HPT question about Desired IAC steps vs. Desired idle effective Area
08-08-2005, 04:37 PM
#1
HPT question about Desired IAC steps vs. Desired idle effective Area Ok ,I have read some people have changed this table for 90 MM TB's.I have a 90 MM TB why didnt my tuner change mine?Mine is Stock.Now what do the Numbers over the Iac steps numbers mean?Do I add a zero to these numbers and that is my Idle correct?So if I multiply by .5 what should I expect?
Thanks for your Help Guys...
Thanks for your Help Guys...
08-08-2005, 04:51 PM
#2
Originally Posted by Pro Mouse
Ok ,I have read some people have changed this table for 90 MM TB's.I have a 90 MM TB why didnt my tuner change mine?Mine is Stock.Now what do the Numbers over the Iac steps numbers mean?Do I add a zero to these numbers and that is my Idle correct?So if I multiply by .5 what should I expect?
Thanks for your Help Guys...
Thanks for your Help Guys...
the table is just what it says:
IAC steps (how far open from full closed-to-full open the IAC motor is) and how much air (effective area) will be getting into the engine.....it tells the computer how big the idle hole in the TB blade is........don't change it UNLESS you KNOW the idle hole is larger.......
usually you just "grab" the entire table, cut, paste 2 cells over, and then fill the blank cells in with zero.......this tells the computer your TB hole is larger and will make it better able to adjust to changing conditions......
08-08-2005, 05:08 PM
#4
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for instance, if you have your first non-zero number at 12mm^2, copy the entire table from the 12mm^2 - 120mm^2 value and then paste it from 16mm^2 - 120mm^2. Then change the values at 12 and 14 to 0
08-08-2005, 05:13 PM
#6
Originally Posted by Pro Mouse
My TB has no hole.The Idle was brought in with the screw and the TPS was retaught.Now what do you mean Cut and paste 2 cells over?Thanks
just like you would in an excel spreadsheat........
"click" on the first >0 number and drag all the way to the left stopping 2 cells short of the end, "cut" those cells, and then paste them so your last cell cut (2nd from the end) is now the end cell.......
ex:
if the following were your cells:
0,0,0,0,0,1,2,3,4,5,6,7,8,9,10
then you would want them to be:
0,0,0,0,0,0,0,1,2,3,4,5,6,7,8 (note 9 and 10 are "gone" and the old 1 and 2 spot are now 0 )
got it?
08-08-2005, 05:15 PM
#7
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Originally Posted by 2001CamaroGuy
just like you would in an excel spreadsheat........
"click" on the first >0 number and drag all the way to the left stopping 2 cells short of the end, "cut" those cells, and then paste them so your last cell cut (2nd from the end) is now the end cell.......
ex:
if the following were your cells:
0,0,0,0,0,1,2,3,4,5,6,7,8,9,10
then you would want them to be:
0,0,0,0,0,0,0,1,2,3,4,5,6,7,8 (note 9 and 10 are "gone" and the old 1 and 2 spot are now 0 )
got it?
"click" on the first >0 number and drag all the way to the left stopping 2 cells short of the end, "cut" those cells, and then paste them so your last cell cut (2nd from the end) is now the end cell.......
ex:
if the following were your cells:
0,0,0,0,0,1,2,3,4,5,6,7,8,9,10
then you would want them to be:
0,0,0,0,0,0,0,1,2,3,4,5,6,7,8 (note 9 and 10 are "gone" and the old 1 and 2 spot are now 0 )
got it?
In physical terms, what does this change represent? I am on a roll today with the questions.
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08-08-2005, 05:26 PM
#8
Originally Posted by KALEL
In physical terms, what does this change represent? I am on a roll today with the questions.
it is the area in square millimeters of air that will enter the engine in a given amount of time (I think it's in seconds....don't remember right off) when the IAC is at a specific point open/closed.......it helps get back to idle faster by preventing the computer from overcompensating with the IAC........
the computer knows (through other tables) that at a given RPM (say 800RPM idle) the engine will need "X" amount of air to run......it then looks at the IAC vs. effective area to see how it will get that "X" amount.........
for basic discussion:
lets say that the engine needs 5mm^2 and with the IAC closed your TB hole (or in your case your TB blade moved off closed) gives 3mm^2.....then the computer will look along the table and see "oh......to get to 5mm^2 I need to move the IAC to step 5".......so the computer will move out to step 5 and see what happens..........if that spot gives the right amount of air then the idle will be right on (or much closer) and all is good......if not, then the engine will either over speed (the hovering at stop lights) or bog and the computer will have to do more trial and error......
next question
08-08-2005, 05:49 PM
#10
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Originally Posted by 2001CamaroGuy
it is the area in square millimeters of air that will enter the engine in a given amount of time (I think it's in seconds....don't remember right off) when the IAC is at a specific point open/closed.......it helps get back to idle faster by preventing the computer from overcompensating with the IAC........
the computer knows (through other tables) that at a given RPM (say 800RPM idle) the engine will need "X" amount of air to run......it then looks at the IAC vs. effective area to see how it will get that "X" amount.........
