Idle air vs IAC park position
05-07-2004, 01:28 PM
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I'd like to add to the above. If you turn on the key without starting the car the IAC's value is higher than at start. Is there another table we need to find? What settings or possible tables might there be that control this. If you guys can find more tables what we think we know could change.
05-07-2004, 04:30 PM
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Originally Posted by gojo
Goodhands,
I've experienced the same thing. I think what we are seeing is that the functions are interrelated. Just as setting the IAC values too high effects results when the car moves, so will setting RAF's too high affect startup. I would think that the car you mention should have had bad cruise affect. At least that is my take. The tables do have a main function though and need to be set with that in mind. That's what seems to work for me. I do think the IAC has the major roll in start up and where the throttle blade wants to rest when we are off the gas pedal. The desired IAC is highest with the key on only. It comes down after startup and continues to come down. I agree the RAF will have an impact, but almost as a side affect. I don't think any of the tables get turned off when we change conditions such as starting to move or coming to a stop. They all affect tuning results but when set correctly I find they are more responsive to their major function. I have seen some posts saying the t. follower and cracker tables don't do anything for them. I had the same experiences and finding they work well when IAC and RAF are close to right.
Joe
I've experienced the same thing. I think what we are seeing is that the functions are interrelated. Just as setting the IAC values too high effects results when the car moves, so will setting RAF's too high affect startup. I would think that the car you mention should have had bad cruise affect. At least that is my take. The tables do have a main function though and need to be set with that in mind. That's what seems to work for me. I do think the IAC has the major roll in start up and where the throttle blade wants to rest when we are off the gas pedal. The desired IAC is highest with the key on only. It comes down after startup and continues to come down. I agree the RAF will have an impact, but almost as a side affect. I don't think any of the tables get turned off when we change conditions such as starting to move or coming to a stop. They all affect tuning results but when set correctly I find they are more responsive to their major function. I have seen some posts saying the t. follower and cracker tables don't do anything for them. I had the same experiences and finding they work well when IAC and RAF are close to right.
Joe
Joe, I'd like to add some more thoughts. I still think the IAC, because they work off gms/sec are not present at start at least until the MAF is reporting. I think the IAC movement that we may see when the key is turned on may be the RESET park postion of 310 being applied. This is just a theory I can not back this up. If ls1 edit would explain what the definition o"running air flow" then that may help decifer the rest. Also we do know that the throttle cracker is a table that is disabled at some point..stock setting on an M6 is enable=1mph disable=2mph. So this table should have no effect until the car is actually moving. I totally agree that all the rest of the tables work together and that we are missing some things. Like airflow changes when the A/C=on. Where is the adjustment for that?
Greg
05-07-2004, 05:21 PM
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I have to side with GOJO on the decay values, In my experience the decay values being increased causes decay to increase (RPMs drop off faster).
On everything else GOJO and Bink said I agree with (have seen the same on my car)
From my experience it made a difference whether the clutch pedal was in or out. (had cruise control effect until I pushed in the pedal, then RPMs dropped) It may be the switch on the Clutch pedal the it looks to.
FYI. My TB had two .180 holes in it from ARE, I managed to tune it pretty good before (last year). But, I decided to put an undrilled TB blade in last week, and now I'm having to make some big changes in the IAC and RAF values. (in the opposite direction)
But I'm getting it close again.
This is a great thread. Thanks
On everything else GOJO and Bink said I agree with (have seen the same on my car)
Originally Posted by QuickSilver2002
I don’t see how the car moving or not would make a difference on a manual tranny car. It seems that in gear would make a diff, but I'm not sure the PCM knows if in or out of gear. Maybe it has something to do with a time delay after the throttle position relaxed to relative 0.
Is it a good general practice to keep them scaled pretty close together?
I think I’ll do some more experimentation this weekend.
Is it a good general practice to keep them scaled pretty close together?
I think I’ll do some more experimentation this weekend.
FYI. My TB had two .180 holes in it from ARE, I managed to tune it pretty good before (last year). But, I decided to put an undrilled TB blade in last week, and now I'm having to make some big changes in the IAC and RAF values. (in the opposite direction)
But I'm getting it close again.
This is a great thread. Thanks
05-08-2004, 07:32 AM
#26
Originally Posted by gojo
I'd like to add to the above. If you turn on the key without starting the car the IAC's value is higher than at start. Is there another table we need to find? What settings or possible tables might there be that control this. If you guys can find more tables what we think we know could change.
This is the opposite of the f-body function - I now see why they confused me!At the time I was fighting Idle transitioning and 11.0 Idle AFR
.....I moved on and never reconciled the two opposing functions. By December I was calculating a new VE table. FWIW.joel
05-09-2004, 04:20 PM
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Goodhands,
I think we see it pretty much the same way. The IAC reset determines the initial start. But as soon as the engine is started the IAC readings come down gradually. Are those IAC values only or do they combine RAF's? It would make sense to think the RAF's, as you say, are what we see having that affect. If you think the IAC controls the resting postion of the blade with the foot off the gas it would seem a nice clean way to do it. You could be right. My opinion is the RAF tables are decay tables along with the cracker and other decay tables. They all set decay for the various functions and do it with more decimal places than the RAF.
