SOLVED 4 port MAC woes

[Tzaks]

I'm having a bit of an issue with my boost controller, everything seemed to be running fine until yesterday when I was logging a new revision. At about 6k RPM I got throttle closure, half engine light and the car decelerated instantly, it gave me a scare, ngl.

Sent me log to my tuner and he advised that the 4 port MAC that i'm using is not great, asked me to switch to a 3 port and an 18 psi spring. Now, I have nothing against that and would do it if I would still have my engine crane or a support bar (sold them as I'm moving out of the country in the next 2 months). To remove the WGs on my car I have to remove subframe and steering, there's no way around it.

A bit about the car:
- Z4 DCT with JMC single turbo kit with GTX3582R
- 4 port MAC bought from MAC on Amazon US
- Dual external WGs with 14 PSI spring
- Aquamist meth kit flowing ~1600cc/m

I see there's a slightly beefier variant of the 4p MAC like this from Haltech. I know its still a rebranded MAC but there are some subtle differences, wire is on the side, the size of it seems slightly smaller and thicker.

My questions/concerns are:
* Can this be a one-off event? Perhaps bad wiring or perhaps I have to secure the solenoid better in the engine bay? It's "resting" next to outlet of the turbo but not able to move much due to all the boost lines.
* Do I have a faulty solenoid?
* Is it worth purchasing the haltech version?
* Anyone experienced something similar?

Here's a log:

4 port MAC woes

www.spoolstreet.com

 

[Tzaks]

Had tension on one of the vacuum lines, would explain the overshoot. Redone all lines and seems to be working well

 

[Brule]

4 port solenoid is not a suitable boost control solenoid for most n54 setups. Most tuners prefer using two 3 ports over using one 4 port.

The whole point of a 4 port is to have a wide range of boost pressure.

You have 14psi springs so you can have a range of 14 to 45psi on a mid range turbo on a 3 port solenoid with more resolution.

If you want 3 psi and 50 psi use a 4 port.

You will just get less resolution tuning a 4 port over a 3 port.

On a 14psi spring you can make 45psi on a 6266 with a .84AR housing.

Unless your aiming for 50 or 60 psi you do not need an 18psi spring.

 

[Tzaks]

I'm aware of the poor resolution on a 4 port vs a 3 port. The springs in the wastegates are 14psi but there's exhaust backpressure to take into account which lowers the pressure at which the wastegates will open and translates into less max PSI then you describe in your calculations. Realistically, it would translate to around 28 +- a few PSI.

Regardless, the 4 port should not overshoot as it did in the log. I'm hoping it was due to tension on my lines.

 

[Z4Dude]

Can you clarify what you mean by tension on your line? Was it pulled too tight ? Something pressed against it and collapsing it?

 

[Tzaks]

When I did the install, all lines had enough slack. Not sure exactly what happened but, in the meantime, the lines must have moved because there was quite a bit of pulling force on them. I assume this may have resulted in a kink/kinks on the vacuum lines which caused the overshoot.

If you pull a vacuum line it stretches slightly and the ID of it becomes smaller resulting in a blockage.

 

[Z4Dude]

Understood - thanks for the clarification