Fly-by-wire: Bad for FE?

[AeroModder]

Since my car is in the shop after the power steering blew before I had a chance to bypass it, I'm renting a 2008 Chevy Aveo. I can say with complete certanty that throttle-by-wire SUCKS. Not only is there a 0.2 second lag between pressing the throttle and it responding, but it jerks when it catches up to your foot on the throttle. Also, there is very little pedal feel, since you're just moving the simple lever and not turning a throttle plate. This makes it easier for your foot to relax and make you speed.

I've actually timed the lag, and I can tap the gas and have my foot off of the pedal before it registers and jerks forward. With a throttle cable, I can more precisely control the throttle position and accelerate much smoother.

Now, with that jerking, I'm assuming that the engine is squirting in more gas than it would with a soft, smooth start. This, combined with how easy it is to speed with very little pedal resistance, leads me to conclude that it is much easier to burn more gas with fly-by-wire.




Other general complaints about the Aveo are that I can't see the turn signal indicators, half of the fuel and temp gauges, and the tops of the speedo and tach because they're hidden under the top of the steering wheel. A very poorly designed car, in my opinion. I'll be glad to be rid of it.

Good points include a good helping of low-end power/torque, smooth shifting, and 4 speeds. Sadly, that's where it ends.

[ChrstphrR]

Given your garaged car on the forum (91 Tempo is pre OBDII), you probably didn't have a scanguage to help pinpoint if the throttle response was non-linear in one or more spots. My Jetta's coolant temperature guage is like that, and it's maddening. The 10 year old TDI I'm driving has always had a drive-by-wire throttle, and there isn't the jerkiness or the level of hesitation you describe in my throttle response.

The issues you're having, that sounds like much more confined to the particular make/model you rented. Seemingly, they didn't pay much mind to the programming for the throttle response, which makes sense considering the Aveo will likely never be considered a "sporty" car that would warrant that attention.

[RobertSmalls]

Throttle-by-wire: Good for fuel economy

Throttle by wire, when executed properly, allows engineers to interpret the displacement of the go-pedal as a request for power, which could be filled in the most economical way possible.

Engines are usually efficient at low RPM and wide throttle aperature. With throttle-by-wire + CVT, the best scheme is probably to open the throttle wide, and vary engine RPM to give the driver the power he wants.

If you have a 4-speed auto, the best scheme is probably to keep it in the highest gear you can, with wide throttle angles but fairly lean air/fuel mix. If you press the pedal harder, the throttle should open farther. Once it's wide open, if the driver presses farther, downshift and close the throttle a little. This scheme requires a fast, smooth transmission, or the driver will complain that there's a huge lag between pressing the go-pedal and going.

The Aveo is highly optimized for low cost. It's not the best car in its class, and it doesn't represent what can be done with throttle-by-wire.

[AeroModder]

So it would be good for inexperienced drivers to get better fuel economy.

However, I much preferr to take control of the vehicle myself. I simply can't stand a computer trying to figure out what I want when I already know it, and could achieve my desired throttle position/rate of acceleration with my own right foot.

Microchips are a poor substitute for driver experience, in my opinion. Then again, as someone who's looked at strangely for liking the feel of manual steering, it could just be me.

[NeilBlanchard]

It's not just better FE -- it is *much* cleaner tailpipe emissions, and driver experience has almost nothing to do with it. I think the accelerator by wire is here to stay.

[Thymeclock]

I think it may be the rental car you got. Who knows what condition it is in? I'm not a fan of throttle by wire, but my practically new 2009 Aveo doesn't experience any lag.

I just posted a new thread about the tranny however, which is my main dissatisfaction with it: Aveo transaxle.

[Roger Jolley]

Originally Posted by AeroModder

<snip>I'm renting a 2008 Chevy Aveo. I can't see the turn signal indicators, half of the fuel and temp gauges, and the tops of the speedo and tach because they're hidden under the top of the steering wheel. A very poorly designed car, in my op<snip>

The Aveo has tilt steering wheel, standard. Look under the steering column. You probably didn't notice because you're only renting.

[darcane]

My wife's Vue has throttle-by-wire and I find it highly annoying. It's designed for reducing emissions, and one side effect is that it doesn't close the throttle immediately when you let off. If you rev to 4000rpms with the clutch depressed, it will take about 3-4 seconds to return to idle. This behavior really messes with my upshifts.

[PaleMelanesian]

Originally Posted by NeilBlanchard

It's not just better FE -- it is *much* cleaner tailpipe emissions, and driver experience has almost nothing to do with it. I think the accelerator by wire is here to stay.

How does that work?

[Daox]

It can resist going into open loop much easier I'd say.