FW: MAF Upgrad

[xxalexx at ix.netcom.com]

> Date:          Mon, 23 Feb 1998 16:54:37 -0800 (PST)
> From:          James Weiler <james at brc.ubc.ca>
> To:            diy_efi at efi332.eng.ohio-state.edu
> Cc:            diy_efi at efi332.eng.ohio-state.edu
> Subject:       Re: FW: MAF Upgrad
> Reply-to:      diy_efi at efi332.eng.ohio-state.edu

> Time for my $0.02.  As I understand your MAP is a voltage output and the 
> MAF is a frequency output.  If you want to run two MAF's adn you want to 
> send the resulting signal to where the MAP used to be then might I 
> suggest using Ford MAFs.  They output volts not freq. and thus no fancy 
> converter would be needed.  Problem is that their voltage vs. air flow is 
> not linear.  Well it is for the first part but then it approaches 5.0 V 
> asumptotically. (i.e. it's geometric).  I don't know how to build a 
> circuit that would take the two voltages and put out an average in this 
> case.  It might be easier to just have one MAF supply voltage (and the 
> other is a dummy) and just change your tables to compensate.  i.e. assume 
> that twice the amount of air is entering the engine as the MAF says there is.
> 
> HTH
> jw
> P.S. let me know how you solve this.  I'd love to use two small MAFs 
> instead of buying an expensive large MAF.
> 
I think there are special function op-amp math chips that do 
log linearization and average.
Today less cost to use microcontroller.

> On Mon, 23 Feb 1998 lkurek at smtpgate.anl.gov wrote:
> 
> > 
> >      Now this is a cool idea!
> >      
> >      I could get an elbow (tee) fabricated that has one MAF going off to 
> >      the left, and another to the right, with dual K&N's hanging off either 
> >      side. Sure would look nice and run much better....
> >      
> >      Now, how would we go about building this "interface" box? I would 
> >      assume all it would take is some circuit to do a simple averaging of 
> >      the MAF sensor output (assuming it is a rising voltage type circuit). 
> >      If it was a wave output, wouldn't you have to synchronize and add the 
> >      two frequencies together to generate a sum?
> >      
> >      Just wondering....
> >      
> >      TTYL!
> >      
> >      Larry Kurek
> > 
Would use a 73 PIC to input the two seperate freq. on two ports, use 
timer 0 and 1 to measure frequency, convert frequency to voltage 
apply any corrections, then analog output as PWM D/A using timer2.
alex