Idle Airflow w/ and w/o clutch engaged

[phuz]

I've noticed something a bit more with the cooler mornings lately, and that's when the engine is still below operating temp and I push the clutch, the RPMs will hang around 1500. If I go to neutral and let off the clutch, they will settle to around 900rpm.
I would think that airflow would be coming from the Idle -> Airflow -> Throttle Cracker -> Airflow table, but why the change with clutch engaged/disengaged?

Also, for point of clarification on a manual transmission, I'm assuming it's always using the "In Gear" or "In Drive" tables and the Park/Neutral tables are always ignored?

[Jay@HAP]

Are you moving or stopped when this happens.

Have you logged your STIT and LTIT(if you have them enabled)

A log, tune and a list of mods would be helpful.

My crystal ball is out for repair at the moment.

[edcmat-l1]

Are you moving or stopped when this happens.

Have you logged your STIT and LTIT(if you have them enabled)

A log, tune and a list of mods would be helpful.

My crystal ball is out for repair at the moment.

Here you can borrow mine.

[Alvin]

I've noticed something a bit more with the cooler mornings lately, and that's when the engine is still below operating temp and I push the clutch, the RPMs will hang around 1500. If I go to neutral and let off the clutch, they will settle to around 900rpm.
I would think that airflow would be coming from the Idle -> Airflow -> Throttle Cracker -> Airflow table, but why the change with clutch engaged/disengaged?

Also, for point of clarification on a manual transmission, I'm assuming it's always using the "In Gear" or "In Drive" tables and the Park/Neutral tables are always ignored?

Airflow is a rough way to control idle. You want enough airflow.. beyond that areas like this can be easier to control with timing. Gen 4 is really good at this.. If you look at / watch how it works it's easy to apply to GEN 3

[phuz]

Based on your snarky response, I'm guessing there's nothing obvious that comes to mind.

Attached are current tune and a fresh log. Strangely, I was able to get the hanging idle just sitting still and free-revving a few times. Even more strange, it only did this a handful of times and then the idle would fall as normal.
Look around the 2:16 mark and forward.
Blended.hpt
23-10-09 14-20-06.hpl

[edcmat-l1]

Based on your snarky response, I'm guessing there's nothing obvious that comes to mind.

Yes, there's several obvious things that come to mind. But without knowing what you're tuning, what the tune looks like, and what it's doing, not a verbal description, it's a waste of time throwing crap against the wall to see what sticks.

It gets frustrating people continuously posting, asking for help, with only a verbal description of a problem, and most of the time no description of the vehicle, mods, etc., no tune file attached, and no data log. Hence the crystal ball.

Attached are current tune and a fresh log. Strangely, I was able to get the hanging idle just sitting still and free-revving a few times. Even more strange, it only did this a handful of times and then the idle would fall as normal.
Look around the 2:16 mark and forward.
Blended.hpt
23-10-09 14-20-06.hpl

OK, now that we're this far, what are we tuning? The car in your sig?

[edcmat-l1]

OK, let's have a clinic on what we can tell from a tune and data log.

I could have replied to your original post with "It's in the idle airflow tables" when technically it is, but here's the thing. There's so much more going on in your tune that has manifested in higher than needed airflow numbers and the condition you're describing.

First thing is the injector data is not right. You don't have any low-speed control of your injectors. Forget what your wideband says, look at your narrow bands.

The screen shot attached is the area you should focus on. If you drag your cursor along the line graph starting at 2:15 basically to the end you'll notice your narrowbands are stuck at 900 mv approximately, and your trims are barely moving off zero. If you had complete control over your injectors at idle speed, the narrowbands would toggle below 450 mv to above 450 mv and back again. They don't even get close to dipping TO 450 mv. Ideally it would be able to pull the narrowbands down to 100 mv and then back to 800+ mv without huge swings in the trim numbers.

If you watch your injector pulse width, it stops at roughly 1.6 ms as the lowest I saw. It hovers around 1.6-1.8. That's not nearly low enough for the injectors you have, and I don't even know what they are.

OK, through the same time period, the STITs are pulling as much as -2.8 g/sec. THAT is your idle hang. The BRAF table is too high. But the reason it's too high is because you need ALOT of "dashpot" action because if you didn't, if it was tuned closer to coming back directly to idle, it would stall because it's over-fueling at idle because the injectors aren't setup properly.

[phuz]

Thanks for taking the time to look at the files.
Injectors are 60# Siemens and the fuel data came directly from FIC and Bill @ Second Street Speed (well respected man in the tuning community), so if anyone were to know the injector data, I would say it would be these individuals.

Minimum injector pulse is 0.8ms (and dead time for idle voltage / MAP is about 0.5ms) and AFRs are great. Why would we ignore wideband and solely rely on narrowband?
And if you think it's actually over-fueling at idle, then I would assume the first logical step is to reduce the VE in the idle region. Would you agree?

[edcmat-l1]

Thanks for taking the time to look at the files.
Injectors are 60# Siemens and the fuel data came directly from FIC and Bill @ Second Street Speed (well respected man in the tuning community), so if anyone were to know the injector data, I would say it would be these individuals.

Minimum injector pulse is 0.8ms (and dead time for idle voltage / MAP is about 0.5ms) and AFRs are great. Why would we ignore wideband and solely rely on narrowband?
And if you think it's actually over-fueling at idle, then I would assume the first logical step is to reduce the VE in the idle region. Would you agree?

I don't care where the numbers come from, or who plugged them in. They're wrong and/or incomplete. I'll drop that nugget.

No, it's not as simple as pulling from the VE. If that were the case, you'd have abnormally low trims numbers to get it to target. The way the injectors are setup, that's not possible. That's why they're stuck at 900 mv and the trims are barely moving. No injector control.

