Idle Tips & Tricks

[WeathermanShawn]

In-Memory-of-Shawn-Sankey (http://forum.efilive.com/showthread.php?16849-In-Memory-of-Shawn-Sankey)


LS1 Idle Tips & Tricks


The Basics:

1. Proper Fueling
2. Enough Base Spark
3. Enough Desired Airflow.

Make the least amount of changes to maximize Idle!
Do not Alter the Following:

1. IAC Effective Area (unless different TB size).
2. Start-Up Airflow Corrections
3. Airflow Parameter(s) that affect Idle.

1. B0101-Main VE Table: Perform Calc.VET or AutoVE for the Idle Rpm's 800- 1200. For 400 Rpm's extrapolate the 800 Rpm Values minus 10%.

http://i1126.photobucket.com/albums/l609/weathermanshawn/IdleVETable.png

2. B4307-Desired Airflow: Log SAE.MAF (g/s) vs ECT at Idle. The goal is to have your MAF, VE, and Desired Airflow all utilizing identical Airflow Values. RAFIG may produce values too low.

http://i1126.photobucket.com/albums/l609/weathermanshawn/IdleAir-1.png

3. B4352-Cat Light-off Idle Offset Multiplier: Make Multiplier zero (0). Eliminates additional Airflow Source while tuning Idle.

4. B4504- Airflow learning Control Delay: Change per Idle Tutorial from 1.3 to 4.3 seconds.

5. B4512, B4514, B4515- Learning Parameters: Per Idle Tutorial.

6. B4309-Throttle Cracker Airflow in Gear (TC): Utilize the least amount of air to prevent Rpm's hanging (cruise control), but enough to prevent excessive engine braking and lack of throttle response. A great 'Stall Saver' is to add +4 g/s to the 400 Rpm Values. A good TC Table will gradually decrease throughout the RPM and MPH range, with no 'holes' or added air. I use a 98 Camaro LS1 Automatic TC Table with about 33% less air (-33%).

http://i1126.photobucket.com/albums/l609/weathermanshawn/TC.png

7. B4315-B4320 Throttle Follower: Identical values as Idle Tutorial. Great way to get additional Air when you press the throttle.

8. B5932-Base Spark in Gear: Add +4 degrees to Spark Values in the 400 RPM Idle Region, and +8 to to the 0 RPM Idle Region on Base Spark. If the car wants to stall you automatically get a bump in Spark to help prevent Spark for going to low. If your car wants to stall when you shift into gear (High-Octane Spark), then your Spark is probably dropping to low. Your High Octane Spark and Base Spark in gear should be within 4 degrees of each other.

http://i1126.photobucket.com/albums/l609/weathermanshawn/BaseSparkInGear.png

Note: Tables are for Illustrative Purposes only. Use discretion in modifying Tune..

************************************************** *********
LS1 CAM/IDLE BASE Tune & IDLE PDF (See Below) **
************************************************** *********
Credits: SSpdDmon's EFILive's Idle Tutorial:http: (http://forum.efilive.com/showthread.php?4661-Idle-Tuning-Helpful-Info-Inside)//forum.efilive.com/showthread.php?4661-Idle-Tuning-Helpful-Info-Inside (http://forum.efilive.com/showthread.php?4661-Idle-Tuning-Helpful-Info-Inside).

[Taz]

Thank you WeathermanShawn !!!

I've been in the industry for several decades, but consider myself "new" to the EFILive software as I haven't been using it (or tuning EFI engines) for very long. I use the Idle tutorial you metioned in the first post, but more "how to" info is always welcome.

Acheiving an idle that is reasonable (given components used), and acceptable to the customer is often a challenge for me.

I probably won't have much (if anything) to add to this thread .... but I'll be reading it often !


Regards,
Taz

[5.7ute]

If anybody has unique tips and tricks for Auto's that would help a lot.


Grow some nuts & drive a manual.:angel_innocent:
Seriously though good work Shawn. I will be tuning a large cammed 346 later today. I will keep the logs etc & put some notes together with the process I use. Hopefully watching the process through logs may help some people get a grasp on what we are looking for.

