For those of you that belive shifting the IAC table is correct....its not....
01-21-2006, 05:30 AM
#21
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Dont forget you can reset TPS to zero too, so the PCM wont see the open throttle.
Of course there is a limit. But most of the time you can get 3% with no adverse effect and that will tame most mild cams etc.
Ill still vote for the blade set screw adjustment until you can go no more, then Id entertain the idea of a small hole, plus the set screw, at least you retain as much adjustment from the screw as you can.
Jes has the best idea, open out the IAC bypass hole. Though that will require quite a few tables to be recalculated to measure increased flow baesd on iac counts etc.
Of course there is a limit. But most of the time you can get 3% with no adverse effect and that will tame most mild cams etc.
Ill still vote for the blade set screw adjustment until you can go no more, then Id entertain the idea of a small hole, plus the set screw, at least you retain as much adjustment from the screw as you can.
Jes has the best idea, open out the IAC bypass hole. Though that will require quite a few tables to be recalculated to measure increased flow baesd on iac counts etc.
01-21-2006, 09:02 AM
#22
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Although I can agree with most everything in this thread, I'm still not clear on how drilling a hole is better than adjusting the set screw and re-zeroing the TPS.
I agree with smaller diameter holes making it easier to make small changes to air flow, but if you over shoot (drill) the hole, you are now faced with repairing or replacing the blade.
Where as, adjusting the set screw would make small changes harder to accomplish, you can always make smaller adjustments and best of all reverse your changes.
If you max out the set screw ajdustment, you can take the set screw back to stock, drill a new hole, then start the set screw process over again.
I agree with smaller diameter holes making it easier to make small changes to air flow, but if you over shoot (drill) the hole, you are now faced with repairing or replacing the blade.
Where as, adjusting the set screw would make small changes harder to accomplish, you can always make smaller adjustments and best of all reverse your changes.
If you max out the set screw ajdustment, you can take the set screw back to stock, drill a new hole, then start the set screw process over again.
01-21-2006, 09:50 AM
#24
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The reason goes back to the TPS reading. Of course you could
hog out the TPS holes some and recover the angle error.
What I've also thought of, is drilling, tapping & plugging new
passages in the TB casting to add an old-timey idle air bleed
screw.
I don't like the hole drilling because it's not easily reversible.
Usually you hold off on surgery until psychology fails. I think
in the greater part of cases, the idle -can- be fixed by settings,
it's just needing the right ones.
What I think would be the biggest help, is getting to an open-
loop idle arrangement (based initially on the closed loop's
discovered trims and baseline settings). It's the loop that makes
for surging and crashing; if the IAC wasn't chasing its tail you
would have a steady idle (maybe not exactly where you want
it, but at least not jumping and puking).
You want the idle ait to be just like your old-school fast idle
cam and A/C kick-up solenoid, on a carbureted vehicle. That's
all. Anything else is just because they had to stroke the EPA.
hog out the TPS holes some and recover the angle error.
What I've also thought of, is drilling, tapping & plugging new
passages in the TB casting to add an old-timey idle air bleed
screw.
I don't like the hole drilling because it's not easily reversible.
Usually you hold off on surgery until psychology fails. I think
in the greater part of cases, the idle -can- be fixed by settings,
it's just needing the right ones.
What I think would be the biggest help, is getting to an open-
loop idle arrangement (based initially on the closed loop's
discovered trims and baseline settings). It's the loop that makes
for surging and crashing; if the IAC wasn't chasing its tail you
would have a steady idle (maybe not exactly where you want
it, but at least not jumping and puking).
You want the idle ait to be just like your old-school fast idle
cam and A/C kick-up solenoid, on a carbureted vehicle. That's
all. Anything else is just because they had to stroke the EPA.
01-21-2006, 09:47 PM
#25
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A good first step might even be to determine if you have a problem with the IAC running at 100 or 120 at idle. My own car runs a 242/245@108 cam + s/c + 2bar SD and idles, transitions, AC on/off, cold starts, hot start you name it. I don't think i've ever seen the IAC below 90 and the most i've ever seen on a cold start with AC on is maybe 230? My cold start idle is 1100rpm and warm is 900. I can buzz the engine to the 6700 rpm limit hit the clutch at any mph you like and the engine will gracefully come back down to around 1100rpm and then once i slow right down drop back to normal idle. I've setup the follower to hold the rpms just right for regular streetable gear changing.
