Achieving a stable and strong idle with cams
Jul 18, 2006, 09:18 PM
#1
Evolving Member
Thread Starter
Join Date: Sep 2002
Location: Florida
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
Achieving a stable and strong idle with cams
After reading several threads and being plagued with the cam idle problem- I have decided it is time to put a stop to the lies and misinformation on cams
and idle. First a little light reading on engine timing, as this will relate to why higher lift and longer duration cams idle badly when left untuned. That is right - your bad idle can be completely
solved with a little tuning.
*scroll down about half way down the page and study the engine timing animation if needed*
engine timing
The difference in the strokes with longer duration and/or higher lift cams comes in the fact that with stock ignitition timing there still exists a small amount of pressure in the cylinder
when the intake valve is opened to allow more fuel /air in. This is known as intake reversion; intake reversion is what causes the turbulence in airflow entering the cylinder slowing the mixture down and creating
a loss of vacuum and clean burning mixture.
Now with a little tuning of the timing at idle loads and rpms, we can achieve a stable idle. You will be able to run your air conditioner again!
The following changes are tested HKS 280/280 and HKS 272/272 combos. 264's will require alot less if any timing advance to get good results. YMMV.
On with the how to:
The first step in maintaining a good idle is to raise the rpm levels at which the stock ecu trys to maintain. I run these values a little higher than most would, but I find this achieves the best results for me.
Here are the maps top to bottom: on the top is the before and bottom will be after changes.
Desired Idle rpm with the AC on:
Desired Idle RPM Drive:
Desired Idle RPM Neutral:
And now for the most important changes; the Ignition timing. Advancing the timing will remove nearly all of the turbulence caused by upgraded cams.
The values here work for the combos I listed above. They key here is to advance timing in the areas changed below 1 degree at a time until the vacuum stablizes and no longer wavers. Boost gauges work wonders here. 280's will achieve about ~15 in/hg of vacuum with the ac off and around 11 in/hg with it on. 272's will be
19 and 15 respectively.
*PLEASE BE VERY CAREFUL WHEN CHANGING TIMING*
One wrong flash and things can go very bad for you, triple check before flashing!
Stock Ignition timing:
Advanced Timing:
You will not the different areas with 19 degrees of timing versus the stock 5, tapering to 17 degrees @ >1000 rpm.
*WARM UP THE CAR FIRST*
(not warming it up will scew your attempts to tune the idle properly - dont worry after tuned it will start cold just fine)
Once you have made these changes flash the ecu. Go ahead and open your idle bypass screw (lefty loosy) 4-5 turns. Start the car with the air conditioning off, blip the throttle.
The idle should stabalize to around 1150 rpm with the ac off, if it doesn't dont worry it will after the next step. Now turn the ac on full blast and blip the throttle.
Using the aforementioned steps, continue blipping the throttle and adjusting the idle bypass screw. There will be a zone within about 2/3 of a turn where with either the ac on or off the car will
drop rpms and immediatly settle to a stable idle. (1050 with ac on, 1150 with it off). Once you have achieved this rev the car a little harder slowly up to about 4k with ac on and off. Make any further adjustments
needed to the idle bypass screw.
Congradulations and go enjoy your daily driver again.
P.S. I do not claim this as an end all solution to idling, depending on injectors,etc all of this can change. With properly scaled injetors
I have achieved excellent results on a few cars now.
and idle. First a little light reading on engine timing, as this will relate to why higher lift and longer duration cams idle badly when left untuned. That is right - your bad idle can be completely
solved with a little tuning.
*scroll down about half way down the page and study the engine timing animation if needed*
engine timing
The difference in the strokes with longer duration and/or higher lift cams comes in the fact that with stock ignitition timing there still exists a small amount of pressure in the cylinder
when the intake valve is opened to allow more fuel /air in. This is known as intake reversion; intake reversion is what causes the turbulence in airflow entering the cylinder slowing the mixture down and creating
a loss of vacuum and clean burning mixture.
