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Re: Electronic Throttle Control

To: Kevin_Stevens@Bigfoot.com, autox@autox.team.net
Subject: Re: Electronic Throttle Control
From: Matthew Carson <mcars@vt.edu>
Date: Thu, 15 Jun 2000 22:55:14 -0400
>>Some coworkers and I were discussing today the feel of elctronic
>>throttle control versus conventional throttle cable feel, and I was curious 
>>how people that autox with them (such as in C5s, '99+ V6 F-cars, I am sure 
>>there are others) feel about them.
>
>>I know driving them on our roll test machine I can feel a slight lag in 
>>response, but loadings and such are different, and I have >never autoxed 
>>one.  Does the slight lag make you smoother?
>
>No.  It doesn't really feel like a lag, though that may in fact be what's 
>happening.  It feels like you get a slightly different response based on how 
>fast you press the pedal, like in a stereo knob where when you spin it 
>rapidly you get large jumps, and when you are turn it slowly you get 
<<clip...>>

I don't know if we do anything on the response curve on that or not
(assuming traction control is not active).  My understanding of the system
was that it learned where 0% was on the pedal in counts and where 100% was
and interpolated between them.  The lag just comes from the the fact that a
stepper motor is opening the throttle instead of your foot, which is of
course instantaneous.  It just takes longer to move more counts, so it
feels like more of a lag (or a bigger jump because it probably gets moving
faster) on larger changes.  What I have noticed is during our WOP/WOT test,
if you go to WOP (wide open pedal) from 0% in neutral, hit the pedal stop
and immediately let off, you will pass WOP but not WOT (wide open
throttle).  You have to hold it for a very small but measurable amount of
time to pass WOT as well.  On non-ETC cars you can normally pass this test
very quickly.  

>Something I also noticed was that there were SIGNIFICANT increases in engine 
>power at exactly 5K and 10K miles, and I wondered if there was a break-in 
>program in there somewhere as well.

        Not sure about this one, I will have to look into it...  I know most 
cars
run faster at 20k than when new, but I haven't heard about them being
instantaneous.  Now that you mention it though my Camaro felt faster at 5k.

-Matt


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