[joecar]

Idle is one of the more difficult/tedious areas... so this thread is specifically for LS1B/LS1A idle tuning... anyone with experience please do add your comments.

Thanks Shawn for starting a specific thread. :cheers:

Any non-idle material will be moved to a new thread. :hihi:

[sinr98]

This helps out a ton. I need to change my idle and was trying to get all the information on it before I started.
Thanks for the great write up.

[WeathermanShawn]

Thank you WeathermanShawn !!!

I've been in the industry for several decades, but consider myself "new" to the EFILive software as I haven't been using it (or tuning EFI engines) for very long. I use the Idle tutorial you metioned in the first post, but more "how to" info is always welcome.

Acheiving an idle that is reasonable (given components used), and acceptable to the customer is often a challenge for me.

I probably won't have much (if anything) to add to this thread .... but I'll be reading it often !


Regards,
Taz

Thanks Taz:

Please feel free to comment. We welcome your expertise along with many others.

Very few of us totally understand the workings of the IAC in combination with some of the features of closed-loop tuning.

At some point I will try to synthesize all the information in the next few weeks. Hopefully we can condense it all into 'one-stop' Idle Tuning resource.

If anybody has unique tips and tricks for Auto's that would help a lot.

..Thanks..

Grow some nuts & drive a manual.:angel_innocent:
Seriously though good work Shawn. I will be tuning a large cammed 346 later today. I will keep the logs etc & put some notes together with the process I use. Hopefully watching the process through logs may help some people get a grasp on what we are looking for.

Thats a good one Mick!

I would definitely appreciate any Tips and procedures you might have Mick. You see a whole lot more vehicles and tunes than I do..especially with Open-Loop.

:thankyou2:


This helps out a ton. I need to change my idle and was trying to get all the information on it before I started.
Thanks for the great write up.

Your welcome.

If you encounter any specific problems after using the Idle Tutorial or 'Tips & Tricks' don't hesitate to post up a thread. If you have a Tune & Log that will always help a lot!

Thanks.

[bmax]

Thanks for the information Weatherman,

I have a cam with 6 degrees of overlap @ 0.50".

Before the cam when I used the rafig procedure all was good. After the cam I found the values to be too low also.

Using the maf G/s it is much better. :)

I am wondering why the rafig values are not valid after the cam install, effects of reversion?


Brad

[WeathermanShawn]

Brad:

Thanks for the feedback and the compliment.

As to why RAFIG values sometimes appear to be too low for cammed cars, and why MAF Airflow seems to work, is still unresolved in my mind ( I don't know..:grin:).

The intracity of the IAC function and how it interacts with fueling (MAF/VE) is pretty complex. I know 5.7ute and others have been studying actual case studies to understand their function more.

But I kinda fell upon that observation by happenstance. I knew fueling functions were primarily controlled by the MAF and VE, so I figured that out first. So once LTFT & STFT Trims were +/0, I just used that for my Desired Airflow.

While I would like to take credit for that 'discovery' a search of the literature shows others have figured that out also.

Thanks again, and let us know how it goes..

..Shawn..

[blsnelling]

Now that I've got my Calc. VE tune done, I can work on my Desired Airflow. I'm trying to create the map in step 2 above. I see you're using ECT for the rows. Are you using SAE.MAF for the column? What are you using for data?

[joecar]

Now that I've got my Calc. VE tune done, I can work on my Desired Airflow. I'm trying to create the map in step 2 above. I see you're using ECT for the rows. Are you using SAE.MAF for the column? What are you using for data?For the column, try this:

goto that table in the tunetool, highlight either the column of interest or the whole table and do rightclick->Copy With Labels...

then in the scantool, on that map's column tab click Paste Labels.

[joecar]

For 1-D tables (i.e. only one column), you can put any logged pid for the column data.

If you want to be able to paste-with-labels that map into a tunetool table, then see post #10.

