Orinawak

Hi everyone. I have started to try my hand at tuning my megasquirt before going turbo. I am going to get it professionally tuned at that point, but read that it is best to get familiar with megasquirt when N/A, so that is what I'm trying to do. I have been trying to set my idle, but I am starting to get frustrated with it. I was told to first get a good fuel VE table going before attempting to tune idle, so I went out and tried to autotune the fuel VE table, but encountered an idle issue right off the bat. When coming to a stop, and then clutching in, my car will stall; it won't go into idle. I then have to give it a lot of gas just to start up again. I also noticed while revving with no load, just standing still, the car will stutter at first and the AFRs will jump up to 19-20. I have attached my msq file and a log I took while revving just sitting in the garage, and would appreciate any guidance. I'm not sure where to start. I have been researching and I even subscribed to the $50 Evans Performance Academy subscription (I plan on using him for my final turbo tune), but I just don't seem to really be getting it. I'm using the basemap I got from DIY with my MSPNPPro.

HowPrayGame

Lock out your idle and low load cells in the VEAL menu so it doesn't pull fuel out of the idle region and make the car stall. Set the car to not accept data under 1500RPM and 30 kPA and revert the VE Table back to what it was previously. VEAL will pull fuel out of low load/idle regions till the car stalls, works fine with more air/higher loads assuming that your AFR Gauge inside tuner studio matches your physical afr gauge.

Orinawak

Thanks, I'll give that a try I actually didn't realize it did that. Once I'm starting to tune idle, do you think its best to jump to closed loop, or should I tune open loop? I'm getting mixed information there; from my research some people suggest starting with open-loop, while others say to go straight into closed loop. Evans performance academy, he actually recommends just using open-loop, so I'm a bit confused where to start there.

HowPrayGame

Open loop is fine if its a dedicated racecar and you don't care about idle quality as long as the car doesn't stall. I haven't ever used open loop idle as there are pretty much only two tables to change and little to none of the work transfers over to open loop. It doesn't respond to transient condition changes as it has no way to do so, but if you aren't picky it will probably work.

Orinawak

Thanks! Its a street car, so looks like I should get into closed loop idle then. Time for more research...I have a long road ahead just to get idle to work. I'm a complete noob when it comes to tuning, and most of this terminology is brand new to me.

Orinawak

So, I went and made a few changes to the msq. I locked out the cells for VEAL, and then turned off Idle VE since I realized that was the reason that my idle AFRs weren't at my goal of 14.0. After doing that, I got the car to start once; and it idled at 14. Turned it off to try and start it again, it started then immediately the RPMs dropped and the car stalled. I took a datalog which I will upload below. To me it looks like during startup, the car is running really rich, around 7.5 AFRs, and I'm guessing the car must be bogging out and dying. From what I know, I'm thinking I would need to adjust the warm up duty cycle table to help with this?

HowPrayGame

Some pointers on the DIY Base map

The spark table is way too advanced everywhere, including at idle. Running 20ish advance at idle normally is insane. I posted a decent N/A spark table here that is less advanced everywhere and should be good on premium gas for most cars. Probably makes more power too. Trying to use the DIY spark map and tune idle will be a pain as the transition from 10 degrees advance to the super advanced values they have will be jumpy. I run idle advance at 10 degrees at all loads when in closed loop idle, pressing the throttle goes to 14 degrees and continues linearly as my RPMs go up. Using the RPM Timing Correction curve to prevent large deviations from the target idle RPM is advised. Use the closed loop idle initial value table instead of use last value.

Their basemap has per-cylinder fuel trim tables filled out for some reason, zero those out. It also has VVT enabled at idle, that is dumb and will cause instability. As long as you aren't using batch injection (you are using fully sequential) you can easily idle the car at 14.7 AFR instead of 14.0 on your AFR Target table.

Orinawak

Great, thanks, I really appreciate it! I will make the changes you recommended. Anything I should know about the car starting and then idle dropping until it stalls out? To me, based off the log, it looks like the car is running very rich and bogging down, but again I could be wrong since this is my first time trying this.

