cblink.007
Well-Known Member
So, after an 11-month wait, the Mrs and I recently took delivery of a new GM sports car. Of all the things about this car, I’d have to say that the one thing that fascinates me the most is the LT2 plant that sits right behind me. In particular, I am extremely fascinated with the fuel economy this car gets when driving in the Tour mode. Back on Saturday, we took the car out for a 50-mile drive around the countryside.
We averaged 37.2 miles per gallon with an average speed around the route being 48.7 mph, including a couple stop lights & signs. Remarkable for a 6.2 liter V-8 that’s been officially rated at 495 bhp! Even in and around town, I average more than 25mpg, far better than the 315 bhp 3.0 turbo I-6 that powered the 2013 BMW 335is I used to have.
I knew that the powertrain did this by way of “Active Fuel Management”, also known as literally shutting down half the cylinders, among many things. What amazed me is how the car’s engine control module (we’ll just call it what it is…a FADEC) did this. Out of the maintenance manual, it discusses the theory of operation. Operationally, I still had considerable power margin at cruise speed with just 4 cylinders active, as I only used the cruise control for those portions that had steady state speeds. If I was driving in a 4-cylinder mode, if I let off the throttle or heavily applied it, it immediately switched back to a V-8 mode. It does appear that the FADEC also works in concert with the gearbox do deliver a steady state power output at speed; it also works with the valved exhaust system.
Long story short, this LT2 is a remarkable piece of powerplant engineering, and is probably the zenith of the Chevrolet pushrod small-block V-8 that first saw mass production back in the 1950s.
It makes me wonder. What is stopping groups like Continental from designing a piston aircraft engine that can operate like this? I am assuming money…and the massive a$$pain of certification. I kind of don’t think environmentals could factor into the reason as to why they don’t do this.
Granted, I heavily doubt that a current IO-320 or 540 could possibly be modified to operate like this. An entirely clean-sheet design would likely be necessary. I could envision such an engine that could operate on partial cylinders during taxiing and other low speed ground operations, all cylinders on demand, such as during takeoff and approach, and partial cylinders during the cruise phase. If achieving that kind of efficiency could be done without becoming excessively expensive or heavy without compromising reliability, performance, why not?
Again, I am not a piston engine SME, so this is all purely conjecture at this point, but let’s say you all!
We averaged 37.2 miles per gallon with an average speed around the route being 48.7 mph, including a couple stop lights & signs. Remarkable for a 6.2 liter V-8 that’s been officially rated at 495 bhp! Even in and around town, I average more than 25mpg, far better than the 315 bhp 3.0 turbo I-6 that powered the 2013 BMW 335is I used to have.
I knew that the powertrain did this by way of “Active Fuel Management”, also known as literally shutting down half the cylinders, among many things. What amazed me is how the car’s engine control module (we’ll just call it what it is…a FADEC) did this. Out of the maintenance manual, it discusses the theory of operation. Operationally, I still had considerable power margin at cruise speed with just 4 cylinders active, as I only used the cruise control for those portions that had steady state speeds. If I was driving in a 4-cylinder mode, if I let off the throttle or heavily applied it, it immediately switched back to a V-8 mode. It does appear that the FADEC also works in concert with the gearbox do deliver a steady state power output at speed; it also works with the valved exhaust system.
Long story short, this LT2 is a remarkable piece of powerplant engineering, and is probably the zenith of the Chevrolet pushrod small-block V-8 that first saw mass production back in the 1950s.
It makes me wonder. What is stopping groups like Continental from designing a piston aircraft engine that can operate like this? I am assuming money…and the massive a$$pain of certification. I kind of don’t think environmentals could factor into the reason as to why they don’t do this.
Granted, I heavily doubt that a current IO-320 or 540 could possibly be modified to operate like this. An entirely clean-sheet design would likely be necessary. I could envision such an engine that could operate on partial cylinders during taxiing and other low speed ground operations, all cylinders on demand, such as during takeoff and approach, and partial cylinders during the cruise phase. If achieving that kind of efficiency could be done without becoming excessively expensive or heavy without compromising reliability, performance, why not?
Again, I am not a piston engine SME, so this is all purely conjecture at this point, but let’s say you all!