Wastegate Actuator rod adjustment (proper tightness)

[LRS95TSI]

when reinstalling the wastegate arm and attaching it to the exhaust side of the turbo there is a hole on the rod that you slip over a dile pin on the housing. do you adjust the rod so that the hole is directly over the pin on the housing or do you want to adjust it so that you have to tug/pull on the arm to match the hole over the dile pin. basically should you have to apply force to the arm to get it to fit on the exhaust housing or should it be adjusted to slide right on? I figured you would want to have to pull on it so that it just doesn't freely open up under boost, wanted to check my idea/methodology

 

[CanadianTSi]

You want it as tight as you can get it.

 

[LRS95TSI]

thats what i thought...i just didn't want to over tighten it and cause the turbo to struggle to make boost or open up, i don't need any more lag haha

 

[Kevin Jewer]

Adding more preload than you need will reduce available travel. In an effort to balance spool and resistance to blowing open at high boost against boost creep, I ended up shooting for it being "half a hole" too short. That puts enough preload on it to keep it closed, but allows very close to full travel. This works for 98% of people, adjust accordingly as your situation requires.

IMO, if you're using excessive preload to enable making full use of the compressor wheel's capacity, your turbine housing/wheel combo is too small.

 

[Mr Peepers]

Adding more preload than you need will reduce available travel. In an effort to balance spool and resistance to blowing open at high boost against boost creep, I ended up shooting for it being "half a hole" too short. That puts enough preload on it to keep it closed, but allows very close to full travel. This works for 98% of people, adjust accordingly as your situation requires.

IMO, if you're using excessive preload to enable making full use of the compressor wheel's capacity, your turbine housing/wheel combo is too small.

 

[JusMX141]

IMO, if you're using excessive preload to enable making full use of the compressor wheel's capacity, your turbine housing/wheel combo is too small.

Not always true.

Recently we ran into an issue on my buddy's car when trying to achieve anything over 18psi. The car has a 34mm internally-gated Frank 5 20G (60-trim Garrett compressor, TD06H turbine) and we were using a T25 actuator (the turbo had a welded flapper when I got it, be he wanted to go internal and the T25 actuator was the only one I had that would fit properly.)

Anytime we tried to boost past 18psi, the flapper would blow open. The car has an external dump for the wastegate chamber, so we could hear when the wastegate would open....no hiding that. I began shimming the gate tighter and tighter and we were getting the same results. We were down to 1/4" of arm travel, and I had the boost source going to the actuator completely disconnected- same result. I ended up getting a universal AGP actuator with a much stronger spring and an adjustable arm and manufacturing a bracket to hold the actuator head.

The first time out with the new actuator the car made 28psi....I had far too much preload on the actuator arm. Plently of tuning later, we've found a sweet spot between the actuator having enough spring strength to hold the flapper shut and just enough preload that there isn't a huge spike in boost. The boost now spikes to 23-24psi before settling at 22 and holding it rock-steady to redline.

Lesson learned: If you want to run more than 20psi and have absolutely no issues controlling boost, an external wastegate is highly recommended.


By adding more tension than necessary to the wastegate arm you're preloading the spring which is delaying the opening of the wastegate, and raising the boost level.

Adjustable wastegate arms were previously the only way raise or lower your boost level until the boost controller became a popular item. Basically if you had an 8psi actuator you could run no less than 8psi when the arm was at it's loosest setting, and the boost level would raise slightly as you'd shorten the rod.

The downfall to this method is that by preloading the spring heavily to achieve a very high boost level you're taking the responsiveness out of the actuator. Many times if you have too much preload on the actuator you'll see a slight spike in boost pressure prior to the wastegate opening before it drops and settles to the desired level.

Many of today's solid-rod actuators (like those found on the T25 and 14B/16G) cannot hold much past 18 or 20psi before they begin begin to open on their own. The only way to control this is to use washers to shim underneath the mounting tabs of the actuator and add a bit of preload to the wastegate system. Of course there are tons of variables that determine the final pressure at which a wastegate will open- wastegate hole size and flapper size being the two biggest factors.

You'd be surprised- once you reach higher boost levels, wastegate arm travel and flapper size have absolutely NOTHING to do with controlling the boost level. If the wastegate opens as much as 1/4", the boost level will be limited. For those who think bigger flappers are better at higher boost levels, take a look at a 16cm2 Holset turbine housing for a large diesel truck running 35 or 40psi....the wastegate hole itself is barely big enough to fit your pinky into, and the flapper is about the size of a nickle.

 

[CanadianTSi]

I just like to keep it tight so I know its not blowing open early, if I get a bad spike or creep up top then I know I have it too tight. Its all trial and error.

 

[Kevin Jewer]

It should have gone without saying that using a weak spring to run high boost is ####ing retarded. The quoted statement assumed a decent actuator was being used.