So I've been getting bad herky-jerkyness in low revs/load (parking lot speeds, cruising, even in accel, etc) and tracked the issue down to VVT. I honestly know next to nothing about tuning the VVT. I completely disabled VVT and it runs like a top now. Can you guys please look at this tune and see if you see any VVT red flags, and I assume leaving VVT off for now will not hurt anything besides my powerband?

Thanks!

 

I can't pull up tunes at work so please give more information in your thread.

What ECU is controlling it? Have you installed the flyback diode?

Have you found your minimum and maximum angles? What does your PID table look like? Post a screenshot of your VVT setup page and VVT table from tunerstudio (if it's a megasquirt).

 

MSLabs MS3 baisc.

I believe so on the diode, I'll have to confirm. I'm using the tune from the previous owner as my base map, so I'm not sure o the min/max angles. I attached shots of the settings and table.

 

Do not advance the cam below 60 kPa / below 3000 RPM. set all those to zeroes and try the rest of the map as you have it.

 

I'll give that a go and report back. Thank you!

 

Is this for testing purposes or to actually run the car?

 

whichever. the VVT system had instability at low load on my car. plus you'll never drive under those conditions and be simultaneously concerned about power or efficiency usually. generally speaking, if you're looking for power, you're not going to be looking for it below 90 kPa anyway. still, there's a small region where you can get a little bit more engine torque per throttle angle at a given RPM if you find the lowest MAP value where you can advance the cam. probably not worth the effort though. to test it, just start advancing the cam at lower and lower MAP values at low engine speeds and see where it starts to jerk.


this car have VTCS completely open once it's warmed up?

 

Ok so I tried those setting and it was still bucking from about 2800RPM on. Attached are two log files, the large is with VVT on with the above suggested settings, and the smaller is with VVT off, which was, unfortunately, just a short hop from the stop light where I disabled VVT to the gym parking lot. But still, absolutely zero bucking with VVT off.

 

I've uninstalled all my datalog software. Can you save a screen shot of it?

What about the VTCS?

 

I'll get a screenshot shortly.

No clue about VTCS, I've looked and looked and can't find the section for it. I'm over looking it I'm sure.

As far as min/max angles go; I'm using what was in the MSLabs base map apparently, I googled how to find those numbers but found several different sets of instructions that were not quite the same.

 

Min angle is easy to find. it's whatever the cam sits at at 0 duty cycle. At least make sure you have that right.

Does the car have VTCS? It can cause jerkiness on a turbo car if it's closed--but looking around it looks like you're not turbo. Still if the VTCS is closed under load, it will act like a choke.

 

Change the minimum temperature from -40'F to around 150'F. Cold, stiff oil makes the VVT mechanism unpredictable and you really should not be beating the engine anyways when it's cold. I also don't use VVT under 2800 rpm and ~70kpa. Why would you, anyways?

 

I believe so, looks like it has a Mitsubishi solenoid on there, and you're correct, no turbo. Bear with me,I purchased the vehicle with these mods and I'm figuring it out as I go.

Ode: I'm just using the base map that was stuck in the MS3. I'm just now starting to tweak VVT since it is the cause of my bucking issues.

 

This is what confuses me. If you unplug the VVT you don't get bucking correct? When you plug it back in, set your entire VVT map to 0's. Do you still get the bucking?

I'd be very interested to see a log that has 'VVT ANGLE', 'VVT TARGET', and 'VVT DUTY'.

screenshot of that while driving at low speed when it's bucking.

 

I'll grab that log after work and see whats what.

The way I'm disabling VVT is by going into TunerStudio VVT settings and chaning "No. VVTs" to "off," not actually disconnecting the solenoid.

 

I have found that with the most recent firmware version (1.4.x), that in order to get VVT to be smooth, I needed to play with the Min and Max VVT Duty. My current settings are 30.2 and 48.6 respectively.

When tuning, create VVT Target, VVT Duty, and VVT Angle gauges and watch them carefully as you accelerate through your RPM targets. I do not run VVT based on load, only on RPM, this created the smoothest operation for me.

 

Ok so I followed the instructions to find min/max angle and came up with minimum = 5.6 and maximum = 56.2. Turned off test mode and fired back up and got a VVT err light in TS, tried the test again and now the VVT1 Angle gauge doesn't budge no matter if test output duty is set to 0% or 100%. It's clearly working, as 100% bogs the car down (holding revs at around 2500 RPM when changed).

 

That doesn't sound right.

I have never seen duty as very far off from your original settings.

 

Seemed strange to me too, but those were the numbers the VVT1 Angle gauge gave me... Now it won't change from 5.5 no matter what I do.

 

Those min and max do not sound right at all, I would try whatever you did all over. My Min Angle is 272.7 and max angle is 318.1. Everyone I have ever seen has been close to that. Google Image up some examples...