Hi all...
My N18 auto MCS has been encountering boost issues since flashing a stage2 tune few weeks ago.

On Comfort mode, Boost buildup smoothly up to 15psi with moderate throttle. Pushing harder will see boost climbing to 21psi and shooting back to 15psi rapidly and this repeats 15-21, 21-15, 15-21... it stops when throttle is eased.

On Sport mode, Boost buildup can be rather jerky with boost pullback (akin to above) even on the way to 15psi. Harder throttle will result in the above scenario again.

Other cars having the same tune is running fine so I’m ruling out the tune as the cause.

My setup is below (aftermarket parts are 4mths old):
- stock turbo and engine internals
- NGK plugs (1 range colder)
- Forge Intercooler
- CNT catted downpipe
- JCW catback
- GFB DV
- ARMASpeed panel filter

Had replaced the DV with GFB with no improvement.

Seems like quite a few chaps are encountering this issue with differing outcomes... Anyone has any views or solution to this??

thanks in advance!!

 

I would Check for a boost leak. Maybe on of the fittings didnt get tighten, or loosened up over time. Then i would focus on the waste gate as a cause.

 

What stage 2 tune did you get?

 

A stock MCS turbo cant do 21psi boost, this sounds like a faulty tune
only a JCW turbo or after market 42mm or larger turbo can go that high.
have you contacted the tuner to explain whats happening and to verify that they tuned properly for a STOCK Mini turbo?
no matter the stage its my understanding that a stcok turbo can only go to 15psi max.
is it possible you have a JCW turbo and the tune, and or turbo are trying to make 21psi, but the tune bring it back down to 15 psi when it over boosts?

new stock turbo 4 months ago, or just the original stock turbo that came with the car?
any idea if it was ever replaced.
the extra boost provided by the stage two that bounces like that sounds like a leak of some sorts but could be an improperly adjusted wastegate, or leak elsewhere not allowing the wastegate to stay open properly.
may even be a bad wastegate that is just "flappin in the wind"

 

A stock MCS Turbo can spool to 21psi. I have a Manic Stage 2 R56 and when I put 100 octane in, I can spool to 21.4psi on the stock turbo

 

Check for leaks like suggested above. Then look at the vacuum pump and lines including the pressure converter.
Also, I would check the wastegate diaphragm with a vacuum pump. It should pull shut at around 15inHg. You may also want to check that the wastegate is working properly, and closing fully.... maybe it just needs adjustment.

 

The Stg2 tune is from Quantum Tuning that’s UK based.

 

have checked the lines and no leaks detected.

 

much appreciate the views and inputs. Will be trying them out soon.

Update:
Gotten a new map that reduces peak boost to 16psi. This seems to alleviate the problem significantly.

The boost bouncing is now more apparent on Comfort mode (with gentle throttle). Hard throttle somewhat significantly reduces it. Sports mode pulls well and bouncing only happens at peak.

Any views on a dirty fuel filter being the cause? I’m on 90k miles and it’s unlikely the filter was changed prior. It’s a used car without dealer service record so there’s no way to verify its service history.

 

Is it possible the turbo is "starving" for air?

{Easy test by removing the air filter and trying it. You can remove the air filter for a very short period of time as long as you don't have leaves or something the car could ingest.}

And if you are 90K, you absolutely, positively, 100% need to change the fuel filter if it has never been done. I changed mine at 60K and I will change it every 25K going forward. It's a $30 part for goodness sakes...less than the oil and filter.

I saw one of these simple stage 1's at $250. https://www.racechip.us/shop/mini/mi...QaAqWIEALw_wcB

I also found another one for $99. https://www.performancechiptuning.co...QaAkVoEALw_wcB

I wonder how well the $99 one performs.

 

Update:

Changed the intake to a JCW airbox. This should eliminate the air starvation concern.

Changed the fuel filter. It’s black.


Now awaiting the works to be completed. Will update again.

 

The boost bouncing issue is significantly reduced. Have feedback to QT and they will be adjusting the map.

Anywhere else or area I should look at?

 

Yeah, these are always a mess. Hopefully, you remembered to suck the nasty stuff out of the filter bowl as well. I dropped mine and half of went back into the tank.
t smells like oil/unrefined petroleum.