Turbocharging and drive by wire

Honest John Back Room » Technical matters
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Thu 10 Jul 2003 23:35
Turbocharging and drive by wire - SjB {P}
I am still delighted with the V70 2.4T that I purchased new in March. On a recent drive to the Czech Republic and back, four up with a boot load of kit, it would pull hard out of uphill hairpins from low RPM that a modern turbodiesel would shudder at, or spin effortlessly up to high revs when the mood took. I did however find two characteristics I have never experienced in any previous car, which I share here:

1) The amount of acceleration available when laden remains prodigious at all times, but is strongest when a quick gear change down is followed instantly by full throttle, rather than by changing down in ample time, waiting a few seconds for the opportunity to go, and then giving full throttle. This is not just subjective, and when in second gear especially, the additional torque is easily felt.

2) I like to change gear as near to 'chauffeur smooth' as I can get, even when changing up at high revs from full throttle. This obviously entails a finely judged, very brief, feathering of the throttle, rather than simply snapping it closed as the clutch pedal is depressed. When doing this in the Volvo however, I sometimes get a considerable rush of power for a split second as I come OFF the throttle at high revs (5500-6000).

I'm guessing that both of these characteristics stem largely from the fact that a computer is controlling turbo boost as well as a stepper motor that opens the throttle, instead of my foot doing it directly.

Purely out of interest, have any Backroomers noticed similar oddities, whether Volvo or not?

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Fri 11 Jul 2003 00:39
Turbocharging and drive by wire - jud
i have a A4 1.8T , i find this is the only car that does not have a "best" gear for over taking. With max torque from 1950 to over 4500 rpm rapid overtaking can be achieved provided revs are around 2500. This usually involves a very short full throttle then lift off to normal cruise position, as you mention the car seems to still be accelerating after lift off, i put this down to the turbo and perhaps the flywheel? but am only guessing. Its a very relaxing car to drive at 30 or 40mph (4th & 5th gear)
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