Boost control is giving me the runaround

[Jon Early]

Without getting too out of control with details, the inconsistent nature of this wastegate is driving me nuts.

My car has a Bowling Green Customs 3" downpipe and elbow with a TA49 turbo. The actuator is an unknown adjustable unit that came with the car. I removed the solenoid and tried an MBC, but currently have the hose looped from the turbo directly to the wastegate actuator for simplicity. I've confirmed with the mightyvac that it will begin to move the arm at around 10 psi when it's detached from the puck. With a whole bunch of preload on the actuator I'm able to achieve the 23 psi opening pressure with the mightyvac, and when I hooked it up directly to the turbo, it gave me the 23psi of manifold pressure I've been wanting.... for about a day. Now its stuck at 16 psi and pretty laggy.

This is only the most recent information as I've been battling this issue for over a month now. The puck is NOT sticking. I've made a couple changes to be completely sure of that. The hole which the puck arm passes through was drilled one size bigger, so the arm has a little wiggle room and won't get stuck with heat expansion or corrosion. The puck itself would would get stuck in the turbo outlet hole but I fixed that with a small amount of porting. The Bowling Green Customs elbow also allows the puck to crash into the elbow body. I fixed that too.

I found out that the actuator is an 1011-673 which is standard duty. I'm curious how they figure this, but I'm guessing that I'm just overpowering the actuator with exhaust backpressure? Even with the hose pulled off the turbo, 20psi is all I can make. I thought that preloading the spring was supposed to allow you to push the limits of the actuator, but I guess I was wrong. I thought that removing the hose would essentially send my connecting rods into orbit due to infinite boost too, but maybe not.

Am I on the right track? Should I be looking for an HD actuator? Thanks.

 

[mblum]

What are you wanting for boost?

I remember your running E85, so no reason not to run mid 20's all the time, which is very safe with a proper tune.

I would ditch the STD duty actuator and get a HD. I have a TA60 turbo, which is basically a TA49 with an updated compressor wheel to a 60-1. With my HD actuator (with adjustable rod) and the RJC MBC my car gets into boost very easy with the converter I'm running. It's a very responsive setup and in cool weather makes boost off idle basically, but even in the warm weather we had here yesterday (about 92 degrees) the combo still makes boost very easy.

I have my wastegate hole ported slightly, I cannot remember but either at 1" or 1-1/6" and my boost curve in PowerLogger is excellent. I have good boost control when spooling without a boost spike and no boost creep. Right now I drive around at 28lbs and the car is a blast.

 

[Jon Early]

What are you wanting for boost?

I remember your running E85, so no reason not to run mid 20's all the time, which is very safe with a proper tune.

I would ditch the STD duty actuator and get a HD. I have a TA60 turbo, which is basically a TA49 with an updated compressor wheel to a 60-1. With my HD actuator (with adjustable rod) and the RJC MBC my car gets into boost very easy with the converter I'm running. It's a very responsive setup and in cool weather makes boost off idle basically, but even in the warm weather we had here yesterday (about 92 degrees) the combo still makes boost very easy.

I have my wastegate hole ported slightly, I cannot remember but either at 1" or 1-1/6" and my boost curve in PowerLogger is excellent. I have good boost control when spooling without a boost spike and no boost creep. Right now I drive around at 28lbs and the car is a blast.

Yes, I'm I'm on E85 with a restalled D5 converter made by Husek. I'd like to run 23-25psi since that's what's on the chip. I got an older RJC boost controller from a member here, but it leaked really bad. I haven't had a chance to take it apart and apply new thread sealant.

I'm definitely picking up an HD actuator. I have a buddy looking for his old one, but I'll just buy a new one if he doesn't find it.

 

[mblum]

Yes, I'm I'm on E85 with a restalled D5 converter made by Husek. I'd like to run 23-25psi since that's what's on the chip. I got an older RJC boost controller from a member here, but it leaked really bad. I haven't had a chance to take it apart and apply new thread sealant.

I'm definitely picking up an HD actuator. I have a buddy looking for his old one, but I'll just buy a new one if he doesn't find it.

At 23-25 psi I think the HD is the right actuator. I believe the HD starts boost levels around 18psi where the STD is around 12 psi. The problem with trying to make high boost on a STD actuator is you need to really crank down on the adjuster rod, this can cause boost spikes if not careful and may have to play with the MBC settings, actuator settings and wastegate hole size.

I run about .1" of preload on my HD actuator and have zero boost spikes up until about 32 psi. Above that I have the rod cranked down really tight start to see about a 2 psi spike at spool up.

Your going to like that TA49 at 25lbs, it's much happier there than in the high teens.

 

[626gn]

Not sure if this is an apples to apples comparison but I was able to easily make 25psi with a standard wastegate and an RJC mbc, and could have made more if I wanted to. In any case, I think I may have a hd actuator laying around that I won't ever use, since I have switched to external. Your welcome to have it if you want.

I thought I read in your other post that you already purchased an external set-up? Any reason you don't just transition to that?

