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Old 08-28-2013, 10:22 AM   #201
Commander Keen
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I think they have less, the viscous coupler is a constant drag, the electronic differential in the CVT sends less power to the rear unless required to maintain traction.
The VC is only dissipating power during turns or traction loss. The CVT's MPT clutch dissipates power as well. The CVT has a torque converter, much more fluid, a system of chains, active cooling and a slower 0-60. More power gets to the wheels through the 5MT.
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Old 08-28-2013, 11:46 AM   #202
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Originally Posted by Commander Keen View Post

The VC is only dissipating power during turns or traction loss. The CVT's MPT clutch dissipates power as well. The CVT has a torque converter, much more fluid, a system of chains, active cooling and a slower 0-60. More power gets to the wheels through the 5MT.
50% of the power is constantly being transferred to the rear of the 5 speed vs only 10-30% with the CVT's electronic differential.

The difference in acceleration is more likely due to the gearing and difference in weight (the 5 speed is lighter).

Since no one has measured the drivetrain loss, and Subaru won't tell you how much power the CVT sends to the rear, neither of us is gonna convince the other.

Personally I think they don't share the information because it undercuts their marketing, what Subaru owner wants to be told that their car is mostly FWD, most of the time?

Since the Electronic Differential is more efficient at transferring power quickly, there is no need to send more power to the rear wheels than necessary, the differential might even be completely disengaged in the CVT during normal driving conditions.

As far as the CVT fluid, and chain, sure there is some drag there, but I don't think it is nearly the loss that comes from the viscous coupler and powertrain loss of a manual.

In any case, the difference in engine RPM is clearly favoring the CVT, and nobody has produced any evidence whatsoever that a 5 Speed can achieve better highway mpg's than a CVT in the same exact driving conditions.

I've got the EPA testing, Fuelly, and NASIOC reports that confirm the opposite is true.

Last edited by Zeeper; 08-28-2013 at 11:53 AM.
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Old 08-28-2013, 12:17 PM   #203
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Better EPA numbers don't necessarily mean less drag. The CVT has lower cruise RPMs than the 5MT due to gearing.

Subaru doesn't share CVT torque split information because there's no reliable way to measure it. The CVT does not have a center differential, it has an electronically actuated clutch. The clutch doesn't "split" power as a center differential does and torque distribution varies constantly with turning radius and available traction.

Regardless of front/rear power distribution, your car can't disengage the moving parts in the rear half of the car. The rear differential and shafts are spinning just the same.

The CVT's torque converter sinks much more power than anything in the 5MT. There's a reason manual gearboxes don't need external coolers.
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Old 08-28-2013, 12:35 PM   #204
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Better EPA numbers don't necessarily mean less drag. The CVT has lower cruise RPMs than the 5MT due to gearing.

Subaru doesn't share CVT torque split information because there's no reliable way to measure it. The CVT does not have a center differential, it has an electronically actuated clutch. The clutch doesn't "split" power as a center differential does and torque distribution varies constantly with turning radius and available traction.

Regardless of front/rear power distribution, your car can't disengage the moving parts in the rear half of the car. The rear differential and shafts are spinning just the same.

The CVT's torque converter sinks much more power than anything in the 5MT. There's a reason manual gearboxes don't need external coolers.
Spinning vs powered? Very different.

Most of what you are writing about the differential is marketing information, it has nothing to do with how it actually works, cause, who wants to be driving a FWD Impreza most of the time? You certainly don't...

In any case, you cannot prove your own theory, so it remains just that, an unproven theory.
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Old 08-28-2013, 12:49 PM   #205
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Well ... I don't mind if my impreza is fwd most of the time, because most of the time im driving down the highway in a straight line anyway... I can't tell a difference. I just hope its still capable of a 50/50 split if I need it.
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Old 08-28-2013, 01:09 PM   #206
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Fact: The CVT does not have a center differential.

A clutch is not a differential. It is possible to combine a differential with a clutch, but that is not what the CVT has.

The difference in 0-60 times between the 5MT and CVT is more than a difference in weight would account for.

The 5MT does not require external cooling because it converts less kinetic energy into heat than the CVT does.
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Old 08-28-2013, 01:23 PM   #207
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Originally Posted by Commander Keen View Post
Fact: The CVT does not have a center differential.

