For those of you that belive shifting the IAC table is correct....its not....
01-20-2006, 02:06 PM
#1
For those of you that belive shifting the IAC table is correct....its not.... http://www.hptuners.com/forum/showth...8974#post28974
your best method and most correct is still drilling the TB blade to get your IAC counts down into the 45-60ish range at warm start
Cracking the Idle set screw which moves the blade of the TB is also incorrect....
its a good bandaid so you can start the car to get it warm so you can work on the warm count being 45-60 and it allows you to get a starting point doing RAF with the idle screw...so you can 0 it out again and get Idle RAF straight..
look at your Idle underspeed/overspeed spark adders and try looking there...
most of the time the IAC motor just doesnt move fast enough...which is why the spark takes over...causing more dipping as theyt both try to correct and it goes to far....and it becomes a neverending oscilation..
drilling your TB allows it to still keep the full IAC motor range and gives it a beter chance of keeping up with the needs of the motor...you still may need to curve the response of the underspped overspeeed spark stuff
MAF and RAF do not have to match..
all you are doing by changing IAC table is a bandaid fix that throws other things ion the PCM out of whack as well
if you think "drilling is bad" then you dont understand the operation of the car or the pcm to its fullest.
just because a piece exists doesnt mean that it has to be used....look at how many of us remove our EGR stuff and still pass emmissions
your best method and most correct is still drilling the TB blade to get your IAC counts down into the 45-60ish range at warm start
Cracking the Idle set screw which moves the blade of the TB is also incorrect....
its a good bandaid so you can start the car to get it warm so you can work on the warm count being 45-60 and it allows you to get a starting point doing RAF with the idle screw...so you can 0 it out again and get Idle RAF straight..
look at your Idle underspeed/overspeed spark adders and try looking there...
most of the time the IAC motor just doesnt move fast enough...which is why the spark takes over...causing more dipping as theyt both try to correct and it goes to far....and it becomes a neverending oscilation..
drilling your TB allows it to still keep the full IAC motor range and gives it a beter chance of keeping up with the needs of the motor...you still may need to curve the response of the underspped overspeeed spark stuff
MAF and RAF do not have to match..
all you are doing by changing IAC table is a bandaid fix that throws other things ion the PCM out of whack as well
if you think "drilling is bad" then you dont understand the operation of the car or the pcm to its fullest.
just because a piece exists doesnt mean that it has to be used....look at how many of us remove our EGR stuff and still pass emmissions
01-20-2006, 02:21 PM
#2
I never stopped drilling them. Just never mentioned it because it was IMPOSSIBLE to defend doing it. I always thought why did GM put a hole in it in the first place if it was so bad. I always got inconsistant results keeping the PCM using the idle timing tables once you opened the throttle too far with the screw even after resetting the TPS.
01-20-2006, 03:06 PM
#5
anywhere on teh face of the blade...
you can even just enlarge the existing one...but theres less control as the lrger the hole the more it increases teh area...exponentially
so its smarter to start with a second small hole....and work your way up
you can even just enlarge the existing one...but theres less control as the lrger the hole the more it increases teh area...exponentially
so its smarter to start with a second small hole....and work your way up
01-20-2006, 03:11 PM
#6
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Does this only apply to cable driven TBs? Because I went from my 78mm ETC TB that was drilled on my Z06, to a 90mm LS2 ported TB and just adjusted my ETC Scaler till I got it almost dead on and have no issues.
Dixit
Dixit
01-20-2006, 03:30 PM
#7
if you had a hole to begin with then you should have a hole on the new one
no hole..then no hole in new one
if you have an ETC scalar..then its still the same IAC table....
I'm not 100% sure of the ETC vehicles....
but as it would make sense to me...on OEM ETC vehicles that you would want to drill a small hole(for aftermarket cams) so to retain all of the full ranges of idle stuff..but only if changing cams
no hole..then no hole in new one
if you have an ETC scalar..then its still the same IAC table....
