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Old 02-04-2018, 08:28 PM   #1
dispoz
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Default Overboosting, out of ideas :(

First time having to ask a question on here, couldn't find anything other than what I already tried by searching google and nasioc.
What could be the cause of overboost in this situation?

New wastegate actuator, wastegate flapper seemed to open fine by hand.
All wastegate duty cycles are set to 0 in the ECU.
New vacuum line goes from turbo straight to the actuator, bypassing the boost controller.

Car still boosts to about 18-19 psi as I get closer to redline; 2nd, 3rd gears.
Car is an 02 WRX, VF39 turbo, no cats, turbo back exhaust with large bellmouth downpipe, TGV deletes, turbo inlet, etc.
And I am using a mechanical Autometer boost gauge that is reading 17-20 in vacuum.

Any help is greatly appreciated.
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Last edited by dispoz; 02-04-2018 at 11:28 PM.
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Old 02-04-2018, 10:04 PM   #2
Brother EddieJ.
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Do you still have the pill in the vac line?
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Old 02-04-2018, 10:06 PM   #3
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No, I have a Grimmspeed EBCS so the pill was removed
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Old 02-04-2018, 10:14 PM   #4
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Is it a divided bellmouth? Some turbo/dp combocs can have the wastegate flapper hit the divider, but I don't think I've seen that with a vf39.

So it sounds like boost creep. Kind of annoying to do but you may have to take off the turbine housing and port the wastegate passage a bit.

Or an external gate and just hold the stock flapper closed.
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Old 02-04-2018, 10:20 PM   #5
dispoz
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It is not a divided bellmouth.

And I was thinking that I just have to go external, but does a setup like mine really push the internal wastegate that much? I've seen other threads where people with vf39 were considering running external gates, but nothing was said about overboosting?

If nothing else comes up I will have to just try porting the passage next then
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Old 02-05-2018, 12:33 AM   #6
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Not sure if I interpreted correctly. You have bypassed the boost controller completely? If so 0 wgdc would not matter. Have you adjusted the length of the wastegate arm? Sounds like it may be too short. If you want to run spring pressure you should hook up the EBCS properly and run 0 wgdc
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Old 02-05-2018, 12:41 AM   #7
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Yes, at this point 0 WGDC does not matter as I just have a hose running from turbo nipple to wastegate actuator. I mentioned the duty cycles being 0 because I tried running it both ways, not bypassing the controller, and still had it overboosting.

But running it with the hose like that should force it to run spring pressure too.

And unfortunately the vf39 wastegate actuator is not adjustable.
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Old 02-05-2018, 12:10 PM   #8
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I see, hmm. I have heard of overboosting issues with the vf-39 but mostly from 2.5ís. I ran one on my bugeye for a while without issue. Have you compared the readings of the boost gage to the MAP in RR or AP?
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Old 02-05-2018, 05:51 PM   #9
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I logged the boost with Romraider and it is accurate.
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Old 02-05-2018, 10:22 PM   #10
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if you supply about 10 psi to the actuator from an air compressor does the flapper open?
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Old 02-05-2018, 10:30 PM   #11
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I don't have access to a compressor right now to check that, but the actuator is new so it shouldn't be sticking
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Old 02-05-2018, 10:55 PM   #12
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You have to try pressurizing the actuator like Carmel mentioned. The diaphragm could be leaking and not pushing the wastegate open or open enough.
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Old 02-05-2018, 11:03 PM   #13
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Ok, got it, I will find a way to do that.

If it is leaking, what exactly is a diaphragm? And where would it leak? Sorry not familiar with that
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Old 02-05-2018, 11:08 PM   #14
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The diaphragm is inside the actuator you said is new. If you pressurize it with it's rated opening pressure, it will extend and stay that way until you release the pressure. What you want to do is pressurize it and seal the line in between it and the pressure source, maybe with a valve. This way you can see if it leaks down and contracts, which would mean it's leaking.

A vf39 is not a huge turbo, shouldn't be that much pressure if its wastegate is working. Otherwise maybe the map sensor is screwed up and giving a false signal to the ecu, and it's really not boosting that high.
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Old 02-05-2018, 11:25 PM   #15
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could also be a sticky hinge on the wastegate.
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Old 02-06-2018, 05:38 PM   #16
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Ok so I made a little system with a bicycle pump and pressurized the actuator pretty high (about 30psi according to the cheap pump gauge) and I couldn't find any leaks near the actuator.

