The 2019 Chevrolet Silverado is the only full-size pickup in America offered with a four-cylinder engine. But it’s not your old S10's Iron Duke under the hood—no, this 2.7-liter turbo is sophisticated, employing some cool modern technologies that help it produce more power than most naturally aspirated V6s, while still managing okay fuel economy.
I didn’t have a long time to speak with Chevy about their Silverado’s 2.7-liter engine, since I was there reviewing two trucks in a single day (the Silverado and the ZR2 Bison), but the 2.7-liter turbo’s assistant chief engineer, Kevin Luchansky, did agree to walk me through the engine’s coolest bits, and I wasn’t about to deprive readers from the hardware you all deserve to see.
The upshot is that this thing’s got lots of advanced fuel-savings technology bolted to it. Things like a 600-Watt electric water pump, whose output is—unlike a conventional pulley-driven pump—not directly tied to engine speed, but instead can vary flow based on cabin warmup and engine cooling/warming needs.
Another fancy bit of tech is the coolant control valve, which takes the place of a wax element thermostat. A conventional setup allows an engine to warm up, and once coolant temperature reaches a certain “set point,” the wax in a thermostat expends, presses a plunger, and ultimately sends coolant to the radiator to cool. You can see how that works here.
It’s a simple system, but it’s a fairly “dumb” way of cooling an engine, and doesn’t really allow for precise optimization of coolant temperature or distribution to yield the best warmup times to minimize friction.
One of the main benefits of the electronically controlled rotary coolant control valve, Luchansky mentions, is that it can send coolant only to the cylinder head, and not to the block. This lets the block warm up quickly to reduce oil viscosity and thus friction, while keeping the valve seats (which get very hot) cool and also sending coolant to the integrated exhaust manifold.
Always having water in that integrated exhaust manifold, Luchanksy told me, makes sense since the heater core pulls its coolant straight from it, and because the control valve can send the free heat picked up from the exhaust to warm up the engine and transmission. Plus, grabbing heat from the exhaust reduces gas temperatures entering the turbo, which means fuel doesn’t have to be dumped into the cylinders to reduce temperatures to increase turbo life.
Speaking of the turbo, Luchanksy tells me that its location, and the length and shape of the exhaust runners going to it, has been optimized for quick turbo response. Here’s GM’s slide showing that torque response as a function of time:
GM claims that the truck’s response is among the best in the segment, especially at 1,500 RPM (I found the response to feel good, but not quite instant):
GM also says the “dual volute” turbo setup helps with reducing lag as well, and it’s more efficient. BorgWarner, who supplies the 2.7-liter’s turbo, writes about the design’s main benefits, saying in a press release:
The dual volute geometry allows for the complete segregation of engine exhaust pulsations so more exhaust energy is available to the turbine wheel, compared with traditional twin-scroll turbochargers
Chevy expounds upon the benefits of the dual-volute design—which Automobile Magazine writes has been used in diesels, but is a first in the small-displacement gas engine class—in its own press release:
Rather than a single spiral chamber (volute) feeding exhaust gas from the exhaust manifold to drive the turbine on the turbocharger, the dual volute design has a pair of separate chambers with two exhaust gas inlets and two nozzles to drive the turbine. The design allows the exhaust pulses of the engine to be leveraged for faster spool-up and subsequent boost production, particularly at low rpm, where the effect significantly enhances torque output and drivability.
Other tech on this motor includes direct injection, variable valve timing and solenoid-actuated sliding exhaust and intake camshafts, with the latter having three lobes: One for high lift and high power, one for low lift and better fuel economy, and one to shut off lift to the cams of cylinders two and three for “active fuel management.” The exhaust cam has only two modes: normal and “off” for active fuel management.
Here’s how it looks on the engine:
GM describes the fuel economy benefits at certain operating points below:
There’s also a variable oil pump, which I thought was pretty hot, especially since pumping excess oil through your engine is simply wasteful.
Anyway, this was just a quick look at this motor, and at some of things that jumped out to me during my brief look last week. It’s an all-aluminum, dual overhead cam, direct injected, variable valve lift-having, cylinder deactivating turbocharged motor with an electric water pump, variable oil pump, and electronic thermostat.
The technology on this motor is not brand new, but it’s definitely modern, and it’s cool to see that GM has thrown it all into one place.