mx5 vvt

[Gtr_lee]

I had an MOT booked today. Tried to drive round the block a few times to collect some data before I went to the MOT station.

I was using the math block that lets me use mixture map with closed loop active.

But the car was driving pretty bad  Was trying to cut out when coming to a stop and did cut out once, Map readings seemed very high with barely any throttle. Afr's were all over the place even after making adjustments using the logs. Something is definitely not right at the moment.

While I had it on the drive I had adjusted fuelling out of closed loop and got idle stable and it seemed to run smooth.

Could someone take a look at my log and tune file to see if they could spot something.

PC Datalog - 2024-04-4 6;23;40 pm.llgx Lee MX5 Back up Traditional from 1.4.24.pclx

[Vaughan]

Is this a car that has previously been tuned and was running well and something has changed? I can see that your VVT isn't working properly

[Gtr_lee]

No, has not been tuned before. Had a new ecu sent over from NZ after my orginal one needed the mod for the VVT. Because it was unopened and the guys in the Uk couldn’t do the mod they agreed to send a new one. 

[Vaughan]

Then get it tuned, the supplied sample map is only intended to be used for getting it started and I can see that the tune you are using isn't the Link sample map. Where did your tune come from if it wasn't done on your car?

[Gtr_lee]

I know that it was a sample map and is just to get it started, the reason I got the an mx5 and put a link on it in the first place was to teach myself how to tune. I have spent a decent amount HPA courses and read hours and hours of info from this forum. I get that the easy way out is to just get someone to do it for me, but I like trying to have a go myself.

I have made the changes in the ecu myself apart from the ignition table which a local tuner sent me to try. It is the first time I have attempted to even drive the car today. If it's a case of there is nothing seriously wrong and it just needs more work on the tune, then I will just keep having a go until I figure it out.

[Vaughan]

Sweet, I didn't see anything obvious other than the VVT not working correctly so I would start by running the calibration on that in VVT Control -> VVT Setup -> Cam Angle Test -> Calibrate, it'll turn itself off after it's done, you can watch the status of the cam in the VVT tab of the runtime view (F12 or R to bring the runtime view up), this needs to be done while above the VVT engine speed and ECT lockouts.

I assume you've set the timing with a timing light?

I've also attached a copy of the last tune I have from my car before I sold it, was a G4X Fury (so different pinout than the plugin) on a 1.8 VVT motor with factory coils, 36-2 crank wheel, G19 turbo manifold, TD04HL turbo and 700cc injectors. Note it was a modelled tune so the fuel table numbers won't be particularly relevant.

What injectors are you running out of curiosity?

last copy of tune 9-5-2023.pclx

I did find when tuning mine that I had difficulty accounting for how heat soaked the intake manifold gets when you've been sitting idling, would be fine while running and driving but would come to a stop and the pre throttle IAT wouldn't noticeably change but the lambda would despite all else being equal, this might have been solvable by fitting the IAT sensor to the manifold instead of the pre throttle pipe so that the heat soak in the manifold is seen by the ECU

[Gtr_lee]

I did do the VVT angle test when I first got it up and running but I will try it again in case I did not do it correct. I did notice the angle never really changes from 9 degree advanced regardless of target. 
 

Yes, timing was set and I double checked this a couple of days ago to make sure. 
 

thanks for the tune, I will have a look in the morning to see what I could be missing to make mine run so bad. 
 

I am using EV14 0280158235 713cc injectors. They come with the Kraken turbo kit. 
 

I have noticed that too actually when I had the car idling for long periods. I had a walbro 255 pump in originally, which seemed to also make it worse! Figured out it was overpowering the stock reg in the tank, so put the stock pump back in. Made it slightly more manageable. 
 

 

[Vaughan]

4 minutes ago, Gtr_lee said:

I did do the VVT angle test when I first got it up and running but I will try it again in case I did not do it correct. I did notice the angle never really changes from 9 degree advanced regardless of target. 

You can select the Inlet bank 1 cam in the cam angle test to check the actual angles it is seeing (angle of each tooth shows up in the 'Cam Angle #x runtimes'), maybe try adjusting the duty cycle output on Aux 1 using a gp pwm to see if you can make it move at all, odd for it to be consistently sitting somewhere other than 0deg especially after a successful calibration as that implies that when you do the cam calibration it moves to 0 and then moves back to the 9deg after.

[Gtr_lee]

I will give that a go later and see if it changes anything. I did think it was strange how at barely any throttle and rpm it was sometimes shooting up to 80kpa and turbo spooling up like mad. 

Just had a look through your tune file, the one the local tuner sent me and the stock base map. My no1 VVT tooth offset looks a bit off compared to the others especially compared to the base file and the one the local tuner sent. They both has an offset of around 90 and mine is 203. Could this be causing my issues?

I had to rebook the MOT for this evening. So going to have a play when I get back from work. 

[Adamw]

Most Mazda cam sensor signals invert somewhere around idle speed and only one edge will remain accurate when this happens.  Given your cam position is showing non-zero after calibration it could be that the calibration was performed at idle when the signal was inverted.  Redo the cal at about 2000RPM, and then keep an eye on Inlet Bank 1 Sys status and Inlet bank 1 position runtimes over a range of RPM's, and immediately after a restart etc.  If it reports faults or the position doesnt return to zero reliably at idle then that would suggest the wrong edge is being used so try swapping trigger 2 active edge and then redo the cal.  

[Gtr_lee]

Managed to do the VVT calibration this afternoon and it now floats around 0 at idle with around 30ish% duty cycle. 
 

I don’t know how it got the number it did in the first place, I definitely calibrated it at 2000rpm. I remember reading a post Adam replied to with instructions on how to do it, so I screenshot what you said and did it the next day.
 

I will see how it drives in an hour or so while on the way to an MOT and fingers crossed all is good and it passes. 
 

Will make sure to get a few logs and report back with an update. 
 

appreciate all the help.