HowPrayGame

The AFR Gauge will show full rich for 20ish seconds after starting the car, that isn't an actual AFR its just MS attaining a connection to the wideband. AFR data on startup is garbage and shouldn't be referenced for any changes to fueling

The car looks like its stalling due to the idle valve closing and not letting enough air in (open loop idle setting issue). It also has super high spark values due to the DIYAutoTune spark table that aren't really helping the startup instability(left side of spark table issue). I recommend also zeroing out your MAT air density table to 100 across the board so when/if the IAT sensor heatsoaks it doesn't lean out due to pulling 25% fuel. My table is more like 90-110 across the entire IAT Sensor table instead of 136-75.

Zeroing out the VVT Intake Table in idle and also only turning it on when coolant reaches around 140F is good for stability too. Cold oil + VVT = weird behavior. VVT at idle/low loads also equals weird stuff.

Orinawak

Thank you! I will go through my tune and make these tweaks, and then see how it goes.

Orinawak

Currently in the middle of making some tweaks. I ended up using Brain's ignition table since I plan on boost, and see that it is scaled for boost. It definitely seems a lot better than DIYAutoTune's spark table, and I tested it with just that change, the car started and idled. When I zeroed out the fuel trims for cylinders 1-4 however, the car then would start and die again as before. I reverted it back to using the trims for now, but will revisit that. Changed the MAT air density to 100s across the board.

One thing that I am concerned about is the VVT intake table settings. I don't have any knowledge on VVT or how it works, so I'm sorry for the inexperience. I cross referenced what I got from DIY with what Brain has in his basemap for the 01-05, and the VVT tables are drastically different. I will have to research more about VVT, but the difference between the two VVT Intake tables are very noticeable. I did change the settings in my current table to turn on when coolant temps reach 140. I just don't want to make a drastic change and end up breaking something, so I would appreciate additional guidance or reference material here! From my research it seems that DIY put a lot of time into their VVT table, but just wanted to get some second opinions.

deezums

iTrader: (3)

DIY put time into the table and using it is for sure worth it, problem is nobody takes the time to actually try and use VVT at low load because it's a righteous pain in the *** and will totally kill driveability if it's even slightly wrong.

So most people don't, they only use VVT when the engine is loaded and moving because that's the easiest part of VVT to control. Leaves a whole lot on the table if you care about driving around like a normal person. You can feel how much easier the car accelerates with the cam advanced, it takes way less throttle to get around, loose a lot less speed and maintain more manifold vacuum running up hills in high gears. If you don't care about any of that, run Brian's map.

My experience with temp has been the polar opposite. VVT is easy as pie to control when the oil is cold, could run the full map all day long. As soon as the oil gets hot the oscillations start, and if they hit at low load you might eat the steering wheel from the jerkyness.

I am running the latest and greatest beta firmware, pretty much the DIY VVT table with 50% less advance below 3K and P57 I21 D180 as PID values. It looks a little like this at the moment. You probably shouldn't expect yours to behave similarly with the same values, gonna have to read up on tuning PID.

Orinawak

Thanks for the info! So you think I should get rid of the 0s I put in and just revert it back to what it was originally? I zeroed out the first 4-5 cells at low load; kept the rest of the table from DIY as is. I can see how VVT would be helpful in those scenarios you listed; my small understanding of VVT tells me that looking back at DIYs table, it seems like they accounted for many driving conditions. Still, wondering if I should revert the zeroes back to the original values. Thanks for the information on PID, I will have to research that further. I would just like to get idle dialed in so I don't have to worry about that, and then my only thing will be tuning the fuel VE table and AFRs. I'm running short on time, just because I put the car away for winter to keep it away from the salt, so trying to learn as much as possible to get this running right. Then this winter its turbo install, and then a trip to the tuner in spring. I have been able to get the car to idle currently after playing around with closed loop idle today, although it does stutter on start up and the RPMs rev up then there is a small zone where the RPMs fall quick before it settles around 900 RPM. Not sure why, but I'm going to mess with it more tomorrow, but would appreciate any tips!

HowPrayGame

You can do either with VVT, my base VVT table didn't have advance originally under 1500RPM and I tried DIYs table as I was curious and it didn't work so well for me, especially when driving around in parking lots at low load, that was probably due to my unchanged PID settings from the basemap I was running (MS3 Basic). Hits the target perfectly above 1500RPM, I don't care about power under 1500 RPM as long as the car moves. If turning off VVT at low RPMs fixes it you don't lose much. You could definitely tune with it advancing that low but I am lazy and take the path of least resistance.