I'm not 100% sure of the ETC vehicles....
but as it would make sense to me...on OEM ETC vehicles that you would want to drill a small hole(for aftermarket cams) so to retain all of the full ranges of idle stuff..but only if changing cams
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01-20-2006, 03:39 PM
#8
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I cant remember or know off hand if the OEM LS1/LS6 ETC 78mm TBs come with small holes or not. But when I removed my ls6 intake/78mm tb setup, it has a good 1/8-3/16" size hole for the cam I got. Now the LS2tb I have which was ported has no hole and no slot on the side of the TB like the LS6 tb had. I managed to just adjust my ETC scaler and have no problems, the idle sits at 900 as I have it set, I can go from 7000rpm and hit the clutch and it stops right at 900rpm all the time. Never have idle hunting issues. Im not saying I have luck. But I agree with Chris, if you dont let the LTIT learn it will hunt around for awhile as it did in the beginning. Once I got my LTIT learned and as close to 0 as possible, its never given me trouble.
Dixit
Dixit
01-20-2006, 05:34 PM
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You can open the TB bump stop screw up till 0.63v without entering non-idle trim cells and is infact what I did to bring my IAC counts down. After retuning my base running airflow and tweaking the throttle cracker, it idles purrfectly and starts up with no idle flare whether its cold or warm.
IMO opening the blade is beneficial in that there is less motor control needed by the IAC, and provides a bigger holeshot of air for a stable return-to-idle.
As long as your IAC counts are around 40-60 at ilde, adaptive idle advance is switching around 0* as closely as possible and your VE map doesnt have large variations around your idle MAP (45-60 and 800-1200RPM) I cant see why you would have too many idle problems.
Some TBs have issues in that their CAD design did not take into account the large IAC rear breather hole needed on our V8s. Usually, though, a dremmel will fix that.
IMO opening the blade is beneficial in that there is less motor control needed by the IAC, and provides a bigger holeshot of air for a stable return-to-idle.
As long as your IAC counts are around 40-60 at ilde, adaptive idle advance is switching around 0* as closely as possible and your VE map doesnt have large variations around your idle MAP (45-60 and 800-1200RPM) I cant see why you would have too many idle problems.
Some TBs have issues in that their CAD design did not take into account the large IAC rear breather hole needed on our V8s. Usually, though, a dremmel will fix that.
01-20-2006, 05:43 PM
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Me too, I cant see the difference with a hole vs the blade set screw. And at least you can adjust the blade open or closed, a drilled hole is a one way street. If its too big, what do you do then!? Patch it back up?
01-20-2006, 08:21 PM
#14
Originally Posted by ringram
Me too, I cant see the difference with a hole vs the blade set screw. And at least you can adjust the blade open or closed, a drilled hole is a one way street. If its too big, what do you do then!? Patch it back up?
I would like to see the reasoning on how driling a hole is different and more beneficial then adjusting the set screw as numerous of us have for some time with great luck.
01-20-2006, 09:37 PM
#15
Originally Posted by Dixit
I cant remember or know off hand if the OEM LS1/LS6 ETC 78mm TBs come with small holes or not. But when I removed my ls6 intake/78mm tb setup, it has a good 1/8-3/16" size hole for the cam I got. Now the LS2tb I have which was ported has no hole and no slot on the side of the TB like the LS6 tb had. I managed to just adjust my ETC scaler and have no problems, the idle sits at 900 as I have it set, I can go from 7000rpm and hit the clutch and it stops right at 900rpm all the time. Never have idle hunting issues. Im not saying I have luck. But I agree with Chris, if you dont let the LTIT learn it will hunt around for awhile as it did in the beginning. Once I got my LTIT learned and as close to 0 as possible, its never given me trouble.
Dixit
Dixit
you get RAF correct..and you wont have to mess with the ETC scalar at all regaurdless of cam size....
all you really need to know is that your idle is fast enough to make it so that the cam doesnt choke on its own exhaust gasses because of reversion from overlap
after that any dipping and surging you might experience is all spark issues..usually the overspeed and underspeed tables...
just reduce the amounts of spark they command...try it on a car that has some idle dippig issues after doing RAF and watch the problems go away
Originally Posted by MNR-0
You can open the TB bump stop screw up till 0.63v without entering non-idle trim cells and is infact what I did to bring my IAC counts down. After retuning my base running airflow and tweaking the throttle cracker, it idles purrfectly and starts up with no idle flare whether its cold or warm.
IMO opening the blade is beneficial in that there is less motor control needed by the IAC, and provides a bigger holeshot of air for a stable return-to-idle.
As long as your IAC counts are around 40-60 at ilde, adaptive idle advance is switching around 0* as closely as possible and your VE map doesnt have large variations around your idle MAP (45-60 and 800-1200RPM) I cant see why you would have too many idle problems.
Some TBs have issues in that their CAD design did not take into account the large IAC rear breather hole needed on our V8s. Usually, though, a dremmel will fix that.
