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  #1  
Old 09-23-2011, 05:15 PM
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Intro and another VNT mech control idea

Hi all. I've been lurking for a while both here and STD and I love the great information that I've been mining. Thanks a bunch. I've got an '87 300d, and an old FJ40 that's about to get an OM617 swap from an '85 300d donor. My GF drives an '85 300td.

Has anyone seen this push-pull wastegate actuator?


See the lower port that's plugged? It appears to be plumbed to the spring side , which is sealed. I was thinking that for those who no longer have auto transmissions that the vacuum control valve could be used to vary boost pressure to this second port and effectively add pressure to the WG actuator's spring at light throttle.

I haven't seen mention of this actuator in either forums' archives. It seems so simple that I can't help but think that I've overlooked something obvious.

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  #2  
Old 09-23-2011, 05:44 PM
aaa aaa is offline
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Can the vcv work backwards like that?
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  #3  
Old 09-23-2011, 06:52 PM
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Quote:
Originally Posted by aaa View Post
Can the vcv work backwards like that?
Not sure. Luckily it doesn't matter since I overlooked the fact that weakening the WG actuator's spring by applying vacuum to the second port will open the WG (or open the vanes) at lower boost pressure. For this to work the VCV will need to work as it normally does with vacuum.
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  #4  
Old 09-23-2011, 07:54 PM
Goodentight
 
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I think the concept has merit. The way you would want to do it, tho is to hook vacuum from the VCV to the second port that is plugged in the picture and add boost to the first port that already has the nipple installed. With it that way, the vanes would be open at idle (good) due to the vacuum from the VCV being high. They would close proportional to load (good) because the vacuum would crop as the pedal was depressed. They would open again when the boost pressure rose above the spring pressure (good). That would be ideal and offer very similar operating parameters to my mechanical control in this thread: Mechanical VNT Control Would the added vacuum volume mess with the trans shifting properly? One other potential downside that pops to mind is that it would have a greater likelihood of having the vanes get sticky but probably not worse than a lot of stock VNT installations that only rely on the vacuum can. $160 also strikes me as a bit expensive for a wastegate actuator, but it sure looks like a well built unit.
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  #5  
Old 10-04-2011, 04:25 PM
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Quote:
Originally Posted by raysorenson View Post
Has anyone seen this push-pull wastegate actuator?
Thats not push-pull. The lower port is to allow boost into it to keep the wastegate closed on its seat and raise the set pressure.

The stock vacuum system is only good for 7-9psi of opposing vacuum force (15-18inHg).
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  #6  
Old 10-04-2011, 05:20 PM
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Originally Posted by Group49 View Post
Thats not push-pull. The lower port is to allow boost into it to keep the wastegate closed on its seat and raise the set pressure.

The stock vacuum system is only good for 7-9psi of opposing vacuum force (15-18inHg).
Is this Forced? If so, I thought you were smart. I think the quality of your post in the other VNT thread speaks volumes. It's the first time in like 8 hours that someone on the internet has astounded me. Thank you.

Now, to correct you, once vacuum is applied to the lower port, it does indeed become push-pull. If the lower chamber holds boost, it's reasonable to assume that it will hold vacuum.

You make a good point about the amount of available vacuum. If the WG was sprung to crack at say 15# of boost, then subtracting 7# by applying that amount of vacuum may give one 8# of boost at cruise. That's better than 15. In practice, the results may be even better, but not worse. Tweaks would almost certainly have to be made. One would have to approach the project with problem solving skills.

I've pondered and read a few threads about mechanical VNT control and I think this one holds great promise given it's simplicity. Your combative post certainly hasn't done a thing to change my mind.
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Old 10-04-2011, 08:34 PM
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Quote:
Originally Posted by cando View Post
Most seals only seal in one direction of flow.
ex. Put the seal on your crank backwards and you'll dump out the engine.
Without knowing what type of seal it uses, buying it would be a gamble based on assumption.
The crank seal, I assume, is a lip seal or a garter lip seal and yes, they do seal better in one direction than another. This WG almost certainly doesn't have either of those. An o-ring would suit their purpose perfectly and that's what expect they've used. O-rings seal in both directions like many other seals.

Quote:
That would also assume you're at (or have the VCV adjusted to) idle conditions while cruising.
Good point. If I try this, it's going to be in a landcruiser transplant which will have a manual trans. I'll have the luxury of tweaking the VCV and even more drastic vacuum system manipulations for boost purposes without worrying about shift issues. A manual trans is the only logical test bed for this setup. I would be happily surprised if a good vacuum curve for the trans translated to a similar curve for the WG actuator.
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  #8  
Old 10-04-2011, 09:29 PM
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Quote:
Originally Posted by cando View Post
Most seals only seal in one direction of flow.
ex. Put the seal on your crank backwards and you'll dump out the engine.
Without knowing what type of seal it uses, buying it would be a gamble based on assumption.

That would also assume you're at (or have the VCV adjusted to) idle conditions while cruising.
... the crank on the 617 engine at least is a rope seal... it does not have a backwards...
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  #9  
Old 10-09-2011, 04:43 PM
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Quote:
Originally Posted by Group49 View Post
The stock vacuum system is only good for 7-9psi of opposing vacuum force (15-18inHg).
If boost were applied to one nipple and vacuum to the other, then the vacuum would not be opposing, it would be assisting.

Quote:
Originally Posted by raysorenson View Post
Is this Forced? If so, I thought you were smart. I think the quality of your post in the other VNT thread speaks volumes. It's the first time in like 8 hours that someone on the internet has astounded me. Thank you.
Are you talking about his post in my mechanical VNT thread? If so, then I don't understand what you found impressive about his post other than it being mostly wrong with just enough insight to it to confuse the unknowing...
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  #10  
Old 10-10-2011, 07:57 AM
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Originally Posted by libbybapa View Post
Are you talking about his post in my mechanical VNT thread? If so, then I don't understand what you found impressive about his post other than it being mostly wrong with just enough insight to it to confuse the unknowing...
It was impressively stupid. He basically jumped in a thread that details and diagrams how you've added a load-based input to a mechanical VNT control system and says, "You need a load-based input. That's how everyone else is doing it!". He either has a reading disability or was just trolling. Fortunately, his comments seem to be mostly ignored.
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  #11  
Old 10-10-2011, 11:33 AM
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I was hoping that was what you meant. Sarcasm is sometimes confusing when typed.

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