Quote:
Originally posted by amuse
Hi Harvey, is this the general concensus? At what point do you put it into Drive (to go to fourth)?
Any downsides? I assume the fuel efficiency will be worse, but the tranny will be better off
Cheers,
Pete.
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Hi Mate, I use 3rd every where, unless I am on the boring freeways, when I use drive and the cruse control.
If you are in drive at 100kph the engine is only doing about 2200rpm. This is below the meaty part of the torque curve, which starts to gain substance at about 3100rpm. This is also the engines efficiency curve, in other words the engine will make the best use of the fuel it consumes. This does not mean that you will use more fuel, as this depends on the how wide open the throttle is.
If you are in driving in "D", to over take or just to move out into the next lane, you need to give it more throttle, because of the high ratio it is in. The torque converter has to slip more to produce the torque, the more work the converter has to do, the more heat it will produce, the more fuel it will use.
In 3rd at 100kph the engine is doing about 3300rpm. This is right in the start of the useful curve. The engine is now putting out ample torque to do the job, so the torque converter does not have to work as hard to provide the necessary torque, less heat. You also don't have to give it as much throttle as you would in drive. More rpm, less throttle, same fuel consumption.?
The gearbox will appreciate the saving also. In "D" the gear sets are working to produce the ratio. In 3rd all the gear sets are locked together and turning as a solid unit . In other words nothing is working or wearing, in the box. As most of the driving is done in this gear, the saving in wear and heat on the box can be appreciate.
The SVX is a bit of a slug in "D" around town. In 3rd it jumps
Harvey.