Now with a little tuning of the timing at idle loads and rpms, we can achieve a stable idle. You will be able to run your air conditioner again!
The following changes are tested HKS 280/280 and HKS 272/272 combos. 264's will require alot less if any timing advance to get good results. YMMV.
On with the how to:
The first step in maintaining a good idle is to raise the rpm levels at which the stock ecu trys to maintain. I run these values a little higher than most would, but I find this achieves the best results for me.
Here are the maps top to bottom: on the top is the before and bottom will be after changes.
Desired Idle rpm with the AC on:
Desired Idle RPM Drive:
Desired Idle RPM Neutral:
And now for the most important changes; the Ignition timing. Advancing the timing will remove nearly all of the turbulence caused by upgraded cams.
The values here work for the combos I listed above. They key here is to advance timing in the areas changed below 1 degree at a time until the vacuum stablizes and no longer wavers. Boost gauges work wonders here. 280's will achieve about ~15 in/hg of vacuum with the ac off and around 11 in/hg with it on. 272's will be
19 and 15 respectively.
*PLEASE BE VERY CAREFUL WHEN CHANGING TIMING*
One wrong flash and things can go very bad for you, triple check before flashing!
Stock Ignition timing:
Advanced Timing:
You will not the different areas with 19 degrees of timing versus the stock 5, tapering to 17 degrees @ >1000 rpm.
*WARM UP THE CAR FIRST*
(not warming it up will scew your attempts to tune the idle properly - dont worry after tuned it will start cold just fine)
Once you have made these changes flash the ecu. Go ahead and open your idle bypass screw (lefty loosy) 4-5 turns. Start the car with the air conditioning off, blip the throttle.
The idle should stabalize to around 1150 rpm with the ac off, if it doesn't dont worry it will after the next step. Now turn the ac on full blast and blip the throttle.
Using the aforementioned steps, continue blipping the throttle and adjusting the idle bypass screw. There will be a zone within about 2/3 of a turn where with either the ac on or off the car will
drop rpms and immediatly settle to a stable idle. (1050 with ac on, 1150 with it off). Once you have achieved this rev the car a little harder slowly up to about 4k with ac on and off. Make any further adjustments
needed to the idle bypass screw.
Congradulations and go enjoy your daily driver again.
P.S. I do not claim this as an end all solution to idling, depending on injectors,etc all of this can change. With properly scaled injetors
I have achieved excellent results on a few cars now.
Last edited by Agent-Smith; Jul 19, 2006 at 07:32 AM.
Jul 18, 2006, 11:31 PM
#2
this is horribly written and very hard to understand.
After reading several threads about people being plagued with the cam idle problem I have decided it is time to put a stop to all the lies and misinformation about cams and their proportedly poor idle.
First a little light reading on engine timing. This will illuminate why higher lift and longer duration cams idle badly when left unattended. That is right - your bad idle can be completely remedied with a little tuning.
*scroll down about half way down the page and study the engine timing animation if needed*
engine timing
The difference in idle quality of longer duration and/or higher lift cams comes from the fact that with stock ignitition timing there is a small amount of exhaust pressure in the cylinder when the intake valve is opened. while the intake valve is allowing more fuel /air in, exhaust gases contaminate the cylinder. This is known as intake reversion; intake reversion is what causes the a contaminated and hence slower burning air fuel mixture which then creates a loss of vacuum.
Now with a little tuning of the timing at idle load and rpm, we can achieve a stable idle. You will be able to run your air conditioner again!
The following changes are tested HKS 280/280 and HKS 272/272 combos. 264's will require alot less if any timing advance to get good results. YMMV.
On with the how to:
The first step in maintaining a good idle is to raise the rpm levels at which the stock ecu trys to maintain. I run these values a little higher than most would, but I find this achieves the best results for me.
Here are the maps top to bottom: on thetop is the before and bottom will be after changes.
