All the air flowing into and out of an engine flows through this area formed by the open valves. The AMG V-8 has two 40mm-diameter intake valves per cylinder operating at a maximum lift of 12mm.
That makes for a total intake-curtain area of The single 55mm intake valve in the LS3 V-8 opens farther with a maximum lift of 14mm, but that still yields a curtain area of only When measured at 1mm of valve lift, the AMG V-8 has an intake duration the number of degrees of crankshaft rotation that the valves are open of I also suspect that with its more-direct-acting valvetrain, the AMG V-8 pops open its valves faster than the Chevy can.
The shorter intake duration pays off in torque production for the AMG engine. Its peak twist of pounds is well above the pound-feet produced by the LS3. The ability to advance the intake camshaft by up to 42 degrees reduces the compromise between mid-rpm and high-rpm breathing.
All this high-tech stuff does take up some space, however. Both engines have aluminum blocks and heads, but as nearly as we can determine, despite its far more complex valvetrain, the AMG engine, at pounds, weighs no more than the Chevy V The German product is pricier, however.
Clearly, its enormous production volume helps hold down the cost of the Chevy engine. This cost advantage and the addition of technology such as two-stage intake manifolds and variable-valve-timing systems [see Tech Highlight, page 70] will likely keep pushrod engines viable for years to come. On another subject, I want to remind everyone that the EPA fuel-economy ratings are changing dramatically for cars and trucks.
I explained the changes in gory detail in this space in our April issue; the capsule version is that the new ratings will more closely reflect the way most of us drive. Typical city mpg will drop by about 12 percent, and highway ratings get an eight-percent haircut. As you might surmise, we are not conducting this sweepstakes for philanthropic reasons.
A single camshaft in the center of the V-8 engine makes for small cylinder heads, which means the engine doesn't have to be very wide or tall, and it is often lighter than a DOHC engine. That helps when packaging the engine under the hood of a vehicle.
It can also lead to suspension improvements and an improved center of gravity. By comparison, the DOHC is wider and taller and often heavier because those two cams sit atop each cylinder head and require larger heads.
Last but not least, the final reason is cost. When you multiply that figure or an updated figure by hundreds of thousands of cars, trucks, and SUVs, the cost advantage quickly becomes clear. The pushrod engine may be behind the times in terms of technology, but there are at least five good reasons why it continues to exist. Sign up to get the latest performance and luxury automotive news, delivered to your inbox daily!
I agree to receive emails from Motor Authority. I understand that I can unsubscribe at any time. Privacy Policy. Contribute: Send us a tip Contact the editor.
Share This Article:. Follow Us Today:. Stephen Edelstein - Contributing Writer. More than one third of Cadillac dealerships bail on brand's electric future.
Viknesh Vijayenthiran - Editor. Buzz: Car News Headlines. Acura Integra prototype debut set for Nov. Porsche reportedly has 3 classic-inspired specials coming. Motor Authority Newsletter Sign up to get the latest performance and luxury automotive news, delivered to your inbox daily! Sign Up Today!
0コメント