Tech Tips
 

In the May 2010 issue of Road and Track magazine, the following two questions were asked in the Tech Correspondence section:

MISSING TORQUE

Q: "Is it my imagination, or are more high-performance cars producing much less torque as compared to their horsepower output?"

A: "It's not your imagination. Pretty much since the invention of the automobile, engines have been shrinking in displacement to save weight for improved handling and better fuel economy when cruising. By turning higher rpms, the newer engines make the same or greater horsepower than their larger predecessors. What they make less of is torque. Fundamentally, a product of displacement, torque comes naturally to a large displacement engine. So, where a 1970's era performance engine may have displaced 7 liters, made around 430 bhp and 460 lb.-ft of torque while revving to 6,000 rpm, your 4.8 liter Lexus has gained power but lost torque. It also redlines at 9,000 rpm. Advances in tuning-fuel injection, variable cam timing, porting, etc.- also gain efficiency for the newer engines, naturally, but the fundamental of big engine, big torque; small engine, small torque, holds true.

In more mathematical terms, Horsepower equals rpm times torque divided by 5252 (a constant that accounts for the leverage the torque is measured at). Thus, increasing either rpm or torque increases horsepower. Older engines had more torque, modern engines have more rpm."

EXOTIC OIL

Q: "I have an exotic that I drive only 500 miles a year. It has synthetic oil and I understand that synthetic does not oxidize or deteriorate when not in use. The manufacturer recommends 1 year or 15,000 miles. Is that necessary under the circumstances?"

A: "Due mainly to water accumulation, the one-year interval still stands. Mobil One uses that as a general recommendation, for example. It makes sense as low annual mileage, typically, means short, cold trips, but yours may be different."