Benching Ecms

[Mike Dillon]

Hi Bruce,

 If the input resistance of the ecm map input is still much greater
 (10 times or so) of R1 + R2 then going to 10K + 50K sould be OK for
 a bench setup. But in the real world with lots of electical noise 
 around (Under the hood) the signal to noise ratio of the 10K , 50K
 restistor set up will be lower, also transiant responce will be slower
 as the currnet will be lower but the capacitance of the wires and 
 ecm input etc .. will be the same as the 1K 5K set up. (May not be significant
 as the ecm input is most likely low pass filtered anyway)

Mike D. 

> From diy_efi-owner at esl.eng.ohio-state.edu Wed Jul 29 23:11 CDT 1998
> Return-Path: <diy_efi-owner at esl.eng.ohio-state.edu>
> From: "Bruce Plecan" <nacelp at bright.net>
----Original Message-----
> From: goflo at pacbell.net <goflo at pacbell.net>
> To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
> Date: Wednesday, July 29, 1998 10:53 PM
> Subject: Re: Benching Ecms
> 
> Slowly I'm starting to get this,
> 
> How can one tell what a devise can source?.
> 
> I got such cunfusin measurements from a MAP I broke it apart,
> and found some dodads in it so it wasn't a resistive devise.  But,
> the TPS was and as I recall had like 6K resistance, so I used a 5K
> pot.  If I do the same with 1K+5K, and 10K+50K and get the same
> outputs would using the higher be better?.
> TIA
> Bruce
> 
> 
> >Not clear from description how you are rigging the map input to the ecm.
> >For 0-5V approx you need a voltage divider across the voltage source.
> >
> >
> >*          R1           pot
> >5V ------/\/\/\-----/\/\/\/\/\------ground
> >                         |
> >                         |__________ to ecm map input
> >
> >R1 is for current limiting. If your 5v source can source 5 ma then
> >use 1k for R1 and your 5K pot. If not increase R1 to 10K and use a
> >50K pot.
> >
> >Regards, Jack
> >
> >Bruce Plecan wrote:
> >>
> >> Finally applied power to the bench ecm project today, and all seems
> >> good and well so far.  Upon reflection I want to run something past the
> >> folks that have already done this, is using a 5K pot OK for the MAP,
> >> and TPS??..
> >>     The reason I ask is that with the MAP twisted to high and with a
> >> 1K ohm resistor in line, I still get a MAP voltage of 5.1volts.  Should I
> >> increase the value of the "limiting" resistor?.
> >>     I also used a 470 ohm resistor thinking that would keep the min
> >> TPS to about .5volts, but it's .18volts.
> >>     What's the error in my thinking here.
> >> TIA
> >> Bruce          Ya shoulda seen the staff run when I yelled "Fire in the
> >>                     Hole", when I flipped the main switch on.
> >
> >
> 
> 
>