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Bill Dube wrote:
The difference in pressure across the injectors is what matters, not the absolute fuel pressure. If you hold the difference in pressure constant, the injectors deliver the same amount of fuel per pulse, regardless of manifold pressure changes. If you run a fuel pressure that is not referenced to the manifold, you will have less and less difference in pressure as the boost comes on. This will make your situation worse, not better.
Agreed. But with a fuel pressure over 50 PSI, it will take a very significant turbo boost to cut off the flow altogether. The two question that then remain are, "Do the injectors have the time to dribble in enough fuel at full boost?" and (on the other end) "Can we turn the firehose off quick enough not to flood the engine?"
The stability issue is a subtle one, but important. Let's pick high manifold pressure (boost) as an example. You open the throttle. Pressure instantly goes up. The difference in pressure across the injectors goes down. The fuel per pulse goes down. The fuel flow instantly goes down before the injection computer can compensate. The engine goes lean. The engine slows down a bit. The manifold pressure is starting to go up a bit more because the engine slowed down a bit. The difference in pressure across the injectors now goes down a bit more. They instantaneously deliver less fuel. The engine goes even leaner. The computer is now catching up. It calls for more fuel. The injectors open for longer. The engine starts to speed up. The manifold pressure goes down. The difference in pressure across the injectors increases. They instantaneously deliver more fuel. The engine speed up more. The manifold pressure drops more. The injectors deliver even more fuel per pulse, instantaneously. The computer now catches up and calls for less fuel. ............
Bill Dube'
This reasoning hinges on the assumption that the mechanical manifold to fuel pressure reference system is instantaneous and that the computer will be lagging behind. I'm not sure I can swallow that pill unless there is a lot of unnecessary hysteresis built in front of the computers pressure sensor (perhaps from using an overly large hose). I don't think I've ever heard of a problem tracked back to the EC2 not being able to keep up.
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,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o www.ernest.isa-geek.org |
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