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Old 03-26-2012, 01:14 PM   #1 (permalink)
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"Short-shifting" a Jeep Patriot & Audi A4 CVT (forcing early "upshift") saves gas

I just drove a friend's 2012 Jeep Patriot from Ontario to Nova Scotia, about 1800 km (~1100 miles). It has a 2.4L 4-cylinder engine, automatic CVT.

That's the farthest I've driven in a CVT equipped car before. Interesting.

I mistakenly assumed that the thing would generally aim for the lowest engine RPM it could get away with for a given load for best economy. Nope.

But one thing I discovered fairly early on was that you could force an early "upshift" when cruising/accelerating below ~75 km/h (47 mph) by using the manual "Autostick" gate, which is also where "D" is:

Push right to "upshift", left to "downshift".

Now, if you just shifted to "D" and left it alone to do its own thing, it did not do "fake" upshifts/steps as you accelerate, like some companies do with their CVT's.

But if you bop the lever left or right in that gate, the dash display changes from "D" to up to 6 "gears", which is of course kind of silly in a CVT.

But I played around with this gear selector and learned some neat things about it that could be useful, fuel-economy wise, for anyone driving one of these:

Most importantly, when cruising or accelerating at speeds below ~75 km/h (~47 mph), tapping the lever to the right would cause the CVT to "upshift" sooner than it would by default if just left in "D", effectively short-shifting.
  • Accelerating from a stop or when cruising below 75 km/h, I could merrily, repeatedly, bap the lever to the right, and it would upshift ASAP - though it wouldn't let me ever lug the engine. (E.G. if the computer determined road speed was too low or load too high for "6th" fake gear, it would just stay in "5th".)
  • But if you just keep randomly tapping the lever to the right while accelerating, it will permit the "upshift" at the lowest possible RPM threshold.
  • It was surprising how willingly it seemed to grant me high load, low RPM acceleration when "shifted" manually. Much lower than when left in "D". I didn't try any pulse & neutral engine-on gliding, but it may potentially pay off with this transmission.
  • One warning though: once past 75 km/h / 47 mph, you have to remember to shift back into "D". If left in "6th" manual gear selection, engine RPM would be slightly higher (few 100 RPM) than when in "D" at cruise.
I also did a speed vs. MPG graph for this car:


Update: Oct 4, 2013...

2004 Audi A4 3.0L CVT

I just spent about 30 minutes driving this car, and was completely surprised to learn after the fact that it has a CVT instead of a "regular" automatic. Audi programmed it to simulate gear shifts, and I have to say they did a thoroughy convincing job. I fell for their trickery.

Regardless, here's another car with a manual shift gate that permits significantly earlier upshifts than the default programming of automatic mode.

Automatic mode shift RPM:

- Left to its own devices, under the lightest possible load, the shift from 1st to 2nd happens at ~1800 RPM, and subsequent shifts at ~2100 RPM.

Manual mode shift RPM:

- You can upshift at ~1200-1400 RPM.

EG, you can shift into "5th gear" at a far lower road speed in manual mode vs. automatic: 45 vs. 70 km/h (28 vs. 44 mph).

And after a short shift, the car is perfectly happy to go down the road at ~1200 RPM. (If you drop below that in manual mode, it will automatically downshift.)

And the icing on the cake: in manual mode, it will hold the "gear" you're in under heavy engine load, until you actually floor the go pedal. (There's a detent at the very bottom of the pedal travel that activates a downshift when you push past it.)

A neat transmission. Kudos to Audi for giving the automatic driver this much control. (Too bad I've read some suffered with reliability problems.)

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Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
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Ecodriving test: Manual vs. automatic transmission MPG showdown

has launched a forum for the efficient new Mitsubishi Mirage - fuel efficiency info for Geo Metro owners - electric car conversion on a beer budget

Last edited by MetroMPG; 10-04-2013 at 11:48 AM.. Reason: added Audi A4 info
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