[sleeeper90]

Hey guys, Im just curious what setups are being ran on external wastegates for boost control on these n55s or what the preffered method is. Ive read about some trying to run the without a spring and using vaccum, also some mac solenoids which I am not very familiar with, also ive seen Gforce boost controllers being used. Ive got a Hypergate coming with the kit I bought. Is there a seamless way of getting that to regulate boost? I found one option thats a pneumatic wastegate but it wont fit my manifold, Id have to build and adapter, and also its over 700 dollars so im just trying to see other options you guys might be having success with.

Thanks

[wheela]

Have you come across this thread yet?

https://f30.bimmerpost.com/forums/sh....php?t=1656323

I'll be exploring this route and doing some bench testing with that Pierburg valve for use with my speedtech kit.

[wheela]

Also, is the $700 wastegate you mentioned that vacuum operated straight gate from Turbosmart? Those look pretty awesome, but would need some custom fab since they plumb so differently than a standard wastegate.

[sleeeper90]

Originally Posted by wheela

Also, is the $700 wastegate you mentioned that vacuum operated straight gate from Turbosmart? Those look pretty awesome, but would need some custom fab since they plumb so differently than a standard wastegate.

That thread is pretty informative but i think mostly for stock location wastegates. Could translate to an external though ill have to read it more thouroughly. And yes, that would be the Turbosmart Straightgate 50, I actually came across you mentioning it on a spool street forum. It might be the easier route even though its twice as much as other options, I got a hypergate45mm coming but Im thinking to get the pneumatic one working Id just have to weld a vband adapter and modify the dumptube from SpeedTech. To be a plug and play that would be the vacuum based option, not boost based, is that correct?

[wheela]

That thread is actually for running conventional (normally closed, open with pressure) wastegates on the stock DME. He happened to have an internal wastegate turbo, and he fitted it with conventional wastegate actuator vs. stock vacuum wastegate actuator, which is normally open, and closed with vacuum. So it's directly applicable to running a conventional external wastegate, like with a speedtech kit.

It's a challenge because the stock vacuum boost solenoid runs on a 250Hz (maybe 300Hz? I could be off a bit) duty cycle signal from the dme. But boost solenoids for pressure are generally designed to run on a duty cycle signal in the neighborhood of 32Hz. Those valves designed to run at lower frequency duty cycles generally won't work so well trying to run them at higher frequencies.

Alot of people running a conventional wastegate use a Mac valve, which is designed for the 32Hz duty cycle signal. Since the DME is 250Hz, they usually end up running some kind of secondary boost controller with a Mac valve for boost control.

However, that pierburg valve he used in that thread seemed to work well enough at the 250Hz signal, despite being designed for 32Hz.

I don't want to use a secondary boost controller, so I'm planning on using that pierburg valve. Before I do though, I'm going to do some bench testing to see how much performance the valve loses running at 250Hz vs. 32Hz.

As far as that straight gate goes, if you get the vacuum based version, it would be plug and play from a control stand point; you'd control it with vacuum from your stock boost solenoid (pressure converter) just like with a stock vacuum wastegate actuator. No additional boost controllers or solenoids required.

[wheela]

One of the things I like about the speedtech manifold is that it's divided for twin scroll turbos. It's only shortcoming in this regard is the external wastegate implementation; both halves of the manifold (cylinders 1,2,3 and 4,5,6) are routed to the same wastegate port vs. having a seperate wastegate for each side of the manifold. This port is divided which is good, but the baffle is flat, so it can't fully seal against the wastegate plug, which is rounded. It creates a gap for pressure pulses from one side of the manifold to bleed over to the other side. It's a very small gap, so probably a negligible effect.

However, this is what pushed me back away from the straightgate. It's a butterfly valve, so there is more inlet area when it's closed, which would increase the size of that gap at the wastegate port on the speedtech manifold. Plus, I'd probably have to put a 90 degree elbow between the manifold wastegate port and the straightgate to get it to fit, also because the flange is a different size than the speedtech port. This would create a pretty big leak area Between the two halves of the manifold. I was concerned it could be big enough to negate some of the benefits of having a divided manifold and twin scroll turbo. So I decided the straightgate wasn't for me given my speedtech manifold. But I'm super picky and particular with my build, lol.

Here's some pics of the divided wastegate port, and the rounded plug of a hypergate 45. I think the Gap will be small enough not have meaningful effect. Also a pic of the straightgate. You can see that big inlet area which wouldn't mate against the divider in the speedtech wastegate port. It would create a leak path between the two halves of the manifold.

[wheela]

Here's a good article showing actual results from an A-B comparison of twin scroll vs. single scroll on the same car, with same mods - only difference was swapping out single vs. twin scroll turbine housing. Twin scroll is a SIGNIFICANT advantage.

https://dsportmag.com/the-tech/twin-...-great-divide/

Thank you to Calvinnismo for sharing this link in a different thread.

[sleeeper90]

Originally Posted by wheela

That thread is actually for running conventional (normally closed, open with pressure) wastegates on the stock DME. He happened to have an internal wastegate turbo, and he fitted it with conventional wastegate actuator vs. stock vacuum wastegate actuator, which is normally open, and closed with vacuum. So it's directly applicable to running a conventional external wastegate, like with a speedtech kit.

It's a challenge because the stock vacuum boost solenoid runs on a 250Hz (maybe 300Hz? I could be off a bit) duty cycle signal from the dme. But boost solenoids for pressure are generally designed to run on a duty cycle signal in the neighborhood of 32Hz. Those valves designed to run at lower frequency duty cycles generally won't work so well trying to run them at higher frequencies.

Alot of people running a conventional wastegate use a Mac valve, which is designed for the 32Hz duty cycle signal. Since the DME is 250Hz, they usually end up running some kind of secondary boost controller with a Mac valve for boost control.

However, that pierburg valve he used in that thread seemed to work well enough at the 250Hz signal, despite being designed for 32Hz.

I don't want to use a secondary boost controller, so I'm planning on using that pierburg valve. Before I do though, I'm going to do some bench testing to see how much performance the valve loses running at 250Hz vs. 32Hz.

As far as that straight gate goes, if you get the vacuum based version, it would be plug and play from a control stand point; you'd control it with vacuum from your stock boost solenoid (pressure converter) just like with a stock vacuum wastegate actuator. No additional boost controllers or solenoids required.

I see now, i glanced at it last night and only saw the stock wastegate.
Is that pierburg supposed to just plug in and replace the stock solenoid? How about manual boost controllers on these cars? is that even possible to run one and bypass the boost contol solenoid or would that cause issues and codes?

Also i see what you mean about the manifold and straightgate, that mating area probably isnt very desirable. Hopefully I can get the hypergate to work well so i dont have to spend extra on that and open another can of worms. I had no idea boost control on these cars was so complex.

[wheela]

Yeah, I haven't verified against my own harness yet, but he said he selected that particular valve due to having a compatible connector, and tabs for mounting with screws .

I believe some guys run a GFB III, and others JB4, so there are options for external boost controllers. Motiv reflex seems like a really powerful option, but I think they're still working some bugs out. I haven't looked into them too much though, since I'm very set on controlling everything with the DME.