for basic discussion:
lets say that the engine needs 5mm^2 and with the IAC closed your TB hole (or in your case your TB blade moved off closed) gives 3mm^2.....then the computer will look along the table and see "oh......to get to 5mm^2 I need to move the IAC to step 5".......so the computer will move out to step 5 and see what happens..........if that spot gives the right amount of air then the idle will be right on (or much closer) and all is good......if not, then the engine will either over speed (the hovering at stop lights) or bog and the computer will have to do more trial and error......
next question
the computer knows (through other tables) that at a given RPM (say 800RPM idle) the engine will need "X" amount of air to run......it then looks at the IAC vs. effective area to see how it will get that "X" amount.........
for basic discussion:
lets say that the engine needs 5mm^2 and with the IAC closed your TB hole (or in your case your TB blade moved off closed) gives 3mm^2.....then the computer will look along the table and see "oh......to get to 5mm^2 I need to move the IAC to step 5".......so the computer will move out to step 5 and see what happens..........if that spot gives the right amount of air then the idle will be right on (or much closer) and all is good......if not, then the engine will either over speed (the hovering at stop lights) or bog and the computer will have to do more trial and error......
next question
08-08-2005, 06:11 PM
#11
There's really no such thing as a square millimeter of air. It's actually the area of the hole that the air can pass through. Also, i'm pretty sure the pcm takes into account engine vacuum because more vacuum results in more airflow, at least until the flow is choked (mach 1) through the hole.
The pcm knows how much air it wants from the idle air tables and the idle trims. From that and engine vacuum it knows how much area it needs (how big of a hole) to flow that air. From that area and the iac position vs effective area table, it knows what iac position it wants.
The pcm knows how much air it wants from the idle air tables and the idle trims. From that and engine vacuum it knows how much area it needs (how big of a hole) to flow that air. From that area and the iac position vs effective area table, it knows what iac position it wants.
08-08-2005, 09:18 PM
#12
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The PCM process to control the stepper motor/ETC is 3 steps:
1. PCM determines how much Airflow it wants to command the stepper motor/ETC to maintain idle. This means how much air (g/sec) do i want to flow thru the IAC/ETC (this has nothing to do with the TB hole size).
2. PCM then converts this to a cross sectional area (ie. square millimeters). you can imagine this to be how wide the stepper motor is open (IAC) or how much area around the throttle blade do i want (ETC).
3. This step varies depending if you have IAC or ETC. For IAC the PCM then converts this cross sectional area (effective area) into a number of steps for the stepper motor using the table you are talking about. For ETC the PCM ignores this table completely and uses the ETC Scalar value which converts from square millimeters to % TPS.
I hope that removes the mystery.
Chris...
1. PCM determines how much Airflow it wants to command the stepper motor/ETC to maintain idle. This means how much air (g/sec) do i want to flow thru the IAC/ETC (this has nothing to do with the TB hole size).
2. PCM then converts this to a cross sectional area (ie. square millimeters). you can imagine this to be how wide the stepper motor is open (IAC) or how much area around the throttle blade do i want (ETC).
3. This step varies depending if you have IAC or ETC. For IAC the PCM then converts this cross sectional area (effective area) into a number of steps for the stepper motor using the table you are talking about. For ETC the PCM ignores this table completely and uses the ETC Scalar value which converts from square millimeters to % TPS.
I hope that removes the mystery.
Chris...
08-09-2005, 12:50 AM
#15
To answer one of your original questions;"Why didn't the tuner adjust this table in your tune" , he probably isn't aware of this table. This table I think is only available in the newer version of HPTuners and maybe EFI Live. It just recently became a well covered topic.
The gurus here really are a blessing to us green horns. They deserve much more credit than they are given. I would have never considered tuning my own car if I didn't have them as a my primary tuning resource. Thanks guys!
The gurus here really are a blessing to us green horns. They deserve much more credit than they are given. I would have never considered tuning my own car if I didn't have them as a my primary tuning resource. Thanks guys!
08-09-2005, 01:03 AM
#16
Originally Posted by TXCAMSS
The gurus here really are a blessing to us green horns. They deserve much more credit than they are given. I would have never considered tuning my own car if I didn't have them as a my primary tuning resource. Thanks guys!
........when your local "tuner gods" cant tune their way out of a cardboard box, having people you can get ahold of who do know something is a big help........
08-09-2005, 01:31 AM
#17
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Originally Posted by P Mack
Chris, in step 2 does it take vacuum into account or is there the assumption that the flow is always choked?
08-09-2005, 05:34 PM
#18
Originally Posted by TXCAMSS
To answer one of your original questions;"Why didn't the tuner adjust this table in your tune" , he probably isn't aware of this table. This table I think is only available in the newer version of HPTuners and maybe EFI Live. It just recently became a well covered topic.
The gurus here really are a blessing to us green horns. They deserve much more credit than they are given. I would have never considered tuning my own car if I didn't have them as a my primary tuning resource. Thanks guys!
The gurus here really are a blessing to us green horns. They deserve much more credit than they are given. I would have never considered tuning my own car if I didn't have them as a my primary tuning resource. Thanks guys!
08-09-2005, 05:37 PM
#19
Originally Posted by gameover
It uses the pressure ratio (MAP and Baro) in normal circumstances to determine the area from the desired airflow.