Originally posted by reh321 consumers mostly use automatic transmissions these days. Race car drivers are known for wanting exact control
My car is auto transmission but I can nudge the gear lever up or down which is what I do most of the time in the hills. I'm never very satisfied with the way it changes.
Originally posted by reh321 My Ford Fiesta is equipped with Ford’s “high mileage” package, which includes vents to close off the radiator when starting {so engine will warm up faster}, special flaps to improve airflow around the wheels, and a special automatic transmission with a fifth gear which gives better MPG at 50+ MPH {it’s basically what used to be called ‘overdrive’}
That sounds like most UK cars since at least 1980, starting with the 5-gear Austin Maxi. The thermostat in cars' water cooling systems has always shut the radiator out of the circuit until the engine warms up - has the Fiesta done away with the thermostat and has air-side vent flaps instead?
Originally posted by wadge22 a manual trans offers the driver more leeway to choose whether they want to optimize shifts for acceleration or efficiency, assuming the driver knows how to do so effectively.
I'm more concerned about engine life. Car makers are hell-bent on reducing their published mpg figures (however unrealistic they may be), so auto transmissions are programmed to use lower ratios than are good for engine wear. The cost of having to replace an engine would wipe out any slight savings from forcing the engine to labour up gradients without changing down. I'm not talking about motorway cruising, but about the short sharp rises around where I live. Lady L's car is manual but
recommends gear changes on the dashboard display, and its choices are astonishing. I'm an engineer and hearing the labouring makes
me feel stressed, let alone the engine.
PS : Regarding the term "overdrive". In olden days, top speed was the main selling point (just like mpg today) - 40 mph! 50 mph! 60 mph!! During development the maker would try different final drive ratios and choose the one that gave the highest speed. This did not (of course) give the most mpg in cruising at intermediate speeds, which is always achieved at a higher ratio. So the more expensive cars offered a second gearbox bolted on the back of the standard one that had two ratios like 1 : 1 (straight through) and 0.8 : 1 (a speed-up). The latter was considered to be
over-driving the engine because it required more torque from it at any speed, and the car could not achieve its top speed, but it was more efficient at cruising. But the overdrive box was very expensive (more than the main box) so it made sense to incorporate an overdrive fifth gear into the main box, whether auto or not, which I believe the Austin Maxi was the first to do in the UK at least. I guess that with some auto gearboxes having six or eight gears today, two or three of them are overdrives.