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flightlead404 flightlead404 is offline
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Join Date: May 2015
Posts: 798
Yeah forget about the AFR. The controller has a calibration sequence on startup and that is the sudden drop you are seeing. With AFR disconnected the problem still exists unchanged, which is why I performed the test with it hooked up - to eliminate it as a cause. Its neither responding to, or causing, any issues. A complete red herring.

"flattening VE2 around idle should go a long way toward eliminating some factors"

Flattening? or fattening? Can you explain a little further?

"cause and effect relating to MAP, RPM and VE and the resulting frequency valve duty is definitely in question, with MAP being the point of interest I think"

I'm convinced the change in MAP is an effect not a cause. What would cause a sudden change in MAP? The only thing I can think of is a change in RPM, which would obviously cause MAP to change, and what I think we're seeing here. The only other thing I can thing of that would cause MAP to change, in other words making MAP the cause not the effect, would be the idle valve. But that works perfectly as demonstrated by the non-FCIS starts.

So, what causes a sudden change in RPM other than the sudden addition or reduction of pressure in the intake (opening or closing a throttle or valve)? Well there's only two others options, spark and fuel. I'm still using the factory dizzy so the only possible way the timing can change is a change in vacuum or pressure on one or both of the ports on the vacuum capsule on the dizzy. Well the thermovalve has been eliminated and the advance side runs straight to the throttle body, and the Pierburg switch on the retard side can be seen operating on the cold starts, not the warm starts, and at a grossly different time than this stumble. I think that eliminates ignition as a cause.

"It the change an MAP and the resulting VE2 values changing the RPM, or is the cause resolving itself and subsequently changing MAP and RPM and therefore we get a new VE2 value."

I think its the latter. Something is changing to cause RPM and therefore MAP to change. The only thing I can see that is changing is the FV duty cycle, adding a bit more fuel. So the question is why is that changing?

"Is MAP fed from the manifold or is it tapped into an existing line somewhere which may be either ported or affected by the oem valves and switches? "

It is teed into the vacuum line from port IV on the throttle body to the WUR. AFAICT this port is below the throttle valve.

Last edited by flightlead404; 05-01-2017 at 06:40 AM..
Old 05-01-2017, 06:13 AM
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