Throttle: Electrical vs. mechanical linkage

great reasoning but you would have to back it up w/the computer . This may be happening or not

 

Elctronic throttles have simplified the design and helped eliminate a few other components in the system. Also it dramatically improves traction control function. It is really rather simple and makes more sense when you see its implementation and how well it integrates with other systems. I suspect it makes cruise control better and easier but that is not a factor so far here.

 

The throttle opening need not have quite as direct an effect as you state. Timing can be retarded, A/F can be allowed to lean out, cylinder(s) can be cut, *brakes can be applied*, etc. I guess I'm basically describing traction control.

 

Not to mention allowing a mechanical device to instantly shut the butterfly on the throttle body creates all kinds of emmisions from unburnt fuel.

 

The TOYOTA problems are BOGUS as far as the pedal problem. There have been instances of the cruise control taking off and the reported problems with the pedal only occurred in cars with cruise control.

The little reported fact is the software in the cruise control caused ALL issues and Toyota is changing the computer chips while throwing the blame on the silly pedal.

 

I'll throw in my thoughts. The increase in servos and actuators that remove the 'direct mechanical' link is an advantage to the 'system' and inversely a disadvantage to the driver.

I had a new Audi that decided to cut control to the throttle due to a ground short in the alarm system. Only problem was that I was towing uphill in the mountains and suddenly without warning the Q slows and drifts. I'm left with steering and brakes that are vague as that too is servo controlled. Sure these systems help with emissions and lower risk of damage to the drive train but at the sacrifice of driver safety. loss of control is HUGE problem I see going into the future of the automobile.

When you have a 4,000+lb vehicle traveling down the road with steering, throttle and brake controlled by ECU's it's an open invite to increased auto accidents.

 

Why would the ECU not also cut the fuel as it cuts the throttle?

 

Yes, this is my understanding also. 50% call on potentiometer at accelerator pedal does not necessarily translate into 50% open butterfly valve in throttle body. ECU determines best setting of valve dependent on engine RPM and sets accordingly. Greater air velocity for example can be achieved with a smaller valve opening. Cool isn't it?

 

I'm pretty sure it's a one sided offset so under normal conditions there is a direct relationship to the throttle plate and the ecu only has the power to reduce the throttle setting. Allowing the ecu to open the throttle beyond the pedal setting would be very unsafe.

The only way to make cruise control work is to let the ecu open the throttle a little but this requires some serious software testing to be sure there is no condition that the ecu will decide to slam the throttle open….and this has to be the problem with the Toyota, most people aren’t going to describe a stuck throttle as anything except a stuck throttle, the words “unintended acceleration” imply the throttle opened all by itself to me.

 

It would by default as the ecu's main mission is to match the fuel to the air. Generally most modern ecus cut the fuel supply completely during deceleration.

 

No, there should be no question of the ECU ever opening the valve by a greater proportion that that called for by the accelerator pedal but often times opening it (at least initially) by a lower proportion.

 

I thing we are saying the same thing.

Although cruise control does mean the ecu has the power to open the throttle....which alway scares me a little.