heads/cam idle
heads/cam idle I've been searching and reading, but haven't found exactly what to do in my situation. Mods in sig.
Car idles fine, set at 850 rpm (the only idle adjustment I've done, other than timing). Totally fine when warmed up and just sitting there.
However, on cold start, with a/c on, when I back out of the driveway, after going in reverse, the idle will drop to like 400 rpm, then go back up and down about three times. It's even died once or twice.
After that, it idles perfectly fine while driving, stopping, whatever.
What do I mess with to fix this? What do I need to log with HP tuners, and what values should I look at?
Please be as specific as possible.
Car idles fine, set at 850 rpm (the only idle adjustment I've done, other than timing). Totally fine when warmed up and just sitting there.
However, on cold start, with a/c on, when I back out of the driveway, after going in reverse, the idle will drop to like 400 rpm, then go back up and down about three times. It's even died once or twice.
After that, it idles perfectly fine while driving, stopping, whatever.
What do I mess with to fix this? What do I need to log with HP tuners, and what values should I look at?
Please be as specific as possible.
On The Tree
Joined: Sep 2004
Posts: 143
Likes: 0
From: St. Clair
First, I would turn your idle up just a bit, otherwise you are just going to be fighting a loosing battle...You'll have really bad air velocity at low rpms, especially with heads and a cam, let alone just adding a cam...And that makes for poor idle characteristics...
Second, what I did, that pretty much eliminated the up and down rpm swings, was the following...
In the VE table set your values from 15 kPa to 105 kPa for both the 400 rpms and 800 rpm columns to a very level values, i.e. my 400 rpm column starts at 38 and ends at 56, each row is 1 higher than the previous (38, 39, 40.....56), for the 800 rpms column I have 40, 41, 42.....58...
What I found when the rpms were jumping between 950 rpms (my idle rpm) and 400 rpms, was the MAP values would go up to around 12 and 13, which made it read a higher VE number, which seemed to me to be sort of choking the engine...I leveled the VE numbers out so that, even on a high MAP reading the VE stayed about where it should be for idle...And it rarely does the bouncing up and down...Only once in a while, at hot start up, but then it only does it once and normalizes at my set rpm...
Peace...Gman
Second, what I did, that pretty much eliminated the up and down rpm swings, was the following...
In the VE table set your values from 15 kPa to 105 kPa for both the 400 rpms and 800 rpm columns to a very level values, i.e. my 400 rpm column starts at 38 and ends at 56, each row is 1 higher than the previous (38, 39, 40.....56), for the 800 rpms column I have 40, 41, 42.....58...
What I found when the rpms were jumping between 950 rpms (my idle rpm) and 400 rpms, was the MAP values would go up to around 12 and 13, which made it read a higher VE number, which seemed to me to be sort of choking the engine...I leveled the VE numbers out so that, even on a high MAP reading the VE stayed about where it should be for idle...And it rarely does the bouncing up and down...Only once in a while, at hot start up, but then it only does it once and normalizes at my set rpm...
Peace...Gman
Well, I changed my idle timing to what was recommended in the threads.
Leaned out my VE table to 85% at 400 rpm, 90% at 800 and 95% at 1200 rpm.
Then changed my base running airflow IAF vs. ECT table according to the excel spreadsheet from my log.
The car definitely idles smoother. But, it still dropped to 500 rpm, back and forth about twice when I first backed out of the driveway.
And, the rpms stuck around 1200 rpm when I pushed in the clutch after a short cruise around the block.
They've also been hanging up from time to time around 2000 rpm when I push in the clutch. Sometimes after full throttle, sometimes after part throttle.
Suggestions??
Leaned out my VE table to 85% at 400 rpm, 90% at 800 and 95% at 1200 rpm.
Then changed my base running airflow IAF vs. ECT table according to the excel spreadsheet from my log.
The car definitely idles smoother. But, it still dropped to 500 rpm, back and forth about twice when I first backed out of the driveway.
And, the rpms stuck around 1200 rpm when I pushed in the clutch after a short cruise around the block.
They've also been hanging up from time to time around 2000 rpm when I push in the clutch. Sometimes after full throttle, sometimes after part throttle.
