Modifying O2 output

[Jonathan R. Lusky]

Robert Gallant writes:
> Now the problem I ran into is that my car like to idle VERY rich and the 
> computer only lets you set O2 trigger voltages up to 0.8v.  The computer tries 
> to adjust the O2 compensation to maintain the trigger voltage.  As a result the 
> car won't idle.
> 
> Holley is going to burn me a custom chip (they are being EXTREMELY helpful) and 
> they are thinking about the best way to accomplish the rich idle I need.  So in 
> the mean time I was going to try and fool the computer by droping the O2 sensor 
> voltage.  This would let, say 0.8 volts into the computer be something like 0.9 
> volts out of the sensor.  Ya, ya I know the sensors are not linear way out there
> but it lets the car idle!

What's your EGT like, Rob?  You may not even be able to get 800mv out of
your EGO at idle...  (depends on the sensor).  On our M85 car, I
couldn't even get 700mv at idle when I was blowing raw fuel out the
exhaust (mega rich).  Anyway, it sounds like you need an open loop
idle...  is there any way to set the holley system to go open loop
below a certain TPS output?  Does the Holley system have a water
temp threshold for going into closed loop?  If so, maybe you can put
a throttle actuated double throw microswitch on the CTS lead and use
two seperate coolant temp sensors with majorly different calibrations?
(one thats guaranteed to keep you in open loop at idle).  You'd have an
interesting spike in your coolant temp (fuel) correction curve (if you have
one), but it might work :)


-- 
Jonathan R. Lusky                        lusky at knuth.mtsu.edu
http://www.edge.net/~lusky/                 (615) 726-8700
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68 Camaro Convertible - 350 / TH350  \_/ 80 Toyota Celica - 20R / 5spd