Fuel Economy - manual transmission

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bootymac
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That's how the CVT behaves as well. It upshifts to sixth "gear" as soon as possible to increase fuel efficiency. An added bonus is that the engine is much quieter.

I haven't noticed any detriments with this behavior. It actually has a decent amount of acceleration and I never felt the need to manually shift.
ipaqxman
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Location: NYC, NY

Is lugging the engine/transmission bad though on the CVT? I feel it sounds like a tractor often when on high gear and low rpm.
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KuroNekko
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bootymac wrote:That's how the CVT behaves as well. It upshifts to sixth "gear" as soon as possible to increase fuel efficiency. An added bonus is that the engine is much quieter.

I haven't noticed any detriments with this behavior. It actually has a decent amount of acceleration and I never felt the need to manually shift.
There are no "gear" positions in the CVT when used in full auto mode. It doesn't upshift at all because there are no gears to shift. The ratios of the pulleys keep changing therefore it's called a Continuously Variable Transmission. When you use the paddle shifters, it merely orders the CVT's pulleys to engage a pre-set ratio between the pulleys to mimic gear shifts as if it had 6 cogs. My understanding is that unless you use the paddle shifters, the preset ratios are not used.
So basically, it doesn't upshift to "sixth gear" as soon as possible. The CVT is continuously varying the ratio for the most efficient output.

While I believe the engine may be quieter while cruising, it's well documented that on take-off the sluggishness of the CVT makes the engine work harder therefore noisier. Many reviewers have stated that the CVT makes the engine actually noisier. When I drove another car with a CVT, I understood this phenomenon.
2011 Suzuki Kizashi Sport GTS 6MT (Black)
bootymac
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Oh yeah, I know that there are no actual gears in a CVT. I was trying to say that the CVT "upshifts" aggressively into a ratio that is equivalent to a sixth "gear" as indicated by the instrument display.

Semantics. Hopefully I used enough quotation marks this time :P
~tc~
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I live in Houston now, there are no hills.

With my MT 4Runner, the mileage is always better when you stay in a lower gear and easy on the throttle. Truck drivers are taught the same way.

The way FI works, your data does not make any sense. The variation in pulse width due to throttle position is FAR more than the variation in number of pulses due to RPM.

I would say the CVT SEEMS louder because it lets the engine max out and stay there, where with a traditional transmission, the RPM and sound are always changing.
2011 Sport SLS with nav Black Pearl Metallic
murcod
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~tc~ wrote:I live in Houston now, there are no hills.

With my MT 4Runner, the mileage is always better when you stay in a lower gear and easy on the throttle. Truck drivers are taught the same way.

The way FI works, your data does not make any sense. The variation in pulse width due to throttle position is FAR more than the variation in number of pulses due to RPM.

I would say the CVT SEEMS louder because it lets the engine max out and stay there, where with a traditional transmission, the RPM and sound are always changing.
Why doesn't it make sense? The fuel injection works by trying to maintain and ideal air fuel ratio (14.7:1 for best operating efficiency.) More revs = more air being "pumped" by the engine = more fuel required!
David
~tc~
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Because the FI only does that in closed loop, and these are open loop scenarios
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murcod
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~tc~ wrote:Because the FI only does that in closed loop, and these are open loop scenarios
You'd be amazed at how long a modern EFI system will hold closed loop. Even if it does go into open loop you'll be looking at say 12 to 13 : 1 air fuel ratio. Not a lot more fuel per cylinder per revolution - compared to a substantial increase in revs by using a lower gear (..... with the engine also probably operating in open loop at similar A:F ratios ;) )
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Woodie
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If you need 100 hp, it's going to take X amount of air and X/14 amount of fuel to make it. High rpm low throttle opening or low rpm wide throttle opening will both get you there pretty much equally. The difference is, high rpm includes a lot more drag from friction, and also a lot more pumping loss, where the engine is sucking hard against a closed throttle plate, a lot of energy is used up there.
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~tc~
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That's great in theory, but in real life, the air/fuel mix is constantly changing because you let in more air before the fuel gets there and vice versa.

The difference in pulse width of the FI between "light" on the throttle and "heavy" is orders of magnitude, not the maybe 2x in RPM between a low gear and a high one.
2011 Sport SLS with nav Black Pearl Metallic
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