[blsnelling]

For the column, try this:

goto that table in the tunetool, highlight either the column of interest or the whole table and do rightclick->Copy With Labels...

then in the scantool, on that map's column tab click Paste Labels.

I got that part. I thought I had to choose something from the drop down.


For 1-D tables (i.e. only one column), you can put any logged pid for the column data.

If you want to be able to paste-with-labels that map into a tunetool table, then see post #10.
So I'm just collecting the average of each cell, and then pasting that into my table?


Let me see if I got this right.
1. Open map properties.
2. Select the PID for Desired Airflow from the dropdown, set precision to 3. (What's the parameter name? GM.IACDES_B?)
3. Column gets no selection from the dropdown, type ",Value" for label.
4. For Row, select SAE.ECT from dropdown, Paste labels from B4307.

Shawn mentions logging SAE.MAF (g/s) vs ECT at Idle. This table isn't doing that.

[WeathermanShawn]

Based on your last log, I came up with this value for your 92C entry.

Let your car sit for at least 12-18 hours. The next morning when you start it up, just log SAE.MAF (g/s) and ECT...ONLY AT IDLE!!!

Joecar described perfectly how to make the MAP. When you log it, the magic of computers will average your Idle MAF flow. Then just cut and paste those values into B4307. The values/slope should look like an 'inverted' hockey stick.

The technique is totally separate from RAFIG. You can always log a RAFIG separately or concurrently. The technique is only offered as an alternative for those who may have RAFIG values too low to successfully Idle.

[blsnelling]

Sorry, but I'm still not clear on this map. What goes in each of the three drop downs for Data, Column, and Row? I understand the values I'm trying to capture, just not clear on creating the map.

[WeathermanShawn]

Sorry, but I'm still not clear on this map. What goes in each of the three drop downs for Data, Column, and Row? I understand the values I'm trying to capture, just not clear on creating the map.

BLS:

I used the following EFILive Tutorial when I first started creating MAPS. It really walks you through faster and more clear than I could tell you..plus it is a good way to learn..

Try it out first..http://download.efilive.com/Tutorials/Interactive/How to Create a Map.htm (http://download.efilive.com/Tutorials/Interactive/How%20to%20Create%20a%20Map.htm)

[joecar]

Data = the pid that is to be pasted/multiplied/added into some tunetool table
Col = Paste Labels button (after doing copy-with-labels from same tunetool table)
Row = Paste Labels button (the same paste-with-labels info)

i.e. idea is to make the map look exactly like the tunetool table.

[joecar]

The map shows the average data when the x-bar button is clicked.

[blsnelling]

Where I was going wrong, was that I thought it was required to make a choice from the drop downs. I think I've got it ready to go now. Thanks for bearing with me. In the mean time, I did a RAFIG. I'll try again tomorrow morning with this map.

[joecar]

No worries :cheers:

[BlackGMC]

Brad:

Thanks for the feedback and the compliment.

As to why RAFIG values sometimes appear to be too low for cammed cars, and why MAF Airflow seems to work, is still unresolved in my mind ( I don't know..:grin:).

The intracity of the IAC function and how it interacts with fueling (MAF/VE) is pretty complex. I know 5.7ute and others have been studying actual case studies to understand their function more.

But I kinda fell upon that observation by happenstance. I knew fueling functions were primarily controlled by the MAF and VE, so I figured that out first. So once LTFT & STFT Trims were +/0, I just used that for my Desired Airflow.

While I would like to take credit for that 'discovery' a search of the literature shows others have figured that out also.

Thanks again, and let us know how it goes..

..Shawn..

I just dialed in my desired airflow table this weekend using the MAF, it worked great! Like mentioned i had issues with the RAFIG/RAFPN process, it always came out tooooo low. Thanks for the tip!

[WeathermanShawn]

Does look like several people have reported positive results from using MAF Airflow as their Desired Air.

Thanks again for the positive feedback!

[5.7ute]

Does look like several people have reported positive results from using MAF Airflow as their Desired Air.

Thanks again for the positive feedback!