Suggestions??
you need to do your Idle trims to get your RAF correct..
this will fix your problems...
send me 2 logs
1 cold start...turn key...start logging....start car...idle up to full operating temperature
then do a warm start ....same deal..turn key...start logging...start car..let it idle for a few minutes.....
then let me send you some new #'s for RAF and we'll see if it fixes your problems
and I need a bin too
this will fix your problems...
send me 2 logs
1 cold start...turn key...start logging....start car...idle up to full operating temperature
then do a warm start ....same deal..turn key...start logging...start car..let it idle for a few minutes.....
then let me send you some new #'s for RAF and we'll see if it fixes your problems
and I need a bin too
What are "idle trims" exactly? (which tables)
Also, if I log my IAC desired position, and IAC position, what are the numbers I should shoot for, and how do I tune to change my IAC?
Also, if I log my IAC desired position, and IAC position, what are the numbers I should shoot for, and how do I tune to change my IAC?
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On The Tree
Joined: Sep 2004
Posts: 143
Likes: 0
From: St. Clair
If you don't have the of the revised HP Tuners copies, then you can't log the "idle trims"...The revision was something like $350, so I never updated my software...
I don't think you need to do it anyway, if you can't log it with your revision of HP Tuners...Try what I suggested for your VE table...I went the 80%, 90% rule thing when I first put the cam in...But the idle was always goofy, bouncing up and down at start up, nearly stalling, etc...
After I made the changes, that I posted above, the car's idle now is very good...Also, I found that if I had my Idle Airflow too low, the idle will bounce up and down...So, you may want to increase those numbers as well and see what happens...
Here are my current Idle Airflow values:
22.33, 20.42, 16.83, 14.49, 13.65, 12.88, 11.97, 10.82, 9.68, 8.95, 8.24, 8.24, 8.24, 8.24, 8.24, 8.24...
Peace...Gman
I don't think you need to do it anyway, if you can't log it with your revision of HP Tuners...Try what I suggested for your VE table...I went the 80%, 90% rule thing when I first put the cam in...But the idle was always goofy, bouncing up and down at start up, nearly stalling, etc...
After I made the changes, that I posted above, the car's idle now is very good...Also, I found that if I had my Idle Airflow too low, the idle will bounce up and down...So, you may want to increase those numbers as well and see what happens...
Here are my current Idle Airflow values:
22.33, 20.42, 16.83, 14.49, 13.65, 12.88, 11.97, 10.82, 9.68, 8.95, 8.24, 8.24, 8.24, 8.24, 8.24, 8.24...
Peace...Gman
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Verdad Gallardo Well from driving today (after another idle log this morning, and adjusting my RAF again)....
My car idles perfectly when just sitting there, or sitting at a stoplight, whatever. Totally smooth, right at 850rpm.
When I first back out of the driveway, or parking spot, cold or hot, it still drops to about 500 rpm, and back and forth about twice. BUT, it's not dropping as low, not dropping as fast, not stalling, and doesn't do it as often. So, that's an improvement!
A problem that has gotten worse though is that the rpms get stuck while rolling ( pushing in clutch to slow for stoplight at 30 mph +) at about 1200 rpm or so, sometimes higher. Then, they don't go back to 850 rpm till I stop.
My IAC position counts from my log this morning go as follows
Colant temp (F) IAC position
93 172, down to 146 pretty quickly
100 140
110 130
120 110
130 104
140 100
150 93
160 90
170 86
180 85
190 82
200 83
205 80
That's where I stopped logging. Where should these counts be, and how do I change them? Also, will lowering my IAC help keep the rpms from hanging up at 0% throttle while moving?
Or do I mess with the cracker, Min max A/C settings? Is there some speed vs. something table that will keep the rpm from hanging at 0% throttle?
My car idles perfectly when just sitting there, or sitting at a stoplight, whatever. Totally smooth, right at 850rpm.
When I first back out of the driveway, or parking spot, cold or hot, it still drops to about 500 rpm, and back and forth about twice. BUT, it's not dropping as low, not dropping as fast, not stalling, and doesn't do it as often. So, that's an improvement!
A problem that has gotten worse though is that the rpms get stuck while rolling ( pushing in clutch to slow for stoplight at 30 mph +) at about 1200 rpm or so, sometimes higher. Then, they don't go back to 850 rpm till I stop.
My IAC position counts from my log this morning go as follows
Colant temp (F) IAC position
93 172, down to 146 pretty quickly
100 140
110 130
120 110
130 104
140 100
150 93
160 90
170 86
180 85
190 82
200 83
205 80
That's where I stopped logging. Where should these counts be, and how do I change them? Also, will lowering my IAC help keep the rpms from hanging up at 0% throttle while moving?
Or do I mess with the cracker, Min max A/C settings? Is there some speed vs. something table that will keep the rpm from hanging at 0% throttle?