Desired Idle rpm with the AC on:
Desired Idle RPM Drive:
Desired Idle RPM Neutral:
And now for the most important changes: the Ignition timing. Advancing the timing will change the ignition cycle in such a way that you create a more complete burn earlier in the cycle and this will then create more exhaust pressure which translates into more engine vacuum.
The values here work for the combos I listed above. The key here is to advance timing in the areas changed below 1 degree at a time until the vacuum stablizes and no longer wavers up and down. Boost gauges work wonders here. 280's will achieve about ~15 in/hg of vacuum with the ac off and around 11 in/hg with it on. 272's will be
19 and 15 respectively.
*PLEASE BE VERY CAREFUL WHEN CHANGING TIMING*
One wrong flash and things can go very bad for you, triple check before flashing!
Stock Ignition timing:
Advanced Timing:
You will note the different areas with 19 degrees of timing versus the stock 5, tapering to 17 degrees @ <1000 rpm.
*WARM UP THE CAR FIRST*
(not warming it up will scew your attempts to tune the idle properly - dont worry after tuned it will start cold just fine)
Once you have made these changes flash the ecu. Go ahead and open your idle bypass screw (lefty loosy) 4-5 turns. Start the car with the air conditioning off, blip the throttle.
The idle should stabalize to around 1150 rpm with the ac off, if it doesn't dont worry it will after the next step. Now turn the ac on full blast and blip the throttle.
Using the aforementioned steps, continue blipping the throttle and adjusting the idle bypass screw. There will be a zone within about 2/3 of a turn where with either the ac on or off the car will
drop rpms and immediatly settle to a stable idle. (1050 with ac on, 1150 with it off). Once you have achieved this rev the car a little harder slowly up to about 4k with ac on and off. Make any further adjustments
needed to the idle bypass screw.
Congradulations and go enjoy your daily driver again.
P.S. I do not claim this as an end all solution to idling, depending on injectors,etc all of this can change. With properly scaled injetors
I have achieved excellent results on a few cars now.
my wiki contribution was to rewrite it so that it shows a higher level of mastery in the english language.
Originally Posted by Agent-Smith
After reading several threads about people being plagued with the cam idle problem I have decided it is time to put a stop to all the lies and misinformation about cams and their proportedly poor idle.
First a little light reading on engine timing. This will illuminate why higher lift and longer duration cams idle badly when left unattended. That is right - your bad idle can be completely remedied with a little tuning.
*scroll down about half way down the page and study the engine timing animation if needed*
engine timing
The difference in idle quality of longer duration and/or higher lift cams comes from the fact that with stock ignitition timing there is a small amount of exhaust pressure in the cylinder when the intake valve is opened. while the intake valve is allowing more fuel /air in, exhaust gases contaminate the cylinder. This is known as intake reversion; intake reversion is what causes the a contaminated and hence slower burning air fuel mixture which then creates a loss of vacuum.
Now with a little tuning of the timing at idle load and rpm, we can achieve a stable idle. You will be able to run your air conditioner again!
The following changes are tested HKS 280/280 and HKS 272/272 combos. 264's will require alot less if any timing advance to get good results. YMMV.
On with the how to:
The first step in maintaining a good idle is to raise the rpm levels at which the stock ecu trys to maintain. I run these values a little higher than most would, but I find this achieves the best results for me.
Here are the maps top to bottom: on thetop is the before and bottom will be after changes.
Desired Idle rpm with the AC on:
Desired Idle RPM Drive:
Desired Idle RPM Neutral:
And now for the most important changes: the Ignition timing. Advancing the timing will change the ignition cycle in such a way that you create a more complete burn earlier in the cycle and this will then create more exhaust pressure which translates into more engine vacuum.
The values here work for the combos I listed above. The key here is to advance timing in the areas changed below 1 degree at a time until the vacuum stablizes and no longer wavers up and down. Boost gauges work wonders here. 280's will achieve about ~15 in/hg of vacuum with the ac off and around 11 in/hg with it on. 272's will be
19 and 15 respectively.
