Hello everyone,

I recently upgraded the turbo in my 2013 JCW (N18) and I am having trouble holding 23 psi until redline. This is with both Marios 43mm turbo and the GTD 47.

Right now I have an RPM tune by Mario with switching kept from a previous manic tune. Map C should be holding 23 psi until redline with the GTD.

I have tried a few things to diagnose the issue,

- Adjusted the wastegate arm of both turbos multiple times.
- I got a boost leak check done, no leaks.
- tried multiple stock diverter valves, with and without the upgraded spring.
- I checked to see if my ebay intercooler was a massive restriction, 2 or 3 psi drop from the turbo outlet to the intake manifold, even at high RPM/load
- I purchased a DV+

When using the stock diverter valves the car drives quite normally until around 5k RPM then the boost drops to 21 psi and hold there until redline.
When using the DV+ I hold boost until 4500 or 5k rpm then the boost starts pulsing between 20 and 22 psi about 3 times a second. This makes the acceleration very jerky. It is almost as if the diverter valve is rapidly opening and shutting.
When configuring the DV+ to act as a block off plate (by disconnecting the plunger line and plugging it) I can hold 21 or 22 psi until redline.

When tightening the wastegate a small amount I hold 24 psi until 5k then it drops off to 21 psi.
When the wastegate seems to be set properly I hold 23 psi then it drops off. to 21 psi
When the wastegate is slightly looser I cant hit 23 psi at all.

I am running methanol so I know it is not high intake temps causing a boost cut.

I am using a high flow drop-in DRY panel filter.

I am using a fully decatted exhaust with a JCW muffler and 2 resonators.

This issue is present on map B as well, holds 22 psi until 5k then drops to about 20.

I don't have any codes or CELs, even when read with a BMW code reader.

Mario has assured me that it is not the tune that is lowering the boost on the top end.

The only things I can think that could be causing this issue are:
- A boost leak ONLY at high flow (would have been missed during the static boost pressure test).
- A bad MAF or MAP sensor (map sensor seems to be within 1 psi of my boost gauge but ODB only outputs up to 21 psi or so).
- A bad pressure converter or vacuum pump.

Does anyone here have any idea of what could be causing this issue? I don't want to spend a bunch of time and money changing components that arent bad.

Edit: here is a video of the pulsing with the DV+ installed.

https://youtu.be/HnBAPQMeeFg


Thank you all so much,

Daniel

 

I couldn't see where to upload a file when editing my OP. Sorry for the double post.

Anyway, here are some data logs. 0.1s per point, taken with torque pro app.

 

Me and another guy both have a similar if not the same issue as you. I just don't know what it is tbh. The only things left to do (for me at least) is put t-bolt clamps on all the boost hoses and see if that changes anything. Like you said there might be a leak only underload. Was also told to check for a vacuum leak after the maf but before the turbo inlet. Also if you start out in second gear floor it to red line shift to third red line it then shift into fourth, does your boost get lower as you go up through the gears? So second gear it might hit 22psi then third gear will only hit 18-20psi or so, then fourth gear it hits like 18psi then falls off?
Here's my whole thread= https://www.northamericanmotoring.co...ent-boost.html
And here's his= https://www.northamericanmotoring.co...sues-gone.html

 

I had actually read through both if those threads about a month ago. You're right, the symptoms are very similar. I will try rowing through the gears tomorrow, I'm not sure if I had the issue with boost getting lower as I shifted.

Have you changed the MAF sensor?
Have you changed the pressue converter?
Who did your tune?

I am going to try spraying the MAF sesnor with MAF cleaner tomorrow. I will update the post here.

 

Another similar problem but at a higher boost level --- while on a dyno, my boost peaks at 30psi and around 4K RPM, then gradually drops to about 24 psi at 7K. My tuner assures me that the turbo is max'd out --- it can't provide the air needed to sustain 30psi. The fact that max boost has been achieved, if only for a second or two, confirms everything else is functioning correctly. If you guys are running a K03 / 04 hybrid turbo, there's a strong probability you have the same problem --- turbo can't provide the needed air --- it's not a leak or adjustment problem. Opening the pre and post-turbo air passages, or cleaning the FMIC might help, but not likely. Maybe your cat is blocked / plugged? Anything blocking airflow can cause this problem too.

 

Did you apply a tiny amount of transfluid/oil to the brass piston for the DV+ like instructions indicate? What do your charge and discharge pipes consist of? You said you used a drop in filter, assuming you have stock airbox?

 

If I was using a smaller turbo then that would be correct but this turbo can flow MUCH more than I am asking it to flow.
I may have a restriction somewhere, I don't have any cats in my exhaust, the only real restriction there(other than the turbo itself) is the muffler which is a JCW muffler. There could be a restriction pre-turbo inlet but I can't find one. I only have a 2 psi drop at hgh flow/load from turbo outlet to manifold so I don think there is much of a restriction there.

