Boost controller on stock turbo

[casioqv]

Has anyone here had luck using a mechanical ball and spring type boost controller with the stock turbo long-term?

Tom Bryant pointed out that the wastegate actuator on these turbos is unique in that it's mounted directly to the exhaust housing and uses a constant stream of flowing boost (through 2 ports with a restricted exit orifice) to cool the diaphragm and keep it from burning up. Since these ball and spring controllers provide no air to the wastegate actuator until peak boost is reached, under partial boost conditions the wastegate would operate uncooled and experience a potentially shortened lifespan.

I have a G-valve type controller like this one:


I am considering adding a small adjustable screw valve, to allow an adjustable orifice "bypass flow" for cooling the wastegate without opening it. I would just set the G-valve to a specific opening pressure (say 15psi) and then slowly adjust the bypass valve closed until it's as open as possible while still allowing the boost set-point to be reached.

Bypass valve example:


Any comments/suggestions? I want to stick with the stock turbo because I'm not hoping to get super aggressive with performance modifications. I'm only hoping to add about 20 reliable horsepower, so I don't need to downshift as often climbing grades.

[casioqv]

Another idea would be to have an electric solenoid valve that bypasses the boost controller, so it only actuates at high throttle positions (when it would be presumably at max boost anyway and the g-valve would continuously flow air). Then the engine would have stock boost except at full throttle, which might also reduce unnecessary wear on the turbo.

[Jason]

Tyler, you are way way way over thinking this!! The standard old ball/spring type controller will work just fine. The diaphram is housed in metal that is bolted to the exhaust, however its a very high temp rubber. Every other type of waste gate out there just has one hose going to it, and nothing for cooling. It just isn't needed... I have been running that style setup for close to 2 years with no problem.

Jason

[casioqv]

Other wastegates with a single hose usually have a long actuator rod, and the diaphragm mounted on the cold side. The green book "design and function" goes into depth about the design/importance of the wastegate cooling system, but I can point out several other obvious mistakes/misunderstandings printed in those books.

Did you use the stock exhaust housing and wastegate to build your new turbo?

way way way over thinking things is what I *always* do- I can't help it, but it's kinda fun too

[Jason]

I have a different waste gate setup now with the larger turbo. However thats how I had the stock turbo for a while, and Alex also had the same setup on his car for quite some time, in fact it had the controller on it when he got the car from my friend Fred. You have to remember that some of this turbo theory is from the very early 80's, and some things were done that didn't need to be... The time when the exhaust is going to be the hottest is under full acceleration and full boost, at which point air will be flowing through anyway. At part throttle conditions and less than wastegated boost, the EGTs are low anyway. Also, look at the external waste gates used on some turbo setups, they are bolted directly to the exhaust and don't incorperate any kind of vent/air pass through system. If your waste gate gets fried I have another stock turbo for you!

Jason

[casioqv]

Okay, I guess I'll just throw it on and try it then.

That's a very good point about 80s turbo theory- they really didn't know much about turbocharged passenger cars yet in the early 80s. For example, all of the manuals say you have to idle the engine for ~30 seconds to let the turbo "spin down" when really it stops almost instantly, and any benefit of the idling is probably to keep the oil from coking in the bearings which probably doesn't happen with synthetic even without idling down.

[ThickasaBrick]

Guys, it could very well be that the rubber technology of the day prevented them from building an actuator that could last without the extra cooling means that they employed to help it live. I would reconsider and go ahead with one of the two original plans. ALL of the car companies are disgustingly cheap. They wouldn't have gone through the trouble of that more complicated setup if it wasn't necessary. I'm sure they found out through testing that they had a problem, which is why we have this more costly for them to build more complicated setup. (Even just an extra 50 cents per car sends the bean counters into a tizzy!)
Regards, Eric

[Rederic]

Wondering the same thing –
I’ve been attempting to control boost with a bleed type controller… Not having a lot of luck considering the size of the wastegate actuator hose in the length to the controller bleed valve…
Thinking about switching over to a ball and spring…
Concerned about the need for a cooling bypass air

Originally Posted by casioqv

Has anyone here had luck using a mechanical ball and spring type boost Any updates on your Boost Controller success?
controller with the stock turbo long-term?

Tom Bryant pointed out that the wastegate actuator on these turbos is unique in that it's mounted directly to the exhaust housing and uses a constant stream of flowing boost (through 2 ports with a restricted exit orifice) to cool the diaphragm and keep it from burning up. Since these ball and spring controllers provide no air to the wastegate actuator until peak boost is reached, under partial boost conditions the wastegate would operate uncooled and experience a potentially shortened lifespan.

I have a G-valve type controller like this one:


I am considering adding a small adjustable screw valve, to allow an adjustable orifice "bypass flow" for cooling the wastegate without opening it. I would just set the G-valve to a specific opening pressure (say 15psi) and then slowly adjust the bypass valve closed until it's as open as possible while still allowing the boost set-point to be reached.

Bypass valve example:


Any comments/suggestions? I want to stick with the stock turbo because I'm not hoping to get super aggressive with performance modifications. I'm only hoping to add about 20 reliable horsepower, so I don't need to downshift as often climbing grades.

[v8volvo]

Originally Posted by Rederic

Wondering the same thing –
I’ve been attempting to control boost with a bleed type controller… Not having a lot of luck considering the size of the wastegate actuator hose in the length to the controller bleed valve…
Thinking about switching over to a ball and spring…
Concerned about the need for a cooling bypass air

I used a ball and spring type controller on my 760 for a while. It didn't suffer any negative effects although I had to make sure the plumbing parts were all large enough to work with the unusually large air signal hose.

In theory there is a way to take the wastegate actuator assembly apart and shim the spring in there to increase the WG opening pressure. But that would be a lot of work with the trial and error to get to the desired pressure.

However -- I think one key is that you only need the cooling bypass air once the WG has begun to open and exhaust is flowing hot across the WG valve. If the WG is kept completely CLOSED by the use of a ball and spring, then the valve is in contact with its seat and can transfer heat there plus it's not exposed to continuous flow of hot gas.

This was my logic at least in believing the common ball and spring type controllers would be fine for this type of turbo, as long as the plumbing (and the ball and spring themselves) were sized large enough that once air does begin to flow to the WG, it can flow at a high enough rate to help keep the parts cool.

I hope my speculation is right.