Here is a log of a cold start and my tune for comparison with yours, if you want to see a normal transition from cranking into idle gradually. Almost have it perfect, pretty sure I just need to lower my cranking RPM to 350 or get a new battery so it catches properly.

You could try turning off VVT during a cold start to see if that helps your weird RPM after cranking by changing the coolant limit in VVT to something like 140, don't have to keep it like that. As far as cold stability with VVT Advance YMMV. Running 1.4.0 so PID algorithm is a bit different from yours with engine states.

Orinawak

Great, thank you! I will probably keep the advance under 1500RPM at 0, since like you said, the car just needs to get moving. I'll take a look at your tune and play around with mine and see what I can come up with! I'll be back with where I'm at later today. I appreciate it!

Orinawak

So just wanted to give an update. Looks like I am slowly getting to a pretty decent idle, so thank you for all the help! There are a few things I was hoping I could get some help with for my tune currently. So one of the biggest things I have noticed, after changing the VVT initial table and setting it to activate at 140 degrees, the car suddenly will die when the temperature reaches 140 degrees. I tried playing around with a few different values in the VVT table, but it is still dying at 140 degrees. Any help on figuring that out would be appreciated! Another thing I noticed is that at idle, my ignition advance fluctuates between 8-9 degrees. Is this normal, or is there something I'm doing wrong there?

I also believe I will have to play with my PID values, since after giving the car throttle, it drops very slowly to idle, and it goes lean when returning to idle (around 16-17 AFRs). Again, I believe that is just something I will have to play with the PID value to solve. The car also never really gets down to the target RPM of 850; it seems to sit around 940-900 when fully warmed up.

Other than that, I have attached my tune and if any other information is needed, please let me know, because I appreciate all the help!

HowPrayGame

Turn off this setting in VVT settings, there was an injector timing bug that causes the injector timing to freak out when VVT activates. I think firmware 1.5.2 R7 or something fixed that issue, if you do want to fix that issue and still use adjustment of inj timing. For now turn this off and it should fix it.


Your Idle VE Table is 37 across the board for every RPM, you will want to add more fuel at higher loads so it doesn't run lean when in closed loop idle. Sit with the car idling at temp and tune whatever cell you are in, then turn on just the A/C fans with no compressor, see what cell you are in, tune that cell, turn on your lights and defroster, put the windows up and down and see what you hit, change the values appropriately, etc. I took my current Idle VE table and used it on a 93 NA and basically just tuned the Idle VE with A/C on and with A/C off by highlighting the entire Idle VE Table and adding/pulling values and the spread between the numbers was very similar, some slight adjustments required.

The timing being at 8-9 is normal, as you are above the target RPM the timing curve pulls timing trying to reach the target idle. Fix your VE table and it will probably hit and maintain 850 RPM when at temp.

Orinawak

Great, thank you for the info! I will go and turn that setting off, see what results I get. I'll tune the idle VE table as well like you said. I had it all 37 across the board just as a starting point, but that makes sense about it leaning out at higher loads in closed loop idle due to that. I will keep you updated, thank you!

Orinawak

So while tuning the idle VE table, I decided to take a little break and come back to it. 5-10 minutes later, I come to start the car, and the idle hangs around 1400rpm or so, and then rapidly drops to almost stalling, then comes back up again. I shut the car off and tried to replicate it again, and it seems to be doing that on random starts now. It happens maybe 3 out of 4 starts that I have done. I'm a bit confused at why it may be doing this. During my search, I did find something about VVT angle that may cause that, but I'm not sure that is what's causing this. I'm not sure why it began occurring all of a sudden, but I have attached a log of the issue and my current tune. Thanks again for any help, and I'm sorry if this is a noob question!

HowPrayGame

Did you have your A/C on during the cranking? It sorta looks like the A/C compressor was on and it turned off when the dip happened, idle duty drops 10.2% instantly which matches the A/C compressor idle up duty. The closed loop idle handoff is fine and doesn't seem to be causing it. What also happens is your VVT Duty shoots way up (hits the 1800 column in the table) which allows in lots more air and doesn't help stability as well. That's why the VVT table I have has the 1500 column next to the 1600 column, stops it from advancing as soon as the RPM goes above 1k RPM, starts when it advances at 1500 so I usually don't hit that during idle or during startups.

You can check if the VVT is causing it by changing the coolant on value to something like 220C when testing hot starts so its disabled entirely.