Yep, get maf,raf & dynamic airflow to match & you shouldnt have too many issues.
FWIW I think the rafig issue is something to do with the way the pcm uses IAC effective area to calculate airflow. I dont have the necessary skills to read exactly what formula the pcm uses, so I am currently trying to work this out.
IMO what is happening is the lower pressure delta across the IAC from the cammed cars lower idle map has a few flow on effects. These being that the IAC port may be too small to allow enough air to flow through at idle,(Common with some aftermarket throttle bodies) Or quite a few more steps are needed by the IAC to get the required area. We get around this by either cracking the TB blade or drilling a hole in the TB. When this has been done the IAC effective area needs to be changed.
If you have only drilled a hole in the TB it is quite easy to get this table back in line. For example a 5mm hole in the TB will increase the effective area by 7.8sq mm.(compared to no hole) So you would shift the IAC effective area values down 4 cells.(there is 2sq mm per cell). If I fit an aftermarket TB I measure the IAC passage & compare this with stock. If it is smaller I will also calculate this difference, & once I have it idling at the right amount of steps use this value with the hole size(If drilling was needed) to calculate effective area.

[WeathermanShawn]

I have added a link (also on Idle Tips & Tricks page 1..) that illustrates various tunes for LS1's. These have the majority of Idle Parameters included! As always, I highly enocurage you to build your own custom tunes..

Enjoy:http:///forum.efilive.com/showthread.php?14661-LS1-Beginners-Tunes&p=131973&viewfull=1#post131973 (http://forum.efilive.com/showthread.php?14661-LS1-Beginners-Tunes&p=131973&viewfull=1#post131973)

[white01ss]

I had a problem in my FI/cammed/M6 car where the RPMs would hunt from 500-1200 whenever I pushed in the clutch after being in gear. Like when rolling up to a traffic light, push in the clutch, then the engine would rev up and down by itself. Once at a complete stop, it would settle down to a steady 850rpm idle.

I tried B4309-Throttle Cracker Airflow in Gear (TC) and it did absolutely nothing to solve this problem. Then I did a little experiment and got the car moving, pushed the clutch in, put the tranny in neutral and let out the clutch (still moving). Ahhh, the RPMs held at 1200 rpm with no hunting. Pushed the clutch back in and the RPMs started hunting again.

That experiment made me start looking at the B4310 Throttle Cracker Airflow in P/N table. Mine was originally set to all 0s. For grins I set the entire table to 3 g/s. Took it out for a spin and pushed in the clutch and the engine held a steady 1100 RPM or so. A little tweaking of that table to get the RPM where I wanted and reducing it a bit at the lower speeds got it transitioning real nice as the car rolls to a stop. So B4309 is only active when the clutch pedal is out, and B4310 is active when the clutch pedal is in.

Might be worth adding to the first post as M6 cars are in P/N much more that auto cars.

[WeathermanShawn]

I'll have to try that out. I guess I was under the impression in a M6 that those Tables are generally not applicable..but your experiment indicates it has more of a role than previously thought.

Probably most of us want Airflow to decrease during shifts..no one wants Rpm's to increase during the shift, but I will definitely try it out on the RoadRunner this week.

I appreciate the tip. I may have to think it out a bit, but again many thanks for sharing your experiment..:cheers:

[Sid447]

Just to add hopefully,

I used to get frustrated when manoeuvering a car at slow speed; such as in and out of a garage, or over speed bumps. As a habit had fprmed, over 14 years of BMW manual cars, of not touching the throttle and just working the clutch pedal. The Bee-Ems had a great set-up with instant response to changes in engine load at or near idle that didn't need you to keep adjustinging the accelerator to keep the engine from stalling.

Have worked at trying to achieve the same with the GM PCM's for a manual car. One of the changes tried was to adjust (raise) the timing in BSIG {B5932} right at the low-speed area where the engine would be when letting out the clutch at 0% TP.