*PLEASE BE VERY CAREFUL WHEN CHANGING TIMING*
One wrong flash and things can go very bad for you, triple check before flashing!
Stock Ignition timing:
Advanced Timing:
You will note the different areas with 19 degrees of timing versus the stock 5, tapering to 17 degrees @ <1000 rpm.
*WARM UP THE CAR FIRST*
(not warming it up will scew your attempts to tune the idle properly - dont worry after tuned it will start cold just fine)
Once you have made these changes flash the ecu. Go ahead and open your idle bypass screw (lefty loosy) 4-5 turns. Start the car with the air conditioning off, blip the throttle.
The idle should stabalize to around 1150 rpm with the ac off, if it doesn't dont worry it will after the next step. Now turn the ac on full blast and blip the throttle.
Using the aforementioned steps, continue blipping the throttle and adjusting the idle bypass screw. There will be a zone within about 2/3 of a turn where with either the ac on or off the car will
drop rpms and immediatly settle to a stable idle. (1050 with ac on, 1150 with it off). Once you have achieved this rev the car a little harder slowly up to about 4k with ac on and off. Make any further adjustments
needed to the idle bypass screw.
Congradulations and go enjoy your daily driver again.
P.S. I do not claim this as an end all solution to idling, depending on injectors,etc all of this can change. With properly scaled injetors
I have achieved excellent results on a few cars now.
Last edited by trinydex; Jul 18, 2006 at 11:38 PM.
Jul 19, 2006, 07:34 AM
#4
Evolving Member
Thread Starter
Join Date: Sep 2002
Location: Florida
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
Yeah so my grammer is not great, but at least I took the time to post it.
Adding timing alone has never alleviated the problem for me. The biggest change was the raising of the idle rpm, without that it would sputter and die quite often.
Also could you link the wiki?
Adding timing alone has never alleviated the problem for me. The biggest change was the raising of the idle rpm, without that it would sputter and die quite often.
Also could you link the wiki?
Jul 20, 2006, 02:14 PM
#7
Evolving Member
iTrader: (3)
Join Date: Jan 2004
Location: SoCal
Posts: 443
Likes: 0
Received 0 Likes
on
0 Posts
What should my afr at idle look like? My LC1 constantly shows that I am idling around 15.0 with brief dips to 14.7 and rises to 15.1-15.2, and an occasional jump to high 15/low 16. Is that OK or should I enrich the fuel table? I am thinking it is just the limitation of the narrow band O2...
Trending Topics
Jul 21, 2006, 03:03 PM
#9
You aren't tuning **** this way. Once you dick with the BISS screw your fuel trims are going to be off.
I have 272s with cam gears (-2/-2) and I have a lumpy idle. The only time its (RARELY) unstable is creeping ahead slowly from a stop as you would have in stop and go traffic.
If it starts to choke (after awhile you will learn when this will happen) all you have to do is blip the throttle and it recovers. I would rather blip the throttle than throw off my fuel trims and add 14* of timing!!!
Adding 10% fuel also helps the car overcome the occational stumble but I prefer not to run soo rich at idle. I noticed when I did add fuel I could DEFINATELY smell more raw exhaust fumes (catless).
For daily driving, adjusting cam gears can also eliminate the rough idle. Personally I think if you are hard core enough to toss in cams you should be savy enough to read your car and manually prevent the stumble from happening.
I have 272s with cam gears (-2/-2) and I have a lumpy idle. The only time its (RARELY) unstable is creeping ahead slowly from a stop as you would have in stop and go traffic.
If it starts to choke (after awhile you will learn when this will happen) all you have to do is blip the throttle and it recovers. I would rather blip the throttle than throw off my fuel trims and add 14* of timing!!!
Adding 10% fuel also helps the car overcome the occational stumble but I prefer not to run soo rich at idle. I noticed when I did add fuel I could DEFINATELY smell more raw exhaust fumes (catless).
