Back pressure and torque

[John Hess]

I DID go to the books.  Back pressure (and flow) effects the exhaust
temperature.  The exhaust temperature of a free flowing exhaust can have
an effect on the O2 sensor, since most depend on the exhaust to heat
them up into their operating range.  I have consistently had troubles
with cars with header systems not going into closed loop, simply because
the O2 sensor didn't get hot enough.  That is why I now install
electrically heated O2 sensors on cars with headers.


> ----------
> From: 	swagaero[SMTP:wb7omm at flash.net]
> Sent: 	Wednesday, August 27, 1997 5:05 AM
> To: 	diy_efi at coulomb.eng.ohio-state.edu
> Subject: 	Re: Back pressure and torque
> 
> John Hess wrote:
> > 
> > > ----------
> > > From:         Keven D. Coates[SMTP:keven at ti.com]
> > > Sent:         Wednesday, August 27, 1997 6:17 PM
> > > To:   Bronco Group; Tom Cloud; diy_efi at coulomb.eng.ohio-state.edu;
> > > EEC-EFIList
> > > Subject:      Backpressure and torque
> > >
> > > Tom wrote,
> 
> > 
> > a modern fuel injected engine) can have DRASTIC effects on what your
> O2
> > sensor THINKS it is seeing.  Indeed, low enough back pressures (on
> > unheated O2 sensors) can prevent the system from ever going closed
> loop!  
> 
> I think you need to go back to the books on this one an O2 sensor is
> not
> looking at pressure but a voltage generated by tempeture which varies
> by
> the oxy content in the exhaust my exhaust system is only 6" past the
> o2
> sensor and it does a ful voltage scan within 18 sec after startup.
> That
> also includes using 100 low lead av fuel.
> 
>  
> Steve Parkman
>