Drive By Wire - I was wrong

[Wires]

In the Toyota thread, Blackened300a and I were discussing the move from a simple cable to the drive by wire system. I mentioned that I couldn't see the advantage, and I said it was a big mistake for no benefit.

Blackened300a said "There MUST be a reason, or else they wouldn't do it." Or some words to that effect. I couldn't see that reason, so I stupidly thought there wasn't one.

After I saw yet another news story about Toyota, I thought about it some more. Then it hit me: Idle Air Control. (I don't remember what Ford calls it)

The IAC system is a small stepper motor that controls a valve that lets air into the engine. It is controlled by the computer, to keep the engine idling.

Hmm, isn't that what the throttle butterfly does? Yep. By using a slightly larger stepper motor, the IAC motor and valve can be eliminated, and the butterfly is controlled by the computer, as well as the driver's input. There's already a harness going to the throttle body - DBW doesn't add one.

So, we get to the part where I admit I was wrong. I didn't consider the ENTIRE system.

No IAC means a simpler throttle body without the carburetor like passages, and no valve.

No throttle cable means no added brackets - and Cruise control doesn't need a separate module and cable.

I have to admit, I was short-sighted, and incorrect. But that's why I discuss things on the internet - I'd have never thought about it, otherwise.

[RR|Suki]

An even larger benefit in the consumer market is probably traction control. They can develop "better" traction control systems if the throttle is controlled by the ECU.

[FordNut]

Functionally I don't like DBW at all. Part of it is in programming though. There seems to be a delay, then lurch when accelerating. Not smooth at all. That part could probably be cured with programming. Also, when you have the cruise control set and want to accelerate to pass a car using the pedal it is strange. In a normal car the pedal position is proportional to the throttle position so when you press it a little bit the vehicle accelerates. With DBW, when you activate cruise and take your foot off the accelerator pedal, the pedal returns to the home (fully up) position. Then if you press the pedal to accelerate there is a lot of slack to take up before anything actually happens.

[CBT]

I do not own a vehicle with DBW, the first time I heard of it was a few years ago when a friend was complaining about it one day. He was stopped at a red light and when it turned green and he stepped on the gas pedal nothing happened. So, he gets out and pops the hood to check the throttle cable/linkage and didn't see anything so he thought it must have fell off. He said he was looking behind the vehicle, under it, all around it, even looking underneath the cars stuck behind him. Truck just sat there idling while everyone honked at him, lol.
Then he had it towed to the Ferd dealer and was raising hell about how parts could be falling off a brand new vehicle, and that's when they kindly informed him of the DBW "technology" his vehicle had. HAD.

[Wires]

I don't own one either, but my dad's Fit is DBW, I believe.

When he lets up off the pedal, it closes the flapper slowly, I believe this is for emissions. Don't quote me, but I think it keeps unburnt fuel out of the exhaust. (popping out of the exhaust on older cars when you close the throttle???)

My MGB Carburetor had little "poppet" valves in the carb butterflies, to do the same thing. The computer mus close the valve awfully slowly (long lag) because when you push in the clutch to shift, the engine revs up a little, after it's unloaded. This is VERY IRRITATING. You have to let off of the gas in gear, and wait before pushing the clutch.

For that matter, I think the programming of newer, cable controlled cars uses the IAC to do the same thing, so you still get a bit of that irritating lag at throttle close.

I'm not a controls guy, but I do know you've got to have a well tuned system to satisfy "car guys" with an appropriate throttle action. Of course, emissions regulations tie the designer's hands.

I know there are folks who have considered changing from DBW to cable, but I'd think it would be almost impossible to keep the computer happy and keep an acceptable idle.

[CBT]

I'm not a controls guy, but I do know you've got to have a well tuned system to satisfy "car guys" with an appropriate throttle action.

If they can make the throttles on fuel powered Radio Controlled toys so sensitive, one would think they could make full size vehicles respond as quickly.

[RR|Suki]

When my buddy got a tune for his car they did change the throttle response and it was fine. So it is certainly something that can be fixed in the tune.

[Big Black Beast]

It's still fairly new isn't it?
I'm guessing they'll get better at it with time.

[-Matt-]

My 06 CVPI has DBW and its fine for me.

[jdenning002]

I had a 2009 CV PI complete motor and trans installed into my 2004 CV sport, I wnet with the entire 2009 harness and ecm with DBW.

It drives great, no complaints. I was surprised.

[BobC]

It's still fairly new isn't it?
I'm guessing they'll get better at it with time.

Michael Schumacher was using it 10, or so, years ago - worked pretty good. :lol:

[guspech750]

My 2005 GTO has DBW. I think it responds pretty quickly.

[BigCars4Ever]

There's a very scientific reason for drive by wire. First look at our cars with a standard cable activated butterfly. When you WOT there is a sudden inrush of air. The motor will ingest the air faster than the fuel injection can supply fuel for the extra air. So this is handled by something called tip-in to avoid detonation. During tip-in timing is pulled until the a/f is rich enough to advance timing again. Our custom tunes improve this but I don't think they eliminate it. They just make the wot a/f more rich and add timing. OK for power but not for efficiency. On a car with drive by wire the computer will open the butterfly only as fast as the fuel system can supply fuel for the incoming air. This allows better control over the timing and a/f and keeps the car more efficient. At least that's how I've heard it explained.