 5500 stall. Found when hot lapping the thinner fluid picked up .1 sec. Sent to PTC and they loosened to 6200 stall. Fall back on shift 6300. Changed converters due to breakage and found that you can have 2 converters with same stal but different stator package and 60' much different than each other. Also found when doing brackets that a tighter up top converter can be more temperamental with lapping and weather change. You can see differences on the grid playback where a tighter converter puts a "belly" dip in the run vs a more "linear" curve from a little looser after the shift. Pulling down the motor helps mph but can move et enough with a gulp of good air to think I'm holding .03 but I'm really holding .05 and break out by .01 taking the stripe by the same. I also seen effects of sprag vs spragless. Whats this all mean? Dont worry about the thinking of stall where pk tq is. Think about it this way. Do you want to accelerate UP to peak hp from 1000/1500 below it or start where its pretty much within 25hp of peak and as long as the converter does not gets pushed through it will do the job. Like I said, in my experience there won't be huge et swings from it anyway. Me and Darby both tested converters and found same info. By the way my current converter was built spragless to run radials and from 1st or 2nd. Not too aggressive stator to over power tire, and enough stall to work with leaving in 2nd to slow down in 10.0. It stalls at 6200 ish and falls back on shift at 6300. Engine is 535 and made peak hp at 6450. Leave in 2nd currently, shift at 6500. Will see what 1st can do in the fall with no restrictor plate and all ballast out and will most likely need a fin tweak.

[John Langer]

Converters are an interesting topic. Getting one to do exactly what you want/need can be quite a challenge. If you race a small tire class and have to pull timing on the hit, the converter may or may not do what you spec'ed it for. How fast it couples to accelerate your car can be a tricky endeavor. I race a tire limited class so I cant be as aggressive as I like compared to a car with a much larger tire. Blade number and fin angle will determine how fast and hard a converter locks up. I have a stator that pulls more g's then what is in the car now but kicks the tires at 1.1 seconds every time because it couples too fast. If your flash is too close to your fall back, it can knock the tires. If you flash is too far from your fall back it will be a dog out of the hole. If the converter in a NA application is too tight on the big end it can slow down your rate of acceleration in high gear. If it is too loose, it just wont accelerate. You really need to dyno your motor, talk to a reputable company and get a base line. You will need a data logger that logs, engine rpm, acceleration in g's and driveshaft to fine tune a converter.

[opeliac]

Originally Posted by John Langer

Converters are an interesting topic. Getting one to do exactly what you want/need can be quite a challenge. If you race a small tire class and have to pull timing on the hit, the converter may or may not do what you spec'ed it for. How fast it couples to accelerate your car can be a tricky endeavor. I race a tire limited class so I cant be as aggressive as I like compared to a car with a much larger tire. Blade number and fin angle will determine how fast and hard a converter locks up. I have a stator that pulls more g's then what is in the car now but kicks the tires at 1.1 seconds every time because it couples too fast. If your flash is too close to your fall back, it can knock the tires. If you flash is too far from your fall back it will be a dog out of the hole. If the converter in a NA application is too tight on the big end it can slow down your rate of acceleration in high gear. If it is too loose, it just wont accelerate. You really need to dyno your motor, talk to a reputable company and get a base line. You will need a data logger that logs, engine rpm, acceleration in g's and driveshaft to fine tune a converter.

Are dump valves permitted in your class?

[John Langer]

Originally Posted by opeliac

Are dump valves permitted in your class?

Yes but I am NA and for my application tightening my converter on the big end slows down my rate of acceleration so.... Dumps, lock-ups etc work great on power adder cars.

[slowbird]

Originally Posted by blaktopr

It stalls at 6200 ish and falls back on shift at 6300. Engine is 535 and made peak hp at 6450. Leave in 2nd currently, shift at 6500. Will see what 1st can do in the fall with no restrictor plate and all ballast out and will most likely need a fin tweak.

So yours stalls at 6200, you shift at 6500 and falls back to 6300?

[blaktopr]

Originally Posted by slowbird

So yours stalls at 6200, you shift at 6500 and falls back to 6300?

Something like that, yes. If you want to get technical and scrutinize over exact figures, here you go. 2nd gear leave. 1.83" restrictor plate. Through 3" exhaust, 3460 race weight using 100 pounds ballast, 2900da. A full and a partial run. We can discuss if flash at hit is stall, or the pulled down coupled dip before accelerating up is stall....but I leave that to the guy who builds it. I think he set it up a little looser stall to work with the 2nd gear hit. I do know is that he tamed down the aggressiveness of the stator because the 60' is the same as the old 434. I made sure he did that because i was killing the tire at the hit with the SLR and the old stator design which was giving me 1.31 60' times.
These graphs are 10.0 @ 138.75 for 10.0 index. Barely a burnout, and they think with a 1.56 60' that they got me at the tree and drop their guard on the top.

[chuckies76ta]

We also have Sprag, Spragless or Mechanical diode. So much to know.

video on sprags..https://www.youtube.com/watch?v=J12OKnF8F0A

[slowbird]

Chris thanks for sharing

[blaktopr]

The spragless killed the old combo .1 and about 1.5mph mostly the back half. I went with spragless this combo because radial shake broke the old converter and input shaft. Didnt need every last ounce of ET/MPH with new combo.

[Scott Stoneburg]

Will a spragless converter live with some street driving?

[John Langer]

Why run a spragless converter?

[Scott Stoneburg]

Originally Posted by John Langer

Why run a spragless converter?

I was under the impression that a spragless converter has less slippage up top.

[blaktopr]

Don't run spragless. Its slower. And creates more heat. I chose it for reliability reasons due to # of runs.