Idle timing ?
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From: San Diego, CA
Idle timing ? Noob questions about idle timing please... 
I recently got HPTuners
and am working on my first tune. I pretty much understand the idle RPM vs. ECT and idle airflow and how they work. I have the idle decaying from 1100-900RPM over the temp range, raised a bit for park and raised 50-60rpm over the range for A/C.
I'd like to know more about the timing side of idle.
What I've read is that ~22 degrees (20-24) is good, and that raised idle timing helps keep cylinder pressure and will smooth the idle. Where in the timing tables exactly needs to be 22 degrees ? Which table specifically and what airflow range ? I'm GUESSING it's the Main Spark vs. Airflow vs. Open Throttle (High Octane) table ? What idle airflow range needs to be changed, or do I need to log my airflow at idle RPM vs. ECT to figure that ?
Also, does VE need to be touched for idle with a cam, and how/where ? I realize that the entire VE table needs to be tuned for the individual car but is there anything specific that needs to be done/helps specifically for idle ?
Thanks !
Rob (Bad30th)
I recently got HPTuners
and am working on my first tune. I pretty much understand the idle RPM vs. ECT and idle airflow and how they work. I have the idle decaying from 1100-900RPM over the temp range, raised a bit for park and raised 50-60rpm over the range for A/C.I'd like to know more about the timing side of idle.
What I've read is that ~22 degrees (20-24) is good, and that raised idle timing helps keep cylinder pressure and will smooth the idle. Where in the timing tables exactly needs to be 22 degrees ? Which table specifically and what airflow range ? I'm GUESSING it's the Main Spark vs. Airflow vs. Open Throttle (High Octane) table ? What idle airflow range needs to be changed, or do I need to log my airflow at idle RPM vs. ECT to figure that ?
Also, does VE need to be touched for idle with a cam, and how/where ? I realize that the entire VE table needs to be tuned for the individual car but is there anything specific that needs to be done/helps specifically for idle ?
Thanks !
Rob (Bad30th)
Last edited by Bad30th; Mar 10, 2005 at 08:45 PM.
I was told 25-28 for idle with a cam. I would add 2 degrees to all points 400 to 1000 RPM, .08 to .32 g/sec. On the VE Main table multiply column 400 rpm by .60; column 800 by .80 and column 1200 by .90. Check out tuning by NoGo. That where I got the numbers from. I am still tuning my cam.
What cam do you have?
Bill
What cam do you have?
Bill
Thread Starter
12 Second Club
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From: San Diego, CA
Thanks Bill ! I didn't see NoGo's post when I used search for "idle timing". Lots of good reading there and in the stickied posts, and now this thread will turn up in "search" for idle timing for other folks with the same question.
I have a 222/224 .571"/.571" 114 LSA cam. That's about as big as I can go and still pass smog.
So, off to make some changes to my "test" tune...
HERE is a direct link to some great info.
Cheers !
Rob (Bad30th)
I have a 222/224 .571"/.571" 114 LSA cam. That's about as big as I can go and still pass smog.
So, off to make some changes to my "test" tune...
HERE is a direct link to some great info.
Cheers !
Rob (Bad30th)
Last edited by Bad30th; Mar 13, 2005 at 09:55 AM.
Here are some things you can try. From NoGo:
Idle Limiters --> Idle Speed: 950
Idle Limiters --> IAC Park Position: Raise all points from 40C and up to 21
Idle Limiters --> Idle Air In Gear: All points 60C and up to 8.6
Fuel --> Main VE Table: Multiply column 400 rpm by 60. Multiply column 800 by 80. Multiply column 1200 by 90.
Ignition --> High Octane Table: Add 2 deg to all points 400 to 1000 RPM, .08 to .32 g/sec
Once done with this program, start the car and check for surging. If the car surges, unplug the IAC and see if the surging stops. If the surging stops follow below.
Idle Limiters --> Idle Air in Gear --> All points above 60C to 9.2
Take the car for a drive and check your idle. If the car goes on cruise control reduce the Idle Air in Gear Table .2 (further if necessary). If the idle holds at 2000 RPM for extended periods of time reduce the P/N Airflow Decay table for all points above 10 MPH by 5% (multiply by 95) until this stops. Be vary careful on this table.
If car keeps surging with the IAC unplugged two more things to try.
Multiply Main VE table by another 95% (total reduction of 85%). Repeat until the surging goes away, or until the car begins to hesitate when you take off.
High Octane Ignition Table. Reduce timing for all points 400 to 1000 RPM, .08 to .32 g/sec by 2. Repeat, but don't reduce it any more than 6 degrees.
Idle Limiters --> Idle Speed: 950
Idle Limiters --> IAC Park Position: Raise all points from 40C and up to 21
Idle Limiters --> Idle Air In Gear: All points 60C and up to 8.6
Fuel --> Main VE Table: Multiply column 400 rpm by 60. Multiply column 800 by 80. Multiply column 1200 by 90.
Ignition --> High Octane Table: Add 2 deg to all points 400 to 1000 RPM, .08 to .32 g/sec
Once done with this program, start the car and check for surging. If the car surges, unplug the IAC and see if the surging stops. If the surging stops follow below.
Idle Limiters --> Idle Air in Gear --> All points above 60C to 9.2
Take the car for a drive and check your idle. If the car goes on cruise control reduce the Idle Air in Gear Table .2 (further if necessary). If the idle holds at 2000 RPM for extended periods of time reduce the P/N Airflow Decay table for all points above 10 MPH by 5% (multiply by 95) until this stops. Be vary careful on this table.
If car keeps surging with the IAC unplugged two more things to try.
Multiply Main VE table by another 95% (total reduction of 85%). Repeat until the surging goes away, or until the car begins to hesitate when you take off.
High Octane Ignition Table. Reduce timing for all points 400 to 1000 RPM, .08 to .32 g/sec by 2. Repeat, but don't reduce it any more than 6 degrees.