Though still way short of the responsive nature I had from the 1980's Bosch Motronic system, five years of fiddling (sometimes going backwards, sometimes in a circle) there is a decent improvement!
:cheers:

[WeathermanShawn]

Sid, I have done the same thing at times with timing in BSIG in the same manner you are describing. I agree raising the timing in those areas allows the car to 'crawl' around better at little to no throttle.

The trick is to remember that is also the area of BSIG where general start-up and Idle also is referenced. So the timing that gives you that nice crawl is also your Idle Spark.

So, a lot is preference. On my mildly aggressive cam (10 degrees of overlap) I settle on ~26 degrees of Spark in that same BSIG you are referencing. I then tweak the TC in Gear and add a 'dash' of air at a 1000-1600 RPMS and 0-6 mph to insure it crawls in the manner you are describing.

I guess its the little things like that to help add to the comfort of your ride..:rolleyes:.

[Sid447]

Yes,

though @ zero TPS in 1st gear and when crawling (1-6 kph) the scan shows in the .24/.28g/cyl window, especially after a cold start.

Good idea on the {B4309} TC In Gear tweak (with B4311/12 at stock M6 values of 3.2 & 1.6)
Tried with this same 1.6 figure into {B0107} and 1.2 (from table B5916) entered into {B0108} but unsure if it made any difference.

Steve :cheers:

[WeathermanShawn]

I have published a LS1 Idle Tuning Tutorial in PDF Form..http://forum.efilive.com/showthread.php?14439-Idle-Tips-amp-Tricks&p=129525&viewfull=1#post129525

..WeathermanShawn..

[tinindian]

Hey Shawn - In the initial post you suggest not tweaking any of these:

1. IAC Effective Area (unless different TB size).
2. Start-Up Airflow Corrections
3. Airflow Parameter(s) that affect Idle.

Is it possible to get a list of specific parameters for #3? I'd like to check them against my tune to see if they have been adjusted before I go thru your tutorial.

Thanks.

[WeathermanShawn]

Yea, it is kinda of a generic statement. There are so many Airflow parameters under 'Trim', Start-Up', etc..I have seen a few Tunes that had dozens of Tables altered..so my general premise is to load a Tune then run an 'Alternate Calibration' of a stock tune.

Here was an example of about the most changes you should see on a LS1 cam/Idle Tune (see attachment). Thats about the maximum airflow parameters described in my Idle Tutorial and SSpdDmon's Idle Tutorial. Any more changes than that may be a case of diminishing returns. I'll add it to the Tutorial if I can think of a simple way of saying it..:).

Hope that helps.

[rpmauto]

ok, dont know why this one is kicking my butt, but I cant get it to copy/paste. I loaded the b4307 desired airflow IG/AC OFF imperial map, changed data to airflow rate from maf g/sec. And when I try to copy/paste it says it cant find any matching row/column data will not be pasted. I then changed the units in b4307 in tune tool to metric and loaded the metric map and it does the same thing. I will attach log and tune. What am I missing for units??

[joecar]

In tunetool, goto B4307, click in upperleft corner of table (where x and y axis intersect), and copy-with-labels.

Then in scantool, goto map, for each of Row and Col do Paste Labels and save map;

make sure units in map data/row/col match those in B4307.

now try again.

[rpmauto]

Joecar,
I tried that before, and again just now. If I copy at the axis it puts park/neutral in the map too. Then it will copy/paste, but only in the park/neutral column. If I just copy the IG it wont do copy paste. Do I need to log desired IAC airflow?? I tried that on my first log and it did the same thing. I assumed that using the maf g/sec data I wouldnt need IAC airflow

[WeathermanShawn]

Len, can you just open your Tune Tool and manually type in those values?

Probably fastest that way. I just did it here on my end with no problem (typed in)..

Edit: I then blended in the colder ECT's..

P.S. I had the same problem you did with cut and paste..

[rpmauto]

yea, I dont know what the problem with the cut/paste is. I can just enter the data in. It is just kinda aggravating not knowing why I couldnt get it to work. Might have to try it on another car and see what happens later.

