When is it necessary to subtract fuel with a controller?

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Apr 6, 2011 | 08:41 PM

jacknthebox

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From: Pluto

When is it necessary to subtract fuel with a controller?

I am trying to decide if I will encounter a need to have a controller that not only adds fuel but subtracts it too. Deciding between a dobeck tfi (only adds) and a pciii (adds and subtracts).

Dobeck says that 80% of the time, adding fuel is enough in the tuning. So, when is it necessary to subtract fuel?

Thanks.

Apr 6, 2011 | 09:30 PM

smithbrl

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Joined: Oct 2008

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From: Denham Springs, La

I counted 40 places where my PCV map from FuelMoto has negative numbers. They're mostly above 4500 rpm and between 15 and 60% throttle position.

I can't explain why.

Cecil

Apr 6, 2011 | 09:45 PM

jacknthebox

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From: Pluto

Quote:

Originally Posted by smithbrl

I counted 40 places where my PCV map from FuelMoto has negative numbers. They're mostly above 4500 rpm and between 15 and 60% throttle position.

I can't explain why.

Cecil

I seriously don't know a damn thing but if I had to guess, I would say with that throttle position it has something to do with removing fuel during decel....maybe to eliminate popping....and I don't think I ride in the above 4500 region so I wonder if it's more for racers and doesn't pertain to me so the dobeck might be fine? maybe more will chime in...thanks.

Apr 7, 2011 | 12:30 AM

ke5rbd

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From: Monroe, Louisiana

If you leave everything stock you probably can just add fuel. If you change to better/higher lift, longer duration, and more overlap cam, you will need to remove fuel at idle and low end. Better flowing exhaust needs to have fuel taken away in certain areas.