CVT / Fuel economy discussion

[~tc~]

Let it out quickly with the engine at high RPM.

[KuroNekko]

What do you mean by "dump the clutch"?

Let it out quickly with the engine at high RPM.

Yup.
I remember getting my Impreza serviced at a Subaru dealership once and in the showroom, they had a sign that said "No test drives for STI." Next to the sign was a picture of a ruined manual transmission gear case from someone dumping the clutch and busting up the gears.

[Moto]

Clutch Dump:
Long story short one of three things has to happen
Wheel Spin

Clutch Slip -->
Broken gear/transfercase/diff/Driveshaft -->

Dumping or slipping the clutch is basically any time you do a bad launch whether it be intentional or unintentional (slow or fast). The clutch should last longer in FWD cars because they tend to spin the tires rather than slip the clutch. AWD cars have so much traction that the tires have a very hard time spinning. If you drop the clutch when the engine is revved something has to give. If the tires do not spin that means that you clutch plates are slipping past each-other. If your clutch plates are too good then something else will give like one of your gears/transfercase.

Examples
Yep...
[youtube][/youtube]

If this really was the clutch it was slipping from the very beginning of the video.
[youtube][/youtube]

The good news is that if you do not slip your clutch much when you drive they will easily make 150K miles.

I have over 200K on my 91 corolla--> Still on Original clutch and that one does have some hard miles as it was the car I learned on in highschool.
250K on my family Camry --> Original Clutch
115K on my Mazda Protege 5 --> Original Clutch
121K on My saab 92x Aero --> Original Clutch

So the point is that if you know how to drive a car with a clutch it will be significantly more reliable than an auto of the same make and model. Additionally if you are good with a manual you can usually limp a car with a failing clutch back to a safe location.

I drove my 91 Corolla with a failed master cylinder for 23 miles. (I did run a few lights and stop signs.)

People who destroy clutches in normal driving are spending too much time in the intermediate zone between having the clutch fully depressed or all the way up. The reason is often that people are just lazy. I knew one guy who went through three clutches because he drove with his foot resting on the clutch all the time. (I'm not even sure how he did it)

And now I hand back to the original discussion of the CVT.

[coref1]

My trip computer is showing my long term average as 8.1litres per 100 klms or 34.87 mpg but most of my driving has been highway driving. The worst actual figure I've recorded so far is 12 lites per 100 klms or 23.54 mpg. The newer generation cars might be better then the Kizashi but the Kizashi is still a step a head of my previous car which was Toyota Camry v6.

[murcod]

Here's some real world fuel consumption figures from road tests for the new model Mazda 6:

The claim is 6.6 litres per 100 kilometres, and, while nailing that target may be the stuff of fancy, it'll sit below 9-10L/100km around town.

referring to 2.5l Skyactiv auto
http://news.drive.com.au/drive/new-car- ... 2dafo.html

You wouldn’t expect it to come anywhere near the diesels’ fuel consumption figures, so we were pleasantly surprised when the 6 returned 8.8 litres/100km

2.5l petrol Skyactiv
http://www.racq.com.au/__data/assets/pd ... Wheels.pdf

Our petrol Atenza got 7.6L/100km overall – against an official figure of 6.6L/100km – but we did get 6.7L/100km on a 768km run from Adelaide to Melbourne.

http://www.racv.com.au/wps/wcm/connect/ ... enza+sedan

The i-Stop fuel-saving system didn’t have a huge effect in our hands - the week we spent with the 6 was hot and humid, so while the engine would shut down, it wasn’t long before it re-fired (putting air-con as the priority). We agreed, but it meant 8.4 l/100km.

2.2l diesel, claimed economy 5.4l/100km
http://www.themotorreport.com.au/55837/ ... tic-review

The result is power output of 129 kW at 4500 rpm and torque of 420 Nm at 2000 rpm. The wagon is good for a zero-to-100 km/h time of 8.6 seconds, though driving like that will lift it well above the official fuel consumption number of only 5.4 litres per 100 km.
During our test period we had it averaging in the low sixes on a mix of town work and motorway driving. That’s impressive for a car of this size and performance.