I think we see it pretty much the same way. The IAC reset determines the initial start. But as soon as the engine is started the IAC readings come down gradually. Are those IAC values only or do they combine RAF's? It would make sense to think the RAF's, as you say, are what we see having that affect. If you think the IAC controls the resting postion of the blade with the foot off the gas it would seem a nice clean way to do it. You could be right. My opinion is the RAF tables are decay tables along with the cracker and other decay tables. They all set decay for the various functions and do it with more decimal places than the RAF.
05-09-2004, 10:00 PM
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Originally Posted by gojo
Goodhands,
I think we see it pretty much the same way. The IAC reset determines the initial start. But as soon as the engine is started the IAC readings come down gradually. Are those IAC values only or do they combine RAF's? It would make sense to think the RAF's, as you say, are what we see having that affect. If you think the IAC controls the resting postion of the blade with the foot off the gas it would seem a nice clean way to do it. You could be right. My opinion is the RAF tables are decay tables along with the cracker and other decay tables. They all set decay for the various functions and do it with more decimal places than the RAF.
I think we see it pretty much the same way. The IAC reset determines the initial start. But as soon as the engine is started the IAC readings come down gradually. Are those IAC values only or do they combine RAF's? It would make sense to think the RAF's, as you say, are what we see having that affect. If you think the IAC controls the resting postion of the blade with the foot off the gas it would seem a nice clean way to do it. You could be right. My opinion is the RAF tables are decay tables along with the cracker and other decay tables. They all set decay for the various functions and do it with more decimal places than the RAF.
1. If I increase/decrease the RAF's significantly in either direction (with or without adjusting IAC's or adjusting IAC's down) it eventually affects how the starts, in terms of the highest rpm level reached at start up.
2. Both decay tables are just that.... they allow the rpm (air flow) to decay at a specified rate to the asked for idle rpm. Raising these tables increase the rate at which decay is applied.
3. If I increase the RAF's enough they eventually affect the car while driving and results in a "cruise control" affect.
4. It is fair to say that the cracker is always used when the car is moving>1mph.
I suspect:
1. That RAF's are used to start the car, initially, maybe until the MAF is reporting then p/n decay kicks in to reduce RAF's to meet the idle rpm requested.
2. That IAC's are the resting position for the blade to achieve the target idle based on MAF flow gms/sec and temp?.
3. The blade is moved further by the RAF's, as a part of TPS%, which are also part of the throttle follower and t. cracker.
The fourth and final thing is that I may have done too many
drugs in my youth!I gotta go take some Motrin and get some sleep. I"ll post some more tomorrow.
P.S.
You have already verified this stuff above I am just posting here that I agree with ALL of your findings previously posted. I am starting to get this stuff but here are some questions:
1. How does one know how to claculate new IAC's/RAF's after mods?
2. NoGo says he uses a "Gizmo" can we get one?
3. Re:M6 while driving then engaging the clutch while going to 0% TPS and coming to a stop what decay is used? I know P/N decay is not or is it? But is in gear or t. cracker or both?
4. Re: M6 what about the same as number 3. but not engaging the clutch just going to 0% TPS on decel in gear? Would that be just the in gear decay used?
Last edited by goodhands; 05-10-2004 at 09:35 AM.
05-10-2004, 09:30 AM
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To add to the above: load also seems to be a factor on RAF's. With the A/C=on = more RAF's. Recently I had all aspects of my idle completely perfect for my H/C setup. I loved it. Then I had an electric water pump installed. Well the electric water pump=<load at idle. My return to idle transition while the car was moving was not as smooth. The rpm was dropping about 150 rpm below the asked for 900 where as before the install the rpm would drop only 50 - 75 rpm below the asked for 900. This may sound ridiculous but I verified this by reinstalling the factory pump.
05-10-2004, 11:31 AM
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Interesting you should bring up load. As I was trying different settings to see what affect they had, I noticed that as the relationship between IAC's and RAF's changed so did the cruise affect with air on and air off. It seems that there is a need to find the correct ratio of IAC and RAF settings in order for the car to react the same with the air on as with air off. Once I found those settings it was necessary to raise or lower the IAC and RAF values together. It kept air on and air off in sync and was effective in creating cruise, or too low idle stumble when coming to a stop, when changed together.
I did lower the IAC reset from 310 to 300 and did a hard reset. This dropped the startup RPM's from 1400 to 1200. In my testing, RAF had no affect on warm start RPM's but had a definite effect on how quickly the RPM's came down at startup.
I did lower the IAC reset from 310 to 300 and did a hard reset. This dropped the startup RPM's from 1400 to 1200. In my testing, RAF had no affect on warm start RPM's but had a definite effect on how quickly the RPM's came down at startup.