Originally Posted by Gman2002Z06
If you don't have the of the revised HP Tuners copies, then you can't log the "idle trims"...The revision was something like $350, so I never updated my software...
I don't think you need to do it anyway, if you can't log it with your revision of HP Tuners...Try what I suggested for your VE table...I went the 80%, 90% rule thing when I first put the cam in...But the idle was always goofy, bouncing up and down at start up, nearly stalling, etc...
After I made the changes, that I posted above, the car's idle now is very good...Also, I found that if I had my Idle Airflow too low, the idle will bounce up and down...So, you may want to increase those numbers as well and see what happens...
Here are my current Idle Airflow values:
22.33, 20.42, 16.83, 14.49, 13.65, 12.88, 11.97, 10.82, 9.68, 8.95, 8.24, 8.24, 8.24, 8.24, 8.24, 8.24...
Peace...Gman
I don't think you need to do it anyway, if you can't log it with your revision of HP Tuners...Try what I suggested for your VE table...I went the 80%, 90% rule thing when I first put the cam in...But the idle was always goofy, bouncing up and down at start up, nearly stalling, etc...
After I made the changes, that I posted above, the car's idle now is very good...Also, I found that if I had my Idle Airflow too low, the idle will bounce up and down...So, you may want to increase those numbers as well and see what happens...
Here are my current Idle Airflow values:
22.33, 20.42, 16.83, 14.49, 13.65, 12.88, 11.97, 10.82, 9.68, 8.95, 8.24, 8.24, 8.24, 8.24, 8.24, 8.24...
Peace...Gman
Your IAC effective area is off. Don't mess with anything else until you fix it. You need to make sure your Calculated Airflow (dynamic airflow from VE Tables) matches your Desired IAC airflow at idle with AC off and the AC on. Typically, you will need to shift the table several spots to the right to make it work, but often, you will have to rebuild the table if your TB is not stock. Running a 90mm TB meant I had to modify my IAC effective area table a great deal.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Every cam is going to have a different best-fit
low-RPM VE reduction required. The rule-of-
thumb values are a starting point at best. The
final optimum -will- be lower than stock values
but you can go too far. A stock VE table will
calculate more air than actual on a cammed
motor making idle fuel delivery over-rich.
For cold starting and cold idle problems look at
the Open Loop Fuel Air vs ECT vs MAP table.
A cammed car runs higher idle MAP and when
cold, this table commands some large enrichment.
This multiplied by the VE table error can be really
hard to run with, pushes the required idle MAP
even higher (because motor is running inefficiently)
and makes matters even worse. If you back off
on this enrichment things will be less "soggy" and
the idle loop will work better.
low-RPM VE reduction required. The rule-of-
thumb values are a starting point at best. The
final optimum -will- be lower than stock values
but you can go too far. A stock VE table will
calculate more air than actual on a cammed
motor making idle fuel delivery over-rich.
For cold starting and cold idle problems look at
the Open Loop Fuel Air vs ECT vs MAP table.
A cammed car runs higher idle MAP and when
cold, this table commands some large enrichment.
This multiplied by the VE table error can be really
hard to run with, pushes the required idle MAP
even higher (because motor is running inefficiently)
and makes matters even worse. If you back off
on this enrichment things will be less "soggy" and
the idle loop will work better.
On The Tree
Joined: Sep 2004
Posts: 143
Likes: 0
From: St. Clair
Originally Posted by foff667
If i remember correctly everyone that bought even the earliest version of hpt gets up to 1.7 for free which has that in there...the most anyone has paid out for updates of any sort is $99 for the old yearly fee(many of which have been refunded that due to the new free updates software policy) so i have no clue where your getting $350.
From their website...
Post by Chris@HPTuners
it is simple.
1. Hardware updates will never be free
2. Anyone with valid support as at Apr 15th 2005 will receive all future software updates free
3. Anyone without valid support as at Apr 15th 2005 will pay $99 (one time only) and receive all future updates free.
Anyone who ordered support post Apr 15th should have been refunded. If not please email sales@hptuners.com
I am one who chose not to purchase "support"...So by the looks of the website, I could pay the $99 and get software updates...I miss read the website, is where I got the $350 from...Sorry...
Well, I'm still on Version 1.4...At the time I bought it, I did not need any of the additional capabilities that the later revisions had. I just don't see the need to update at this point, when I have the car running very well without all the additional bells and whistles...
I did have a whole lot of trial and error to see what worked performance and driveability wise and what didn't work...But to me, that was the interesting part...
