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All good info, thanks to everyone. This is one of those things where you study it over and over and then actually come to understand how it works. I'm only halfway through that process. In my case, unless I misunderstood Kevin, the spring upgrade he installed for me will simply allow my stock X50 motor to run a bit better without requiring a tune. I will basically be setting the WGs to sync via the recommended factory procedure before re-connecting the hoses from the N75. I had him rebuild the actuators because when I pressurized the intake, it was obvious air was escaping rapidly from the passenger side actuator. So, this is just a first stop on my leak testing journey, but it can't continue until I install the rebuilt actuators & try again.
All good info, thanks to everyone. This is one of those things where you study it over and over and then actually come to understand how it works. I'm only halfway through that process. In my case, unless I misunderstood Kevin, the spring upgrade he installed for me will simply allow my stock X50 motor to run a bit better without requiring a tune. I will basically be setting the WGs to sync via the recommended factory procedure before re-connecting the hoses from the N75. I had him rebuild the actuators because when I pressurized the intake, it was obvious air was escaping rapidly from the passenger side actuator. So, this is just a first stop on my leak testing journey, but it can't continue until I install the rebuilt actuators & try again.
Heh good on you, i gave up on understanding hkw the vacuum system works and just imitated diagrams and replaced piece by piece hose by hose. All i know about 1 bar wastegates on small turbos like k16 is that they stay shut at low gears. And high boost at low gearing can destroy lots of things in any car.
...the spring upgrade he installed for me will simply allow my stock X50 motor to run a bit better without requiring a tune.
The full answer probably has some nuance to it, but my understanding is that 1) if your actuators, N75 valve, and boost control plumbing are all in perfect condition and operating as they should, and 2) you are running a stock tune at stock boost pressure, then upgraded actuators or higher pressure wastegate springs wont do dick.... On K16's at least, not sure how the X50 turbos change the equation.
But higher boost applications, there is absolutely a place for them.
By the way, wastegate actuator diaghprams and associated N75 plumbing is usually not tested by pressurizing the whole turbo system like you do for normal boost pressure leak testing,, but rather with a small hand-held pressure tester.
Disconnect the hose from the back of the wastegate actuator, connect the pressure tester, pump and note pressure when actuator rod begins to move and when fully open.
You can also disconnect the hose from the output (bottom connector) of the N75 valve, connect the pressure tester, pump and see that *both* rods move and at the same time.
Very good explanation, I am still learning a LOT about turbo cars (this one’s my first) and these kinds of discussions are very helpful!
I had asked for and received a Mitivac for Christmas, can it be adjusted to make pressure instead of vacuum too? (I haven’t gotten it out of the box yet)
Am thinking I should have changed these when I put on the new TB...
The N75 valves actually don't fail all that frequently.... Much more common to have a split hose, leaky connection, or the electrical connector not fully seated on the N75. I replaced mine, but mostly because the mounting tab was broken. The valve itself still worked perfectly.
There's no need to replace the N75 (wastegate control) or N249 (diverter valve control) valves unless something is wrong with them, which isn't too often.
[QUOTE=pfbz;16351623 upgraded actuators or higher pressure wastegate springs wont do dick.... On K16's at least, not sure how the X50 turbos change the equation.
But higher boost applications, there is absolutely a place for them.[/QUOTE]
I wish I could remember exactly what Kevin told me, but the essence was that slightly upgraded springs are supposed to help a stock X50 car, which I believe mine is. My prior 3rd gear "test" seemed to indicate stock, but I will re-check the boost behavior on a 3rd gear pull once I get the rebuilt actuators installed. I'm going to install them while setting the "preload" to match the measurements I took prior to removal, then attempting to sync them via pressure & dial indicator before re-connecting the hoses coming from the N75.
After your initial actuator setup, try pressurizing from the single hose that connects to the N75 valve. That way you can make sure they both are completely synchronized... Just look for them to crack at the same pressure. the one thing the ECU and N75 valve can NOT do is adjust if one turbo is opening the wastegate slightly earlier than the other.
As with all sensors they do fail. N75 rarely fail, but some have..
With the larger K24 turbine housing, turbine wheel and larger wastegate "GATE" >>the turbine pressure will push the gate open and hang it open between shifts. Installing engineered progressive springs will prevent this from happening.
You will get a 10th of a bar over pressure with 1 bar wastegate springs over the stock tired springs.. I have tested this on the STOCK X50 and GT2 ECU...
The wastegate kits are not recommended for stock K16's..
01-13-2020, 08:14 PM
