CVT's (non-hybrid) = fewer opportunities for fuel-cut mode (DFCO) when coasting?

[Joggernot]

Originally Posted by Michaelflat1

Oh that's not very good, i guess this could be changed using ECU and transmission remapping tools.

Perhaps in DFCO engine braking was too much, try without aircon maybe?

I don't use A/C, so this is without A/C.

[cRiPpLe_rOoStEr]

Originally Posted by jakobnev

Is there no L-mode like a conventional automatic?

No, there is nothing like that.

[CVTCivic]

Originally Posted by cloowisa

Considering pretty much the only reason for building CVT's is improved fuel economy, it sure is odd that they don't do DFCO as much as other transmission types

I don't think the Williams F1 team built a CVT in one of their F1 cars to get better fuel economy

[cRiPpLe_rOoStEr]

Originally Posted by CVTCivic

I don't think the Williams F1 team built a CVT in one of their F1 cars to get better fuel economy

I didn't even remember Williams had tested a CVT, yet I'm also not sure to which extent it would be so much of a good idea for Formula 1.

[CVTCivic]

Williams experimented with a CVT in the early 90s, but FIA banned it.

They did this to gain speed. While the car changes gears it looses speed. There is a good video about the CVT in the formula 1 car.

https://youtu.be/Sp228-39WhQ

[cRiPpLe_rOoStEr]

Originally Posted by CVTCivic

They did this to gain speed.

I guess the software was substantially different from what we see on road-going vehicles, which tend to rely on the CVT to keep the RPM steadily within a narrower band.

[some_other_dave]

On a street car, you have to optimize for a number of different things. Sometimes power, sometimes torque, sometimes fuel economy, sometimes noise, and so on. Depending on how you control the CVT, you can run the engine somewhere near its peak of one of those things.

For a race car, you basically just want peak power. Which basically means running the engine at its peak power RPM, at least for a given throttle setting. A much simpler optimization problem, but at power levels that are almost certain to be pretty punishing for the hardware.

-soD

[cRiPpLe_rOoStEr]

Originally Posted by some_other_dave

A much simpler optimization problem

With pit-stops being part of the racing strategy, eventually having different modes at the very same CVT controller could be reasonable even for a racing application.

[Tahoe_Hybrid]

Originally Posted by MetroMPG

The last CVT I spent much time driving was the 1.2L, 3-cylinder Mirage pictured above.

I was genuinely impressed by how much it was programmed to pursue fuel economy: It tries its little heart out to keep cruising revs as low as possible (see chart).

I remembered being pleasantly surprised that...



That has me wondering: do CVT's programmed for such low RPM, fuel-saving operation offer fewer chances for zero fuel burn (DFCO) when releasing the throttle and coasting in gear? Seems possible you might only get a brief fuel cut before injection resumed to keep the engine running.

Other types of transmissions would have the engine at a higher RPM for a given road speed at the start of coasting. So, more time in fuel cut-off mode.

If that's the case, a CVT hypermiler might benefit from more neutral coasting.

Splitting hairs? Probably! These are the things that keep me awake at night.

i got a EVT transmission DFCO is a neutral like coasting No engine breaking the rpm goes to 1,000 too

[cRiPpLe_rOoStEr]

I noticed most of those Chinese side-by-side ATVs resort to some sort of CVT.




However, as such vehicles are meant to be driven in a more spirited way on recreational off-roading, most likely it will behave differently from a normal car with a modern CVT. Not to mention the cheapest Chinese models have no electronic controls on the transmission to adjust it to driver's behavior.