HI all,

Was working on 2012 MCS today trying to adjust the wastegate as I have had the car tuned and ever since has been spitting out boost, went to adjust it today and got a bit confused and I think i have adjusted the wastegate poorly. My boost gauge is reading that i am running at a vacuum and the car is idling rough now. I cant find any guides on where to start in terms of adjusting the wastegate correctly when it is already out of place. Any help or advice would be appreciated.

 

The info I have seen is to set the wastegate so the length of the rod from the mount to the nearside of the flapper is 151.5mm +- 2 mm

 

I saw that graphic and set mine up that way and it just caused boost to come in too early and boost cut. The stock turbo on my N18 MCS was set to something like 157mm so I'm very skeptical of that picture.

I think the right way is to use a hand vacuum pump/gauge and set it up so the WG is fully closed at 15inHg but tbd.

 

This is how I would adjust the wastegate. Using a hand pump, pull vacuum on the wastage actuator, then adjust the rod slightly shorter to make sure the flapper fully seats.

 

Well, I've tried the 151.2±2mm method, 7inHg that some old post mentioned, and 15inHg that was mentioned elsewhere (and seems to be the travel limit for the WG actuator)

None of this has worked for me, still have the wild boost oscillation, like a continuous spike/cut.
WG seems to move fine, no codes thrown or shadow.
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Not sure where to go from here, probably start throwing money at it - wastegate refurb, new solenoid, throttle pedal, etc...

 

Time to take a step back, I think. How did the car drive before the tune? An aftermarket tune is going to exaggerate any issues the car already has. Have you replaced the vacuum control solenoid? What is the condition of your vacuum pump? What about the vacuum hoses from the pump to the collection tank to the control solenoid to the wastegate? Are they all in good condition? If you put a vacuum pump on the wastegate and it moves freely, then it doesn’t need to be replaced. What is the condition of your diverter valve?

 

Stock tune as far as I know, if there's a tune on it it's not doing much lol.
Car came with a butchered exhaust and BOV Spacer, I think that's it. Also has a K&N panel filter, new Bosch coils and NGK 1422s to resolve a misfire when I bought it.

Car started doing this last summer when I was hauling a 2 other large guys + luggage and accelerated onto the highway. It's only gotten worse since.

Haven't changed the solenoid.
Lines look fine but I haven't taken much apart to get deeper.

DV seems to work fine, can hear it because of the spacer but I haven't bothered to figure out how to bench test it.

Haven't checked the pump.

I've been through a lot of threads and most of them settled on the wastegate so I figured I'd start there, but I'll go back and take a better look at the above. Time is the biggest issue.

 

If stock tune, then remove the 1422s and put OEM plugs in there. The 1422s will foul up on a stock tune - wrong temperature code for stock.

Next, remove the diverter valve and check for blown diaphragm.
Check this thread for pictures of what to check:
https://www.northamericanmotoring.co...diaphragm.html
Here is the better design valve:
https://www.northamericanmotoring.co...ml#post4279023

Here is a thread that sows the vacuum lines, accumulator tank, and solenoid locations:
https://www.northamericanmotoring.co...uum-lines.html
The vacuum hoses can dry out and crack. The control solenoid can malfunction. The tank can start to leak.

 

Keeping the 1422s. Really want a tune but the car needs to run, then supporting mods, then bother someone to tune it, or maybe some sort of open source movement will happen, but I'm not holding my breath.

Thanks, I appreciate the help and links. I'll take a look tonight

 

Bad idea. If the heat range of the plug is too cold, the plug will foul and cause mis-fires or stalling. The heat range of the plug needs to match the engine operation and design. Running a colder plug does not give you better performance - it can hurt performance.
https://www.championautoparts.com/Te...ine%20stalling.
https://ngksparkplugs.com/en/resourc...rk-plug-basics
https://www.onallcylinders.com/2012/...ug-heat-range/
https://www.denso.com/global/en/prod...sic/heatrange/

 

Just adjusted the wastegate like that and is running perfectly, thanks for the help

 

I tried a few things on this list. I pulled hoses off the vacuum pump. There was still vacuum in the reservoir when I pulled it, and everything seemed to hold vacuum when tested.
I tried to pull the diverter valve/spacer, but Neanderthal PO stripped all the fasteners and I couldn't get the last one out. Coolant pipe is directly in the way of that fastener as well.