IMO opening the blade is beneficial in that there is less motor control needed by the IAC, and provides a bigger holeshot of air for a stable return-to-idle.
As long as your IAC counts are around 40-60 at ilde, adaptive idle advance is switching around 0* as closely as possible and your VE map doesnt have large variations around your idle MAP (45-60 and 800-1200RPM) I cant see why you would have too many idle problems.
Some TBs have issues in that their CAD design did not take into account the large IAC rear breather hole needed on our V8s. Usually, though, a dremmel will fix that.
I asked ken about this too...
Quote:
Originally Posted by soundengineer
I understand that after a certain TPS it gets into no longer being Idle cells....
something like.62 volts or something around that amount....or something like that..LOL
Originally Posted by KEN @ HP Tuners
That is the exact reason to leave it alone. There are over 5000 parameters in the VCM. Not everything you can adjust that sees the TPS is in the editor.
You will just wind up screwing things up.
You will just wind up screwing things up.
01-20-2006, 09:49 PM
#16
Originally Posted by ringram
Me too, I cant see the difference with a hole vs the blade set screw. And at least you can adjust the blade open or closed, a drilled hole is a one way street. If its too big, what do you do then!? Patch it back up?
hence the rason for a second..or in some cases a 3rd small hole....the bigger the hole....the more exponential the area size gets...
several small holes results in more control....
its also the reason why you should go with 1/64 or 1/32 incriments....the area of that hole goes up exponentially(area of a circle is Pi*radius^2)as it get bigger...
smaller holes alow for smaler increases allowing for more control.
if you drill the hole only large enough to get the car into the 45-60 IAC count range then you did it right...if you went too far you can alway patch it back with a little welding and grinding back to flat..or you can go get another TB blade from the dealer..or go find a junker or a used one somewhere else
people want to spend money on parts, and then want to tune it themselves so they can get it right..then they dont want to do it the correct way....and worry about going back to stock and dont even think about costs involved to go back when they are planning their mods top begin with....
if you are worried about putting things back later...then maybe you shouldnt have modded in the first place
01-20-2006, 11:25 PM
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Originally Posted by soundengineer
as far as ETC vehicles are concerned.....its all about RAF...
you get RAF correct..and you wont have to mess with the ETC scalar at all regaurdless of cam size....
all you really need to know is that your idle is fast enough to make it so that the cam doesnt choke on its own exhaust gasses because of reversion from overlap
after that any dipping and surging you might experience is all spark issues..usually the overspeed and underspeed tables...
just reduce the amounts of spark they command...try it on a car that has some idle dippig issues after doing RAF and watch the problems go away
you get RAF correct..and you wont have to mess with the ETC scalar at all regaurdless of cam size....
all you really need to know is that your idle is fast enough to make it so that the cam doesnt choke on its own exhaust gasses because of reversion from overlap
after that any dipping and surging you might experience is all spark issues..usually the overspeed and underspeed tables...
just reduce the amounts of spark they command...try it on a car that has some idle dippig issues after doing RAF and watch the problems go away
Dixit
01-21-2006, 02:28 AM
#19
lol, If the engine is needing to supply more air into the engine via another route, "the hole in the throttlebody blade"
Then that just means that the Iac passage way that supplys the "extra needed air" is not sufficient enough to flow the needed air for the gm/s the engine is consuming.
So, the real fix would be to modify and make the iac passage way larger. So that way it would be able to supply or take away the air that it needs.
A hole in the throttle blade is much harder to put back or change than if you just simply open up the throttle blade.
As for the minimum tps stuff. Most of it is efilive on what the minimum voltage ect. also for the electronic throttle, you can specify how much the computer is allowed to open the throttleblade in idle modes.
Ill look thru the code tonight and ill make a list of anything that references the idling tps voltages.
Then that just means that the Iac passage way that supplys the "extra needed air" is not sufficient enough to flow the needed air for the gm/s the engine is consuming.
So, the real fix would be to modify and make the iac passage way larger. So that way it would be able to supply or take away the air that it needs.
A hole in the throttle blade is much harder to put back or change than if you just simply open up the throttle blade.
As for the minimum tps stuff. Most of it is efilive on what the minimum voltage ect. also for the electronic throttle, you can specify how much the computer is allowed to open the throttleblade in idle modes.
Ill look thru the code tonight and ill make a list of anything that references the idling tps voltages.