For daily driving, adjusting cam gears can also eliminate the rough idle. Personally I think if you are hard core enough to toss in cams you should be savy enough to read your car and manually prevent the stumble from happening.
Jul 21, 2006, 03:09 PM
#11
Originally Posted by Jeff_Jeske
You aren't tuning **** this way. Once you dick with the BISS screw your fuel trims are going to be off.
I have 272s with cam gears (-2/-2) and I have a lumpy idle. The only time its (RARELY) unstable is creeping ahead slowly from a stop as you would have in stop and go traffic.
If it starts to choke (after awhile you will learn when this will happen) all you have to do is blip the throttle and it recovers. I would rather blip the throttle than throw off my fuel trims and add 14* of timing!!!
Adding 10% fuel also helps the car overcome the occational stumble but I prefer not to run soo rich at idle. I noticed when I did add fuel I could DEFINATELY smell more raw exhaust fumes (catless).
For daily driving, adjusting cam gears can also eliminate the rough idle. Personally I think if you are hard core enough to toss in cams you should be savy enough to read your car and manually prevent the stumble from happening.
I have 272s with cam gears (-2/-2) and I have a lumpy idle. The only time its (RARELY) unstable is creeping ahead slowly from a stop as you would have in stop and go traffic.
If it starts to choke (after awhile you will learn when this will happen) all you have to do is blip the throttle and it recovers. I would rather blip the throttle than throw off my fuel trims and add 14* of timing!!!
Adding 10% fuel also helps the car overcome the occational stumble but I prefer not to run soo rich at idle. I noticed when I did add fuel I could DEFINATELY smell more raw exhaust fumes (catless).
For daily driving, adjusting cam gears can also eliminate the rough idle. Personally I think if you are hard core enough to toss in cams you should be savy enough to read your car and manually prevent the stumble from happening.
also adding that much timing at idle is normal. ask any tuner, this is typically the way idle vac issues are solved. you start the burn earlier at idle cylinder pressures and it creates a more complete burn which then creates a stronger exhuast pulse which promotes more scavenging and gets right of more contaminates in your idle mixture.
Jul 21, 2006, 03:55 PM
#12
Evolving Member
iTrader: (4)
Join Date: Nov 2004
Location: SJ, CA.
Posts: 397
Likes: 0
Received 0 Likes
on
0 Posts
Does anybody know what the STOCK biss setting is? How many turns from fully closed?
I'm going to start from stock setting and first try adjusting my idle with ecuflash.
I'm going to start from stock setting and first try adjusting my idle with ecuflash.
Jul 21, 2006, 05:57 PM
#13
Evolving Member
Thread Starter
Join Date: Sep 2002
Location: Florida
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
I just checked the manual and it is of no help. To put it back to stock you would need a scan tool that can place the car in "test" mode - which basically disables the IAC motor.
If you have access to one, turn everything off ac, lights,etc. Use test #30, then adjust the idle to 850 +-50 rpm.
If you have access to one, turn everything off ac, lights,etc. Use test #30, then adjust the idle to 850 +-50 rpm.
Jul 21, 2006, 10:35 PM
#15
Evolving Member
Thread Starter
Join Date: Sep 2002
Location: Florida
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
Try it with your xede going slowly. That is how I discovered the technique in the first place. You can watch you will hit a point where the vacuum really starts to strengthen. 19* of timing is right in line with what the cams require for a clean burn. Remember that opening the BISS adds more air and leans the mixture out; thus causing a slower burn and requiring more advance. I am sure you could mix it up a little and add some fuel in as well, and perhaps run a degree or 2 less timing. I dont see the need to waste the gas though.
You must also remember this is basically little to no load situation.
Btw to the other guy mentioning fuel trims, I just did a log tonight with evoscan. Mine were dead on.
You must also remember this is basically little to no load situation.
Btw to the other guy mentioning fuel trims, I just did a log tonight with evoscan. Mine were dead on.