 

[Jon Early]

Not sure if this is an apples to apples comparison but I was able to easily make 25psi with a standard wastegate and an RJC mbc, and could have made more if I wanted to. In any case, I think I may have a hd actuator laying around that I won't ever use, since I have switched to external. Your welcome to have it if you want.

I thought I read in your other post that you already purchased an external set-up? Any reason you don't just transition to that?

You aren't the first one to tell me that and I believe you. I'm just not fully convinced that something isn't wrong with mine. It's kinda ugly in it's corroded state anyway.

I appreciate the offer and wish I heard it before I placed my Gbodyparts order. lol I did buy a nice TA downpipe, but I think it's going to look really silly in my car. I still run a stock air box with the bottom removed because the car looks so stock. An external 46mm wastegate with everything else looking stock is just a huuuuuge clash. I was a little spend happy at the nats when I bought that.

I won't say it's not happening though. Some day. I just don't want to go too overkill on my all stock long block and break stuff.

 

[626gn]

Understood. Well, once you decide it's time, you may just wonder why you didn't switch sooner . Nothing wrong with an internal set-up though when it's working properly.

 

[LANDAU LIMITED]

A member had problem not getting over 19 psi with his mbc, took it apart and found a piece of crap inside. Put it back on and boost went up to 25.

 

[Jon Early]

I got an HD actuator installed last night and I think my understanding of how all this works is a bit flawed.

I started by seeing when the wastegate would open with the mightyvac. I adjusted so that it would open with 25 psi on the diaphragm. I went for a drive and immediately blew the hose off which gave me 22psi at the manifold and no lag. I can basically control boost with the throttle pedal. I almost wanted to leave it that way, but I kept playing with it because I want more.

With the hose attached directly from the turbo to the HD actuator and the rod cranked all the way in. I only get 21psi at the manifold and it takes a lot longer to get there. My mightyvac can't even open the gate like this, so I can only assume that exhaust back pressure plays a much bigger factor in boost control than I once thought. Now I'm wanting to put my MBC into the mix to get up to 24 or 25 psi and get rid of that lag. The old RJC MBC I got was leaking around the inlet fitting and the main body, so I put some thread tape on that and it's good to go again. I throw that in on Friday. I have no time tonight. What I fail to understand is how that dinky spring is able to hold back enough boost pressure to make much of a difference. The way I understand it is that this will only stop about 4psi of pressure and then push the ball out of the way. It might make a tiny difference in lag but not give me any extra boost. I guess I'll find out. Hopefully it proves me wrong and works great.

 

[Jon Early]

A member had problem not getting over 19 psi with his mbc, took it apart and found a piece of crap inside. Put it back on and boost went up to 25.

I trust RJC a lot more than I trust myself. They tell the same story as yours, so I need to let go of my ego and try this again.

It would be really nice to have less preload on the actuator anyway. I need to use vice grips just that I have a bigger handle for installation.

 

[mblum]

The MBC's purpose is to isolate boost signal from the actuator's pressure port which should yield fast spool up as the HD actuator is seeing no pressure on the diaphragm until the MBC's internal ball/spring is overcome by the positive pressure. The size of that little spring is only relative to the orifice size feeding it, after all PSI is Pounds per Square Inch and the orifice size and spring relationship are directly related.

I don't remember reading, but have you confirmed that your getting a great seal between the wastegate puck and the turbo housing? From what your describing I think you have a major internal exhaust leak (assuming you have no external exhaust leaks into atmosphere) causing limited boost. Exhaust back pressure certainly plays a role, but with a stock engine and I would assume no more than 400 hp as it sits currently I wouldn't think back pressure pushing the puck open here. Granted you must ensure there is great seal between the puck and turbo. That puck's head should articulate +/- 15-20 degrees to ensure it conforms to the turbo's surface while completely covering the wastegate hole and ideally not right on the edge of the puck.

Have you measured the wastegate hole size in that TA49? Was this turbo already on the car when you acquired it and is it possible that someone unknowingly ported the wastegate hole too large? This is another function of PSI acting on the puck. The larger the wastegate hole the more "square inches" is allowed to push on the puck even at the same level of exhaust back pressure. If the wastegate hole is too large you may also see boost come up quickly and once the puck opens the boost will fall off because too much exhaust pressure is being bled off too quickly.

With your combo and a HD actuator I don't see why you need much more than .1" of preload on the wastegate rod to easily achieve low 20psi of boost, assuming your wastegate hole is being perfectly sealed by the puck.

 

[mblum]

For example, this is where the puck on my RJC 3" downpipe sits in relation to the wastegate hole. Narrowest point of coverage is about .150"
My wastegate hole size when I started was about .940" which gave me boost creep. I ended up opening it up to 1.0" which works great for me. This final number may vary from car to car. I snuck up on this final dimension in small increments.

 

[Jon Early]

The MBC's purpose is to isolate boost signal from the actuator's pressure port which should yield fast spool up as the HD actuator is seeing no pressure on the diaphragm until the MBC's internal ball/spring is overcome by the positive pressure. The size of that little spring is only relative to the orifice size feeding it, after all PSI is Pounds per Square Inch and the orifice size and spring relationship are directly related.

