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.

[GTSBoy]

And now the bloody flapper is jammed slightly open. Lazy as all f**k in 3rd-5th (very hard to convince it to make much boost before you run out of revs), but will make 12 psi in 1st, which shouldb't be possible with a 5 psi spring and controller set to <10 psi.

Methinks I'm lucky it jammed where it did, rather than fully closed. It's actually a well weird situation. Careful examination of what's happening in the back of that housing when the gearbox comes out and all the other stuff (injectors, AFM retune) is supposed to be done, next week.

[MBS206]

5 hours ago, GTSBoy said:

And now the bloody flapper is jammed slightly open. Lazy as all f**k in 3rd-5th (very hard to convince it to make much boost before you run out of revs), but will make 12 psi in 1st, which shouldb't be possible with a 5 psi spring and controller set to <10 psi.

Methinks I'm lucky it jammed where it did, rather than fully closed. It's actually a well weird situation. Careful examination of what's happening in the back of that housing when the gearbox comes out and all the other stuff (injectors, AFM retune) is supposed to be done, next week.

Is it possibly wastegate actuator itself is sticking, or even the rod to flapper? Otherwise I reckon things are getting a bit rusty/worn

 

Also odd it won't boost in 3rd to 5th, but will in 1st, I'd expect the other way around with it slightly open as there's more time on your way to redline for it to spin up

[GTSBoy]

49 minutes ago, MBS206 said:

Is it possibly wastegate actuator itself is sticking, or even the rod to flapper? Otherwise I reckon things are getting a bit rusty/worn

Yeah, nah. I had the actuator rod off it today. The arm will not move at all. Neither out, nor in.

50 minutes ago, MBS206 said:

Also odd it won't boost in 3rd to 5th, but will in 1st, I'd expect the other way around with it slightly open as there's more time on your way to redline for it to spin up

Yeah, you'd think so, but I've been thinking about that. Even when the actuator rod fell all the way off at the beginning of this saga, it would build more boost and faster in lower gears than it would in higher gears, and you'd think that that was the opposite of what should happen. But I strongly suspect that there is a thing with the gearing getting the revs to rise faster, that there must be some transient effect with the gas flow rate rising quickly, that you don't get with the more steady state case of the higher gears.

Keep in mind - the gate is not shut in either of my weirdnesses. So things are not "normal". We normally think about a turbo spooling up (below the wastegate target) with the gate shut. I have all sorts of mental models running now where the gate is a little bit open, and having it stuck open allowing gas out while it should be going through the turbine has all sorts of weird effects (in these mental models). I'm thinking in the higher gears, the ex mani pressure builds to the point where enough gases spill out the wastegate to just prevent the pressure rising much more at all, or just creeping up, all the whole the revs are increasing and getting closer to the point where a gear shift becomes necessary.

[GTSBoy]

Well, after the full circus this week (new gearbag, 14 psi actuator on, injectors and AFM upgraded, and.....turbo repair) the diagnosis on the wastegate is in.

It was broken. It was broken in a really strange way. The weld that holds the lever arm onto the wastegate flapper shaft broke. Broke completely, but broke in such a way that it could go back together in the "correct" position, or it could rearrange itself somewhere else along the fracture plane and sit with the flapper not parallel to the lever.

So, who knows how and when exactly what happened? No-one will ever know. Was it broken like this the first time it spat the circlip and wedged itself deep into the dump? Or was it only broken when I tried to pry it back into place? (I didn't try that hard, but who knows?). Or did it break first? Or did it break between the first and second event of wierdness?

Meh. It doesn't matter now. It is welded back together. And it is now held closed by a 14 psi actuator, so...the car has been tuned with the supporting mods (and the order of operations there is that the supporting mods and dyno needed to be able to be done first before adding boost, because it was pinging on <<14 psi with the new turbo with only a 6 psi actuator). And then tuned up a bit, and with the boost controller turned off throughout that process. So it was only running WG pressure and so only hit about 15-16 psi.

The turbo is still ever so slightly lazier than might be preferred - like it is still a bit on the big side for the engine. I haven't tested it on the road properly in any way - just driven it around in traffic for a half hour or so. But it is like chalk and cheese compared to what it was. Between dyno numbers and driving feedback:

• It makes 100 kW at 3k rpm, which is OK, could be better. That's stock 2JZ territory, or RB20 with G series 550.
• It actually starts building boost from 2k, which is certainly better than it did recently (with all the WG flapper bullshit). Although it's hard to remember what it was like prior to all that - it certainly seems much, much better. And that makes sense, given the WG was probably starting to blow open at anything above about 3 psi anyway (with the 6 psi actuator).
• It doesn't really get to "full boost" (say 16 psi) until >>4k rpm. I am hopeful that this is a feature of the lack of boost controller keeping boost pressure off the actuator, because it was turned off for the dyno and off for the drives afterward. There's more to be found here, I'm sure.
• It made 230 rwkW at not a lot more than 6k and held it to over 7k, so there seems to be plenty of potential to get it up to 250-260rwkW with 18 psi or so, which would be a decent effort, considering the stock sized turbo inlet pipework and AFM, and the return flow cooler. According to Tao, those things should definitely put a bit of a limit on it by that sort of number.

I must stress that I have not opened the throttle 100% on the road yet - well, at least not 100% and allowed it to wind all the way up. It'll have to wait until some reasonable opportunity. I'm quite looking forward to that - it feels massively better than it has in a loooong time. It's back to its old self, plus about 20% extra powers over the best it ever did before. I'm going to get the boost controller set up to maximise spool and settle at no more than ~17 psi (for now) and then go back on the dyno to see what we can squeeze out of it.