It did open up around 10psi, but what I am not sure about is if it opened enough. It seemed to barely move the flapper, 15-20 degrees or so. Then it stops and if I keep pumping it it doesn't go more. Maybe that's how much it should open, but I am not sure? I took a video of it, I'll try to attach now.

You can see it open, then I pump it 3 more times, and then release the air to close it.
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Old 02-06-2018, 09:06 PM   #17
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Is that an oem actuator or aftermarket? It may have too much preload pulling back on the flap and has to be wide open just to open it a little.
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Old 02-06-2018, 11:44 PM   #18
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It is a replacement VF39 actuator, but I did but it from ebay. Seems to be a good seller, maybe a distributor for IHI or something, because they have all kinds of turbo related components. They sold over 50 of these actuators and I don't see any bad reviews claiming overboost.

I did notice some heavy preload however. I took a picture, the white line is with the flapper disconnected. So I had to pull on it some to hook it back up. I'll take another picture tomorrow and mark another line when the arm is fully extended under pressure, to get a better perspective on how much preload there is. I'll also put the old actuator on and see what preload that had.



I'll message the seller and ask them about this preload too.
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Old 02-06-2018, 11:49 PM   #19
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If it's aftermarket with no adjustable preload, I wouldn't use it. You may be able to use a washer/spacer between the bracket and compressor housing for both holes if you have to. If you preload too much, the actuator will be pulled forward so far it will take forever to open and possibly not have enough travel left to open fully. There are some adjustable ones on fleabay if you want to stick with the cheaper models.

Also, adjustment isn't an exact science and not all actuators have the same thread pitch. When you see someone say "adjust this many threads/turns" they are referring to the same brand and model actuator they are using only. There are several different manufacturers making these things. You can watch MRT's video on youtube about actuators and get a fair idea on why preload is important and how it affects boost.

Even the Steamspeed turbo (that I'm selling) has a weird adjustment setup. There are two separate pieces to the arm, and the inner piece has a different thread than the outer piece. There is also a long center hex section that is threaded on both ends and draws both pieces together or pushes them apart....with a lock nut on each end . Definitely a few ways you can screw up adjusting this one.

Last edited by 2slofouru; 02-06-2018 at 11:55 PM.
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Old 02-07-2018, 12:33 AM   #20
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Haha that sounds complicated! I wish the vf stock actuator was adjustable

I think trying the washer setup would be best next, since I can minimize the preload and see if I get any significant changes in boost. I would probably have to start from Home Depot and look for longer screws for the actuator because it will take a lot of washers to compensate for the amount of preload I am having now.
I'll try to get this done tomorrow.

And I did find some nice universal adjustable actuators available in case I need one soon.
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Old 02-07-2018, 01:24 AM   #21
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You can find spacers that are thicker than most washers, at many hardware stores. There should also be metric bolts with the same pitch. Using a thicker spacer on each side would be more secure and less likely to loosen, but getting the correct thickness would be easier trying multiple washers.
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Old 02-08-2018, 11:17 AM   #22
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Welll, I got the spacers in to the point where the flapper had zero preload on it and was open just a very little bit (couldn't go any less on the spacers) so on idle the flapper rattled a bit. Then I go out to make a pull and hit 18 psi like nothing was done to it lol. So confused by what's going on
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Old 02-08-2018, 02:19 PM   #23
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Quote:
Originally Posted by dispoz View Post
Welll, I got the spacers in to the point where the flapper had zero preload on it and was open just a very little bit (couldn't go any less on the spacers) so on idle the flapper rattled a bit. Then I go out to make a pull and hit 18 psi like nothing was done to it lol. So confused by what's going on
The idea is to back it off until there's no preload, then add just a little to keep the wastegate sealed tight. It shouldn't be anywhere near loose or rattling. Still may not be opening enough
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Old 02-08-2018, 03:35 PM   #24
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I understand, but if lets say you disconnect the wastegate arm completely, you will not build any boost. So having zero preload will let some gasses out and juts delay my turbo from spooling a little longer, but overall, it still overboosts.
I could get it perfect with this spacer and washer setup, but I think I would just be wasting time, since it overboosts with no preload at all. So I see what you're saying, but that's not what is causing the overboost.

Correct me if I'm wrong
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Old 02-08-2018, 04:49 PM   #25
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I think it just comes down to the wastegate not being able to flow enough exhaust. With a vf39 and all that free flowing intake/exhaust stuff it happens, despite what you may read elsewhere on the internet about creep just being a tuning issue.

So it seems your options are to try porting the wastegate, go to an external gate, or try a different turbo.
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