Episode #7: Wastegates and exhaust
Jay Leno’s Tank Car is just one of several high profile development programs ongoing in the Banks Advanced Prototype Engineering labs.
Part Seven in a Series: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8
Our first task on the “hot” side of the Tank Car’s turbo system was to route tubing from the exhaust manifolds to the turbochargers. We started by replacing the original mild steel tubing with stainless tubing and installing a V-band flange at the exhaust manifold outlet. Fabricator Daniel Dominguez and Bob Robe check the angle and elevation of the initial bend section.
The Tank Car has a grille above the engine’s two vertical cooling fans. A part of this grille had to be cut away to clear the new exhaust tubing. Jay reports that, while driving, all the hot air from the engine and exhaust blows back into the cockpit. “On a cool day, it’s great, on a hot day, you live with it.”
Because our turbochargers are solidly mounted to the engine, and the tubing between the exhaust manifolds and the turbos can grow more than an eighth-inch when hot, some means must be provided for expansion. We installed these stainless, 4-inch diameter bellows sections in the center of the horizontal tube runs.
We incorporate a slip joint within the bellows to isolate the thin convoluted material (it’s only .012 inch thick) from direct contact with the 1600F exhaust gasses and to reduce turbulence in the pipe. The slip joint is made loose enough to provide some angular as well as axial movement.
To control boost pressure, Gale chose a pair of these “Indy-style” wastegate actuators that were popular on Champ-cars in the 1970’s. Boost from the intake manifold lifts the actuator’s diaphragm and poppet valve, allowing some of the exhaust to be bypassed around the turbine to reduce the speed of the turbine/compressor wheel shaft. These wastegate actuators feature big valves and a large diameter diaphragm for precise control and high gain (lift vs. boost).
The original application for this wastegate actuator was on industrial engines where the valve body and seat was part of the exhaust manifold. We designed and built our own valve body with an integral seat and v-band inlet/outlet connections, fabricated from stainless steel. The outlet tube and v-band flange will be added later.
The valve seat is machined into the base of the valve body to align with the actuator. The valve seat is machined into the base of the valve body to align with the actuator. This actuator is being assembled in a tack-welded valve body for a trial fit. The boost pressure control point is set by changing springs under the actuator cover.
Like the turbochargers, the wastegates are mounted outside the bodylines of the vehicle for visual impact and for cooling. Here the wastegate inlet tube is being fitted to the completed turbine inlet pipe assembly. Each tube junction takes a number of trial-fits before finish welding can take place. Once the exhaust system is finished, there’s not much left to do before we fire her up. Be with us next time as twin-turbo Tank Car torque tries to tear up our chassis dyno!
Read more! Episode 8