There is other interesting news too. I put together a replacement tube to fit the R35 AFM in the stock location. This is the first time the tuner has worked with one, because anyone else he has tuned for has gone from Z32 territory to aftermarket ECU. No-one has ever wanted to stay Nistuned and do what I've done. Anyway, his feedback is that the R35 AFM is super super super responsive. Tiny little changes in throttle position or load turn up immediately as a cell change on the maps. Way, way more responsive than any of the old skool AFMs. Makes it quite diffifult to tune as you have to stay right on top of that so you don't wander off the cell you wanted to tune. But it certainly seems to help with real world throttle response. That's hard to separate from all the other things that changed, but the "pedal feel" is certainly crisp.

[Duncan]

Sounds like a good outcome, must be nice to have it working well, and yes everyone seems to top out under 250rwkw with a low mount rb25 so you are in the right ballpark.

It really would have been worth setting up the boost controller at the same time, but at least now you can share some back to back data on how much difference holding the gate closed until you need it makes

[GTSBoy]

3 hours ago, Duncan said:

It really would have been worth setting up the boost controller at the same time, but at least now you can share some back to back data on how much difference holding the gate closed until you need it makes

Experience has shown that trying to get the simple boost controllers (I have a Profec) set up on the dyno leads to needing to do it all on the road again afterwards. The dyno load is sufficiently different that the gain always ends up wrong and the start boost is wrong, and it ends up surging. Not compressor surge - just overboosting and carrying on. People are probably somewhat acustomed to the modern reality of Haltechs, et al, controlling to a closed loop target.**

It's no skin off my nose. The dyno is easily accessible for the little extra tuning that will be required afterwards. And as you say - I stand to gain some useful info.

** On that subject, the idea of torque modelling/targetting is apparently a big OEM thing now. Look at Jason's Engineering Explained YT video on the new Corvette's turbo control system. This sort of thing would appear to be quite achievable in modern aftermarket ECUs, I should think. Is this what people are already doing to avoid the "boost target is 20 psi and I'm going to get there even though the throttle is only 50% open!!!" that I imagine simpler closed loop control would yield?

[Duncan]

Yeah it has been a real mind bender trying to understand the VR30DDTT tune, it is very much target torque based and with electric waste gates theoretically easier to have them open and closed as much as desired without waiting for the vacuum system to respond. Also a pain because there is no sign of aftermarket so you have to remap the factory one, like a nistune but with a billion dimensions on the maps

[Komdotkom]

On 21/06/2025 at 11:26 PM, GTSBoy said:

 

• It made 230 rwkW at not a lot more than 6k and held it to over 7k, so there seems to be plenty of potential to get it up to 250-260rwkW with 18 psi or so, which would be a decent effort, considering the stock sized turbo inlet pipework and AFM, and the return flow cooler. According to Tao, those things should definitely put a bit of a limit on it by that sort of number.

Return flow cooler will be killing you I reckon. You can certainly push more through a low mount setup but they're good numbers for a stock looking engine bay. 

Mine made 345rwkw (hub) at 22psi on 98 with a "highflow" on a stock manifold but it's a long way from a normal high flow or standard engine. I used one of those Turbosmart IWG-75's and it was great with the Motec running closed loop boost with pressure being applied to both sides of the diaphragm. 

[MBS206]

On 22/06/2025 at 10:58 AM, Duncan said:

Yeah it has been a real mind bender trying to understand the VR30DDTT tune, it is very much target torque based and with electric waste gates theoretically easier to have them open and closed as much as desired without waiting for the vacuum system to respond. Also a pain because there is no sign of aftermarket so you have to remap the factory one, like a nistune but with a billion dimensions on the maps

There are advantages, and disadvantages to remapping the factory.

 

The factory runs billions of different maps, to account for sooooo many variables, especially when you bring in things like constantly variable cams etc. By remapping all those maps appropriately, you can get the car to drive so damn nicely, and very much so like it does from the factory. This means it can utilise a LOT of weird things in the maps, to alter how it drives in situations like cruise on a freeway, and how that will get your fuel economy right down.

 

I haven't seen an aftermarket ECU that truly has THAT MANY adjustable parameters. EG, the VAG ECUs are somewhere around 2,000 different tables for it to work out what to do at any one point in time.

So for a vehicle being daily driven etc, I see this as a great advantage, but it does mean spending a bit more time, and with a tuner who really knows that ECU.

 

On the flip side, an aftermarket ECU, in something like a weekender, or a proper race car, torque based tuning IMO doesn't make that much sense. In those scenarios you're not out there hunting down stuff like "the best way to minimise fuel usage at minor power so that we can go from 8L/100km to 7.3L/100km. You're more worried about it being ready to make as much freaking power as possible when you step back on the loud pedal as you come out of turn 2, not waiting the extra 100ms for all the cams to adjust etc. So in this scenario, realistically you tune the motor to make power, based on the load. People will then play with things like throttle response, and drive by wire mapping to get it more "driveable".

 

Funnily enough, I was watching something Finnegans Garage, and he has a huge blown Hemi in a 9 second 1955 Chev that is road registered. To make it more driveable on the road recently, they started testing blocking up the intake with kids footballs, to effectively reduce air flow when they're on the road, and make the throttle less touchy and more driveable. Plus some other weird shit the yankee aftermarket ECUs do. Made me think of Kinks R34...