Who here is using PE on E38 PCM to disable closed loop idle with large Cams?

[Allen Vos]

How many of you guys are turning on PE at idle to force open loop on a large cammed engine to keep it from over fueling and drowning itself?

How are you guys doing this?

I have an LS3 with a TSP Stage 2 Cam 229/244 .629"/615? 112 LSA, 109 ICL

I have long tube headers with an off road x pipe and rear O2's deleted and turned off.

I am using both MAF and VVE tables for tuning.

I have got the car fired up and running fine with a very stable idle at 800 rpm


However you can literally watch the fuel trims go positive and continue to add fuel making it terribly eye burning rich and if left to idle long enough will load up and misfire.

So I would like to run this thing in open loop up to around 1000 rpm and then have closed loop take over for normal driving.

Is there any other options to do this or is PE the only way to force open loop at idle?

[GHuggins]

Dial in the injection timing and the O2 settings. Open loop idle can be done really easily via PE enable and pedal settings, but the base settings need to be fixed regardless so why not fix the base settings and leave it in closed loop?

[Allen Vos]

Dial in the injection timing and the O2 settings. Open loop idle can be done really easily via PE enable and pedal settings, but the base settings need to be fixed regardless so why not fix the base settings and leave it in closed loop?

Its my understanding that the overlap of the camshaft causes the oxygen sensors to read lean and therefore commands more fuel making it excessively rich.

Pardon my ignorance but if there is a way around this I am all ears.

I cant seem to find anything if much at all on this subject.

Is there any guides that you know of that could help me understand and change this?

[LS ROB]

If trims go positive, it isn't rich; it's going lean. I'd do as Greg suggests and get the injection timing & O2 settings dialed in a little closer then tune it for closed loop.

Also, post your tune and a log for the most help.

[GHuggins]

Its my understanding that the overlap of the camshaft causes the oxygen sensors to read lean and therefore commands more fuel making it excessively rich.

Pardon my ignorance but if there is a way around this I am all ears.

I cant seem to find anything if much at all on this subject.

Is there any guides that you know of that could help me understand and change this?

Gave a basic write up here.

https://forum.hptuners.com/showthrea...each-commanded

Use 40 as the plus and minus shifts for testing. You also need to make sure you don't have exhaust or intake leaks. Fueling shouldn't be shifting.

[Allen Vos]

If trims go positive, it isn't rich; it's going lean. I'd do as Greg suggests and get the injection timing & O2 settings dialed in a little closer then tune it for closed loop.

Also, post your tune and a log for the most help.

If the trims go positive it wants to add more fuel because its reading lean. Yes I got that. Now did you catch the part where the cam overlap is causing a False lean condition causing it to over fuel?

In my eyes I don't see how one could tune the idle with a false AF reading.

Is'nt this why guys put their car into Open loop to avoid this?

If you have a guide please post a link to it.

[LS ROB]

If the trims go positive it wants to add more fuel because its reading lean. Yes I got that. Now did you catch the part where the cam overlap is causing a False lean condition causing it to over fuel?

In my eyes I don't see how one could tune the idle with a false AF reading.

Is'nt this why guys put their car into Open loop to avoid this?

If you have a guide please post a link to it.

What does your trims say @ idle? What does your wideband read @ idle? Going purely on my experience and not what i have read or heard, but if you have tears in your eyes from exhaust, then it's more than likely lean. Does the car smoke @ idle? Is it black smoke?

[Allen Vos]

What does your trims say @ idle? What does your wideband read @ idle? Going purely on my experience and not what i have read or heard, but if you have tears in your eyes from exhaust, then it's more than likely lean. Does the car smoke @ idle? Is it black smoke?

OK, so I must confess here I just recently got the car up and running and I do not yet have a wideband on the car for tuning.

I have some time here before spring up here in Canada so It will be 2-3 months yet before I can take this thing on the road and tune it.

Right now I am trying to just get it up and running so I can idle it and move it around a bit.

There is no black smoke or smoke of any kind coming out the exhaust, however its bringing tears to my eyes and gets worse the longer it idles.

LTFT's are around 6-7% so its defintley adding fuel.

I have not changed the MAF curve or the VVE table yet. I had planned on doing that once I get the wideband in there come spring time but would love to get a clean stable idle out of it without having the O2's correct it.