A clutch is not a differential. It is possible to combine a differential with a clutch, but that is not what the CVT has.

The difference in 0-60 times between the 5MT and CVT is more than a difference in weight would account for.

The 5MT does not require external cooling because it converts less kinetic energy into heat than the CVT does.
What is the 5sp 0-60? Cvt in m mode is 8.5
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Old 08-28-2013, 01:30 PM   #208
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Originally Posted by Commander Keen View Post
Fact: The CVT does not have a center differential.

A clutch is not a differential. It is possible to combine a differential with a clutch, but that is not what the CVT has.

The difference in 0-60 times between the 5MT and CVT is more than a difference in weight would account for.

The 5MT does not require external cooling because it converts less kinetic energy into heat than the CVT does.
What is 0-60 difference between 5MT and the cvt in M mode using paddles? A normal auto is almost always slower than a manual transmission in acceleration times. However, an auto with paddle shift is usually quicker. I know first hand the Porsche Pdk was quicker than the manual transmission. It has been mentioned the cvt in m mode is a second quicker than in auto mode. With the cvt really only being a single linear gear with software shift points I think it acts like a different animal all together. I think if the cvt would start with a little lower gearing it might be a different outcome. My cvt is dead taking off for the first 60-80 feet then it wakes up and does a pretty good job of keeping in the power band at wot. I like m mode better, as 4500-5800 seems to be where it wants to hang around
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Old 08-28-2013, 01:34 PM   #209
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Motor Trend claims 9.4 vs 8.0
zeroto60times.com claims 8.9 vs 7.9

Couldn't tell you which mode they used.
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Old 08-28-2013, 01:41 PM   #210
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Originally Posted by Commander Keen View Post
Motor Trend claims 9.4 vs 8.0
zeroto60times.com claims 8.9 vs 7.9

Couldn't tell you which mode they used.
I'm just throwing this out, as my brain is fried from dealing with work so far today, it hurts to think very hard :-(
If in fact there is a second, or close to difference in the cvt between auto and m mode, how would the argument be altered if you considered the 5MT vs cvt in m mode with regards to the prior posts? I'm just thinking out loud since thinking to myself has proved too stressful today.
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Old 08-28-2013, 01:52 PM   #211
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Originally Posted by Commander Keen View Post
Fact: The CVT does not have a center differential.

A clutch is not a differential. It is possible to combine a differential with a clutch, but that is not what the CVT has.
Semantics and theories, the CVT has an electronic clutch to transfer power to the rear, the manual has a viscous coupler.

Same difference, relax and enjoy the fuel economy boost that your lower rpm and less power to the rear wheels provides.
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Old 08-28-2013, 01:55 PM   #212
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Well ... I don't mind if my impreza is fwd most of the time, because most of the time im driving down the highway in a straight line anyway... I can't tell a difference. I just hope its still capable of a 50/50 split if I need it.
All evidence I have seen is that the electronic system is more responsive (or quicker to respond) than the viscous coupler.

So either works, the electronic version might even work better, and may in fact transfer more than 50% power to the rear if needed...
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Old 08-28-2013, 02:08 PM   #213
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Semantics and theories, the CVT has an electronic clutch to transfer power to the rear, the manual has a viscous coupler.
You think these are semantics and theories because you haven't seen a mechanical drawing of both systems.

The manual has a viscous coupling AND a center differential.

The CVT has only a clutch.
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Old 08-28-2013, 03:08 PM   #214
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Originally Posted by Commander Keen View Post
Motor Trend claims 9.4 vs 8.0
zeroto60times.com claims 8.9 vs 7.9

Couldn't tell you which mode they used.
it was tested somewhere, and I remember seeing it, that they were able to drop the time from 9.4 to 8.5 by using M mode, and it was a major car tester (not just a random NASIOC member)

either way, it is slightly slower than the 5sp
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Old 08-28-2013, 03:26 PM   #215
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Between the CVT's 6th "gear" and a taller final drive ratio, it can keep the engine spinning at 70% of the RPM of a 5MT in 5th.

