12secSS

iTrader: (30)

So I dyno'ed my SS with the B&M Holeshot 3000 converter (70442) a couple of weeks ago before the cam, and again last week with the addition of an F13 cam. The converter is a 10" rated at a 3000 true stall with a 2.0 STR. I found the results of the dyno comparison between the lock and unlocked numbers very interesting. As you can see, the above numbers are from the dyno session without the cam, below it are the results with the addition of the F13. Interesting to note that the flash stall was at 3200 before the cam, and now it is at 3700 when logged with HPTuners. On both dyno sessions the locked run was done right after the unlocked run.

Dyno results to reference:
Before Cam:
https://ls1tech.com/forums/dynamometer-results-comparisons/781681-dyno-ed-ss.html

After Cam:
https://ls1tech.com/forums/dynamometer-results-comparisons/827220-hms-dyno-results-f13-cam-only-44rwhp.html

Cars mods in my sig.

Ragtop 99

iTrader: (7)

You can also see that you gained about 300 - 400 rpm in shift extension from the extra torque of the cam.

JNorris

iTrader: (4)

I do not understand.....It seems that up to 4400 rpm you lost HP when you locked the converter?

John

performabuilt

iTrader: (25)

I noticed that to ussually its the other way around, Could the locked/unlocked numbers be reversed , Never heard of gaining HP on a dyno by unlocking the converter?

Ragtop 99

iTrader: (7)

No, the data is exactly what you expect to see. Look at the 5000 rpm line of the second group (after F13 cam). It shows locked HP was 389 versus unlocked of 376 HP. Just what you would expect from a converter that is passed its shift extension. Passed the shift extension, the converter is eating HP.

Prior to the end of shift extension, the converter should provide torque multiplication. At 3000 rpm (dynojets measure rpm as if they were an manual with no slip) output, the engine is up around 4400 rpm. The converter is using the slip to its advantage to create torque multiplication. Its not very great at this point, because the output shaft of the converter is 3000 rpm and not 10 rpm. If this were a 2.5 STR converter, and you measured it at say 1000 rpm, you'd see unlocked torque was almost two times the amount of torque as the locked. That is why a converter is so great, when the car is not moving fast, it multiplies torque.

performabuilt

iTrader: (25)

I understood the multiplication of torque in the lower end. I guess I have not seen a dyno chart like that most is see are just locked and unlocked at wot in 3rd gear. Not at various rpm throughout the run, Its very interesting.

12secSS

iTrader: (30)

Exactly as Ragtop 99 said, that is how a converter works. It "exagerates" torque down low, that is the function of the Stator and the STR. Once you lock the converter, it can no longer utilize the multiplier design. This is why a converter get's you out of the hole a lot quicker then a stock one or even a manual equally modded and stalled. If the figures were reversed, I would lose power up to when I lock the converter which would be impossible.

Here is a graph showing locked converter numbers (solid line) vs unlocked converter numbers (dashed lines). This was from before the cam:

Ragtop 99

iTrader: (7)

Here is a graph from the development of the Yank Pro Thruster. This was probably the YTP 4400, but it may have been the YTP 4000. The test mule was Mike's Camaro. It was heads and cam, but back then it was probably low 400s peak HP. It was locked into 3rd gear on the dyno to force the converter to work and slow down the acceleration to get a lot of data points. We couldn't start at zero rpm without having problems on the dyno and generating obscene amounts of heat in the tranny.

You can see how much extra torque is created from a big stall. This was using the stock converter as the baseline. Had we tried to lock the stock converter for the baseline, the gap would be even bigger.