IAC position vs effective area
My impression of this table is that really isn't what it is for...basically, it just tells the computer that it has access to more air than it originally thought. This could be caused by a different throttle body, using the set screw to open the blade a little (which is usually a necessity when trying to get a cam to idle well since it needs more air), etc...
Maybe I just need to think about this some more...for whatever reason though, my car's idling problems have been cured.
Maybe I just need to think about this some more...for whatever reason though, my car's idling problems have been cured.
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Originally Posted by WS6FirebirdTA00
ah never mind i think i see, are you using this to just allow the IAC to open more at idle to compensate for the cam so you dont have to drill or use the set screw?
1) cam
2) throttle set screw (or :shudder: drilling the TB blade hole bigger)
3) idle speed
The base running airflow controls how much the IAC opens at idle, the cam requires you to crack it open further, and raising your idle required you to crack it open further. This will usually put you beyond the IAC's capability to compensate, so you crack the throttle blade with the set screw. This can be used to put you close, but you will often end up with ECTs at which your car will not idle properly. The way to calibrate that is through the base running airflow table. You can adjust it close with your trims (I usually put mine a hair higher than it needs to be), but it worked out best after I did that and then poly smoothed it. I hope that answers your question without completely hijacking the thread.
Originally Posted by WS6FirebirdTA00
ah never mind i think i see, are you using this to just allow the IAC to open more at idle to compensate for the cam so you dont have to drill or use the set screw?
The computer knows the IAC is open less, but doesn't know the tb is open more so you have to tell it that by changing the table.
One thing that might make you have to move the
table to the left is, if you went and got / made a
TB with the IAC ports filled and a bleed-hole drilled
for the IAC air passage, that hole is smaller than
stock. You will have less than expected air for a
given IAC position in that case.
table to the left is, if you went and got / made a
TB with the IAC ports filled and a bleed-hole drilled
for the IAC air passage, that hole is smaller than
stock. You will have less than expected air for a
given IAC position in that case.
ok, so let me get this strait, im not trying to hijack just trying and understand
so you cant use that table to compensate, makes the IAC open too far so it really has no room for error. so you crack open the TB and now you have the problem that the computer is still opening the IAC and doesnt realize you are actually letting more air in. so you have to tell it that it can close a little more??
another_user, you said you use the trims to measure this? im going to pm you about this so we dont take up 2 pages trying to get this through my head lol
so you cant use that table to compensate, makes the IAC open too far so it really has no room for error. so you crack open the TB and now you have the problem that the computer is still opening the IAC and doesnt realize you are actually letting more air in. so you have to tell it that it can close a little more??
another_user, you said you use the trims to measure this? im going to pm you about this so we dont take up 2 pages trying to get this through my head lol
ok well i just went out and check, i have ported and epxoied tb
on start up IAC position was 157 but then when the car warmed up it dropped down to 35-45 in that range, should it be that high on initial cold start or no?!
my idle doesnt drop, the desired was lower than dynamic, and i adjusted and the idle slightly hung on the first switch at 900-1050 rpm but it doesnt dip below the set idle anymore. idle seems much smoother.
if you guys could comment on the cold start IAC i would appreciate it, i dont know if thats normal or not.
on start up IAC position was 157 but then when the car warmed up it dropped down to 35-45 in that range, should it be that high on initial cold start or no?!
my idle doesnt drop, the desired was lower than dynamic, and i adjusted and the idle slightly hung on the first switch at 900-1050 rpm but it doesnt dip below the set idle anymore. idle seems much smoother.
if you guys could comment on the cold start IAC i would appreciate it, i dont know if thats normal or not.
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Originally Posted by jimmyblue
One thing that might make you have to move the
table to the left is, if you went and got / made a
TB with the IAC ports filled and a bleed-hole drilled
for the IAC air passage, that hole is smaller than
stock. You will have less than expected air for a
given IAC position in that case.
table to the left is, if you went and got / made a
TB with the IAC ports filled and a bleed-hole drilled
for the IAC air passage, that hole is smaller than
stock. You will have less than expected air for a
given IAC position in that case.
Who knows, maybe the table is off even from the factory. Or maybe the tubes are big enough in relation to an iac position of 40 that it doesn't really make a difference.
i wonder if the smaller hole effects the scale as it increases? cause it seems like when the car was at a higher IAC position there was deviation in the numbers, may have to scale it down some??
i think as the IAC is open a LOT, like cold start, that is a restriction, i can hear a whistle its cool lol
the IAC vs effective area table goes to 120, now i was getting readings at idle of 157, is that what those readings are, on the top, for IAC position as in the PID readout?
the IAC vs effective area table goes to 120, now i was getting readings at idle of 157, is that what those readings are, on the top, for IAC position as in the PID readout?
Originally Posted by WS6FirebirdTA00
i wonder if the smaller hole effects the scale as it increases? cause it seems like when the car was at a higher IAC position there was deviation in the numbers, may have to scale it down some??
Originally Posted by MeentSS02
That's why I was going to check my base airflow tables and see what impact that has (if any) on this table. I have my laptop with me at work, and will log enough data to hopefully see what's going on as the car is warming up and the IAC is settling down.
Originally Posted by WS6FirebirdTA00
im with my g/f now but i have data i will try to look at once she gets busy with something lol so i dont get in trouble
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Joined: Mar 2003
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From: La Porte, TX
Worked well here. Guys you will have to rebuild your RAF table after completing this. In my case, my effective area was so far off, that I actually had to rework the RAF twice LOL...My effective area now starts at 30. 
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Joined: Mar 2003
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From: La Porte, TX
Originally Posted by HumpinSS
what values did you use for your raf. was it the actual values after everything matched
HOLY ****...I never would have thunk it. RAF in drive at 177 is 12.5....desired airflow and dynamic airflow are both 1.66 which calculates to 12.58...Damn that's some cool ****.