This is probably why it beats the 5MT in EPA tests despite higher internal losses.
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Old 08-28-2013, 03:40 PM   #216
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What is 0-60 difference between 5MT and the cvt in M mode using paddles? A normal auto is almost always slower than a manual transmission in acceleration times. However, an auto with paddle shift is usually quicker. I know first hand the Porsche Pdk was quicker than the manual transmission. It has been mentioned the cvt in m mode is a second quicker than in auto mode. With the cvt really only being a single linear gear with software shift points I think it acts like a different animal all together. I think if the cvt would start with a little lower gearing it might be a different outcome. My cvt is dead taking off for the first 60-80 feet then it wakes up and does a pretty good job of keeping in the power band at wot. I like m mode better, as 4500-5800 seems to be where it wants to hang around
There is much more power loss going through the CVT. In a perfect world with 0% power loss through a CVT, it should be notably faster than the manual transmission since it should always be in the exact maximum power band. What happens instead if you deal with a ton of transmission drag and power management from the ECU (trying to protect the CVT).
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Old 08-28-2013, 03:43 PM   #217
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Between the CVT's 6th "gear" and a taller final drive ratio, it can keep the engine spinning at 70% of the RPM of a 5MT in 5th.

This is probably why it beats the 5MT in EPA tests despite higher internal losses.
RPM is not one of the biggest factors in MPG. My 2009 Jetta 5 speed had a 5 cylinder engine that ran 3K RPM @70 MPG and beat my 2012 Impreza CVT in HWY MPG on everything except perfectly flat highways. The Impreza was usually chugging away just over 2K RPM.
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Old 08-28-2013, 04:02 PM   #218
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Apples and oranges. If you want to control for RPM, kick each car down a gear and observe the MPG.
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Old 08-28-2013, 04:36 PM   #219
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Ain't it peculiar that the CVT has more drag than the 5 speed (according to some), and RPM is way overrated (according to some), and the gearing isn't optimal (according to some)

Yet the CVT returns higher mpgs than the 5 speed (according to some? LOL)

Peculiar as all get out...
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Old 08-28-2013, 06:56 PM   #220
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I think there have been posts about the correlation between rpm and mpg, or rather the lack of a direct correlation between the two. It's more of a factor of balancing load, vs rpm, gearing. There is prob more of a direct correlation between gearing and mpg than rpm and mpg. You can run in any lower gear with very light throttle and high rpm and use less fuel than running in a gear that's too high and much higher load at a lower rpm. Gearing is the common denominator between the two examples
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Old 08-28-2013, 07:14 PM   #221
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Apples and oranges. If you want to control for RPM, kick each car down a gear and observe the MPG.
Try throwing into a lower gear with your foot off the accel and watch as the RPM'S jump up, your instant mpg will top out at 99 mpg. That's because the TPS is reading no load. If you bog it down in a higher gear and use all of your petal the mpg drop like crazy even though its at a very low rpm. It's not necessarily the rpm as much as it balanced with the load on the engine. Gearing plays prob the biggest role in it. Obviously apples vs apples long drive lower rpm and lower TPS reading means lower injec pulses and or shorter duration cycles. This results in higher mpg. But there is a balance to be had, if the car isn't powerful enough to maintain itself at the higher final drive ratio on cruise, it'll apply more load automatically. Even though it might be a 5-speed and have enough power to pull a hill, if it takes a much higher load reading ( applied by ECU since its on cruise) it'll rapidly increase injector duty cycle thus forcing more fuel into combustion chamber than it would down shifting with a higher rpm and much less load or lower TPS reading ( hence less fuel being fed by the injection system). So to just say you can pull a hill without down shifting to keep rpm lower will save fuel just isn't always accurate. It does seem logical for sure, but the reality sometimes doesn't follow everyday logic
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Old 08-28-2013, 07:51 PM   #222
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Try throwing into a lower gear with your foot off the accel and watch as the RPM'S jump up, your instant mpg will top out at 99 mpg. That's because the TPS is reading no load. If you bog it down in a higher gear and use all of your petal the mpg drop like crazy even though its at a very low rpm.
How is this in any way a reliable experiment? The idea is to keep other factors constant.