That's all I tried so far because I still nowhere to work on this. I brought it to the local BMW/MINI guys and had them check a few things:

They mentioned these cars often act weird with colder plugs, basically exactly as you said, so apologies for not taking that seriously.
They found the post-cat O2 sensor is shorted, so I'm going to pick up a new one when I order the plugs. I should've replaced this long ago, but was holding off for a tune.
They mentioned that it could have something to do with the BOV spacer, so I guess I'll try to pull the compressor housing once I have my driveway back. Otherwise it's going to stay there until I get a new turbo.

Last issue they found is that the hackjob exhaust is split at the flex joint, so I ordered a resonated Scorpion catback. Long lead time unfortunately.

I'm going to also throw a new fuel filter on the shopping list.

EDIT Dec 2023:

Fuel filter was dirty, but no change. Scorpion exhaust and generic downpipe is here, WG flapper rebuild, intercooler, intake muffler delete. Just need to find time to swap it all over.
At this point I think the WG flapper is just worn out.

 

Since all the history is here, I'm going to update instead of making a new thread...

Since last update:

• New stock plugs.
• New Scorpion resonated exhaust.
• New big cheapo bar&plate/cast end-tank FMIC
• Intake muffler deleted
• No DV/BOV spacer
• New updated DV - old diaphragm was not torn.
• Vacuum pump pulls >27inHg at idle, checks good per the pelican parts article.
• Pump side of the vacuum system seems to hold vacuum - it hisses when removing vacuum line after the car has sat for a day.
• WG looks good on borescope. Seats tight under vaccum, actuates smoothly, no real play to speak of.
• Using stock N18 WG actuator now, currently set to seat at 12inHg per Lou's testing, but I've tried basically every other setting out there, as well as a different N14 actuator. ( https://www.northamericanmotoring.co...ml#post3930072 )
• Oscillation happens under cruise control, so I'm ruling out the throttle pedal. ( https://www.northamericanmotoring.co...ctuations.html )
• New downstream O2.
• Currently no codes, car performed flawlessly for 1500km round trip last week, other than this issue and some minor stuff like bulbs and exhaust knocking the bumper.
• Car only makes 12psi or so, so I am pretty sure it's not tuned.

I haven't checked for issues with:

• pressure converter valve
• Vacuum lines: WG to pressure converter valve
• Any K&N air filter / MAF foul play
• Boost leak
• smoke test/vacuum leak.

This is more for documentation than help, njaremka has given me plenty to chase yet.

Really want to figure this out before I start throwing mods or a tune at this.
If something is bad, I want to find it before it becomes obfuscated by more mods.

 

Ok...

I pulled the vacuum line for the vacuum tank/pressure converter/WG off the vacuum pump and applied vacuum.
Held something like 23inHg (which is as far as I can get the hand pump to go) for 2 hours while I was running errands, so I think the pump-tank line, tank, and tank-converter line are OK, and the Solenoid isn't leaking pressure while closed/off.

I reinstalled that line, and pulled the WG vacuum line off the WG actuator. Try to pull vacuum but can't - so the valve is venting as I assume it should be.

I reinstall the WG vacuum line with a tee to my vacuum gauge and what I get is a little weird:
While car is idle warming up + no throttle: 21.5inHg.
While car is idle warming up + any throttle: 0inHg.

Once car has run for a while:
Car at idle/coasting/shifting + no throttle: Gauge pulses between 14.5inHg and 16.5 inHg. at ~9Hz.
Light-medium throttle: Gauge goes to 0 inHg, sometimes 5inHg.
Heavy-WOT: Gauge will Spike to 21inHg then oscillate between something like 10-16inHg.
I think boost is cycling 8-11 psi while this happens, maybe as high as 12psi.

SO:
I think all of this is working as designed. Trying to NOT make boost at part throttle when there isn't demand for the power, then closing the WG for higher pedal % when the demand calls for it.

Still need to do a boost leak check, and ideally a smoke test.
If those are inconclusive, I'm going to re-adjust the WG to 15inHg again for ***** and giggles? I just feel like it shouldn't spike to 21inHg of vacuum at the WG, and then drop down so low - unless this is some sort of spool function like an EBC would do (holding the gate closed to build boost faster?).