If you’ve ever driven around with a hot cup of joe, you’ve seen the coffee slosh as you corner, accelerate, and brake. The 40-weight in the engine’s oil pan and the fluid in the transmission do the same thing. But you can tilt your cup to prevent the coffee from spilling; a car’s roll, pitch, and squat actually affect the movement of internal fluids.
This phenomenon is the reason most racing cars have dry-sump lubrication systems. With this setup, oil is stored in remote reservoirs that are not susceptible to sloshing, thereby ensuring that the oil pumps never suck air. But how do manufacturers know that production lubrication systems work under all conditions, especially as cars become faster and tires provide increasingly better grip?
The traditional approach has been to test cars on a high-speed handling course while monitoring the behavior of the oiling systems. But this requires building a test mule, using skilled drivers, and traveling the world in pursuit of appropriate weather conditions. About 10 years ago, manufacturers began building laboratory test rigs that, by tilting the engine, could simulate the lateral and longitudinal accelerations a car produces. You can see (and hear—be sure to turn up your speakers) one of Porsche’s setups in action in the video below.
Can You Do the Cant Cant?
If we go back to our coffee cup, it takes acceleration of 1.0 g to tilt the surface of the coffee to a 45-degree angle. If you cant a stationary engine 45 degrees, you get the same effect as if it were cornering at 1.0 g. For these tests to be useful, the engine needs to be working hard, meaning the tilting platform has to support the engine as well as a dynamometer capable of absorbing its output. Also required are flexible connections to the test sensors and to the engine’s cooling, exhaust, and electrical systems.
General Motors has been using dynos like this for a while. The company has two that can tilt up to 53 degrees, simulating 1.3-g loading, with a maximum pivot rate of 40 degrees per second. Tilting-dyno testing is helpful for engines destined for serious off-roading.
According to Steve Nash, the manager of GM’s Powertrain Laboratory in Pontiac, Michigan, these tilting dynos are programmed to simulate a variety of strenuous courses, with the engine revving to redline, delivering full power, and experiencing the rpm migration associated with gearchanges.
The test stands can absorb up to 800 hp and accommodate engines designed for front- and rear-drive applications. A complete test program, including cycles at varying temperatures, takes about two weeks with the computer-controlled dyno running 24/7.
GM also has a tilting transmission test rig. It’s used primarily for automatics, as they have a fluid reservoir that’s similar to an engine’s oil pan. And unlike a manual transmission, an automatic depends on a continuous flow of pressurized fluid to operate the various actuators that control its operation.
This tilting transmission stand has a 190-hp electric motor to drive the transmission and an electric dynamometer to absorb its output. The transmission test cycles mirror the ones used on the engines, but they have special tests, such as operating at minus 40 degrees Fahrenheit at a significant angle, simulating what an off-road vehicle might experience on uneven terrain in an Alaskan winter.
These tilting engine and transmission test stands run essentially nonstop to speed the process of taking new engines from the computer to the showroom. They ensure that modern cars survive our skidpad test without the heartbreak of clattering valves from oil-starved lifters or smokescreens caused by oil trapped atop the heads. Now, if only someone would do something about the heartbreak of coffee-stained floor mats.