Peace...Gman
May 22'nd, 2005: Announcing HP Tuners VCM Suite v1.7.0!!
HP Tuners is pleased to announce the release of VCM Suite v1.7.0. This release includes our new "1 bar - Speed Density Enhanced" option for all 1999 and later LS1 V8 powered vehicles and also expanded support on "2bar Speed Density" for forced induction applications on 2004 and later LS1 V8 powered vehicles with 1Mb PCM's. This release also includes other minor enhancements such as improved table axis labeling, units display and other minor bug fixes.
This is a recommended (and free) update to all current customers.
Click here for all the details!
this is from their front page...at least get 1.7 there are many many improvements over 1.4
HP Tuners is pleased to announce the release of VCM Suite v1.7.0. This release includes our new "1 bar - Speed Density Enhanced" option for all 1999 and later LS1 V8 powered vehicles and also expanded support on "2bar Speed Density" for forced induction applications on 2004 and later LS1 V8 powered vehicles with 1Mb PCM's. This release also includes other minor enhancements such as improved table axis labeling, units display and other minor bug fixes.
This is a recommended (and free) update to all current customers.
Click here for all the details!
this is from their front page...at least get 1.7 there are many many improvements over 1.4
Originally Posted by Patrick G
Your IAC effective area is off. Don't mess with anything else until you fix it. You need to make sure your Calculated Airflow (dynamic airflow from VE Tables) matches your Desired IAC airflow at idle with AC off and the AC on. Typically, you will need to shift the table several spots to the right to make it work, but often, you will have to rebuild the table if your TB is not stock. Running a 90mm TB meant I had to modify my IAC effective area table a great deal.
So what do I change?
This is what I've learned so far:
Problem 1- idle drops to 400-600 rpm and back and forth, may stall.
Solution- lean out VE table for 400, 800, and 1200 rpm. BUT, if you lean 1200 rpm too much, you'll lean out your part throttle acceleration, and car may hesitate.
Problem 2- car idles rough/ stumbles.
Solution- Log your STIT and LTIT park and drive and adjust RAF(base idle air flow) accordingly. BUT, increasing RAF will increase IAC position, and may cause RPMS to hang, decrease slowly, and even create a "cruise control" effect where rpms don't go down hardly at all.
Problem 3- RPMs hang at 1200 or 2000 rpm while coasting clutch in.
Solution- Decrease IAC position to X level?
1. Drill hole in throttle body- allows more air in at idle, lowers IAC. BUT, it's permanent (not for me).
OR
2. Turn **** on throttle body to make it open more. BUT, people say this is only if you can't tune. And it can cause more "cruise control" effect https://ls1tech.com/forums/showthrea...+throttle+body
OR
3. Tuning. But, I don't know which tables EXACTLY (please don't use abbreviations or short names) to change, and whether to change up or down, what percent...
I want to learn more about what tables to tune and how.
Problem 1- idle drops to 400-600 rpm and back and forth, may stall.
Solution- lean out VE table for 400, 800, and 1200 rpm. BUT, if you lean 1200 rpm too much, you'll lean out your part throttle acceleration, and car may hesitate.
Problem 2- car idles rough/ stumbles.
Solution- Log your STIT and LTIT park and drive and adjust RAF(base idle air flow) accordingly. BUT, increasing RAF will increase IAC position, and may cause RPMS to hang, decrease slowly, and even create a "cruise control" effect where rpms don't go down hardly at all.
Problem 3- RPMs hang at 1200 or 2000 rpm while coasting clutch in.
Solution- Decrease IAC position to X level?
1. Drill hole in throttle body- allows more air in at idle, lowers IAC. BUT, it's permanent (not for me).
OR
2. Turn **** on throttle body to make it open more. BUT, people say this is only if you can't tune. And it can cause more "cruise control" effect https://ls1tech.com/forums/showthrea...+throttle+body
OR
3. Tuning. But, I don't know which tables EXACTLY (please don't use abbreviations or short names) to change, and whether to change up or down, what percent...
I want to learn more about what tables to tune and how.
Last edited by silverTA2002; Oct 5, 2005 at 05:01 PM.
Originally Posted by silverTA2002
When I logged my desired IAC position and my IAC position, they were always within 1 from each other.
So what do I change?
So what do I change?
Again, tweaking the IAC effective area is the key to happiness.
Originally Posted by silverTA2002
They're within 1 of each other at all temps. That's at 0% throttle with A/C off.
I haven't logged with A/C on or cruising.
I haven't logged with A/C on or cruising.