How come can't boost over 12 with no contoller?

[MikeL.]

saw the buggy on another thread....

I've used this Grainger check valve (about $10) since Feb. on my turbocharged VW air-cooled motor.
It's allowed me to get 18 lbs. of boost out of a wastegate actuator that's set up for 10-12.
Set-it-and-forget-it accuracy and repeatability.
I couldn't be happier.

As for tuning it, I started out with zero tension on the spring/poppet ball and slowly tightened it to increase boost.
Personally, I wouldn't go trimming the spring.....I think it's good for 0-20 PSI right out of the box.

Bill

....and that looks to be fun to zip around in. Light weight and turbo'd...I'm sure it surprises a lot of people.

I'm probably going to have to stretch or add a stiffer spring. I've now tried both approaches to increasing boost. I started out with having to only pull on the actuator rod and 1/8" to attach to the WG arm, turned in the boost controller all the way and got a max of 18#'s. I then did the opposite, adjusted the stock actuator to approx 18-19#'s then started out with the boost controller adjusted to only one ot two threads and started going up from there. I'm now 5 or 6 turns clockwise on the boost controller and still no gain in boost.

Time to either stretch the spring or go heavier on the spring. I'm open to any and all suggestions.

 

[WSLN 6]

Can you get more out of the stock actuator? With my wastegate rod about 1/8"away, I can get 18psi with the grainger fully tight, even with the tight spring. If I tighten the actuator as far as it will go, I get 24psi. You will have to use a vise grip to get the thing on there, but it works....

 

[Missouri T]

Mine has a bleed hole right at the exit of the valve (about 1/16" or so). Without it, I would get boost surging back and forth.

Mine has a bleed hole as well.
It's on the bottom of the valve in the picture.....otherwise it'll get crud in it being out in the open like it is in the buggy.

 

[Missouri T]

Can you get more out of the stock actuator? With my wastegate rod about 1/8"away, I can get 18psi with the grainger fully tight, even with the tight spring. If I tighten the actuator as far as it will go, I get 24psi. You will have to use a vise grip to get the thing on there, but it works....

I know we're talking about a whole different animal here with the T25 on my buggy but it's the same basic idea.
I threaded the T25's stock actuator rod and run it with zero preload and let the Grainger valve take care of the level of boost.
I KNOW the Grainger will do 20 lbs. alone.....I've done it.
BUT the T25 is GROSSLY inefficient over 20 lbs. boost from what I've read.
And me not having intercooling (or any way to intercool drawing fuel through the compressor like that), all it'll do is superheat the air and fuel anyway.

So I'll walk the line at 18 and leave it at that.
The stock VW bottom end is fairly stout but was NEVER intended for the kind of cylinder pressure I'm generating.
Basically, I'm driving a grenade with the pin pulled when I go to WOT.
But it's only short bursts, I watch my A/F and no audible knock thus it's long life.