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I am trying to get VVT working but am seeing something weird with the VVT angle. I put it in the test duty mode and at 0 the VVT1_angle is reading 2 degrees. All the forum posts I have read shows this should be around 275. Any ideas what to check?
I am currently setting up my VVT settings as I forgot to do it when I initially setup my MS3 Basic, my VVT1_angle was reading ~6.4 at idle when I was commanding -0.1 advance in that region, so I added 6.4 to the current Minimum Value to make it 276.7, and now VVT1_angle now shows between 0 to -0.2 at idle
With 276.7 as the start point, I kept the throttle at 3k RPM and set the duty to 100%. The VVT1_duty was oscillating between 44.7 and 44.6, so I took 44.7 and added that to 276.7 and got 321.4, which I made the maximum abs degree value. As my previous settings all had at least 6 degrees of advance I now need to retune a bunch of stuff, bummer.
Still need to find the Max VVT Duty % and Min VVT Duty %. I believe the correct way to do this is to raise the Duty % til the VVT1_angle rises from the value it has at 0% duty, and then do the opposite for Max VVT Duty %, hold the throttle at 3k RPM, lower the duty % til the VVT1_angle starts going down. My Minimum value was something around 36.5, and my Max was around 55 or so, I still need to get the exact value down and put that in.
I had a different experience. Yes to your method of min and max angle but leave duty min and max and 0% and 100% and go do some testing. I have near perfect lines for commanded and actual with the megasquirt figuring out the duty % but with my actual min and max angles.
Alright, I will test it as is and see how it functions. I have been getting some weird idle drops and oscillations when returning to idle following the VVT calibration, just trying to rule out different things to try and fix that.
My original procedure was based off of this post, shame it isn't too well documented
Alright, I will test it as is and see how it functions. I have been getting some weird idle drops and oscillations when returning to idle following the VVT calibration, just trying to rule out different things to try and fix that.
My original procedure was based off of this post, shame it isn't too well documented
Having seen your vvt table over in Miata.net I think you might have a bit too much low end vvt actuation. I’d get your vvt angle min and max set as you already did and then not touch duty cycle and focus attention on your vvt target table.
I agree, I reverted it back to Reverant's table just now due to stability issues when starting the car and when idling in general. Doing that and fixing my closed loop idle initial value table (I never changed it after installing the Junk2 Throttle Body) really helped. I still have the 1600 RPM part filled in cause I like the power I get around there.
In all the VVT-threads I saw Min and Max values at around 270 and 320.
However my Min and Max values where at around 290 and 340.
So it looks around 20° off the common values.
Strange is also, that torque and power are increased over whole rpm range when I set VVT to 30° advance.
In the graph the gray lines are with 30° advance and coloured are initial measurement with 0° advance.
Does anyone expered this before?
I am currently assuming, that my Intake cam is off by one tooth but I checked everything when building this engine.
I had a similar situation where the angle was off by 20 degrees or so. The solution was I had my ignition timing set to either rising edge or falling edge. I don’t remember which it was set to but I flipped it and re set my crank angle offset and then my vvt angles made more sense.
I am on falling edge now and it should be the correct for my application (36-2 wheel, LS3 Coils).
Can't imagine that ignition input capture could effect the cam timing or is it just for the calculation of camshaft angle?
Anyway I will try as soon as possible rising edge ...
I now changed to rising edge and needed to change ignition offset by 5°. Now values are at Min 273° and Max 316°.
Its strange, that the actual VVT from table is not what I see in datalog.
entered 0° -> datalog 0°
entered 10° -> datalog 0°
entered 20° -> datalog 10°
entered 30° -> datalog 20°
entered 40° -> datalog 30°
This might be related to my DutyCycle I guess. I figured out min 40.4% and 41.5% but inserted 38.4% and 43.5% because of margin to compensate oil viscosity aso.
However maybe this margin (+-2%) is to high. I also dont like the small delta in duty cycle.
Next step is to make again some pulls with 0°, 10°, 20°, 30° and 40° (over all rpm) and check if the torque is again increased on so high level and over whole rpm range.
If so, I think my Cam timing is 1 tooth off and I have to advance by one tooth.
For what it is worth, I use a 36-2 trigger wheel and also use the LS coils setup as a sequential ignition. This is what my VVT settings are set to and commanded vvt follows damn near exact to actual vvt angle. I had to set up some graphs to compare for myself in tuner studio.
I now changed to rising edge and needed to change ignition offset by 5°. Now values are at Min 273° and Max 316°.
Its strange, that the actual VVT from table is not what I see in datalog.
entered 0° -> datalog 0°
entered 10° -> datalog 0°
entered 20° -> datalog 10°
entered 30° -> datalog 20°
entered 40° -> datalog 30°
This might be related to my DutyCycle I guess. I figured out min 40.4% and 41.5% but inserted 38.4% and 43.5% because of margin to compensate oil viscosity aso.
However maybe this margin (+-2%) is to high. I also dont like the small delta in duty cycle.
Next step is to make again some pulls with 0°, 10°, 20°, 30° and 40° (over all rpm) and check if the torque is again increased on so high level and over whole rpm range.
If so, I think my Cam timing is 1 tooth off and I have to advance by one tooth.
Wouldn't it make sense to check the timing of the cam first? I am pretty sure, there is your problem. The setup angles of the VVT are within 1-2 degrees on falling edge for every single setup I have heard of up to now...
Yep, you are right. Now I have time for this because I mihght have a much bigger problem as the car wont start anymore.
Yesterday we went to the dyno for some tuning. Car runs well on wastegate spring pressure and here the VVT worked well.
Pretty happy with the result for 100octane.
However the engine and drivetrain is build for +450Hp, so we raised up the boost to ~255kPa (on dyno run boost falling to 120kPa because wastegate spring seems too soft).
Boost build-up is insane with VVT -> 255kPa at 3300rpm
After some pulls the water cooler cap (Mishimoto) cracks open and leak some water (at 70°C). Closed again and try again.
Peak pressure at 255kPa but holding longer. Same issue occure. So stop tuning for this day and I went back home.
450Nm @ 4000rpm is really impressive and we think, that ~400Hp would be possible at 140kPa and 6800rpm.
Car ran relatively smooth on the way back home but now after 1 night the car wont start again.
I assume that cylinder head was lifting and I pressurized the cooling system with turbo boost -> head gasket might be broke again (after 1 year) and now compression is low.
As a good thing I now have time to also deeper investigate the VVT issue. Falling edge is the way to go I think. Then check Cam-Timing again when valve cover is off.
Thank you Zaphod. By the way, from wich region in germany are you from?
07-16-2019, 11:04 PM
Question about VVT angles
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