Ecm role expanding?

[Eric Bryant]

> From: Jeremy Gonyou [mailto:jgonyou at hotmail.com]
> Subject: Re: Ecm role expanding?
> 
> How are these drive-by-wire throttles actuated?  Stepper motor?
> 
> Jeremy

Yea.  You have a dual-trace pot on the pedal to detect position, with
another dual-trace pot on the TB.  There's a 4-pole stepper on the TB that
drives the throttle shaft.  I believe that the GM system uses a stand-alone
ECU to control the system.  That's it.  

Considering that most cruise systems already use a stepper motor, the system
can be pretty cost-competitive.  A pull-only cable (such as the throttle or
cruise cables) can cost $5/each, which isn't real cheap (that'll pay for the
two pots, or about half of the ECU).  I'm not sure what the warranty costs
are like on a cable-driven throttle, but that might provide an additional
savings. 

10 years ago, BMW introduced a ETC system on their V12 models (750iL and
850), but they actually retained a cable that would crack open the throttle
about 5% in case of failure. 

Eric Bryant
mailto:bryante at ghsp.com
http://www.novagate.com/~bryante 

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