This is just some thought for the winter season, even if I knew exactly how to do it, I don’t have the money or expertise to build it. But anyways, for discussion here is something to think about. Fluid couplings are routinely used in industry with variable speed control. The fluid coupling is typically used in constant input speed applications. The fluid coupling also does not multiply torque, but has better coupling efficiency then a torque converter….
I was curious if a similar approach has been used to vary stall speed in an automotive torque converter application as has been used to vary speed in a fluid coupling. A fluid coupling will vary the amount of fluid in the coupling with a devise to drain the fluid to a certain level, which can be varied continuously. The concept actually is used by FB Performance(found via a google search), but with a different implementation. The feed to the torque converter has a step control. So you can stall at one speed, deactivate a solenoid which increases the fluid feed to the torque converter, and reduce the stall and lower the coupling rpm.
http://www.fbperformance.com/Product-Release-Blog/2004/4/Variable-Stall-Control-TM
My thought, an enhancement to the FB performance system would be to continuously modulate the feed so that you could hold a preset rpm. With a turbo car running a large turbo, you could hit the gas, engine comes right up to a preset rpm, and then modulate the fluid flow into the torque converter to hold the rpm as the boost increases. Once up on power, you could allow full normal flow, or tune for the launch.
What you would probably sacrifice is some lost power(due to slip and reduced torque multiplication) on the start with a reduced amount of fluid in the torque converter, but as soon as you hit with full flow, you get it back. Depending on how much power you are making, may not be a draw back.
With a purpose built design you may be able to build a lower rpm coupling capability with the ability to quickly stall a large turbo. Maybe somebody is already doing something similar?
This leads into the next point. If you could practically apply and spool a large turbo, you may be able to use one in which you can hit the crossover point, make more boost pressure then the exhaust back pressure. At this point, instead of having net pumping losses by pumping against more exhaust back pressure, you would have a net pumping gain on the intake stroke with a higher manifold pressure than atmospheric and higher than the exhaust back pressure(better recovered exhaust energy). This also opens the door to different cam grinds and probably a host over things I have no idea about.
Any thoughts?
I was curious if a similar approach has been used to vary stall speed in an automotive torque converter application as has been used to vary speed in a fluid coupling. A fluid coupling will vary the amount of fluid in the coupling with a devise to drain the fluid to a certain level, which can be varied continuously. The concept actually is used by FB Performance(found via a google search), but with a different implementation. The feed to the torque converter has a step control. So you can stall at one speed, deactivate a solenoid which increases the fluid feed to the torque converter, and reduce the stall and lower the coupling rpm.
http://www.fbperformance.com/Product-Release-Blog/2004/4/Variable-Stall-Control-TM
My thought, an enhancement to the FB performance system would be to continuously modulate the feed so that you could hold a preset rpm. With a turbo car running a large turbo, you could hit the gas, engine comes right up to a preset rpm, and then modulate the fluid flow into the torque converter to hold the rpm as the boost increases. Once up on power, you could allow full normal flow, or tune for the launch.
What you would probably sacrifice is some lost power(due to slip and reduced torque multiplication) on the start with a reduced amount of fluid in the torque converter, but as soon as you hit with full flow, you get it back. Depending on how much power you are making, may not be a draw back.
With a purpose built design you may be able to build a lower rpm coupling capability with the ability to quickly stall a large turbo. Maybe somebody is already doing something similar?
This leads into the next point. If you could practically apply and spool a large turbo, you may be able to use one in which you can hit the crossover point, make more boost pressure then the exhaust back pressure. At this point, instead of having net pumping losses by pumping against more exhaust back pressure, you would have a net pumping gain on the intake stroke with a higher manifold pressure than atmospheric and higher than the exhaust back pressure(better recovered exhaust energy). This also opens the door to different cam grinds and probably a host over things I have no idea about.
Any thoughts?