Subject: [FlyRotary] Re: [FlyRotary]

Dave,

It sounds like you have a lean surge region. Engine will drop down = in rpm

to where the fuel Map provides ample fuel, the engine produces more = power

and starts to accelerate and at some higher rpm enters a region = of

insufficient fuel delivery where the engine can not maintain that rpm = and

starts to decrease. As the engine drops in rpm it again encounters a = region

where sufficient fuel exists and starts to accelerate again, repeats, = etc.

OK, this I = understand.

Here is what I believe is happening. In my case, When the engine is = both

low in rpm and low in manifold pressure (15" or below) the idle is = fine.

However, if I lower the engine rpm even more the manifold pressure = actually

starts to increase (may go over 17").

This I don’t understand.

Tracy's EC2 actually computes the

fuel injector pulse duration based on manifold pressure sensed (RPM = simply

determines the rate that the injectors are triggered). So as the = engine

rpm is lowered (it should require less fuel). But, past a certain = point

lowering the rpm causes the manifold pressure to start to increase = (engine

speed is simply not sufficient to maintain the lower manifold pressure) =

Normally one = would decrease rpm by further lowering the MAP by further closing of the = throttle plate. Do you mean you reduce the rpm by some means other than = decreasing manifold pressure? Like changing the = mixture?

when

that happens the EC2 senses that INCREASE in manifold pressure and = treats

the increase as a demand for more fuel when in reality the new lower = rpm

requires proportionately less fuel. This gives you an overly rich = condition

so you reduce the air/fuel ratio with you mixture knob. When you do = that

you reduce the mixture sufficiently from the overly rich side to cause = the

engine to increase in rpm this may cause the manifold pressure to = actually

decrease (goes say from 17" to 15" as the rpm picks up a bit). = Manifold

pressure decrease causes less fuel to be injected causing a lean region = and

engine dies back in rpm, etc..

After = sufficient leaning, I was able to get my engine to run OK on the dyno at low rpm = with the 550cc/min injectors (primary in the housing); with fixed 40psi fuel = pressure. The issue I couldn’t resolve was the ‘overshoot’ = – decelerating from a higher rpm and MAP going to a level below where I could make an = adjustment – resulting in the engine dying. The EM-2 is going to allow = me to resolve that; right?

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