[WeathermanShawn]

Perhaps cut and paste is looking for the matching P/N values which are not there.

Main thing is to use those MAF g/s values. That will probably give you +2 g/s over what you currently have. Seems like every cammed car wants more air then doing it solely via RAFIG. See now your VE, MAF, and Idle air will match...:)

Also blend the higher ECTS..

[joecar]

The paste-with-labels is looking for all the axis's to match up.

[5.7ute]

The paste is looking for all the axis's to match up.

I just use straight copy/paste & dont worry about copy/paste with labels. Saves all the headaches.

[joecar]

Len, do what Mick said in post #39... just make sure you line up the paste on the axis's.

[Redline Motorsports]

How do we "properly" calibrate the IAC effective area when making a change to a 90mm TB?

[white01ss]

How do we "properly" calibrate the IAC effective area when making a change to a 90mm TB?

Maybe copy or interpolate the data from a stock tune that has a 90mm? I would think the flow rate shouldn't change too much because IAC effective area has to do with the flow of the idle air circuit at various IAC motor steps not the size of the throttle body. As long as the idle air passage is the same size it should be real close to the 78mm TB data.

[tinindian]

How do we "properly" calibrate the IAC effective area when making a change to a 90mm TB?

Sorry to bring this up again, but I have the same question about IAC area with a 90 / 92mm TB. What cars / tunes would have a 90mm TB?

[Rich Z]

Sorry to bring this up again, but I have the same question about IAC area with a 90 / 92mm TB. What cars / tunes would have a 90mm TB?

I believe all the LS2, LS3 and LS7 engines in Corvettes (2005 thru 2013) have 90mm throttle bodies. Be aware that in 2009 there was a change to the TBs that seemed to affect WOT voltage signals, however. These new ones are identified by having gold or brass colored TB plates instead of silver colored ones.

[white01ss]

Are there any stock vehicles that came with a cable operated 90mm TB? I couldn't find one. They all seem to be ETC (Electronic Throttle Controled) so they don't have an IAC module or passage to use as reference. I just upgraded to a 90 FAST and left IAC Effective alone. Had to tone down the Desired Air and throttle follower to get rid of some hanging idle when hot, but other than that I really didn't have to do much.

[tinindian]

How do we "properly" calibrate the IAC effective area when making a change to a 90mm TB?

For my 92mm NW TB - I did some reading and found I had to map Desired Airflow B4307 vs. ECT and also Desired IAC Airflow (IACDES_B) vs. ECT. If the two tables don't match during warmup you need to offset the entire IAC Effective Area table B4403 up or down, re-flash & map until they do match. It took about 3 tries but I finally got it right - ended up offsetting the table B4403 down about 5 cells. My stock tune had zeros in the top 7 cells (0 thru 12 sq.mm) and now I have zeros in the top 12 cells (0 thru 22 sq.mm). I was amazed how much better the car idled and driveabilty is a little better too. I guess the PCM works better when actual airflow = calculated airflow LOL.

[SOMhaveit]

IAC effective area does not change on a cable throttle body. You use the same idle air control valve on the 90mm TB that you used on the 78mm TB. It opens the same amount for the IAC counts and allows the same amount of air in no matter the size of the throttle body. What does change is that you can get more air around the throttle body blade because it's larger. It should be all about RAFIG when you are cable-driven.

[SOMhaveit]

For my 92mm NW TB - I did some reading and found I had to map Desired Airflow B4307 vs. ECT and also Desired IAC Airflow (IACDES_B) vs. ECT. If the two tables don't match during warmup you need to offset the entire IAC Effective Area table B4403 up or down, re-flash & map until they do match. It took about 3 tries but I finally got it right - ended up offsetting the table B4403 down about 5 cells. My stock tune had zeros in the top 7 cells (0 thru 12 sq.mm) and now I have zeros in the top 12 cells (0 thru 22 sq.mm). I was amazed how much better the car idled and driveabilty is a little better too. I guess the PCM works better when actual airflow = calculated airflow LOL.

