EfiniX
Well-known member
I've been chasing what I initially thought might be blowout at WOT. I was seeing a little bit of knock on some of my pulls, but it never seemed like something that would cause the sort of shuddering I was feeling at-speed. Well I was doing some long logs for SD VE table calibration and noticed something really odd.
My AFRatioEst will spike lean intermittently pretty much throughout my logs. Seems to happen mostly over 3000 RPM's. I got to wondering if it's not related to WOT at all, so I just log myself driving nice and easy up to high RPM's. Sure enough, I started getting the same hesitation with low load at high RPM's. It seems perfectly replicable, in fact.
For example, here's a screenshot from one of the logs I'll link to at the end. This is at a relatively low RPM, but it illustrates pretty clearly what I'm seeing.
I got to wondering what else I could find that might line up with these lean AFRatioEst spikes I was seeing. O2 sensor output looked fine (although maybe someone might see something in my logs?). WB AFR's looked ok (which tells me I wasn't getting blowout or misfire since I would expect a rich condition due to unburned fuel). Then I looked at the fuel flow and injector metrics and bingo!
Here's what it looks like with "fuel flow", "InjDuty", and "InjOn" added. You can see the little dips.
My guess is that at lower RPM's, these slight variations don't really translate into and noticeable hesitation. Now get the car up to higher RPM's...
These spikes I could absolutely feel. For comparison, here's what the fuel inputs look like just a 10ms earlier (off-spike):
I got to looking back at other pulls. In some cases, they look clean:
On others, I see it and feel it:
Now I'm scratching my head... Whatever these lean spikes in AFRatioEst are, they cause a noticeable hesitation. And I'm not sure if the correlating drops in injector flow are a cause, or a symptom.
Logs are here. I'm posting this to the ECMLink forums as well, but I'll take help from anywhere I can find it. Thanks, all!
click
My AFRatioEst will spike lean intermittently pretty much throughout my logs. Seems to happen mostly over 3000 RPM's. I got to wondering if it's not related to WOT at all, so I just log myself driving nice and easy up to high RPM's. Sure enough, I started getting the same hesitation with low load at high RPM's. It seems perfectly replicable, in fact.
For example, here's a screenshot from one of the logs I'll link to at the end. This is at a relatively low RPM, but it illustrates pretty clearly what I'm seeing.
I got to wondering what else I could find that might line up with these lean AFRatioEst spikes I was seeing. O2 sensor output looked fine (although maybe someone might see something in my logs?). WB AFR's looked ok (which tells me I wasn't getting blowout or misfire since I would expect a rich condition due to unburned fuel). Then I looked at the fuel flow and injector metrics and bingo!
Here's what it looks like with "fuel flow", "InjDuty", and "InjOn" added. You can see the little dips.
My guess is that at lower RPM's, these slight variations don't really translate into and noticeable hesitation. Now get the car up to higher RPM's...
These spikes I could absolutely feel. For comparison, here's what the fuel inputs look like just a 10ms earlier (off-spike):
I got to looking back at other pulls. In some cases, they look clean:
On others, I see it and feel it:
Now I'm scratching my head... Whatever these lean spikes in AFRatioEst are, they cause a noticeable hesitation. And I'm not sure if the correlating drops in injector flow are a cause, or a symptom.
Logs are here. I'm posting this to the ECMLink forums as well, but I'll take help from anywhere I can find it. Thanks, all!
click
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