I'm hoping that the concept I have of this that's drawn in my head is just that far off, but the spring in mine bleeds hand pump pressure immediately. I cannot make any more than 5 psi so holding back boost pressure just sounds like a stretch unless I'm missing something.

I don't remember reading, but have you confirmed that your getting a great seal between the wastegate puck and the turbo housing? From what your describing I think you have a major internal exhaust leak (assuming you have no external exhaust leaks into atmosphere) causing limited boost. Exhaust back pressure certainly plays a role, but with a stock engine and I would assume no more than 400 hp as it sits currently I wouldn't think back pressure pushing the puck open here. Granted you must ensure there is great seal between the puck and turbo. That puck's head should articulate +/- 15-20 degrees to ensure it conforms to the turbo's surface while completely covering the wastegate hole and ideally not right on the edge of the puck.

I think this is sorta addressed in post 1 and 9. I don't have measurements or witness marks, but I will take/make some if the elbow has to come off again. I've done a lot of work on this due to the BGC elbow being a big pile of junk. The puck was certainly sealing well yesterday. With no vacuum hose at all I was able to make 22psi really quickly. It would make 5 psi with only about 1/4 throttle input which is something the car has never done and I'd love to retain! I almost want to just cap the turbo nipple and run it like this but it seems so wrong.

I probably do have some external leaks, but they're tiny. I had the engine out to reseal everything and weld up the cracked header just over a year ago.

Have you measured the wastegate hole size in that TA49? Was this turbo already on the car when you acquired it and is it possible that someone unknowingly ported the wastegate hole too large? This is another function of PSI acting on the puck. The larger the wastegate hole the more "square inches" is allowed to push on the puck even at the same level of exhaust back pressure. If the wastegate hole is too large you may also see boost come up quickly and once the puck opens the boost will fall off because too much exhaust pressure is being bled off too quickly.

The turbo is used and I had it rebuilt by boost lab. The wastegate hole is unported. The only thing I can say for sure is that my puck is smaller than most of the aftermarket ones I've seen. I can try sending my borescope through the the external wastegate provision on the hot side since I haven't done that since the post #1 fix. I'm pretty confident that the puck is about centered on the hole though.

With your combo and a HD actuator I don't see why you need much more than .1" of preload on the wastegate rod to easily achieve low 20psi of boost, assuming your wastegate hole is being perfectly sealed by the puck.

This is why I think something else is up. I'm not measuring my preload, but .1" is nothing. I have to use a vice grip just so I can get a grip on the thing and pull it out about 1/4" with the hose looped straight to the turbo that gives me only 21psi.

 

[Jon Early]

Is the RJC MBC supposed to have an oring in it? I cleaned a bunch of nasty black residue out of mine, but I'm wondering now if some of that was the remnants of an old seal.

I put an oring in there that sorta fits, and it will hold back 5 psi now. I can also make up to 15psi on the hand pump now. Maybe I just need a new one instead of this freebie. lol

 

[mblum]

Yours appears to be an older style/version. Neither of mine have an o-ring but they do look a little different than the one you posted.

Confirm the contact pattern of the puck on the turbo to ensure the face of the puck is fully contacting as well as the location of the puck and coverage of the wastegate hole. I used some gear marking compound, but you can use anything that will leave a witness mark. What I did when checking mine was clean both surfaces and apply a thin layer of the marking compound to the puck face. Find a way to secure the puck arm so it cannot swing and contact the turbo while your installing it, you don't want a false mark. Use zip ties, rubber band or whatever to do this. Once the elbow is bolted up allow the puck to swing down and contact the turbo which will give you that witness mark, then re-secure the puck arm so it no longer can contact the turbo. Remove the elbow and see what you get for a contact pattern.

 

[Mr.Spool]

an external gate
Co2
And boost controller
And all these issues
And a million of these type of threads
Go away forever.

 

[Jon Early]

an external gate
Co2
And boost controller
And all these issues
And a million of these type of threads
Go away forever.

Are you actually suggesting C02 on a mostly stock street-driven car? Thanks for the unhelpful input as usual. I'll be sticking around a while (probably forever) so you might as well get used to me.

 

[Mr.Spool]

Are you actually suggesting C02 on a mostly stock street-driven car? Thanks for the unhelpful input as usual. I'll be sticking around a while (probably forever) so you might as well get used to me.

I'm sure you be around posting threads like this
And then....wondering if your puck is sealing or your swing arm is at the right angle or you have enough spring pressure to make 350hp
Add up the time taking things apart and the drama and when this really old stuff that's 40years doesnt work the way it did 25 years ago.
It is really worth it?
Internal gates suck period
Street or track
If you understand how a turbo system and gat and string pressure actually worked you would evolve your thought process.

 

[Mr.Spool]

Without getting too out of control with details, the inconsistent nature of this wastegate is driving me nuts.

Cheatsheat
External 46mm gate
Real boost controller
Co2
your problems disappear because you have full control over the turbo system and your not reacting to a wastegate
You would be ahead of it.

 

[Mr.Spool]

And some more useless info
If you want to run off manifold pressure when running an external gate
You can setup the combo of springs on the gate to target a certain amount of boost while reacting to the gate (depending on backpressure)if you dont want to use co2