Input of exhaust gases from the manifold, at a temperature approaching 700ºC.
Exhaust gases are used to drive the conventional turbocharger, where energy is used to boost power and torque in the combustion process. These exhaust gases, instead of being lost to the atmosphere, are then directed to the turbocompound unit.
The exhaust gases, on reaching the turbocompound unit, are still at a high temperature (around 600ºC); the energy is used to spin the second turbine at up to 55,000 r/min. After passing this point, the gases are down to below 500ºC, and are expelled via a conventional exhaust system and silencer.
The revolutions of the turbine are stepped down in various stages by mechanical gears and a hydraulic coupling. The hydraulic coupling balances out variations between the rotation of the flywheel and the turbocompound turbine.
By the time drive reaches the crankshaft, the rate of rotation is down to around 1,900 r/min.
The flywheel’s momentum is increased, and its rotation becomes more stable and even.
pretty cool i guess, tho i don’t see what kind of torque increase there is to be had…
Dont know the efficiency of it all but it would have two positive side effects. You could run a higher compression ratio which makes for cleaner emmisions and higher combustion efficiency and since you are jamming more lbs/min of air-fuel mixture your gas economy goes up. They only show this on a diesel and all diesel trucking companies care about which is fuel economy and durability. You could also run “off-boost” and still have decent power and eficiency.
that’s how i stumbled upon it, i was looking at old 3500 HP wright airplane motors. I was surprised that i had never heard of it, seeing as the technology was decades old.
^^^ thats what it looks like to me. and thats where the tq increase would come from i would think, because then it is all about the ratios you have in the gearing.
still need an intercooler though at least for the turbo delivering the intake charge.
what a bitch that would be to dial in. c’mon ZD, lets see you make a home built one of these on a b-series. or better yet the saab.
how fast the 2nd turbo is spinning. i would think that that would be pretty important.
a spike in that would be a HUGE issue. crank angle sensor see 3k rpm, wastegate or whatever it has stick/fails/whatever and spikes in no and now the engine is spinning faster. that would throw off spark timing and all sorts of shit.
uh… you are overthinking this. The crank angle/pistons/valves are all constrained together still. The torque boosting turbine spins at the max RPM all the time. If the FW is spinning slower than your turbine (after the gear down), the viscous coupling soaks up the difference (think idling at a light w/ auto trans… engine spinning, trans isn’t).
Even if it wasn’t coupled, the only thing that would happen would the turbine would spin at a faster or slower rate than the exhuast was trying to drive it at, which would have interesting results, but would not affect the motor mechanically, it would be more like increasing or decreasing backpressure. The cam timing, ignition timing and all that jazz is still mechanically coupled to the crank.
not trying to be argumentative, but what are you talking about? (first my rb blew a turbo oil seal)
Let’s assume that there is no viscous coupling, so there is no compliance in the system. Let’s also assume that for an arbitrary RPM, say 5000 that the turbine is geared to be spinning at 50,000 rpm, so a 1:10 ratio. Now, lets say that when the motor is spinning at 5000 rpm, it is producing the pressure differential and heat transfer to naturally spin the turbine at 6000 RPM. Now, since the turbine is mechanically coupled to the crank and spinning slower than the natural frequency, the exhaust gas is going to be somewhat restricted by the wheel. But due to the nature of a turbine wheel, you will develop a pressure differential downstream of the wheel that will increase to the point of steady state flow (where the inlet volume to the turbine manifold=the outlet volume) This can be seen in a car with a seized turbo. Just because the turbine isn’t spinning at it’s natural frequency (or at all) it still allows air to pass, but at a high pressure differential. A car with a seized turbo will run, but poorly.
So essentially, loosing the viscous coupling will merely increase (spinning slower) or decrease (spinning faster) the backpressure of the exhaust downstream of the turbine.
