Controlling external wastegate with the DME?

wheela

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Jun 4, 2021
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Hello all. This question may be more suited for the advanced tuning section, but that's n54 specific and I'm n55, so I put it here.

Those of you running external wastegates, are any of you controlling it directly with the DME? Or is everybody using some kind of boost controller and a mac valve?

I really like the load-based control of the DME, and for my own personal preference, I'd really like to avoid adding any extra controllers to my car. However, turbo upgrade options that run on a vacuum-driven normally open wastegate are very limited unless I stick with hybrid options.

From my reading, I think some of the challenges to running an external wastegate without an external controller are that the stock pressure converter/boost solenoid tends to break apart if you run boost pressure through them vs. vacuum. But then mac solenoids are desiged to run on low (30 hz-ish) duty cycle frequency, whereas the n55 dme runs much higher duty cycle frequency (300 hz I believe?), so controlling a mac valve without some kind of intermediary may not be practical.

I'd really like to run an off-the-shelf aftermarket turbo, but it looks like that means I'll probably be stuck with an external wastegate.

Does anybody know of any proven solutions to control a traditional normally closed pressure driven wastegate with the DME - without any additional controllers? I could just run spring pressure, but that feels like a pretty compromised solution for a daily-driven car.

Any thoughts?

Thanks!
 

wheela

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Jun 4, 2021
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Thanks for responding! I see boost box was just n54 (i'm n55) and is now discontinued.

Motiv Reflex+ obviously has a lot more capabilities than boost box, I'm assuming this would also allow DME control of an external wastegate? Is the level of DME integration for n55 to the point where we can log the reflex parameters through MHD like on n54? It would be cool to be able to add additional sensors through the Reflex and be able to log them through MHD.
 

wheela

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@wheela do you know if they ever got the E series integration working? I would search more but with the .08 mbps download speed out on the boat it's kind of a pain to load websites.
I don't think e-series n55 has it yet, but somebody please correct me if i'm wrong. (My MHD app auto-updates, and I don't see any update notes indicating we have this yet)
 
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wheela

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Jun 4, 2021
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Turbosmart came out with a vacuum operated external wastegatešŸ˜€ I'm very excited about this development.


It's a butterfly valve, so it's extremely high flowing, and won't auto-wastegate since back pressure balances on both halves of the butterfly flap. This runs off vacuum from the oem boost solenoid, so just plumb it and tunešŸ˜ No mac valves, boost controllers, electronic interfaces neededšŸ˜€

Only thing is the straight flow-through design won't easily swap in to replace normal 90 degree wastegates without modification.
 

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Schmidty335i

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@wheela awesome find! it will be interesting to see someone run this; I wonder if the stock boost solenoid provides enough vacuum to operate this properly and if the wastegate can hold high horsepower applications with the butterfly flap? The questions I ask may be answered via the website you posted with it but with my terrible boat internet I can't even load it lol. Happy it can at least load forums though, helps pass the time.
 
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wheela

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Jun 4, 2021
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@wheela awesome find! it will be interesting to see someone run this; I wonder if the stock boost solenoid provides enough vacuum to operate this properly and if the wastegate can hold high horsepower applications with the butterfly flap? The questions I ask may be answered via the website you posted with it but with my terrible boat internet I can't even load it lol. Happy it can at least load forums though, helps pass the time.
It should work, as this is a 6 inHg wastegate, meaning it should take 6 in Hg of vacuum to close it, which is roughly the same spec as the oem vacuum actuator setup. The oem vacuum pump can pull more than 25 in Hg, so plenty on tap.

It would be intersting to see a tune on one. With the stock actuator, any duty cycle beyond what is needed to close the actuator at idle would only be needed to counteract exhaust back pressure against the radiator flap. Since this one is a butterfly valve, any back pressure should cancel out, so the tune shouldn't ever need more duty cycle than it takes to close the valve at idle.
 

wheela

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Twin Cities, MN
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I imagine it would be similar to an electronic wastegate who's position is unaffected by exhaust back pressure - it may end up being just duty cycle vs. Wastegate position, with no influence from exhaust flow.