Having issues returning to idle.

[WS6HUMMER]

Wow this thread has gotten some very good advice added, thanks everyone for the contributions!

[mowton]

Was having similar issues with idle at one time. I followed this procedure exactly and it was unbelievable how well it worked. Not saying it is the only, or best way, but definitely works and its easy to follow step by step...
Full credit to 5_Liter_Eater for the work putting it together.

http://www.hptuners.com/forum/showth...103#post136103

And I agree it is a great procedure for E40 PCM's, the E38 has a different set of control parameters. I have never tried to mix the 2. I Have used Bills procedure as well on E40 setups. The similarities to the 2 procedures is the use of the Idle adaptive spark values to develop you error correction. In Bills he logs the spark values and uses them as correction data. The idea is the closer you get the airmodel to ruight, the less the spark will have to fight to maintain the desired idle rpm.

In the above, it is done "by eye" as you make the TB blade adjustments for max and then the Min Idle air for the min done by return to idle with a blip and then the proportional and integral to manage in between.

The E40 parameters do have a Max (effective area) which is equal to the TB total area and a Min, which I assume is the absolute lowest effective are you could command, but isnt that in conflict with the Base Running Airflow?



Ed M

[realcanuk]

And I agree it is a great procedure for E40 PCM's, the E38 has a different set of control parameters. I have never tried to mix the 2. I Have used Bills procedure as well on E40 setups. The similarities to the 2 procedures is the use of the Idle adaptive spark values to develop you error correction. In Bills he logs the spark values and uses them as correction data. The idea is the closer you get the airmodel to ruight, the less the spark will have to fight to maintain the desired idle rpm.

In the above, it is done "by eye" as you make the TB blade adjustments for max and then the Min Idle air for the min done by return to idle with a blip and then the proportional and integral to manage in between.

The E40 parameters do have a Max (effective area) which is equal to the TB total area and a Min, which I assume is the absolute lowest effective are you could command, but isnt that in conflict with the Base Running Airflow?



Ed M

Ed...

I only tune my own car and obviously have no where near your experience. I have never tuned an E40. I followed the procedure step by step on my E38 and quickly got it to idle as good as stock.

[mowton]

Ed...

I only tune my own car and obviously have no where near your experience. I have never tuned an E40. I followed the procedure step by step on my E38 and quickly got it to idle as good as stock.

Here's to Joel and Simon on a great thread with a great procedure they developed...gotta love the forums

Ed M

[schpenxel]

I've learned I have a lot to learn on idle tuning between seeing Ed's method and the other thread about how the integral/proportional idle adjustments work.. One of these days I'll sit down and read it all

[GHuggins]

It may just be me, but I've never had any luck at all with maxing out the min airflow table and zeroing out integral and proportional to set the % max and % max brake settings of the TB. I always get way too small of numbers and wind up having to add something like "1 or more" back to the numbers I came up with to fix the cold start and idle dipping issues created by lowering them. Is there a better or even possibly another way at all together to get these numbers? This way does seem to get something plausible for the min air value for the min air idle table, but that's all it seems to do for me...

[mowton]

It may just be me, but I've never had any luck at all with maxing out the min airflow table and zeroing out integral and proportional to set the % max and % max brake settings of the TB. I always get way too small of numbers and wind up having to add something like "1 or more" back to the numbers I came up with to fix the cold start and idle dipping issues created by lowering them. Is there a better or even possibly another way at all together to get these numbers? This way does seem to get something plausible for the min air value for the min air idle table, but that's all it seems to do for me...

Hey Greg, Hope all is well. How did you make out with that shop car project from way back in September? Man can't believe how time flies.....

Not sure about why you need to add so much when done but the key to me is to get all the engine/trans loads to their max as well as functions like idle rpm (at or above the coldest cell), AC on HI, Fans on 100%, if an auto, in gear and on the brake (the extra idle rpm would also put a bit of TC load and even turning the steering wheel all the way (:-) just to get the maximum torque/load for each scenario.

I am open to any better way to go because sometimes these Gen IVs just fall into idle/return to idle and some times they just don't want to cooperate...

Have a good evening and weekend

Ed M

[GHuggins]

Going to be taking a different all around approach to the shop car... Right now it's on the back burner once again and doesn't look like I'll be able to get back to it for another month or so?

