calculating new effective area table...
Thread Starter
Joined: Mar 2003
Posts: 8,319
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From: North Carolina
calculating new effective area table... ok so say that (and this is my case) i have 20 g/sec desired airflow and my dynamic airflow is 10 g/sec. my stit says +10 and my air count is 170 (this is on cold start low coolant temps)
i have a ported tb and it has epxoy and a copper tube in it, decreasing the effective area. shifting the table wont help because at idle everything lines up pretty good. so i am just trying to think of a way to scale the table. i figure that if i am at 170 for the IAC count then there must be a way i can figure out where that will relate to and switch it in the table. but i cant seem to figure out a good way to get the table right. maybe its just too late but i dont have any ideas on setting up a correct effective area table besides trial and error...any ideas?
i have a ported tb and it has epxoy and a copper tube in it, decreasing the effective area. shifting the table wont help because at idle everything lines up pretty good. so i am just trying to think of a way to scale the table. i figure that if i am at 170 for the IAC count then there must be a way i can figure out where that will relate to and switch it in the table. but i cant seem to figure out a good way to get the table right. maybe its just too late but i dont have any ideas on setting up a correct effective area table besides trial and error...any ideas?
What do you mean "everything lines up pretty good"? Do you mean that the hot IAC count comes down to 30 like it "should"? Unless your TB hole is too small/large it will just about always get to 30 but the problem is that it will either take a while to come down or will continue to creap down once it hits 30 when sitting for a while (as the computer trys to deal with the added air flow it does not know about). Cold numbers are worthless for tuning.
Without actually putting the TB on a flow bench and flowing it, there really isn't any way to KNOW how much airflow is actually moving with the IAC @ 0 so you have to kind of "play with it" and see what you get. Also, the IAC steps vs. effective area table is in square millimeters, not g/sec. so I guess you could measure the hole/s in the TB, figure their area, and then add a small extra for leakage around the blade and whatnot. Most people just move the table to the right a few blocks, go try it, if it got better/didn't do anything they move more, and keep doing that till it starts to get bad, then move back one step.
Without actually putting the TB on a flow bench and flowing it, there really isn't any way to KNOW how much airflow is actually moving with the IAC @ 0 so you have to kind of "play with it" and see what you get. Also, the IAC steps vs. effective area table is in square millimeters, not g/sec. so I guess you could measure the hole/s in the TB, figure their area, and then add a small extra for leakage around the blade and whatnot. Most people just move the table to the right a few blocks, go try it, if it got better/didn't do anything they move more, and keep doing that till it starts to get bad, then move back one step.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
the stock tables kind of slope up and increase in the slope of the line, however that throws my car off. 50-90 counts is good but then the higher it goes the more its off
Well yeah....the table is going to slope up because as the IAC moves from "0" (closed) to wide open, you will flow more air into the engine and that "IAC Position vs. effective area" table reflects the amount of air getting "through" (into the intake manifold) vs. where the IAC is.
Try moving the "IAC Position vs. effective area" table a cell or two to the right and see how things go. Like a lot of things, you will just have to try it.
Try moving the "IAC Position vs. effective area" table a cell or two to the right and see how things go. Like a lot of things, you will just have to try it.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
i actually redid the whole table. it has helped out a lot, i am going to post another theread with another question...so i dont go off topic in this one. but the effective area was out of wack, the curve was different
Originally Posted by WS6FirebirdTA00
i actually redid the whole table. it has helped out a lot, i am going to post another theread with another question...so i dont go off topic in this one. but the effective area was out of wack, the curve was different
good deal....just keep at it...
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
can you check out my other post and see what you think, im am not really understanding the idle airflow and if there is an actual number that tells you the ideals...
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Originally Posted by WS6FirebirdTA00
can you check out my other post and see what you think, im am not really understanding the idle airflow and if there is an actual number that tells you the ideals...
well there IS an "ideal" value but as I said, without putting the TB on a flow bench (like GM), good luck..
the best you can do is just "play" and you will get close enough.....
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Originally Posted by WS6FirebirdTA00
car has responded a lot better to the changes, the lines in excel are getting together very well. idle recovery is good as well
sounds like you are getting close...