V E tables

R

rightonjoe

Guest
What is the best procedure for bringing the cells to matching targeted A F in all cells
 
Not an answer to your question, but have you looked at http://pages.sprint.ca/norbz/files/beta65.html

Might find some answers to some basic questions there.

As for your question, when you say "best way" I don't know if you mean how to do it in general, or what specific commands to use to dial it in.

If you are asking in general, then this might help:
At the most basic level, the FAST figures out how much air is flowing, then figures out how much fuel to add to that air flow.

It goes like this:
1. Calculate the air flow from the VE, rpm, manifold air temp and manifold air pressure.
2. Calculate the fuel needed to match that air flow and the a/f ratio you set.
3. Check the O2 sensor, if it says lean add more fuel, if it is rich then take some out.

So if it sees things are lean (compared to the a/f ratio specified), it adds more fuel. Why was it lean? Because the real air flow was more than the calculated air flow. How do you get the calculated air flow higher so that it matches the real air flow better? You give it a larger VE at that spot.

So everywhere you see it adding fuel, increase the VE. Where it is taking fuel out, lower the VE.

How much to increase or lower? Suppose it is adding 10% more fuel at some spot. The real air flow must be 10% more than the calculated air flow. If the VE was 50% at that point, then to increase the calculated air flow by 10% you have to increase the 50% VE by 10%. 0.5 + 0.5 x 0.1 = 0.55, or 55%. So change the VE table value from 50% to 55% and the calculated air flow goes up by 10% and so it will automatically add 10% more fuel and the correction should come down to 0.

If it is taking 10% fuel out, then 0.5 - 0.5 x 0.1 = 0.45 or 45%. Change the VE to 45% and the calculated air flow drops 10% and the fuel delivered automatically drops 10%.

Once you get the corrections down to 0 or close to them, then start dialing in the a/f ratio table to get the a/f ratio you want.

Hope that helps some, if that was the question you were asking.

John
 
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