Big overlap cams and EFI

[Roger Heflin]

Joe Boucher wrote:
> 
> The guy at Turbo City that will burn custom prom chips for GM EFI told
> me the maximum intake duration he can burn a chip for is 220 degrees.
> 
> What is the problem?  It 's centered around the vacuum signal, correct?
> Is the MAP sensor incapable of keeping up with the rate of change or
> magnitude of the signal?  Does the vacuum get too low (air pressure too
> high) versus the map in the prom?  If you didn't care about emisions,
> could you program the prom so the manifold pressure is ignored when the
> throttle position is at idle and just squirts a certain amount of fuel
> based on coolant temperature?  With a MAP based fuel management system
> is the fluctuation of the vacuum signal at low RPM's too wild versus the
> sampling rate of the computer to determine the dwell of the injectors.
> 
> In other words, I don't have a clue why this is.
> 
> Thanks,
> 
> Joe Boucher
> '70 RS/SS Camaro '81 TBI Camaro
> Bedford, TX

There a couple of guys on the f-body list running cams above 220
degrees,
I don't know exactly how far above, but they claim they don't run too
bad.  I have heard one of them idle and it does die sometimes if you
are doing the wrong thing (coming out of the water box off of the gas).
I don't really know how many degrees they are running, just that is 
significanlty more radical than the LT4-HOT (218/228) cam.  They have
put the cams in both a 93 Z28 (prom/maf) and the 94+ (map).  They claim
that they idle better in the 94+.

		Roger
		93 Z28 (wondering if I can put up with their cam)
		rah at horizon.hit.net
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