2.2l diesel
http://www.carsguide.com.au/news-and-re ... sel_review

I can't help but think some manufacturers are "gearing" their vehicles towards achieving high official figures purely as a sales tactic to attract more sales. Real world figures are another matter altogether!

The whole "cost of ownership" needs to be considered too, not just fuel economy. Service costs and intervals (Suzuki in Australia dropped the ball on that one with the last model update ) can make a huge difference.

Edit: Some Kizashi figures for comparison

At the end of our time with the car, however, fuel consumption was averaging 8.8 l/100km. That said, a lengthy period spent in peak-hour traffic saw fuel economy drop markedly, and a couple of spirited stints along winding roads didn’t help the cause.

XLS - isn't clear on manual or CVT
http://www.themotorreport.com.au/50484/ ... est-review

But being able to switch it off means you can save a bit of fuel, which is important because we found it impossible to match the Kizashi's claimed 8.4l/100km - we got closer to 12l/100km.

Sport AWD
http://www.carsguide.com.au/news-and-re ... ort_review

As for fuel consumption, additional kilometres under the belt may prove to put the Kizashi into a more favourable light. At present the average is sitting on exactly 9.0L/100km, which is less impressive than the quoted 7.9L/100km for both manual and CVT versions – although it is still substantially better than Mazda6 and Accord Euro.

2010 XL CVT
http://www.motoring.com.au/reviews/2010 ... i-xl-21299

Although from 2011, this is interesting: http://news.drive.com.au/drive/motor-ne ... 1etyu.html Here's a more current version, but it only lists the top medium vehicle as being the Jetta - there's no further rundown of the medium category rankings. http://news.drive.com.au/drive/motor-ne ... 2ub19.html

[honsonwong]

I always get between 10.5 to 11.5 L/100km by calculation with ethanol free gasoline and almost 100% driving in the city.

[KuroNekko]

I knew one guy who went through three clutches because he drove with his foot resting on the clutch all the time. (I'm not even sure how he did it)

That's called "riding the clutch". I knew a co-worker who complained to me that he had to replace his clutch twice in 2 years driving a bone stock Honda Civic DX. I then asked him if he rode the clutch. He gave me a blank stare. I then asked him to imagine he was driving and then just shift gears. I then asked where his left foot was after he released the clutch pedal. He replied, resting on the clutch pedal. I told him he was riding the clutch and even the light pressure of the foot resting on the pedal can cause slippage and premature clutch wear.

It was the consequence of him teaching himself how to drive a manual and that no one ever told him to not keep his left foot on the pedal. When I enlightened him, he seemed like it would be a hard habit to kick. I then told him it's either rest the foot on the dead pedal/foot rest or keep buying and replacing clutches which are not cheap.

The clutch in my Mazda3 lasted almost exactly 100,000 miles which is considered to be the average life of a clutch. However, I bought the car used with 56,000 miles on it so the previous owners had a lot to do with it's longevity. I wonder how long my Kizashi clutch will last given I bought the car with only 7500 miles on it.

Now back to CVTs...

[SamirD]

True, automatics are easier to deal with, especially in stop and go traffic. However, manuals are hard to beat when it comes to reliability and longevity. The part that takes most of the abuse is the clutch which is a wear item much like brake pads. Unless you are a horrible driver and/or often dump the clutch, your gears will last the life of the car. The only thing you'd have to do is replace the clutch at every 100,000+ miles and change the fluid. Automatic transmissions simply wear out over time due to the intricacies and heat that they generate. The cost of replacing an automatic transmission will usually offset the value of the car so that's why most people will junk them at very high mileage. Nearly all that cars that are still running with over 300,000 miles have manual transmissions for this reason. By that time, most automatic transmissions would have needed a replacement.

Very good points. I wonder how long the true clutchless manuals will be lasting? Since they do have an automatically engaged clutch.

[SamirD]

On my recent 1000mi round trip from HSV to MKE, I got almost 30mpg on the car display, which I was pretty happy with considering the snow tires are slightly smaller and do have a lot more rolling resistance even when at max inflation.