Actually, after thinking about it, this makes sense. What I have thought was correct may well be incorrect. That calibration must be taking into account some air coming either around the TB blade or the factory hole in the oem TB, so a larger TB with more air coming in around the TB blade would have more idle air entering the intake, so 0 steps on the IAC would be more square mm.

[samh_08]

How about MAF-less tunes? Any alternatives to RAFIG/RAFPN?

[Aint Skeered]

i just went for a drive and got a good data log. only surging I'm getting now is when I am going up my drive way off throttle but moving slow. my question is do I copy log then pate and multiply this in my tune or how do I apply the logged values?2206022061

[joecar]

Paste (i.e. no multiply).

[Aint Skeered]

Thanks Joe. I'll try that. It's pretty good driving now but I've learned so much lately ill keep trying things

[joecar]

Thanks Joe. I'll try that. It's pretty good driving now but I've learned so much lately ill keep trying thingsGood job :cheers:

I find I'm learning new things about this all the time.

[dian]

can someone point me to weatrhermans "idle tutorial"? for the life of me i cant find it. (iv seen sspddmons.)

[ChipsByAl]

https://forum.efilive.com/showthread.php?15236-Calc-VET-correcting-MAF-and-calculating-VE-(in-single-log)

This is his work. You can start here. There is good info in this thread.
Al

[joecar]

Al, thanks :cheers:

[jeffro]

Just want to chime in here and add 2c, hope it helps someone else.

Iv been scratching my head for the last 3 weeks desperately trying to idle tune my 6L with 92mm cable throttle running the LSA TVS 1900 blower with the LS1b pcm. After following the idle tips and tricks tutorial and hacking multiple tunes I still wasn't getting any results. No matter how much I hacked my idle settings mentioned in the tutorial or how many times I performed RAFIG nothing had any direct influence on my idle tune quality and it would stall frequently. That was until I modified my IAC effective area (B4403). If you change your TB or IAC motor from stock nothing seems to work correctly if your IAC effective area is not close. Maybe this is mentioned somewhere but I seemed to have overlooked it.

Great forum, thanks for the info and contributors!

[statesman]

If you change your TB or IAC motor from stock nothing seems to work correctly if your IAC effective area is not close. Maybe this is mentioned somewhere but I seemed to have overlooked it.

It was mentioned somewhere in this forum, and there also has been talk about it in other tuning forums... but any talk about it has always been somewhat vague. I remember reading comments like "you need to line up all your airflows" and "you need to shift your IAC effective area table", but I can't remember anyone posting an actual method.

[Supercharged111]

Well this explains why the RAFIG didn't work for me, it spit out lower than stock numbers the last time I tried it. Going to try this once I fix the fire hazard fuel leak. Can someone clarify why effective IAC area matters on a cable throttle when you go up in size? I did bump the 3500 up to an 85mm TB and it idles all over, but I'm pretty sure that's just because I haven't touched the idle from the mishmash crap I dropped in there in the first place. If you put the stock IAC back into any TB is really shouldn't matter, right? I realize the larger blade may flow more at idle, but then again its bypass hole might be smaller too (haven't checked). I can totally understand why a drive by wire car would be affected by this. Or is the effective IAC area only applicable to DBW cars?

[joecar]

The new TB has different cross-section area on its IAC passage...

[Supercharged111]

So you're saying the pintle may seat differently in that passage? I.E. if the passage is smaller the pintle doesn't seat as deeply and thus must open farther to provide the same airflow as a larger hole in which the pintle would seat more deeply? I guess I assumed they'd take that into account when designing a TB for that particular IAC.

[joecar]

The passage 'size' is different, and how the pintle 'seats' is different...

also note that some IAC passages are airflow limited (you have to drill them larger).

[Supercharged111]

Hmm, seems like one could nerd out by simply measuring said passage assuming one had a tool to fit said passage (depending on angles and whatnot). ASSuming the entrance to said passage wasn't also flow limited, right?

[joecar]

You could, and then you would be close, would need just minor tweaking.