The upcoming 2022 Cadillac CT4-V Blackwing compact ultra-high-performance luxury sedan will have the same twin-turbo 3.6L V6 LF4 engine previously fitted to the discontinued Cadillac ATS-V. However, there is one difference between the two applications which can not be seen unless the engine is completely dismantled: the connecting rods.
Here, we must do some preliminary explaining so that everyone can make sense of what follows. For the benefit of anyone unfamiliar with an engine’s inner workings, the connecting rods are what join the pistons to the crankshaft.
Briefly, a fuel/air mixture is ignited when each piston is more or less at the top of its cylinder. The rapidly expanding gas exerts a force on the piston, which in turn pushes the rod, which turns the crank. The turning force of the crank is transferred through the transmission to the road wheels, and that’s how a car moves.
The LF4 engine can turn at over 6,000 rpm, which is 100 revolutions every second. During each of those revolutions, the piston and rod accelerate downward, slow to a complete standstill, accelerate upward and then decelerate to a standstill once more. The heavier those components are, the more they will resist doing what is asked of them. A very small reduction in weight (so small that it would make no difference if applied to a stationary component like a seat or a roof panel) will make the engine noticeably more willing to speed up and slow down.
A common (but expensive) method of reducing the weight of a rod is to make it out of titanium instead of steel. A titanium rod is lighter than a steel rod of the same strength. Titanium rods were fitted to the LF4 engine in the ATS-V with both six-speed manual and eight-speed automatic transmissions. The Cadillac CT4-V Blackwing will also use them, but only if it has the standard six-speed manual gearbox supplied by Tremec. Meanwhile, CT4-V Blackwing models with the optional GM Hydra-Matic 10-speed automatic transmission will have steel rods.
This is related to the reason why car makers have been cramming ever more gears into auto gearboxes in recent years. For any driving condition, there will be an optimal speed where the engine performs at its best. This works in favor of fuel economy, but in the case of the CT4-V Blackwing, performance is a higher priority. Under hard acceleration, the engine should be kept as close as possible to the speed at which it produces its maximum power.
This is much easier to achieve with ten gears than it is with only six. With the manual transmission, the engine will have to be taken well beyond the maximum power speed before each shift, and will fall below it immediately afterwards. But with the 10-speed auto, the engine will stay much closer to its optimal speed, and will not accelerate or decelerate to nearly the same extent. Therefore, steel rods will be sufficient for models with the automatic transmission, to say nothing of being significantly more cost-effective than titanium rods.
Cadillac Blackwing Chief Engineer, Mirza Grebovic, went into further detail on this subject during a recent interview with GM Authority Executive Editor, Alex Luft.
“On the autos, what we actually found out on the ATS-V is that the titanium rods were really not needed,” Grebovic explained. “With the eight-speed [in the ATS-V], it did help a little to spin up the mass, but with the 10-speed, our average rpm was so much higher that the benefit of the [titanium] rods was negligible versus the cost.
“So you can notice that our MSRP is significantly lower on these vehicles, and that was one of the reasons: we were able to pull out the titanium rods from the automatic vehicles.
“However, we did decide to leave them in the manuals because the parts already existed, the parts were already validated, and we wanted the six-speed to catch up a little to the 10-speed. That little extra reduction in mass does help the six-speed rev a little better. So we wanted to celebrate the only manual in its class with what we had, and give it a bit of a catch-up to the 10-speed.”
The LF4 engine in the CT4-V Blackwing produces 472 horsepower and 455 pound-feet of torque, and drives the rear wheels. All-wheel-drive is not available, even as an option. According to Cadillac‘s own figures, the top speed is 189 mph and the 0-60 mph time is 3.8 seconds.
The vehicle is scheduled to go into production at the GM Lansing Grand River plant in Michigan on July 5th of this year. It is priced to start at $59,990 (with the manual), though a fully configured example will cost $84,875. Rights to the first unit off the production line were sold for $165,000 at the recent Barrett-Jackson Scottsdale auction. All proceeds are being donated to the Black Ambition initiative.