MS2 Turbo M20 Low Load Runs Rough

[varg]

Well it looks like any feedback on your tune is pretty pointless until you get it firing on all cylinders, since you created it with the car running on 5. It's good that you've tracked a major problem down, hopefully it will run much better and you can get a good tune started.

[ScottyB326]

Compression is good, I've traced the problem to a bad fuel injector. :(

Yea it may be lean but I haven't gotten into good boost so it's hard to know how it'll behave with 6 cylinders lol but thank you for the heads up so I can be mindful.

And thanks so much for helping me think this through man, I really appreciate it!!!

[BMWManiac]

I would recommend doing a compression test, ASAP! Sounds like you're now running on 5 cylinders, which will make tuning a nightmare.

Also, compared to my VE table, your fuel looks pretty lean in boost, but as long as your AFR gauge reads fine, then its probably just difference in our setups....

[ScottyB326]

Okay new direction entirely (maybe):

Pulled some plugs, cylinders 3,4 and 6 all had great looking plugs (although they're around 20K miles old), cylinder 5 plug was black and sooty. Started the car, pulled plug wires on 5 and 4 to compare, when i pulled 5 no difference, pulled 4 and rpm dropped. Swapped the plugs on cylinders 4 and 5, and no change; pulling wire on 4 dropped rpm, 5 made no difference. I checked visually for spark, both 4 and 5 have very similar spark output. So I've dropped cylinder 5 and that's causing my problems.

Head was replaced 40K ish miles ago with a rebuilt head, and no problems like this right before turbo parts went on, so preliminary thoughts are that it's not a burned valve (although I'll have to get some time to do compression and leak down tests before I can rule out cylinder health). BMW's really gay fuel injector placement means it's a nightmare to pull a single injector plug, or to swap injectors.

Before I start delving into this, does anybody (I think you're the only one reading this thread varg, and I thank you for that :) ) have any input as far as hearing about this happening before, or a BMW specific way to test stuff? I'm still damn new to the BMW realm....

Thanks in advanced

[ScottyB326]

Maybe this link works, maybe it doesn't lol

http://www.filedropper.com/turbotune5

[ScottyB326]

I will do my best, I'm not super tech savvy (I barely figured out how to attach pictures!)

Give me a sec, I'll get it up.

And yea, I found multiple instructions on which point a to point b. I'll finally have a day off tomorrow so another plan is to check plugs, compression, and try pulling injector plugs to see if any cylinders are unaffected. And vac leaks.

For VE tables, I've played with both sides of stoich, from rich to lean, nothing alleviates the symptoms...

Dude thanks for the help too man

[varg]

I have been doing a bit more head scratching....

Firstly, I hadn't checked some settings on the new tune I'd been working with, and I didn't even change it to the wideband sensor from narrowband. So then the ego control set to afr target got things a little better, but not much. Tried running it purely on 've tabled and played with the cells, still running weird. I'm fairly certain it's some sort of hard setting.

Could the vac plumbing to the wastegate and/or boost controller cause this sort of issue? The car is definitely down on power compared to when it does occasionally pull properly at higher rpm

EGO control should be turned off until you have your VE table correctly dialed in. EGO control is not auto tune, tunerstudio's auto tune is useful for getting VE tables on point but the O2 sensor readings must be good and consistent for it to be worth anything. Vacuum plumbing to those is point a to point b, there's not much that can go wrong there as long as it isn't leaking. Can you link to your .msq file so I can go over it?

[ScottyB326]

I have been doing a bit more head scratching....

Firstly, I hadn't checked some settings on the new tune I'd been working with, and I didn't even change it to the wideband sensor from narrowband. So then the ego control set to afr target got things a little better, but not much. Tried running it purely on 've tabled and played with the cells, still running weird. I'm fairly certain it's some sort of hard setting.

Could the vac plumbing to the wastegate and/or boost controller cause this sort of issue? The car is definitely down on power compared to when it does occasionally pull properly at higher rpm

[varg]

I had the ground for the LC2 controller grounded with the gauges. I grounded it to the same ground as the megasquirt instead. I'm not sure I understand why this is better, considering they're all going to ground eventually, but I did it anyhow.

Megasquirt is measuring the voltage potential between the signal wire and the ground. With the wideband's ground attached to the MS ground plane you ensure that there is not any excess voltage drop at the MS unit. Any run of wire, especially one with splices and connectors in it, will have some voltage drop, so it's advantageous to have sensor grounds come back to the thing that will be reading the sensors.

Another question: target AFR setting. I have in the settings set megasquirt to use a target afr. So that means it utilizes the target afr table to calculate the amount of fuel, is that correct? If that's the case, isn't the VE table going to be generated by MS instead of me inputting values? When driving, and i adjust the VE table, it affects the AFR as measured by the gauge, so it seems like both things are affecting the way the car runs. Do I understand this correctly or have I screwed something up?

