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Old 01-12-2008, 11:29 AM   #1
quazimoto
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Default Setting Initial IAM to 16

Is this a bad idea and why?It was brought to my attention it was but I would like to know the specifics.I had done this after getting my tune to safe,optimal place so after ECU resets the IAM would be at max and I wouldn't have to wait for it to cycle through.I thought after a reset it took roughly 100-200 miles to get the IAM back up to 16 from 8 or you can do the Vishnu trick thingy which is a pain to do everytime the ECU is reset.Or does the IAM go up quicker than what I thought?
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Old 01-12-2008, 11:44 AM   #2
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Quote:
Originally Posted by dumdum View Post
Is this a bad idea and why?It was brought to my attention it was but I would like to know the specifics.I had done this after getting my tune to safe,optimal place so after ECU resets the IAM would be at max and I wouldn't have to wait for it to cycle through.I thought after a reset it took roughly 100-200 miles to get the IAM back up to 16 from 8 or you can do the Vishnu trick thingy which is a pain to do everytime the ECU is reset.Or does the IAM go up quicker than what I thought?
I really don't see how the vishnu reset trick is a pain to do every time the ecu is reset. It takes literally like 5 seconds to do it.

on the flip side, my tuner sets my IAM to 16 initially.

Thats all I have to say about that
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Old 01-12-2008, 11:51 AM   #3
quazimoto
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Originally Posted by simon021 View Post
I really don't see how the vishnu reset trick is a pain to do every time the ecu is reset. It takes literally like 5 seconds to do it.
Because I live in a very rural area with very twisty,gravel roads.Trying to drive them and maintain the specific boost and rpm while also trying to navigate the road is not the safest thing.Especially when 50% of the time the rednecks coming the opposite way are going twice the speed limit and driving in the middle of the road. I get very quick spool up and it is hard to get to somewhere straight without hitting boost.This is all going by the specific instuctions on how to do it.Maybe they don't have to be followed exactly.Don't know,I have been running with my default IAM as 16 for a while now.
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Old 01-12-2008, 12:10 PM   #4
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Just be careful with it. If you throw on a bad tune or get hamfisted making changes with max IAM its more likely that to get some bad knock, lean runs, excessive egt, etc... before the ecu can react and drop the IAM.
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Old 01-12-2008, 12:30 PM   #5
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Quote:
Originally Posted by dumdum View Post
Because I live in a very rural area with very twisty,gravel roads.Trying to drive them and maintain the specific boost and rpm while also trying to navigate the road is not the safest thing.Especially when 50% of the time the rednecks coming the opposite way are going twice the speed limit and driving in the middle of the road. I get very quick spool up and it is hard to get to somewhere straight without hitting boost.This is all going by the specific instuctions on how to do it.Maybe they don't have to be followed exactly.Don't know,I have been running with my default IAM as 16 for a while now.
Thats funny ****. I live in a rural area as well, lots of gravel roads and stupid rednecks. I can relate completely.
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Old 01-13-2008, 10:51 PM   #6
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i usually just put my car in a high gear (4th or 5th depending on speed) and boost up to about 5-6psi and it'll raise it. easier than holding brake and gas.
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Old 01-14-2008, 01:10 AM   #7
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OK, to answer the OP's actual question about why you might not want to set Initial IAM to something higher than it's factory value:

http://forums.nasioc.com/forums/show...9&postcount=10
http://forums.nasioc.com/forums/show...3&postcount=12

Summary: It'll go to Initial IAM value at the beginning of every Rough Correction session and that's a bad thing if it needs to move IAM down and you're raised Intitial IAM. Secondly, Initial IAM is an input to functions in the ECU that are not understood, so the effect of changing Initial IAM is not understood.
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Old 01-14-2008, 10:45 AM   #8
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you could reduce the min timing level for the ecu to go through rough correction and this would speed up the learning.
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Old 01-14-2008, 11:15 AM   #9
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When you have an IAM re-evaluation due to knock, the IAM gets reset to its initial value. If the conditions to lower IAM are met again due to knock, then the IAM will drop.

So instead of it doing this:

16->8->12->etc

It will do this

16->16->12->etc

You can see that if the engine is knocking it will take more knock events to make the IAM settle at less than 16 than if the initial IAM was set lower than the max value.

I tune and set it to max value. The last flash gets set at 75% initial IAM on my tunes (12 for 16 bit, .75 for 32 bit).

