Idle Airflow w/ and w/o clutch engaged

[phuz]

My dyno tune had a lot of drivability problems, too. Bucking at low RPM, idle hunting when it got cold, things like that. Ran great otherwise. Reputable tuner. I was ok with it because it's a dyno they can't replicate all conditions. It wasn't until I started messing with HPT that I was able to resolve those issues myself.

Don't be surprised if you have to adjust VE again after doing the injector timing.

Yeah, I'm sure I will.

Bucking is one of those things I occasionally get, but it's few and far between. Usually low rpm and very light throttle.

[SiriusC1024]

Yup. Pretty big idle/base transitions, especially at 1200-1600rpm. Also, I got better results with spark smoothing disabled.

[phuz]

I noticed I had some jumps in the VE table so I'm slowly smoothing them out. I haven't even looked at spark smoothing, so I'll read up on it.
What I really need to do is have the scanner running when the bucking occurs...something I haven't been able to capture yet.

[phuz]

I'm making small changes in the idle portion of the VE map as well as slight decrease in BRAF and this morning the car stalled out 3 times while coming to a stop and I managed to capture it. What I find crazy is that the STIT is going extremely negative prior to the stall, so when it does get close to the idle RPM, the idle airflow is much lower than it should be, so I believe that's exactly what's causing it. Now the question is why. My guess is that coming off the portion of the map where the RPMs are coming down and MAP is very low, the VE values are still very high causing it to represent a much higher airflow than actual and therefore causing the STIT to compensate with those negative values.

The other question (and I know this is not the correct way to resolve this) is: is there a way to limit STIT like you can with LTIT?

[Alvin]

I'm making small changes in the idle portion of the VE map as well as slight decrease in BRAF and this morning the car stalled out 3 times while coming to a stop and I managed to capture it. What I find crazy is that the STIT is going extremely negative prior to the stall, so when it does get close to the idle RPM, the idle airflow is much lower than it should be, so I believe that's exactly what's causing it. Now the question is why. My guess is that coming off the portion of the map where the RPMs are coming down and MAP is very low, the VE values are still very high causing it to represent a much higher airflow than actual and therefore causing the STIT to compensate with those negative values.

The other question (and I know this is not the correct way to resolve this) is: is there a way to limit STIT like you can with LTIT?

In the log you posted they are going POSTIVE and the wideband backs this up reading LEAN. You have more work to do on the VE table. If it is rich or lean returning to an idle its going to stall or dip. The fueling should be corrected first..not the idle airflow.

[SiriusC1024]

Absolutely. You're still not tuning with the narrowbands. Also, STFT's are holding over from whenever. Clear those. Log new STFT's and correct VE.

[edcmat-l1]

It's definitely closing the throttle way more than it should. It's at 3.1% throttle position as it starts to stall and no Y body should ever be that low. You need to do a cold start idle data log and make sure all the numbers jive. Could be you have some unmetered air causing it to learn the very low TPS %. All the numbers have to be sensical. If not you have to figure out why. Looks like you have the injectors operating like they should. VE numbers look fairly normal.

Run a data log from a cold start all the way to full operating temp. Post that log here.

Some details on the PCV system would help. Pics would be even better.

It's also possible the BOV is too small. Seen that many times. Especially on the lower entry level kits. If it's the little cheesy one I'd replace that with a much larger race style BOV.

[phuz]

In the log you posted they are going POSTIVE and the wideband backs this up reading LEAN. You have more work to do on the VE table. If it is rich or lean returning to an idle its going to stall or dip. The fueling should be corrected first..not the idle airflow.

Absolutely. You're still not tuning with the narrowbands. Also, STFT's are holding over from whenever. Clear those. Log new STFT's and correct VE.

STIT, not STFT.

It's also possible the BOV is too small. Seen that many times. Especially on the lower entry level kits. If it's the little cheesy one I'd replace that with a much larger race style BOV.

50mm Turbosmart. Plenty big.

[Alvin]

STIT, not STFT.

Doesn't change what I said.

[edcmat-l1]

In the log you posted they are going POSTIVE and the wideband backs this up reading LEAN. You have more work to do on the VE table. If it is rich or lean returning to an idle its going to stall or dip. The fueling should be corrected first..not the idle airflow.

He's saying the short term idle trims are going way negative and they are. It's closing the blade way more than normal.

[Alvin]

He's saying the short term idle trims are going way negative and they are. It's closing the blade way more than normal.

Yeah likely idle airflow stuff is screwed chasing "why won't it idle" when the VE is so messed up the STFT quickly head like they are going to MAX out with a 18-22 :1 AFR.

[edcmat-l1]

Yeah likely idle airflow stuff is screwed chasing "why won't it idle" when the VE is so messed up the STFT quickly head like they are going to MAX out with a 18-22 :1 AFR.

Wideband is off a couple points. To me it's worthless. Leanest you see when the narrowbands toggle "rich" is about 14.9:1. If it were accurate it should toggle 13.5:1-15.5:1 roughly. Not 15:1-17:1. That's off quite a bit. And I'm talking at cruise not at idle. This is where the velocity of the exhaust should be sufficient enough to not read lean from overlap.