I'll make it really easy. Find a stretch of highway of 10 or so miles, set the cruise control at 60 and reset the trip odometer. At the end of X miles, note the MPG.

Perform the experiment in the highest gear, then in the next-to-highest gear and let us know what you find.

Pulse width is not linearly related to TPS, which is why ECUs have fuel tables. Many factors go into pulse width, but pulse frequency is directly tied to RPM.
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Old 08-28-2013, 08:27 PM   #223
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Ain't it peculiar that the CVT has more drag than the 5 speed (according to some), and RPM is way overrated (according to some), and the gearing isn't optimal (according to some)

Yet the CVT returns higher mpgs than the 5 speed (according to some? LOL)

Peculiar as all get out...
My CVT feels like you're standing on the brakes when it gets above 4k and you let off the accelerator.
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Old 08-28-2013, 08:34 PM   #224
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RPM is not one of the biggest factors in MPG. My 2009 Jetta 5 speed had a 5 cylinder engine that ran 3K RPM @70 MPG and beat my 2012 Impreza CVT in HWY MPG on everything except perfectly flat highways. The Impreza was usually chugging away just over 2K RPM.
My 5sp beats our jetta 2.5 5sp by an average of 15%
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Old 08-28-2013, 08:57 PM   #225
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How is this in any way a reliable experiment? The idea is to keep other factors constant.

I'll make it really easy. Find a stretch of highway of 10 or so miles, set the cruise control at 60 and reset the trip odometer. At the end of X miles, note the MPG.

Perform the experiment in the highest gear, then in the next-to-highest gear and let us know what you find.

Pulse width is not linearly related to TPS, which is why ECUs have fuel tables. Many factors go into pulse width, but pulse frequency is directly tied to RPM.

Pulse width varies linearly with intake manifold pressure regardless of rpm for the most part. It also varies linearly with the TPS. Both the TPS and the MAP are what drives the voltage for the pulse width. By frequency I'm assuming your referring to the duty cycle. The pulse width dictates the volume of fuel used per cycle (cc sizing of injector) and duty cycle dictates fuel flow. You said pulse frequency (duty cycle) is tied to rpm, and that is correct. However, like I first said, even at higher rpm and thus higher duty cycle, you are not necessarily getting a lower mpg. You can have a shorter pulse width and higher duty cycle to achieve the desires AFR. There are two methods really to tuning,
1.) using TPS and RPM to determine fuel map,
2.) using MAP and RPM to determine fuel map.

Both factor rpm as part of the equation, but it depends on engine setup with cams, amount of manifold pressure or vacuum you'll run ( boosted or not) etc. But please notice that the rpm being used as a factor for mapping is half of the equation. To draw the correlation that higher rpm means lower mpg is just not accurate. If you use the TPS method to determine engine load, with a lower TPS reading you get lower voltage and thus shortens the pulse width. Even if the duty cycle is 80-90% or more without the voltage from the TPS there will not be fuel sprayed when the fuel injector is opened. With the MAP method to determine engine load for the pulse width, you must be increasing the manifold pressure to increase pulse width. You increase the manifold pressure by applying more throttle. Rpm and manifold pressure are not necessarily related to the point where they rise together. You can drive around and even redline your car without creating that much manifold pressure if your not putting a load on the engine. An increase in manifold pressure will dictate a longer pulse width, thus at whatever rpm and duty cycle ( or frequency as you stated) the amount of fuel actually sprayed will increase. You can have a higher percentage duty cycle from higher RPM'S, and a shorter pulse width ( actual fuel sprayed from injector due to voltage either from MAP sensor or TPS depending on your setup).
So - Duty cycle increases with RPM'S but that is only when the injector opens. More specifically the percentage of time the injector is open

And- pulse width is the actual time (ms) the injector sprays its volume of fuel at that given duty cycle. So if you have high duty cycle, small pulse width your not using much fuel. It'll probably yield a lean condition. Low duty cycle and longer pulse width will yield a rich condition. So you need a balance, and yes RPM'S play a part in it, but TPS or MAP sensors are what actually tells the EMS how much fuel it needs. So you can have high RPM'S and not use much fuel. And you can have lower RPM'S and dump lots of fuel in. That's my point. Pretty simple.w

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