"Short-shifting" a Jeep Patriot & Audi A4 CVT (forcing early "upshift") saves gas

[MetroMPG]

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:

http://ecomodder.com/forum/showthrea...2-a-21152.html

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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.)

[jtbo]

That is quite interesting feature, I wish my 1981 Volvo would have ability to control it that way, but maybe I will mod such.

CVT itself might be quite efficient if built for fuel economy in mind as belt is more efficient than gears.

It would just require bit of planning, so that there would be no gears in first place, just two belts and fwd, lot less losses that way.

With my Volvo I could actually make switch for early shifting by applying +12V to one solenoid, by switch, that would make it gear up more agressively.

I'm sure that even with CVT it would be possible to get quite ok mileage when making it shift earlier and it is nice that they have put that feature to Jeep.

I wonder if it would be possible to tap controller box somewhere in that to make it programmable how thing shifts. Of course if engine has lean burn it would be better to run higher rpm lower load.

[Daox]

For the record I'd like to state that gears are definitely more efficient than belts. I used to work for a manufacturer of gearboxes in the engineering department. Calculated losses for our gears were ~.5% per gear set.

From wikipedia on belts:

They have high efficiency (90-98%, usually 95%)...

While its not a world of difference I just wanted to clarify things.

[jtbo]

Originally Posted by Daox

For the record I'd like to state that gears are definitely more efficient than belts. I used to work for a manufacturer of gearboxes in the engineering department. Calculated losses for our gears were ~.5% per gear set.

From wikipedia on belts:


While its not a world of difference I just wanted to clarify things.

Hypoid gear I guess is one having issues, 85-90% efficiency I believe?

With belts you would not need that as you can do differential effect by changing ratio of belt pulleys.

Then you have to add up all the gears which makes that 15-25% drivetrain loss, where with belts you probably could get away with less?

Not quite sure about this of course, but it is something that I have been thinking and which might give something, but it would require rather good facilities to actually make such gearing.

[MPGFTW]

I have sports shifter in my Fit and I use mainly in city driving and I always shift it at 2,000 rpm or constantly tapping my shifter to shift. Not sure also if its bad but I drive off in 2nd gear so when I reach 35mph I'm already in 5th gear.

[MPGranger]

I think it would be fun to control the transmission logic like performance traction control. maybe a 1-5 setting for higher gear ratio to lower gearing. Combined with fuel mapping between sportier setting and a more economy minded selection. So many ways to give drivers more control, so little probability that we will see it.

[vskid3]

The Escape Hybrid will drop the RPMs to idle/the lowest ratio if you let up on the gas while accelerating, similar to what you would do when shifting a manual. Its known as "fake shifting", it might work on other CVTs that don't have the "manual" shift option.

[MetroMPG]

I just updated the first post with info about an Audi A4 automatic I just drove.

So far, it's probably the most flexible automatic I've ever tried, in terms of letting the driver control RPM and engine load.

[MetroMPG]

I had a chance to drive a 1st gen., pre-update Cruze this week (first time in a Cruze for me).

6-speed, conventional torque converter automatic with a manual mode like the Audi & Jeep CVT's.

Not surprisingly, like the CVT's, the default programming upshifts a lot later than you can make it shift manually. Though I can't count how many times the car told me "SHIFT DENIED" when I asked for an early upshift. Funny.

The other interesting eco-driving transmission factoid: you can force the car to start off in 2nd gear by requesting an upshift when stopped.

[niky]

Originally Posted by MetroMPG

I had a chance to drive a 1st gen., pre-update Cruze this week (first time in a Cruze for me).

6-speed, conventional torque converter automatic with a manual mode like the Audi & Jeep CVT's.

Not surprisingly, like the CVT's, the default programming upshifts a lot later than you can make it shift manually. Though I can't count how many times the car told me "SHIFT DENIED" when I asked for an early upshift. Funny.

The other interesting eco-driving transmission factoid: you can force the car to start off in 2nd gear by requesting an upshift when stopped.

I do remember spamming the shifter a lot in that car when I drove it before. Frustratingly slow-shifting and slow-responding box.

Very comfortable car, though, for what it is.