Another little story of weird shit happening

[GTSBoy]

6 hours ago, hypergear said:

In many cases, aftermarket dump pipe inlet flanges don't properly align with the outlet of the turbine housing, as they were designed to fit within the constraints of a 3-inch pipe. When an oversized wastegate flapper valve is installed, it can interfere with the dump pipe flange. A bit of die-grinding usually resolves this issue. Additionally, the actuator must be preloaded, otherwise, the flapper valve may rattle. The stock wastegate also tends to open too early, so upgrading to a wastegate actuator with a stiffer spring can improve boost response.

Hi Tao. My dump was ground out to provide clearance over the used swing arc. But when the clip fell off, the flap was free to travel too far. Got stuck. That's all. There's decent preload too.

You may remember that I asked for a low pressure actuator because I wasn't able to tune the car immediately, and a proper actuator probably would have left the car undriveable. Or at least barely safely driveable. But it hasn't been an obvious problem in terms of the gate blowing open under normal use. Well, maybe it has. The turbo is quite laggy compared to stock - so an actuator upgrade will be done first after the supporting mods are done and it's dyno'd to stop it pinging. Hopefully the gate has actually been lifting early. If it has, it has been necessary for me anyway, because as I said earlier in this thread, I had to back off the ramp allowed by the boost controller, to stop it pinging. I might have been in a bit of trouble if it hadn't been as slow to build boost as I have found it.

In fact - given that I will get it onto the dyno soonish - I think I'll order an actuator from you pretty soon, so we've got it there if it is clear that there's no point continuing to try tuning with the low pressure one.

[joshuaho96]

2 hours ago, tylink720 said:

I've always wondered why my brothers BMW is louder in Eco mode. Do they have e-gates from factory?

They have e-gates. At cold start they have the gate fully open to heat the cats faster. Then during cruise as mentioned fully open wastegates reduce exhaust pumping loss. 

[Lithium]

3 hours ago, tylink720 said:

I've always wondered why my brothers BMW is louder in Eco mode. Do they have e-gates from factory?

Depends on the year/model - mine is the version of the N55 which came with an e-gate however the "PWG" (pneumatic wastegate) versions actually can also do this.  They use a vacuum setup to "pull the gate open" against the spring instead of "push it open" like conventional wg setups.   This naturally means they can actually control boost down to a very low level/just open the gate if they want to.

Edited April 30 by Lithium

[joshuaho96]

6 minutes ago, Lithium said:

Depends on the year/model - mine is the version of the N55 which came with an e-gate however the "PWG" (pneumatic wastegate) versions actually can also do this.  They use a vacuum setup to "pull the gate open" against the spring instead of "push it closed" like conventional wg setups.   This naturally means they can actually control boost down to a very low level/just open the gate if they want to.

Yep, the pneumatic wastegate setup is actually quite interesting. The problem is where you plan on sourcing enough vacuum to keep the wastegate fully closed for extended periods under boost. BMW used a vacuum pump + vacuum accumulators to make it all work. I can't imagine trying to package any of that in an RB turbo where it feels like the engine bay is already laughably packed.

[Lithium]

2 minutes ago, joshuaho96 said:

Yep, the pneumatic wastegate setup is actually quite interesting. The problem is where you plan on sourcing enough vacuum to keep the wastegate fully closed for extended periods under boost. BMW used a vacuum pump + vacuum accumulators to make it all work. I can't imagine trying to package any of that in an RB turbo where it feels like the engine bay is already laughably packed.

Yeah, Turbosmart e-gate seems the way if you really want to get fancy - though much can be achieved with a couple of 3-ports and a decent enough ECU as well.

 

[GTSBoy]

23 hours ago, joshuaho96 said:

The problem is where you plan on sourcing enough vacuum to keep the wastegate fully closed for extended periods under boost.

I'm thinking that this is such a small part of the problem that you could easily forego the vac pump and just achieve 90% of what you need, which is keeping the gate open when off boost. It's not as if there are not already techniques to keep a gate fully closed under boost. After all, you have boost. Just use a wastegate actuator that will allow you to apply the boost on the appropriate side, just like every external gate out there.

[MBS206]

On 02/05/2025 at 8:01 AM, GTSBoy said:

I'm thinking that this is such a small part of the problem that you could easily forego the vac pump and just achieve 90% of what you need, which is keeping the gate open when off boost. It's not as if there are not already techniques to keep a gate fully closed under boost. After all, you have boost. Just use a wastegate actuator that will allow you to apply the boost on the appropriate side, just like every external gate out there.

Or you mean the age old problem of early 2000's manual boost tees, where they never let the pressure out of the line between the boost tee, and the waste gate, so after your first trip on boost, the damn wastegate liked to stay open and be laggy on gear change?

[GTSBoy]

6 minutes ago, MBS206 said:

Or you mean the age old problem of early 2000's manual boost tees, where they never let the pressure out of the line between the boost tee, and the waste gate, so after your first trip on boost, the damn wastegate liked to stay open and be laggy on gear change?

Yeah, no matter what bad things people can say about Julian from Autospeed, he at least was capable of thinking and his inclusion of a check/relief valve in the plumbing for the Audi boost controller, that I made a copy of and used for years**, completely eradicated that problem.

**It's still lying on my workbench where I put it about, um, 18 years ago and have never found a home for it!

[MBS206]

43 minutes ago, GTSBoy said:

Yeah, no matter what bad things people can say about Julian from Autospeed, he at least was capable of thinking and his inclusion of a check/relief valve in the plumbing for the Audi boost controller, that I made a copy of and used for years**, completely eradicated that problem.

**It's still lying on my workbench where I put it about, um, 18 years ago and have never found a home for it!

Ha ha, yeah, I've had one following me around in my parts boxes since about 2007 I believe. Just a little iddy bit hole drilled in the one I have to let it vent out once pressure was removed from the engine side. Still no idea what I'd put it on, ha ha.

[GTSBoy]

2 hours ago, MBS206 said:

Ha ha, yeah, I've had one following me around in my parts boxes since about 2007 I believe. Just a little iddy bit hole drilled in the one I have to let it vent out once pressure was removed from the engine side. Still no idea what I'd put it on, ha ha.

No no. The Audi boost controller was made from a Norgren (or equivalent) 1/4" pneumatics pressure regulator, a similar (looking) relief valve (to create the "gated" function to keep the boost off the actuator until wanted) and a check valve plumbed in parallel with those two, to relieve the boost back out of the wastegate line after the boost event was over. It was the inclusion of that check valve, used sort of "backwards" as a relief valve, that was the stroke of genius that made the rest of it work nice.

The only reason I stoped using it was because it was like any other manual/pneumatic boost controller - it's settings changed from season to season. The Profec is much more consistent winter to summer.

[MBS206]

2 hours ago, GTSBoy said:

No no. The Audi boost controller was made from a Norgren (or equivalent) 1/4" pneumatics pressure regulator, a similar (looking) relief valve (to create the "gated" function to keep the boost off the actuator until wanted) and a check valve plumbed in parallel with those two, to relieve the boost back out of the wastegate line after the boost event was over. It was the inclusion of that check valve, used sort of "backwards" as a relief valve, that was the stroke of genius that made the rest of it work nice.

The only reason I stoped using it was because it was like any other manual/pneumatic boost controller - it's settings changed from season to season. The Profec is much more consistent winter to summer.

Ahh! I see what you mean. That's a pretty cool design for an MBC.
I was just meaning my one was at least a MBC that had a path for air out, unlike so many others.