I did oil the piston, the issue is that the ECU is commanding the valve to open, it is not opening by itself, if I set the valve up normally but have a dummy valve attached to the wire harness (instead of the DV+) the pulsing doesn't happen and the valve operates like a blockoff plate.
My charge and discharge pipes are stock JCW right now, but they aren't a restriction (see OP or above reply). It is a stock JCW intake, there may be a restriction there but people are flowing a more than I am with this same setup.


I will try and get a video of what happens and post it here so it is clear what I mean.

 

Have you changed the MAF sensor? I haven't touched the maf at all. But do have the maf up on torque and it won't even max out in 3rd, 2nd, and 1st gear. But it almost seems like when ever it gets close to maxing the maf out the car has its hissy fit and dumps boost. Now I don't know how accurate the reading is but I would think its damn close.

Have you changed the pressue converter? That was the very first thing I changed. I also read in an old post to check the fuel tank vent valve but, idk how to test that and its another $100 down the drain if it doesn't fix it.

Who did your tune? Mario did back over a year ago.

 

What is max for our MAFs? I dont think I am even getting close to a max reading (it actually seems super low on my pulls).

I think the fuel tank vent valve is what connects to that little tube on the side of the post MAF intake tube. If the valve is bad it may be letting too much air into the intake. I may try disconnecting it and plugging the opening on the intake. I have the resistors to trick the ecu into thinking it is still connected.

Mario did mine too. He isn't sure what it could be either. We went through 3 turbos, the first 43mm turbo was bad (cracked housing from factory/rebuild), the second was likely still good but still couldn't hold boost, the third was the GTD.

 

Here's a post from another tuner talking about the mafs. https://www.northamericanmotoring.co...ml#post4362595
The vent valve for me is connected to the intake manifold on the right side, but I have the N14 engine. But RealOEM says its in the same location for the N18.
https://www.realoem.com/bmw/enUS/par...oopS_JCW&mg=13

 

Thanks for that info. I will look into that vent valve.

Here is a video of a 75% throttle pull. Is this what yours seems like? This is with the DV+ installed.

 

This is full throttle with the DV+, it does the same thing at 75% throttle as well.
Here's another one where it just sits at 15psi then goes and hits 18-19psi right before I let off.

 

Is this with the DV+? This wont happen for me with the standard diverter valve. Instead the boost just drops slowly to 20 psi and holds there.

 

Ya it's with the DV+.

 

Does it happen with the standard diverter valve?

 

Yes, it seemed worse with the oem diverter valve. Here's a video of it.

 

I think that i am going to take my mini to the local BMW dealership ams ask if they can diagnose it. Maybe they can see why the ecu is commanding the valve open.

 

My problem hasn’t been loss of boost though i have seen it do it, but generally speaking, loss of boost like that would indicate the system be it turbo or otherwise cant maintain that amount of boost.

my problem has been surging boost 1-3psi bouncing of the boost needle at max boost.
my boost issue is/was related to the cold air intake.
once i put the stock air box and better flow filter in, the boost was much more controlled.
with CIA i would literally hit ½ throttle and be getting maX boost, t what i would consider rpm’s where the engine just isn’t ready for that much boost all at once. It would rarely go 10-15-21psi, it would go from a few psi to max 21psi then the need would bounce very fast 20-23,24psi.
a non mini guy i spoke to locally said with his Subaru when it did that it was the vacuum regulator, not being able to keep up with the demand. But the mini turbo is boost driven but he said still replace the regulator, and get a 3 way he said as they can handle the demand better and control the wastegate better.

but this weekend i replaced the stock MAF with an after market Spectrum Direct on that uses bare sensor wires (stock MAF uses an encases sensor wire) and since them i am running very rich.
rich with sport mode off is wicked, the extra horse power is welcome, though i fear what it is doing to my plugs.
sport mode is just dumping fuel, come to a stop and all you smell is rotten egg/sulfur, so fuel is being dumped, in excess into the exhaust because of the bangs and pops.

today i reset the throttle adaptations, to no avail.
this evening i reset the DME adaptations but haven’t had a chance to drive it yet.
resetting the dme adaptations helped with my horribly bad dead zone in the throttle (very top 1” of the throttle was a dead zone and the car would try to die, then compensate the rpm’s.
in sport mode, at idle the dead zone was still really bad.

i think the MAF is grossly misreporting air, going to call partsgeek.com and get a replacement. Or return and switch back to stock.

but to be honest keeping sport mode off.. that extra fuel is bad ***, and what I had hoped the mini would be with a stage 3 tune.
but i also want to put the CIA back in and see what happens....