BLUEBYU

Just wondering what the benefits are of using an electronic throttle control vs conventional cable linkage throttle. I understand the whole driving uphill and cruise control but is there really an added benefit to using an ETC? I think the IS would have been better off with a conventional, proportional throttle system.

vlad_a

It may, also, have something to do with the traction control system, which cuts power to the engine once engaged.

DtEW

Like conventional throttles, the IS ETCS-i is proportional. The difference is that a conventional throttle is fixed in its proportionality curve, while the ETCS-i can be/is dynamic.

Remember how the IS jumps off the line (esp. pre-ECU reprogram) with only a bit of throttle tip-in? That's the ETCS-i. Many people loved the feel of that sensation, but just as many thought it was hard-to-manage in traffic. So the response was flattened with the reprogram, but some people mistook that for "a loss of torque."

Having systems that require some degree of control over the throttle (A650E tranny, TRAC, and VSC next year), a purely electronic throttle is the more "zen" and less "cobbled together"/"legacy-bound" way of doing it. It also allows for much more precise attenuation of the throttle input without the high cost of low-backlash gears/low-tolerance assemblies that are needed to physically work against the entire throttle cable/pedal return spring, etc. The ability to vary the throttle proportionality curve is a bonus of the inherent precision of electronic signal attenuation.

In actuality, the e-throttle on the IS is a little "legacy-bound" presumeably for the sake of modularity and old-school mechanics that might be called into service to work on the car. The accelerator still works by cable all the way up to the throttle body itself, where it attaches toa cam that operates the position sensor. Only within the throttle body can you see that there is no physical linkage between the cam and the throttle plate. The "better" way would be to place the position sensor right on the accelerator. In the current instance, we've still got the entire throttle cable and a cam to introduce imprecision to the subtlety that we may want to communicate with our right foot.

BLUEBYU

Thanks DtEW that is a great explanation. The only 'problem' I notice is when the throttle curve gets shifted down (i.e: the jump off the line) but leaves nothing for the top side (3/4 to full throttle position). I get a strange feeling when I don't get anymore acceleration when I move past the 3/4 throttle position. I think this is what fools people into thinking the IS is slow because of the throttles reaction at full throttle is not what is expected. I have noticed many times were I have attempted get on it and it is not as quick as other times where it takes off in a hurry. Though this may have to do with transmission reaction as well.