05-10-2004, 03:46 PM
#31
OK- from Nogo's info on the 90mm Tb thread. I think IAC is parked position of the throttle blade at idle, defined as steps, in the PCM. RAF is the Airflow, in grams per second, at the IAC position. So, with drilled Throttle body blades there is unmetered air sneaking past the blade - makes it more difficult to tune since we can't set the RAF properly. I think the decay tables (Throttle Followers) and Throttle cracker then use this airflow in the final cruise-> stop airflow. FWIW.
joel
joel
05-11-2004, 01:52 PM
#33
Thats correct you do have to lower the RAF tables when you punch a hole in the TB. Although it throws off the predicted airflow of the system off, this is easily adjusted for by moving the tables down a bit.
What I have had the TB drilling accomplish is that it dampens the system quite a bit. This can be helpful in eliminating surging on some setups.
What I have had the TB drilling accomplish is that it dampens the system quite a bit. This can be helpful in eliminating surging on some setups.
05-12-2004, 12:55 AM
#34
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Here is a little info (not sure if it helps clarify or not)
I raised my IAC a bit in an attempt to eliminate some stumbling after warm startups (I had previously raised the RAF in the higher temps to match what I saw on the MAF (11 g/s.I think). Anyway, the car acted a little strange when I first drove it. It idled higher than the idle tables demanded and it seemed to have a little cruise control behavior going on. Then I stopped the car and as soon as the wheels stopped moving the idle suddenly dropped (it was previously idling above 1k with the clutch in). After the idle dropped the cruise control behavior seems to be gone and it appears to idle nice and smooth at 825 under all conditions.
I’m not sure exactly what this learning behavior is, but it definitely did something different when the car came to a complete stop.
I knew idle relearn was involved, but was surprised that the car had to be warmed all the way up and come to a complete stop before something happened.
I raised my IAC a bit in an attempt to eliminate some stumbling after warm startups (I had previously raised the RAF in the higher temps to match what I saw on the MAF (11 g/s.I think). Anyway, the car acted a little strange when I first drove it. It idled higher than the idle tables demanded and it seemed to have a little cruise control behavior going on. Then I stopped the car and as soon as the wheels stopped moving the idle suddenly dropped (it was previously idling above 1k with the clutch in). After the idle dropped the cruise control behavior seems to be gone and it appears to idle nice and smooth at 825 under all conditions.
I’m not sure exactly what this learning behavior is, but it definitely did something different when the car came to a complete stop.
I knew idle relearn was involved, but was surprised that the car had to be warmed all the way up and come to a complete stop before something happened.
05-14-2004, 07:40 AM
#36
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Originally Posted by NoGo
Thats correct you do have to lower the RAF tables when you punch a hole in the TB. Although it throws off the predicted airflow of the system off, this is easily adjusted for by moving the tables down a bit.
What I have had the TB drilling accomplish is that it dampens the system quite a bit. This can be helpful in eliminating surging on some setups.
What I have had the TB drilling accomplish is that it dampens the system quite a bit. This can be helpful in eliminating surging on some setups.
NoGo, that is one of the best and simplest explanations I've seen.
The hole in the TB blade is not within the PCM's control. It is a source of constant flow for a given pressure drop. Therefore, more air flow fluctuations can happen at low blade angles without requiring the PCM to be constantly changing the blade angle. This would certainly help dampen surging throttle.
05-15-2004, 02:11 PM
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Nick Williams and I did some more testing on his 90mm TB. We were interested in the effect of changing the TPS Voltage. My C5 was the testee.
We tried changes from .44V to .59V. The effect was across the board. It effected starting, idle and cruising. Higher created cruise and lower, stalling and more engine drag. We settled an .49V for mine. I used Z06 values from 80*C and up in the IAC and RAF tables. I raised the "in gear decay" values, from 2mph to 50mph and that removed almost all the cruise. We did an idle relearn and beat on it, then I drove 60 miles to home and the tune stayed the same. That's a good sign. This TB is a piece of cake to tune.
We tried changes from .44V to .59V. The effect was across the board. It effected starting, idle and cruising. Higher created cruise and lower, stalling and more engine drag. We settled an .49V for mine. I used Z06 values from 80*C and up in the IAC and RAF tables. I raised the "in gear decay" values, from 2mph to 50mph and that removed almost all the cruise. We did an idle relearn and beat on it, then I drove 60 miles to home and the tune stayed the same. That's a good sign. This TB is a piece of cake to tune.
05-15-2004, 03:07 PM
#38
Originally Posted by gojo
Nick Williams and I did some more testing on his 90mm TB. We were interested in the effect of changing the TPS Voltage. My C5 was the testee.
We tried changes from .44V to .59V. The effect was across the board. It effected starting, idle and cruising. Higher created cruise and lower, stalling and more engine drag.
We tried changes from .44V to .59V. The effect was across the board. It effected starting, idle and cruising. Higher created cruise and lower, stalling and more engine drag.
