Tried so much to get this issues solved, but it seems I need your help!
I attached screenshots, tune and logfile.

Issue: When returning on throttle (from 0% to whatever %), I get a lean spike.
This does not happen when I'm on throttle (say 5% TPS and 3000rpm, and I add some TPS (15% --> 100%) ).
So I'm pretty sure it is not related to AE.
Also, I'm pretty sure it is not related to the VE map as this one was pretty spot on.

Note, I had a pretty good VE map until yesterday, then I decided to try one final thing, changing my injector deadtime and pulsewith, according to best practices discussed here: Kraken EV14 700cc discussion thread
So currently my VE map is not spot on anymore, but it did not change anything to the issue I'm having.

To me, it looks like Megasquirt sees my TPS increasing, it sees my MAP increasing, but it is just taking a lot of time to add fuel to the mixture.
As if there is some kind of delay. Turning overrun fuelcut off, does not help.

To start with, a solid throttle response. Note that I'm currently doing 3000rpm and just hitting the throttle. Sure, the AE is a bit too much, but no lean spike and a pretty decent response (fuel is being added)


Here you see at time 0.0 the moment I touch my throttle. And only after 0.863 seconds, I see a change in my AFR, and roughly double that before it is back to where it should be.


Next up, one example with 3 screenshots. First, me applying a little bit of throttle


second screenshot, 0,3s later, the AFR is starting to change


Third and last, AFR Is back to normal (almost 1 second further)

 

Logfile would not attach to start post.

Any help much appreciated!

 

Is there some drivability issue here, or are you just worried about not hitting your target AFRs?

I was reading into this recently when setting up EGO/Closed Loop Lambda. They were discussing how often to have the ECU recalculate how much fuel to add/remove. They were discussing how quickly the exhaust flows at different engine RPM, and also how long it takes to reach the sensor based on where the sensor is located in the exhaust. One of the experiments they mentioned was to have the car idle, add 10% fuel to the VE table and see how long it takes for the AFR change to register on the sensor. With the Kraken kit, which puts the O2 sensor pretty close to the stock location, I would see the change register almost a full second after the ECU changed the fuel value. You could feel an immediate change, but see that the sensor hadn't picked it up for a while after. It was quicker when holding the car around 3k rpm, but still took ~0.75 seconds if I remember correctly.

All of that to say, it's possible that the ECU is adding the fuel back in quicker, but that change isn't being picked up by the sensor for a second. I just double checked on one of my logs, and I see about 0.4 seconds between the injectors turning back on and the AFR reporting a change when cruising around 3K.

I realize that's not exactly what you're asking, but it seems like normal behavior to me.

 

Thanks! Usefull information and food for thought.
my initial response is that I would guess the response times would be equal to hitting throttle from 15%. (So all screesnshots compared to my first screenshot). Problem is, they are not. Is that because the injectors have to be switched on? Does that take so much time?

Back to the problem, not a big one, but it annoys me. I really feel the car/engine stumbling when applying throttle. When I hit the throttle from 0% to wot, it just feels not OK. I might have a log of that too, hold up.

Edit: I can see over half a second of delay. Might be a measurement error, agreed, but I can feel it in the car (shaking, wobbly)

Before applying throttle (TPS 0%)

AFR is measuring solid values (0,55seconds later)

 

It seems the scaling for AFR and AFR 1 Target in MLV are different. It would be easier to see correlations with them being the same. In that last image the graphs are over each other, but the AFR is 1.3 richer than target

That seems like normal delay in sensor readings to me. At lower RPM and load (<2500 RPM) it's not unusual to see up to a full second delay from activating the injectors to seeing a response in the AFR. It also depends in your controller's response time and your logging rate. There is a wall-wetting effect where not all of the fuel sprayed into the port goes into the engine, which is magnified for a split second after a fuel cut, so your AE needs to compensate for this effect. If you feel a shutter (or see those jagged lines in the RPM trace) then it could be too lean or too rich, or could even be drivetrain lash if you have an aggressive clutch. Don't pay too much attention to the AFR data on this and go by feel.

 

I get a jerk if I stab the throttle when coming off of decel cut as well. I haven't investigated it yet. I added some fuel to the lower cells in my fuel map and that seemed to help some, but it could also be placebo. I actually disable DFCO when I go to high boost (which is usually what I'm running at autocross) to try and keep the car from jerking around in sweepers if I'm going on and off throttle (bad driving practice, but that's besides the point). Again, could just be placebo.

I used to use a static Min/Max for AFR and AFR Target in MLV for the reasons mentioned above. You should be able to set them to use a static scale from 10-20 (or whatever you want) which makes it was easier to see how far you are from your target.

 

Thanks a lot of the feedback!

I will adjust the scale (min/max values) in MLV, that will indeed help a lot with readability of the graphs.

For now I will try a bit more finetuning of the VE map and ignore the (non?)issue.
I was looking at the DFCO feature, but it seems I don't have that option in tunerstudio (?)

 

One thing to note that catches a lot of people offguard. Depending on the ECU your running and the firmware version, Tunerstudio will show different menus, features, options,etc... I had people tell me to turn on certain features because I was on "Tunerstudio" when it was an MS3 only feature and I was running a Speeduino.

DFCO is decel fuel cut. Might be called overrun fuel cut or something else. Every ECU manufacturer seems to like to use slightly different terminology (like CLT vs ECT).