Re: quattro-digest V3 #1364

[ptimmerm@mashtun.JPL.NASA.GOV]

>> The Computer goes into open loop when it detects the 2/3 (full throttle) 
>> switch closed and then sets the frequency valve to a duty cycle around
>>   68% to richen up the mixture under full throttle. Using an expensive 
>> portable 4 gas  analyzer I have measured the air fuel ratio to be closer to 12.8 to 1 
>> (upstream of the cat convertor) under sustained full throttle at 1.4 bar
>> and 1.8 bar boost on the 5000 MC and the later 89 200 MC engines
>> with the stock frequency valve duty cycle settings.
<
<As an aside, some benefit can be gained by setting the idle duty cycle low.
<If you set the duty cycle to 50% at idle, 68% is only a 18% increase.
<Set the idle duty cycle to 40% and now you get a 28% increase at WOT.
<(Now I don't know the exact relationship the duty cycle has to the mixture,
<but 40% seems to be the accepted setting.)
<
<Scott, what was the idle duty cycle when you made those measurements?
<
<Orin.

True enough, but you arent going to get that much more fuel out of
the system without some larger control modifications.  Anyone considering
20 + psi should be thinking about a higher rate fuel pressure regulator.  
But don't believe me, read Probst on Bosch CIS from Bentley Pubs.  I think 
I have heard Sportwheels had a tweaked FPR that they sold.  ANyone know 
for sure.  Otherwise  MicroDynamics make one that will work, but doesn't 
look stock like a tweaked Bosch unit. They come in several sizes from MD.

paul timmerman