The VE table is what megasquirt uses to calculate the pulsewidth and thus fuel delivered. The AFR table only has an effect if the EGO correction is turned on, and it's a crutch and shouldn't be relied on in heavy load, you should keep it off until you have your VE cells dialed in. Tunerstudio can use the AFR target table to auto-tune your VE cells though, changing them to give an AFR value that matches the table as you drive, caution and an eye on the AFR gauge is of course required.

I suggest reading up a bit on tuning MS and what each setting and table in the Tunerstudio software does to minimize any confusion you may have and make tuning easier for you.

https://www.megamanual.com/ms2/tune.htm

[ScottyB326]

I had the ground for the LC2 controller grounded with the gauges. I grounded it to the same ground as the megasquirt instead. I'm not sure I understand why this is better, considering they're all going to ground eventually, but I did it anyhow.

Another question: target AFR setting. I have in the settings set megasquirt to use a target afr. So that means it utilizes the target afr table to calculate the amount of fuel, is that correct? If that's the case, isn't the VE table going to be generated by MS instead of me inputting values? When driving, and i adjust the VE table, it affects the AFR as measured by the gauge, so it seems like both things are affecting the way the car runs. Do I understand this correctly or have I screwed something up?

[ScottyB326]

Yea gotcha, I'll double check the wiring and ensure I have the proper grounding.

[varg]

Thank you for the suggestions Varg, I changed the TPSdot value to 100 (played with it from 50-300) and seemed to yield the best results, but is that about the range I want to be in? Everything else seemed to have it bog down before it began accelerating again, but I wasn't sure if that was an issue with the TPSdot or the actual Pulse Width in ms. Perhaps more trial and error would say that even lower than 100 is better but less ms of extra fuel. It does seem to pull a little better though according to the butt dyno.

You want TPSdot threshold to be as low as possible without inducing AE during slow throttle movements. The "correct" value depends on many variables so you just have to find what works best. You also want to play with the AE curve values to get it just right.

I noticed the AFR gauge in the car tends to read a few points higher than the MS reading in the AFR table. For example, if the value in the AFR table is 12.7, the gauge is reading 11.5. I would think if there was a noticeable vac leak then the gauge would read leaner than the AFR table....

That's a significant error. Is your wideband wired up correctly? It is critical that the wideband signal ground is connected directly to the MS ground plane. You don't want the wideband's power ground to be connected to it though. If it is wired correctly, then you need to verify the calibration is correct in tunerstudio.

[ScottyB326]

Thank you for the suggestions Varg, I changed the TPSdot value to 100 (played with it from 50-300) and seemed to yield the best results, but is that about the range I want to be in? Everything else seemed to have it bog down before it began accelerating again, but I wasn't sure if that was an issue with the TPSdot or the actual Pulse Width in ms. Perhaps more trial and error would say that even lower than 100 is better but less ms of extra fuel. It does seem to pull a little better though according to the butt dyno.

Still has a bit of a sputter, almost a chugg to the motor though.

I noticed the AFR gauge in the car tends to read a few points higher than the MS reading in the AFR table. For example, if the value in the AFR table is 12.7, the gauge is reading 11.5. I would think if there was a noticeable vac leak then the gauge would read leaner than the AFR table....

[varg]

It's far worse at accel and deccel, if you keep steady idle it feels slightly better, but still rough. I can only get it smooth if it's full throttle as rpms pick up. Even then lately it doesn't always smooth out. It's very noticeable when it smooths out.

I was looking at your thread on my phone before and I didn't notice your TPSdot threshold was so high, you should back it down a lot from 500. At 500%/sec threshold you basically have no AE unless you're stabbing the throttle (this threshold means that AE won't happen unless you're moving the throttle fast enough to open it from 0-100% in 1/5th of a second). To set that to the correct value you want it as low as possible without having AE occur during slow throttle changes i.e. modulating your speed on the freeway.

1. The pcv type hose from valve cover to throttle body. I removed it because it was pressuring the valve cover and blowing oil out the fill cap. I plugged the tb hole and left the valve cover nipple open.

Should not be a problem.

2. The 02 sensor is fairly close to the exhaust tip. Probably 10" tops from the sensor to the tip with two 45 angles before the tip.

Also should not be a problem, though it will add lag and make transient tuning a little more difficult.

[ScottyB326]

It's far worse at accel and deccel, if you keep steady idle it feels slightly better, but still rough. I can only get it smooth if it's full throttle as rpms pick up. Even then lately it doesn't always smooth out. It's very noticeable when it smooths out.

Hardware wise I thought of two other things:

1. The pcv type hose from valve cover to throttle body. I removed it because it was pressuring the valve cover and blowing oil out the fill cap. I plugged the tb hole and left the valve cover nipple open.

2. The 02 sensor is fairly close to the exhaust tip. Probably 10" tops from the sensor to the tip with two 45 angles before the tip.

I'm checking for vac leaks but I don't have a great way to smoke test it, but I'm using some brakleen to check for rpm spikes. I also had all of the vac reference ports around the tb rtv'd in so they wouldn't leak, but I didn't do that when I put everything back together with the turbo since I'd been pulling stuff out and reinstalling things repetitively, so I'll try to get all the vac leaks solved better first.