I checked out the link that Ghuggins provided and noticed you have a very similar setup to mine?

Were you able to get your to idle well without loading up and how did you do it?


I have a very good understanding on basic tuning but learning a lot about the E38 ECM and at times find it a bit overwhelming but Im sure I will get there soon

I started out with a bone stock tune on the 09 vette LS3 and have made the necessary changes to have it fire up and idle successfully during cold and hot starts.
and a few other tweaks

[Cringer]

First, you need to dial in your EOIT.
https://youtu.be/Td6oC9CIUas

Then, you will need to dial in your O2 settings, specifically for the O2 voltage switch points ([ECM] 12530 and [ECM] 12531) for your idle mode profile. Hint you will want to lower the voltage.
https://youtu.be/5hjzI8wSItk

These will help fight the cam overlap false lean situation.

[LS ROB]

My idle is very stable. In fact I could lower it down to 650rpm if I wished to do so. It sounds like crap but it will idle there. Can't really offer sound advice other than what has been stated because there is no tune nor log to go off of. BUT going off of what you say, i'd throw 7% more fuel at it @ idle. You are correct in stating that there is a steep learning curve on calibrating, but with the guidance and help of Greg and a few others on here, I can now listen in confidently when the "Men" start such discussions. LOL

[Allen Vos]

My idle is very stable. In fact I could lower it down to 650rpm if I wished to do so. It sounds like crap but it will idle there. Can't really offer sound advice other than what has been stated because there is no tune nor log to go off of. BUT going off of what you say, i'd throw 7% more fuel at it @ idle. You are correct in stating that there is a steep learning curve on calibrating, but with the guidance and help of Greg and a few others on here, I can now listen in confidently when the "Men" start such discussions. LOL

650 RPM is low for that cam, I have mine at 800 and thought maybe I could knock it down another 50-100 RPM.

I Watched that youtube video on EOIT and was wondering how you got your Exhaust valve closing degrees?

I checked my cam card and it only gives those values at .050" lift.

Apparently it needs them at .006" or as close to zero as possible.

I am going to get a wideband in there before I start messing around with it a whole lot more.

Would you care to share your tune with me considering we are pretty close on setups?

Not looking to copy or hijack your tune but it would help me understand things a bit better

[Allen Vos]

First, you need to dial in your EOIT.
https://youtu.be/Td6oC9CIUas

Then, you will need to dial in your O2 settings, specifically for the O2 voltage switch points ([ECM] 12530 and [ECM] 12531) for your idle mode profile. Hint you will want to lower the voltage.
https://youtu.be/5hjzI8wSItk

These will help fight the cam overlap false lean situation.

Thank you kind sir. It would appear I have more to learn lol

I would rather get it working so it can read the A/F at idle and not have to run in open loop where I have no control over the idle A/F

I know I need to tune with a wideband but can you run the wideband on the E38 PCM for error correction or do you have to use the narrow bands?

Keep in mind I only have the front O2's now

[Cringer]

Thank you kind sir. It would appear I have more to learn lol

I would rather get it working so it can read the A/F at idle and not have to run in open loop where I have no control over the idle A/F

I know I need to tune with a wideband but can you run the wideband on the E38 PCM for error correction or do you have to use the narrow bands?

Keep in mind I only have the front O2's now

The E38 can only use the narrowbands. When you get your wideband that is something you have to use to incorporate into the tune you work up.

As a starting point for .006" lift you can use the .050" lift values by adding 25* to each valve opening and closing event. So as an example, if the valve opens 20* BTDC, you would use 45* BTDC. And if that same valve closes 50* ABDC you would use 75* ABDC. This is a ballpark guess and some tweaking will be needed. The other option is to degree the cam to manually get the valve events.

[LS ROB]

650 RPM is low for that cam, I have mine at 800 and thought maybe I could knock it down another 50-100 RPM. That is too low, just giving you an idea of how stable the idle is. I idle @800 rpm.

I Watched that youtube video on EOIT and was wondering how you got your Exhaust valve closing degrees?

I checked my cam card and it only gives those values at .050" lift.

Apparently it needs them at .006" or as close to zero as possible. I had to contact TSP for those specs.