I keep saying this but the most important thing is to get the RAF correct under all driving conditions AND when you make changes, allow the PCM to relearn the LTIT's. After that check your IAC steps if they aren't going above 300 and you don't have issues where the IAC cannot open enough to maintain the idle RPM what's the problem? The you can play with the cracker/follower if you want.
If it ain't broke don't fix it
I keep saying this but the most important thing is to get the RAF correct under all driving conditions AND when you make changes, allow the PCM to relearn the LTIT's. After that check your IAC steps if they aren't going above 300 and you don't have issues where the IAC cannot open enough to maintain the idle RPM what's the problem? The you can play with the cracker/follower if you want.
If it ain't broke don't fix it
01-21-2006, 10:19 PM
#26
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Originally Posted by gameover
A good first step might even be to determine if you have a problem with the IAC running at 100 or 120 at idle. My own car runs a 242/245@108 cam + s/c + 2bar SD and idles, transitions, AC on/off, cold starts, hot start you name it. I don't think i've ever seen the IAC below 90 and the most i've ever seen on a cold start with AC on is maybe 230? My cold start idle is 1100rpm and warm is 900. I can buzz the engine to the 6700 rpm limit hit the clutch at any mph you like and the engine will gracefully come back down to around 1100rpm and then once i slow right down drop back to normal idle. I've setup the follower to hold the rpms just right for regular streetable gear changing.
I keep saying this but the most important thing is to get the RAF correct under all driving conditions AND when you make changes, allow the PCM to relearn the LTIT's. After that check your IAC steps if they aren't going above 300 and you don't have issues where the IAC cannot open enough to maintain the idle RPM what's the problem? The you can play with the cracker/follower if you want.
If it ain't broke don't fix it
I keep saying this but the most important thing is to get the RAF correct under all driving conditions AND when you make changes, allow the PCM to relearn the LTIT's. After that check your IAC steps if they aren't going above 300 and you don't have issues where the IAC cannot open enough to maintain the idle RPM what's the problem? The you can play with the cracker/follower if you want.
If it ain't broke don't fix it
What is the key to the "cruise control" some ppl get after having drilled to large, seeing higher IAC's like you have? I have zeroed out the cracker and follower tables on my own car and seen nothing change. If I let off the brake, let it idle out, at first it surges a bit, then beings a cruise control and keeps going.
I favor the blade for smaller cams, and drill for larger more reversioning type cams. (reversioning....new word for me!).
01-22-2006, 03:32 PM
#27
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Originally Posted by CAT3
What is the key to the "cruise control" some ppl get after having drilled to large, seeing higher IAC's like you have? I have zeroed out the cracker and follower tables on my own car and seen nothing change. If I let off the brake, let it idle out, at first it surges a bit, then beings a cruise control and keeps going.
01-22-2006, 08:42 PM
#30
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just remember the limits, especially the max, limit is there for a reason. last thing you want is your LTIT learning to +10 and then you have 2000rpm at idle... due to bad cal.
01-23-2006, 02:16 AM
#33
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once you set the RAF and the other compensation factors correctly the LTITs really shouldn't move much, if they are moving by +/- 3.0 then something is wrong, IMO.
01-23-2006, 08:41 AM
#34
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Presuming I have the right conception of the idle airflow area vs
IAC steps table, I think what a bigger hole wants is the addition
of that hole's area (mm2? I forget now) as an offset to all cells.
Your maximum limit value should be the sum of hole and IAC
path parallel areas (maybe the PCV too; appears hole/PCV aren't
represented in the stock table, which has a zero base, maybe
there are "mystery constants" we don't see for "fixed" physical
airflow attributes?). Anyway this probably bugs me the most
about this deal, how to realistically model the limitations of my
"congested" filled-n-drilled IAC port airflow and keep the PCM
from burying itself trying to get air it can't have. Not that it's
an issue presently.
IAC steps table, I think what a bigger hole wants is the addition
of that hole's area (mm2? I forget now) as an offset to all cells.
