Fighting Rough Idle

[edcmat-l1]

Doesn't matter what you do for tuning, it'll always have a noticeable rough idle with that cam. You can't toon away overlap. There are things you can do to make it smoothER, but it'll never be smooth. You want smooth, put a stock camshaft back in it.

[cessnageek]

Agreed that it will idle rougher. However, between being lean at idle and the sound of the exhaust, it seems like something is wrong. I've attached a link to a video of the exhaust sound. Couldn't think of a better way to do it than upload to youtube. You hear it "puff" a lot, which I think corresponds to when it shakes the worst. You also hear it clean up occasionally and sound nice. I don't know, maybe that's fine. Tell me if I'm getting worked up over nothing.

https://youtube.com/shorts/_YUklBUuRyc?feature=share

I don't know why it turned the video into a short, but there it is.

[cessnageek]

So, did a bunch of checking mechanical things. Plugs, swapped the new wires for the old ones, smoked the intake, compression test, even new O2 sensors. Probably other things I'm forgetting. The truck is fine mechanically as best I can tell.

So - must be a tuning thing. My narrowbands don't really cycle at idle much. They pretty much stay lean and occasionally cycle rich for a short period. I'm assuming this is because of the overlap - fine.

Started digging into other stuff. Decided to try tuning EOIT. Well, now the lack of cam specs are biting me and speculating sucks. So I called BTR, and got 263.5/275.5 at 0.006". Great. Unfortunately, I didn't ask what the advance is. So I should call again and get that info too, but haven't had a chance.

Just for the time being, I'm assuming 0 advance, just to see what happens.

Intake Open: 24.75 BTDC
Intake Close: 58.75 ABDC

Exhaust Open: 64.75 BBDC
Exhaust Close: 30.75 ATDC.

If I do my math right, and with the injector timing in the tunes I've posted previously, if I keep Normal ECT, Normal RPM, Makeup ECT, and Makeup RPM the same, I get my EOIT boundary at ~555 deg at idle, with a few degrees fudge factor. This should delay start of injection until the exhaust valve is closed. Stock is 520 deg at idle. The truck seems to like this, and runs better. The chop is more consistent and has the random shaking and weird exhaust note less.

My question - am I way out off what a more experienced tuner would expect on my EOIT boundary if I move it from 520 to 555 in my idle cells? Do I need to be worrying about washing cylinder walls at this point? If I want/need to go higher, when do I start having to worry about washing the cylinder walls?

Thanks!

[Cringer]

So, did a bunch of checking mechanical things. Plugs, swapped the new wires for the old ones, smoked the intake, compression test, even new O2 sensors. Probably other things I'm forgetting. The truck is fine mechanically as best I can tell.

So - must be a tuning thing. My narrowbands don't really cycle at idle much. They pretty much stay lean and occasionally cycle rich for a short period. I'm assuming this is because of the overlap - fine.

Started digging into other stuff. Decided to try tuning EOIT. Well, now the lack of cam specs are biting me and speculating sucks. So I called BTR, and got 263.5/275.5 at 0.006". Great. Unfortunately, I didn't ask what the advance is. So I should call again and get that info too, but haven't had a chance.

Just for the time being, I'm assuming 0 advance, just to see what happens.

Intake Open: 24.75 BTDC
Intake Close: 58.75 ABDC

Exhaust Open: 64.75 BBDC
Exhaust Close: 30.75 ATDC.

If I do my math right, and with the injector timing in the tunes I've posted previously, if I keep Normal ECT, Normal RPM, Makeup ECT, and Makeup RPM the same, I get my EOIT boundary at ~555 deg at idle, with a few degrees fudge factor. This should delay start of injection until the exhaust valve is closed. Stock is 520 deg at idle. The truck seems to like this, and runs better. The chop is more consistent and has the random shaking and weird exhaust note less.

My question - am I way out off what a more experienced tuner would expect on my EOIT boundary if I move it from 520 to 555 in my idle cells? Do I need to be worrying about washing cylinder walls at this point? If I want/need to go higher, when do I start having to worry about washing the cylinder walls?

Thanks!

Use the last tune I sent. It has some changes you cannot see for fueling on the current HPT software version and EOIT settings that will work well for your cam. If your cam numbers are correct, EVC is 391* and the last tune I sent SOI is 410*. However, EOI should not be playing a role here.

The O2 oscillations are handled by a PI controller. Here is everything you need to know here: https://youtu.be/5hjzI8wSItk

I tuned a car recently with a similar cam...here are the PI settings that seemed to work well. You can try this as a starting point.
08232024_Idle_After_Brake_Booster_Replacement_3_VE_ONLY_3 - PI oscillation changes - cringer.hpt

[cessnageek]

Out of curiosity, what kind of changes that I can't see? Is there a way I can see them?

[Cringer]

Out of curiosity, what kind of changes that I can't see? Is there a way I can see them?

You have to use HPT version 4.8.7.

[cessnageek]

Does it still write the changes if I'm not on that version?

[Cringer]

Yes

[cessnageek]

Sounds good. Might see if I can rustle up an installer for that version. Would be curious to see what is different. Thanks!

[dassaur]

Sounds good. Might see if I can rustle up an installer for that version. Would be curious to see what is different. Thanks!

Be aware if you have an MPVI3 you wont be able to use 4.8.7 to save or write as it requires >5 (though you can still see the changes, just cant save in it unless you link an MPVI2

[Cringer]

Be aware if you have an MPVI3 you wont be able to use 4.8.7 to save or write as it requires >5 (though you can still see the changes, just cant save in it unless you link an MPVI2

I have an MVPI2+ and I cannot use 4.8.7 to flash the tune (I have not tried to read with it though). I use 4.8.7 to edit the .HPT file for specific things and 5.0.4 to do everything else and for flashing the tune.

[dassaur]

Yes but you can save it. Mpvi3 users cant