The way it's setup now, you can pull 10%, 20% from the VE and you'll have the same narrowband reading and the same IPW. It's not going any lower until you fix why it's not.

[Alvin]

OK, let's have a clinic on what we can tell from a tune and data log.

I could have replied to your original post with "It's in the idle airflow tables" when technically it is, but here's the thing. There's so much more going on in your tune that has manifested in higher than needed airflow numbers and the condition you're describing.

First thing is the injector data is not right. You don't have any low-speed control of your injectors. Forget what your wideband says, look at your narrow bands.

The screen shot attached is the area you should focus on. If you drag your cursor along the line graph starting at 2:15 basically to the end you'll notice your narrowbands are stuck at 900 mv approximately, and your trims are barely moving off zero. If you had complete control over your injectors at idle speed, the narrowbands would toggle below 450 mv to above 450 mv and back again. They don't even get close to dipping TO 450 mv. Ideally it would be able to pull the narrowbands down to 100 mv and then back to 800+ mv without huge swings in the trim numbers.

If you watch your injector pulse width, it stops at roughly 1.6 ms as the lowest I saw. It hovers around 1.6-1.8. That's not nearly low enough for the injectors you have, and I don't even know what they are.

OK, through the same time period, the STITs are pulling as much as -2.8 g/sec. THAT is your idle hang. The BRAF table is too high. But the reason it's too high is because you need ALOT of "dashpot" action because if you didn't, if it was tuned closer to coming back directly to idle, it would stall because it's over-fueling at idle because the injectors aren't setup properly.

Yes.. Also closed throttle timing is way to high.

[edcmat-l1]

If you had control of the injectors at idle your narrowbands would look like this.

[phuz]

I'm not sure why you are trusting the narrowband as gold and ignoring the wideband (yes I agree the mV are high) when my AFR is perfectly hanging around 14.5-15 and idling smooth, at 1.95ms. My WB sensor is brand new & calibrated and matches the numbers from the dyno's wideband, so I trust these numbers. What injector data are you saying is wrong, specifically? My minimum pulse is 0.8ms so if it needed to drop that low, it certainly could.

[edcmat-l1]

Yes.. Also closed throttle timing is way to high.

And the idle overspeed is basically ineffective.

[edcmat-l1]

I'm not sure why you are trusting the narrowband as gold and ignoring the wideband (yes I agree the mV are high) when my AFR is perfectly hanging around 14.5-15 and idling smooth, at 1.95ms. My WB sensor is brand new & calibrated and matches the numbers from the dyno's wideband, so I trust these numbers. What injector data are you saying is wrong, specifically? My minimum pulse is 0.8ms so if it needed to drop that low, it certainly could.

I trust what the narrowbands are telling me before I'd ever ignore them and trust your wideband. You PCM could care less what your wideband has to say. Especially at idle in closed loop. The narrowbands are telling me way more than the wideband is.

If you can't toggle your narrowbands from low to high you have no idle control of you injectors. Period, end of story. All of the evidence is there in your data log.

It's not just what the narrowbands are doing. It's the interrelationship between the narrowbands, the fuel trims and the injector pulse width.

[phuz]

I trust what the narrowbands are telling me before I'd ever ignore them and trust your wideband. You PCM could care less what your wideband has to say.

I'm telling you if you can't toggle your narrowbands from low to high you have no idle control of you injectors. Period, end of story. All of the evidence is there in your data log.

So again, what specifically looks wrong in the injector data that is "preventing" injector control at that point? (Yes, I'm aware the PCM cannot see the wideband)

[edcmat-l1]

So again, what specifically looks wrong in the injector data that is "preventing" injector control at that point? (Yes, I'm aware the PCM cannot see the wideband)

I'm not telling you how to tune your car. I do this for a living. I told you what's wrong with your car. Sounds like you have people you have faith in. I'd go back to them. Show them this thread. I stand by all I've said. My company name and contact info is in my sig. There are others here who have just as much experience and will tell you exactly what I have.

If you understand what you're looking at, all of the information is right there.

[SiriusC1024]

The injector data is incorrect.

Here's Deka 60. This is the real FIC data.
https://forum.hptuners.com/showthrea...pository/page2

Tune with narrowbands wherever possible. Really.

Overspeed idle spark correction isn't setup right.

It should be obvious that more air, fuel, and spark means more torque. That's why RPM's rise when you uncouple the load to the engine. People are trying to tell you how to fix it.

[phuz]

The injector data is incorrect.

Here's Deka 60. This is the real FIC data.
https://forum.hptuners.com/showthrea...pository/page2

I got my FIC data directly from Josh @ FIC so I'm even more baffled why his tables and the one you just linked don't jive.

Tune with narrowbands wherever possible. Really.

Overspeed idle spark correction isn't setup right.

It should be obvious that more air, fuel, and spark means more torque. That's why RPM's rise when you uncouple the load to the engine. People are trying to tell you how to fix it.

Thanks. I'll keep working at it.

[SiriusC1024]

I got my FIC data directly from Josh @ FIC so I'm even more baffled why his tables and the one you just linked don't jive.

https://www.aacorvette.com/injectordatahp.html

They use FIC data. Question is which FIC - Fuel Injector Connection or Fuel Injector Clinic? You can see Fuel Injector Connection in the Intro tab of the Excel sheet. Pretty sure FIC got that particular data from Greg Banish at Calibrated Success. Don't remember where I saw that last part, but I do remember seeing it. I'd defer to Greg's data any day.

[phuz]

Fuel Injector Connection.
But actually, the excel sheet I have (from Josh @ FIC) has the Calibrated Success logo in the top of the sheet, so I would expect that one to be Greg's numbers, not the one from the link.

And yes, I would agree with that about Greg.