I am going to get a wideband in there before I start messing around with it a whole lot more.

Would you care to share your tune with me considering we are pretty close on setups? I don't mind sharing the tune at all. It's pretty much plastered all over the place. However, not so sure it will help you much as I have an LS7 and you said yours was LS3.

Not looking to copy or hijack your tune but it would help me understand things a bit better

[Allen Vos]

The E38 can only use the narrowbands. When you get your wideband that is something you have to use to incorporate into the tune you work up.

As a starting point for .006" lift you can use the .050" lift values by adding 25* to each valve opening and closing event. So as an example, if the valve opens 20* BTDC, you would use 45* BTDC. And if that same valve closes 50* ABDC you would use 75* ABDC. This is a ballpark guess and some tweaking will be needed. The other option is to degree the cam to manually get the valve events.

Ok cool, I was wondering if the stock PCM could utilize a wideband for error correction. I am not sure if you have heard of a stand alone system called Megasquirt?

I tuned with it on a 9 second turbo mustang I had 15 years ago and it would let you use a wideband for error correction.

Thank you for the advice on figuring out the valve events. I am going to contact TSP for that information as LS ROB had suggested. I'm still going to figure it out the way you suggested just to see how close it would have gotten me to the actual valve events.

[Allen Vos]

Ok great, I think I will just call TSP for those specs as well.

Ok , I didnt realize you had an LS7, however your cam specs are fairly close to mine and yes I know it would not be the same tune but I would be very curious to have a look at your tune and see how you tackled all the settings that I am about to get into. It would help me learn quicker if anything.

Im going to figure out how to upload my tune here so you guys can take a look at it.

Its far from perfect and definetly needs work but I'm always up for some constructive criticism lol

[Allen Vos]

Attachment 141306

Here is my Starting tune.

I have only gotten into the idle/timing settings on this. I have not touched any fueling yet as I am waiting until I get a wideband in the car.

I was hoping to be able to tweak the A/F ratio at idle without a wideband to at least get it running better.

I am going to change the SOIT and EOIT once I get my valve events figured out and try my best to tweak the O2 sensor settings for the idle.

Hopefully this will stop the fuel trims from dumping even more fuel in and drowning itself lol

One thing I did do I changed the tune for the Drive by wire throttle body so it was a little more aggressive than stock. I was able to do this and notice quite a difference in throttle response and was able to push the limits without setting the car into Reduced power mode.

For reference I am using a TSP stage 2 NA cam 229/244 @ .050" and 629/615 lift with a 112 degrees of separation.

[edcmat-l1]

Open loop idle tuning was something we did way back in the day primarily in C5s with very specific return to idle issues. It's never been a thing in the E38s.

EOIT will help the smell some, but it's always going to stink. Especially if you're catless.

[LS ROB]

Attachment 141306

Here is my Starting tune.

I have only gotten into the idle/timing settings on this. I have not touched any fueling yet as I am waiting until I get a wideband in the car.

I was hoping to be able to tweak the A/F ratio at idle without a wideband to at least get it running better.

I am going to change the SOIT and EOIT once I get my valve events figured out and try my best to tweak the O2 sensor settings for the idle.

Hopefully this will stop the fuel trims from dumping even more fuel in and drowning itself lol

One thing I did do I changed the tune for the Drive by wire throttle body so it was a little more aggressive than stock. I was able to do this and notice quite a difference in throttle response and was able to push the limits without setting the car into Reduced power mode.

For reference I am using a TSP stage 2 NA cam 229/244 @ .050" and 629/615 lift with a 112 degrees of separation.

You can use the fuel trims to make fueling adjustments for low to mid load areas, so you don't have to wait on your wideband. A wideband is needed for WOT tuning though. I honestly feel that you need to give it what the trims say it needs. Worst case scenario, you can change it back to the way you have it now. If you have an idle log, post it up so you can get more help.

Oh, does the throttle seem to hang if you blip it?

[STAGEUP]

If fuel trims are adding fuel to the point where the engine starts to misfire, then that may be an indication of your primary o2 sensors not reading correctly, or not reading at all. Verify your primary o2s are operating correctly.

Hint: Typically, an o2 value of 400-450mv at idle means there is no voltage going to the o2 sensor.