I don't think the VE is off that much numerically. To me it looks pretty close. I'd bet it's 10-15% off at idle.

Need to do a idle log like I posted before. That will tell a lot about a lot.

[phuz]

Wideband is off a couple points. To me it's worthless. Leanest you see when the narrowbands toggle "rich" is about 14.9:1. If it were accurate it should toggle 13.5:1-15.5:1 roughly. Not 15:1-17:1. That's off quite a bit. And I'm talking at cruise not at idle. This is where the velocity of the exhaust should be sufficient enough to not read lean from overlap.
I don't think the VE is off that much numerically. To me it looks pretty close. I'd bet it's 10-15% off at idle.

I'm not overly concerned with the wideband in the off/light throttle conditions anymore, especially at low RPMs after seeing that this is somewhat normal with a cam like this. I'll have to learn to live with it. That being said, when I actually give it some good flow (>30% throttle), it stables out, and under PE, it matches the target.

Need to do a idle log like I posted before. That will tell a lot about a lot.

Yep, will do after it cools off completely.

[edcmat-l1]

I'm not overly concerned with the wideband in the off/light throttle conditions anymore, especially at low RPMs after seeing that this is somewhat normal with a cam like this. I'll have to learn to live with it. That being said, when I actually give it some good flow (>30% throttle), it stables out, and under PE, it matches the target.

Aftermarket widebands are notoriously inaccurate. If it's a stock bottom end engine, I'd be worried about it. I would want to compare it to another known good wideband. Because it matches target doesn't mean anything.

[SiriusC1024]

Don't forget to clear your fuel trims too. They are still showing non-zero STFT.

[phuz]

Don't forget to clear your fuel trims too. They are still showing non-zero STFT.

I'll deal with the VE / fuel trims separately (unless you're insisting that the STFT is somehow causing the STIT to dip low), but for now I'm concerned with the STIT that is causing the stalls. I've been lowering the VE in areas where I saw the dynamic airflow was much higher than the idle desired airflow, and the STIT is now only around -2.6g/s but still causing RPMs to drop significantly lower than desired. I'm done tweaking for the next hour or so, so once it's "cold" I'll grab a fresh warm-up log. Here is the current tune and most recent datalog.

[edcmat-l1]

I'll deal with the VE / fuel trims separately (unless you're insisting that the STFT is somehow causing the STIT to dip low), but for now I'm concerned with the STIT that is causing the stalls. I've been lowering the VE in areas where I saw the dynamic airflow was much higher than the idle desired airflow, and the STIT is now only around -2.6g/s but still causing RPMs to drop significantly lower than desired. I'm done tweaking for the next hour or so, so once it's "cold" I'll grab a fresh warm-up log. Here is the current tune and most recent datalog.

Why would you modify your VE to bring your desired idle airflow down???

You have bad split fuel trims. That is not common for these things. What intake manifold do you have on the car?

Do you know if your BOV is wide open at idle?

See the screen shot. Bank 1 is +30% bank 2 is +8%. And your narrowbands show very rich at the same time. You got something jacked up both mechanically and in the calibration. Your trims shouldn't be damn near pegged along with the narrowbands showing rich. Follow me? That bank isn't even thinking about pulling fuel.

From about 53 seconds to 1:34 the trim and O2 activity says you still have something very wrong in the calibration.

[edcmat-l1]

At 2:42 in the log your trims have back together and are close to zero but narrowbands are still showing rich and your injector on time is still roughly 2.0 ms. So your trims have moved from +30% to near zero and the narrowbands are virtually the same. Something still ain't right in the injector data.

[phuz]

Why would you modify your VE to bring your desired idle airflow down???

If you look at the 3:09 mark, you'll see that dynamic is 10.22g/s and idle desired is 8.17g/s and the STIT / LTIT combined value is -2.6g/s. I was lowering the VE in those specific cells to lower the dynamic airflow and was hopeful this would not cause such a dramatic STIT. I was NOT lowering the VE to attempt alter the idle desired airflow. Idle desired airflow is just BRAF - LTIT - STIT, right?
What is driving the STIT so hard?

Do you know if your BOV is wide open at idle?

No, but even if it was, what would that matter? (Other than sucking unfiltered vs. filtered air)

[edcmat-l1]

If you look at the 3:09 mark, you'll see that dynamic is 10.22g/s and idle desired is 8.17g/s and the STIT / LTIT combined value is -2.6g/s. I was lowering the VE in those specific cells to lower the dynamic airflow and was hopeful this would not cause such a dramatic STIT. I was NOT lowering the VE to attempt alter the idle desired airflow. Idle desired airflow is just BRAF - LTIT - STIT, right?
What is driving the STIT so hard?



No, but even if it was, what would that matter? (Other than sucking unfiltered vs. filtered air)

The BOV should be open at idle. It won't suck in air. It will release pressurized air. This is one of your problems. The injector data that you can't right is another. Your procedure for how you're adjusting your VE is another.

What's that line? "Some people you just can't tell."