I was curious as to what the effects of a high stall converter would have on horsepower and torque readings when run on a Dynojet. The converter is the source of a lot of slipping, how much power would this absorb?

If you go above the converters flash stall speed the H.P. and torque should be fairly accurate.

hmm, i was concentrating in class when my mind wandered to this in school today...

what would happen if you have a... say 4000 stall converter and have a dyno pull... what would happen to the graph at 2000-4000rpm??

The graph would show the torque multiplication. If it truly flashes to 4000 it will almost immeditately go there and show a lot more torque than the engine really makes. If you look at the graphs of tq and HP you can see where the converter starts to get closer to a lower slippage/multiplication area.

The stall speed will increase on the Dynojet because the rollers weigh 5400#. If your converter stalls at 4000 with your 3600# race car, expect as much as a 500 rpm increase. The torque multiplication will be evident in the graph. You can plot the slip by graphing rpm vs. speed. If you use nitrous you can see the difference in slip created by the extra torque.

My son's first pull on a Dynojet resulted in a vertical spike when the operator hit it at 3500. It went to 6000 in less than a second then quickly went on up to predetermined 7200 limit. This all happened in less than 4 seconds, everybody jumped back. The car jumped up about 4" in the rear from the instant center being different than on level ground and the torque spiked at 637 lb. then trailed off. the H.P. peaked at about 7000 RPM @ 561 H.P... The converter flashed about 2000 RPM above its rated stall speed. ( 482" w/Dart "335 CNC" heads & dominator carb.)

Harold..

Just out of curiosity, what is the Chevelle making RWHP without the bottle these days?


JIM

Hi Jim, It made 646 H.P. on the motor the last time we tried it. Just got back from Springfield a few weeks ago and since they grouped all the N/A and N2O cars everybody just made juiced pulls, my son went above the stall speed and made 924.7 H.P. and 738 lbs. Tq. on a 325 shot. He was #3. We should know what it runs at that level at the Oct. 16th race. ( Best is 9.22 so far but it went through low gear on the motor and had a terrible 60'-1.489 with new tight converter.)

IMO a chassis dyno is not accurate with a non-lockup converter for just that reason; you will always have slippage with a non-lockup converter and that does not provide accurate numbers. A good, efficient converter may have as little as 5% slippage, but that still skews the results. With torque multiplication factors varying with different stators and slippage coming into play you will not have a true picture of real flywheel horsepower IMO.

I think your right Steve, any attempt to guess at flywheel horsepower is futile. My sons car has outrun the car that beat him by fourty H.P. on the Dynojet, last year, twice. (636 vs 679 on the Dynojet)

Hi Jim, My son just went to the Dynojet again and the vacuum pump seems to have made a difference. It registered 672 RWHP on the motor. The last big shootout is coming to Mokan, a strip on the Kansas/Missouri border just north of Joplin. This as a eighth mile race and our car just started biting with a new set of tires and wheels. (1.315 - 60').

Hi again Jim, We're back from the shootout race at Mo-Kan and we had a great time. My son drove his way to a class win over a faster car in the finals A 5.93-.415 light vs. a 5.89-.550 light (you snooze, you loose). I think he teased the guy a little and said he got hot, so he quit. The're all friends so i hope it's all forgotten now because no race victory is worth loosing a friend over.

On the dynojet, if you get a file to look at with the dynojet run viewer....... Compare RPM vs Speed.

When the line is straight, and isn't curving anymore, that's when you've got the tightest spin. Usually it's the flash plus around 500rpm. In my experiance atleast.

Higher quality converters will flash then after the flash be dead on with minimal slippage.

I dynoed with a 700R4 and stock converter, Put that Speed vs rpm chart up.. then dynoed with a TH350 and 3000rpm stall... and you can really see the difference. My RPMS were up about 500across the board with the stall. Same rear/gear/tires etc.