Observations on IAC & Timing at Idle
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Observations on IAC & Timing at Idle In effort to get my idle smoother with my 232 cam, I decided to pull some of the extra timing I had added when I had a 224 cam. I ATAP'ed before and after and observed the following:
* average timing dropped several degrees when the car temp crossed 180* (fans come on 183*)
* decreasing timing resulted in a higher IAC count. Here is what I saw:
BEFORE (183*):
Park Timing 23 - 25*
Park IAC 12 - 14
Drive Timing 24 - 26*
Drive IAC 44 - 48
AFTER
Park Timing 21 - 23*
PARK IAC 22 - 24
Drive Timing 20 - 22*
Drive IAC 64 - 68
Idle speed is 1000 in park; 975 in drive.
Now I have to drill the TB out again or restore the timing as the car feels a bit rougher. I think I may go up 1/64" in TB hole size, leave my park spark table alone and put back some timing in my drive table.
Any other thoughts or suggestions?
* average timing dropped several degrees when the car temp crossed 180* (fans come on 183*)
* decreasing timing resulted in a higher IAC count. Here is what I saw:
BEFORE (183*):
Park Timing 23 - 25*
Park IAC 12 - 14
Drive Timing 24 - 26*
Drive IAC 44 - 48
AFTER
Park Timing 21 - 23*
PARK IAC 22 - 24
Drive Timing 20 - 22*
Drive IAC 64 - 68
Idle speed is 1000 in park; 975 in drive.
Now I have to drill the TB out again or restore the timing as the car feels a bit rougher. I think I may go up 1/64" in TB hole size, leave my park spark table alone and put back some timing in my drive table.
Any other thoughts or suggestions?
Re: Observations on IAC & Timing at Idle Why are you pulling out the extra timing? Usually, the bigger the duration of the cam, the more timing needed to keep a stable idle.
Your IAC counts are witin range. I find that the higher IAC counts help reduce the "slow return" to idle, or "dashpot effect". When you have a very low IAC count for idle, and take your foot off the gas when you are cruising, it seems like you are on cruise control for a few seconds. I have observed over 100 IAC counts immdiately after taking your foot off the gas. Then the count number slowly drops down to the normal idle count. Drilling the hole larger will lower your IAC counts, making the effect worse.
It appears to me that you might be going the wrong way in your attempt for a smoother idle. (you dont really expect a smooth idle with that duration do you?)
<small>[ September 28, 2002, 11:34 PM: Message edited by: GTO69JUDGE ]</small>
Your IAC counts are witin range. I find that the higher IAC counts help reduce the "slow return" to idle, or "dashpot effect". When you have a very low IAC count for idle, and take your foot off the gas when you are cruising, it seems like you are on cruise control for a few seconds. I have observed over 100 IAC counts immdiately after taking your foot off the gas. Then the count number slowly drops down to the normal idle count. Drilling the hole larger will lower your IAC counts, making the effect worse.
It appears to me that you might be going the wrong way in your attempt for a smoother idle. (you dont really expect a smooth idle with that duration do you?)
<small>[ September 28, 2002, 11:34 PM: Message edited by: GTO69JUDGE ]</small>
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Re: Observations on IAC & Timing at Idle </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Usually, the bigger the duration of the cam, the more timing needed to keep a stable idle.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That has been my assumption and the reason I raised the timing (as much as 10 degrees) with 224 cam. I just haven't found a lot of confirmation of this theory and thought I would experiment.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> When you have a very low IAC count for idle, and take your foot off the gas when you are cruising, it seems like you are on cruise control for a few seconds. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I agree. I've been slow to drill out the TB more because of that.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That has been my assumption and the reason I raised the timing (as much as 10 degrees) with 224 cam. I just haven't found a lot of confirmation of this theory and thought I would experiment.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> When you have a very low IAC count for idle, and take your foot off the gas when you are cruising, it seems like you are on cruise control for a few seconds. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I agree. I've been slow to drill out the TB more because of that.