This is how I've started setting the %max and %max brake. Most likely not right, but if I do it how it's written up on the EFI forum I have to almost double the min air table from what "I" think it should be - It will wind up way up in the teens... It's even been mentioned under Mike's post that he had to use really high min air values following the procedure... SO basically I start by first setting the ETC Scaler to what it should roughly be - if not a touch under... At the same time I'll set the proportional and integral tables to a "stock" setting from an OE calibration closely resembling the current engine displacement of what ever I'm working on, such as if it's a 416 build - I use the newest 427 OE settings... After this I "guesstimate" the min air values based on cam and so on additions used, then dial in the MAF and VE table at least through 2000rpms... After this if I haven't all ready gotten the g/s reading, I'll fire the motor up and get the g/s reading from the MAF at the "hot running idle rpm"... I then enter this into the min air table up through 800 rpms and increase slightly from there. At this point I use the bi-directional controls of the scanner to force the engine 100 rpms below commanded. If I can't go that low - I lower the % settings. Same goes for if it goes too low - I raise the settings... Then I use the min air to "dial" things in a little better if need be.

Anyway most likely wrong, but that's how I try to do it...

[Quicksand Jesus]

The E38 idle tuning is a bit different than Gen III. Through the years I have read and experimented and this seems to have been the best way at least I can do it.

The Percent Max tables set the maximum the throttle blade will open in a stationary (brake) and rolling situation. You can isolate all the other controls by setting the Airflow Final Minimum to say all 64 g/sec and zeroing out the Proportional and Integral Airflow tables.

To set the max open in 2 scenarios....1) Stationary -- in gear, on the brake, idle higher than normal, AC/Fans ON etc. You monitor the timing and adjust the percentage up or down so your timing is "hovering" right around your desired Idle RPM (Over/Underspeed isn't being called into duty). Once you have that set, add about .2% to compensate for a cold start. 2) rolling is done the same way but in a coast down mode.

Now we bring the Airflow Final Minimum back and we pick a value based on the size of the cam....with a mid/large cam I usually start with say 14 g/sec. Populate the entire table with this value. The Proportional table can be repopulated with the stock values, but usually is too aggressive for a larger cam. Cut the stock vales in half to start. The Integral table is handled the same with an extra step at the end. Once you have cut it in half, interpolate from the 0 to the 512 rpm value and again from the 0 to the -512 RPM Integral. The process for tuning the Airflow Final Minimum Airflow table is to blip the throttle. How the rpms return to idle is the trick. If the return is quick and sagging or even stalling, then increase the table. If the return hangs or slowly (5-10 secs) returns then reduce the values. Once you have the blips responding well, add about 7-8 g/sec to the 6000, 7000 and 8000 rpm columns Interpolate from 1200 to 6000 rpm columns.

The last test is to disable the adaptive idle over/underspeed correction (can do this through the VCM Control) and see how stable the idle is. If hunting or surging occurs, adjust the Integral and or Proportional tables. Remember the Proportional will correct for instantaneous rpm errors and can cause instability if too tight. The Integral is more of an averaging contributor and can be attributed to rolling/wavy idle response. Once you have the idle airflow mode as good as you can get, bring back in the Over/Underspeed. You may have to "dumb down" their effects if you have a large enough cam. Don't want to be fighting the natural lope of the cam....causes instability as well.

Idle tuning can be very frustrating but think about what each of the control mechanisms, what they do and what effect they have on the control of idle. The E38 Idle is based on establishing a max and min blade opening and having the Proportional/Integral air controls manage the idle in between. Hope this helps....

Ed M

I just wanted to reply and tell you thanks for this information. It's VERY helpful when someone takes the time to explain exactly how these tables work. I used your technique to dial in a C6 with a monster intake manifold and TB yesterday and it worked flawlessly!

[mowton]

I just wanted to reply and tell you thanks for this information. It's VERY helpful when someone takes the time to explain exactly how these tables work. I used your technique to dial in a C6 with a monster intake manifold and TB yesterday and it worked flawlessly!

My pleasure, I have spent a lot of time researching and experimenting in idle tuning as it to me is the heart of a good driving tune....glad the info helped....

Ed M