I recently switched from an older Art Carr 9.5" lockup converter (14031) to a newer PTC 9.5" nonlock converter. The Art Carr did not lockup at WOT of course and was very inefficient. With some runs at lower boost on my new setup in the white T, I had concerns that the converter slippage with the Art Carr was going to cost me mph and ET once I started turning the boost up. I never mph'd very well with this Art Carr converter in the past, although it did get out of the hole well. On my old combo, the rpms were too high at the end of the 1/4 and out of the range of the stock cam, even with 28" tires.
With the new PTC converter I noticed that the rpms at the end of the 1/4 were definitely lower and the rpms dropped more on the shift. Below is a screengrab of two Directscan runs with each converter, the Art Carr on the left and the PTC on the right. Nothing else on the car was changed.
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You can tell from the screengrabs that the shifts were dropping a lot more rpm with the PTC. And for a very similar mph at the end of the run, the rpm was about 600 less with the PTC. For the 2-3 shift, on the Art Carr I dropped from 6075 to 4950 while with the PTC I dropped from 6300 to 4750. As shown in the picture, at the end of the run I was at 119mph and 5950rpm with the Art Carr and 120mph and 5375rpm with the PTC.
Using some online calculators, here are the calculated slippages for the runs above:
Art Carr 9.5" lockup 14031 (not locked at WOT)
22.3%
18.2%
PTC 9.5" nonlock
9.5%
8.7%
On other runs with the Art Carr on the older combo with less power and lower rpms, the slippage was even worse. It seemed to improve with more power and rpms. If I turned the boost up for some high 120 mph runs, it might have gotten into the lower teens, who knows. I'm guessing with the PTC that the efficiency will improve to maybe 4-5% once the boost, power, and rpms are raised.
Another factor that came into play is that since the PTC converter is more efficient, at the current boost it drops the rpms down below the power range of the cam after the shifts and all the way through third. I'm figuring that once the boost and power is raised, the stall will increase to right where I want it to be and the rpms where be right on at the end of third. Both of the runs above were in the 15-17psi boost range. Next time boost will be in the low 20's.
With the new PTC converter I noticed that the rpms at the end of the 1/4 were definitely lower and the rpms dropped more on the shift. Below is a screengrab of two Directscan runs with each converter, the Art Carr on the left and the PTC on the right. Nothing else on the car was changed.
.
.
.
.
You can tell from the screengrabs that the shifts were dropping a lot more rpm with the PTC. And for a very similar mph at the end of the run, the rpm was about 600 less with the PTC. For the 2-3 shift, on the Art Carr I dropped from 6075 to 4950 while with the PTC I dropped from 6300 to 4750. As shown in the picture, at the end of the run I was at 119mph and 5950rpm with the Art Carr and 120mph and 5375rpm with the PTC.
Using some online calculators, here are the calculated slippages for the runs above:
Art Carr 9.5" lockup 14031 (not locked at WOT)
22.3%
18.2%
PTC 9.5" nonlock
9.5%
8.7%
On other runs with the Art Carr on the older combo with less power and lower rpms, the slippage was even worse. It seemed to improve with more power and rpms. If I turned the boost up for some high 120 mph runs, it might have gotten into the lower teens, who knows. I'm guessing with the PTC that the efficiency will improve to maybe 4-5% once the boost, power, and rpms are raised.
Another factor that came into play is that since the PTC converter is more efficient, at the current boost it drops the rpms down below the power range of the cam after the shifts and all the way through third. I'm figuring that once the boost and power is raised, the stall will increase to right where I want it to be and the rpms where be right on at the end of third. Both of the runs above were in the 15-17psi boost range. Next time boost will be in the low 20's.