Gabe
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Old 01-14-2008, 11:23 AM   #10
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Quote:
Originally Posted by williaty View Post
Secondly, Initial IAM is an input to functions in the ECU that are not understood, so the effect of changing Initial IAM is not understood.
They are understood as outlined in the posts you referenced. There really is no other logic involved in the normal operation for the 'advance multiplier (initial)', that I remember, other than a failure mode related to specific CELs being triggered.
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Old 01-14-2008, 02:08 PM   #11
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Quote:
Originally Posted by Tea cups View Post
They are understood as outlined in the posts you referenced. There really is no other logic involved in the normal operation for the 'advance multiplier (initial)', that I remember, other than a failure mode related to specific CELs being triggered.
Somewhere, you had said something to the effect of "the Initial IAM value is used an an input to other functions" and left it at that. I took that to mean you guys had seen that address getting accessed by other bits of code without knowing what the other bits of code were up to. Sorry.
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Old 01-14-2008, 03:19 PM   #12
Tea cups
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Quote:
Originally Posted by williaty View Post
Somewhere, you had said something to the effect of "the Initial IAM value is used an an input to other functions" and left it at that. I took that to mean you guys had seen that address getting accessed by other bits of code without knowing what the other bits of code were up to. Sorry.
I might have said that in the past, but from what I remember from looking at it recently, there isn't anymore to it, at least as it relates to the initial IAM constant. That is not to say that I have every detail of knock control worked out (especially for the 32-bit ECU and variations between ROMs).
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Old 01-14-2008, 03:57 PM   #13
quazimoto
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Quote:
Originally Posted by gabedude View Post
When you have an IAM re-evaluation due to knock, the IAM gets reset to its initial value. If the conditions to lower IAM are met again due to knock, then the IAM will drop.

So instead of it doing this:

16->8->12->etc

It will do this

16->16->12->etc

You can see that if the engine is knocking it will take more knock events to make the IAM settle at less than 16 than if the initial IAM was set lower than the max value.

I tune and set it to max value. The last flash gets set at 75% initial IAM on my tunes (12 for 16 bit, .75 for 32 bit).

Gabe
If thats the case why have I seen IAM's of 15?
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Old 01-14-2008, 04:46 PM   #14
Phatron
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Quote:
Originally Posted by dumdum View Post
I thought after a reset it took roughly 100-200 miles to get the IAM back up to 16 from 8 or you can do the Vishnu trick thingy which is a pain to do everytime the ECU is reset.Or does the IAM go up quicker than what I thought?
It only takes my car 2-3 WOT pulls to increase the IAM from 8 to 16. I just set it at 16 to save time and avoid having to do the intial WOT pulls to get it up.

I dont see a problem with it as long as you are increasing boost or timing conservatively on your flashes. IE, if you just did a run and didnt knock and you increase your timing 0.35* or WSGTDC by 1% then you should be fine, but if you are going nutty and increasing boost by 3 psi and timing at the same time then i would leave it at 8 to start.

I went nutty one day and increased my advance from 10* all over to 20* all over just to see what would happen. Then went out and did 3 WOT pulls with the IAM at 16 dont try this at home...
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Old 01-14-2008, 04:52 PM   #15
Phatron
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Quote:
Originally Posted by dumdum View Post
If thats the case why have I seen IAM's of 15?
Mine did this before also. I was confused since my step value is set to 4. And it just went to 15 then back up to 16 in ~1 mile of normal driving. I have had it go 16, 14, 15, 16 in ~1 mile before too. The couple times it did it, it always got back to 16 before i got to my logging road and it stayed at 16 during the runs.
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Old 01-14-2008, 05:01 PM   #16
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Quote:
Originally Posted by Phatron View Post
Mine did this before also. I was confused since my step value is set to 4. And it just went to 15 then back up to 16 in ~1 mile of normal driving. I have had it go 16, 14, 15, 16 in ~1 mile before too. The couple times it did it, it always got back to 16 before i got to my logging road and it stayed at 16 during the runs.
The step value you can modify in Enginuity/Ecuflash is the INITIAL step value. So, when the session begins, the step value is set to 4. When IAM changes directions during the re-evaluation, the step values is halved (2). When it changes direction once again, it is halved once again (1), applied, and then the session is done. This is how the ecu determines when to end the session, when the current step value is <=1 (alternatively, if IAM reaches 0 or 16 for a period of time the session will also end). The idea behind this is to determine the proper IAM based on where it "settles".
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