Your maximum limit value should be the sum of hole and IAC
path parallel areas (maybe the PCV too; appears hole/PCV aren't
represented in the stock table, which has a zero base, maybe
there are "mystery constants" we don't see for "fixed" physical
airflow attributes?). Anyway this probably bugs me the most
about this deal, how to realistically model the limitations of my
"congested" filled-n-drilled IAC port airflow and keep the PCM
from burying itself trying to get air it can't have. Not that it's
an issue presently.
01-23-2006, 09:27 AM
#35
Originally Posted by gameover
once you set the RAF and the other compensation factors correctly the LTITs really shouldn't move much, if they are moving by +/- 3.0 then something is wrong, IMO.
just for the initial RAF run...
I have found that it makes it a little easier to get the downright cold temperature RAF closer on the first shot....
after that its usually small changes like .50 and -.50 to get them 100% in line
05-28-2019, 11:29 AM
#36
TECH Fanatic
Hey all I Just wanted to bump a great thread from the old school days when it was all great tech. I'm very happy now with my new 226/230 112 +4 in my stock headed 02' LS1. I jumped up from a 218/224 113+3 and it was significant enough of a change that I had to look at this again. The car would not restart when it was hot it was starving for air because the iac was closed too much, although it had been adjusted perfectly for the smaller cam for a long time. My car runs strong and feels much better now that it can breath again this new cam is a monster but it still retains great driveabillity with a little adjustment made here.
06-03-2019, 11:04 PM
#38
**Idle/stalling question** Have an 02 formula A4 3600 stall, stock 241 heads, cam only (231/242 .617/.591 @112) and LS6 intake with stock TB. I've been having trouble with stalling once warmed up. The car starts right up no problem when cold, drives great for the first 15-20 minutes and then begins to drop the idle when coming to a stop, and unless I foot brake it slightly it will die. I can then crank it right back up and it starts no problem, idles and drives normal, and then after a few minutes of driving it begins stalling again. Note this seems to be more of an issue as the ambient air temp increases outside. Talked to my tuner and he told me to adjust the TB screw a bit and reset the TPS, I tried doing one full turn which resulted in zero change, then I increased it to roughly 3 turns and this resulted in crazy 2000 RPM idle hang at first start up when i touch the throttle and then a check engine light...Unhooked the battery for a while, set the screw back down to roughly stock position and did another TPS relearn and now its back to "normal" however still have the stalling issue. My tuner is telling me nothing in my tune file should be giving me any issues and is basically telling me "this isn't a tuning issue". I'm at a loss on what to do here...any advice??
06-04-2019, 05:38 AM
#39
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Just a educated guess without data --
Once you get above 0.7 TPS volts, your TPS will not reset to zero, and your car will not stay in idle tables, which is why three turns hung at 2000 rpm. I do not like adjusting set screw without seeing the voltage.
There is a factory hole in the blade. Sometimes that has to be drilled out a bit to accommodate a cam - especially one in the 230's.
There is also a lot in the tune that can be done, but without seeing the tune, cannot give any guidance.
Once you get above 0.7 TPS volts, your TPS will not reset to zero, and your car will not stay in idle tables, which is why three turns hung at 2000 rpm. I do not like adjusting set screw without seeing the voltage.
There is a factory hole in the blade. Sometimes that has to be drilled out a bit to accommodate a cam - especially one in the 230's.
There is also a lot in the tune that can be done, but without seeing the tune, cannot give any guidance.
06-04-2019, 07:07 AM
#40
Just a educated guess without data --
Once you get above 0.7 TPS volts, your TPS will not reset to zero, and your car will not stay in idle tables, which is why three turns hung at 2000 rpm. I do not like adjusting set screw without seeing the voltage.
There is a factory hole in the blade. Sometimes that has to be drilled out a bit to accommodate a cam - especially one in the 230's.
There is also a lot in the tune that can be done, but without seeing the tune, cannot give any guidance.
Once you get above 0.7 TPS volts, your TPS will not reset to zero, and your car will not stay in idle tables, which is why three turns hung at 2000 rpm. I do not like adjusting set screw without seeing the voltage.
There is a factory hole in the blade. Sometimes that has to be drilled out a bit to accommodate a cam - especially one in the 230's.
There is also a lot in the tune that can be done, but without seeing the tune, cannot give any guidance.