Wastegate Actuator Spring Mod

[Marcus_Aurelius]

I have been asked countless times about my wastegate actuator spring mod. I think it's time to make a thread about it that I could link people to; and at the same time have a place to discuss things with some of the guys in the 1.8T technical forums that are starting to catch up.

The purpose of this, is to increase the holding capacity of the wastegate flap by increasing the actuator spring rate. This can also be achieved by buying an aftermarket actuator, but why do all that when you can get the same results or better for a couple of dollars and 10 minutes of your time? The spring mod also allows you to tailor the final spring rate to the boost that you run, while you are stuck with preset rates with the aftermarket units (the fact that it is reversible in 1/2 a minute is also appealing).

Do not confuse this mod with cranking the preload of the actuator by adjusting the rod screw. Preloading the actuator is a bad idea because it considerably reduces the travel of the wastegate flap, and causes high EGTs on top of reduced efficiency.

In my case, boosting anything past 25 psi blew the wastegate flap open at WOT, even without an actuation pressure signal coming from the N75 (a condition AKA as wastegate creep). So to remedy the situation, I added 2 external pull springs rated at 7lbs each (you may want less spring rate and one spring, if you are running less boost and there is less pressure in the hot side). The result is a tested 27-28 psi cracking pressure at rest. Being that I run upward of 30 psi, I am considering adding another small 3 lbs spring to bump the initial cracking pressure to about 30 psi.

Do you need this mod? IMO, as long as you run boost that are considerably higher than stock, the answer is yes. The stock actuator is designed for, and does a fine job around, stock pressure. Increase your boost with a flash and you are generating hot side pressure that is outside the range that the stock actuator was designed for. Once that wastegate creeps open at WOT because the actuator rate is exceeded, you are wasting valuable energy (exhaust pulses) that could be used to spin the turbine wheel harder and generate boost/power. Some will say, why bother if I can hold the desired boost without it? Well, you are not operating at full potential efficiency because you're wasting/bypassing some of the energy your engine/turbo is working hard to produce. Another sign of an overworked/weak actuator is the car's inability to hold boost to redline. The small frame turbos will always struggle up top and have some boost taper, but not the fall-off-a-cliff profile that is associated with an inappropriately sprung wastegate actuator.

This is the best and cleanest pic I've seen of the spring mod (picture borrowed from 96AAAjetta )






This what it looks like in my car. One end is hooked to the actuator rod and the other to the vacuum nipple on top of the actuator. The other pic is the regulated pressure rig I used to test the intitial cracking pressure but a simple hand pump with a gauge could do







The picture below is borrowed from Peter139 (my pix are down momentarily). It shows a single spring added to the actuator.



Another borrowed picture, this time from Boulderhead's build thread! (just as a backup in case my pics are down again )

[Marcus_Aurelius]

Reserved for springs rates, part # and better pictures

Help brand spring assortment part #59001 (use the smaller spring)

Home depot brand, use one or the two small 5lbs springs (the bigger ones aren't preloaded as well as the small ones, and are a better match for our OEM KKK turbo actuators)








The only good picture I was able to snap of the hook on the actuator nipple side (it's really tight in there)








Some more of that side










I rest a washer on the rod nut to give the spring a good spot to rest on, and prevent them from sliding over the nut.







This what your spring hooks should look like before installing it, I like to crush them a bit so they have no chance of coming out. This is a year old spring with many heat cycles and I usually refresh them once every racing season but they will last a lot longer

[96AAAjetta]

I like where this is going and will deff be keeping an eye on this thread. I remember seeing this info somewhere else and have been looking for it but haven't been able to find it till now.

[PLAYED TT]

[All_Euro]

I did this quite a while back after reading one of your posts... simple, inexpensive & works really well.

Thanks

[1.8 skeet skeet]

Well how do you do it man?

[warranty225cpe]

Good stuff. I felt a nice difference when I went with the forge WG with the stiffer spring (thanks Sparti)

[Cryser]

Found this on an evo site and found it to be very true, gives a good difference between adjusting the Wastegate arm length and using external springs

I'll letcha know, I just did that today. I'll log tomorrow. Anyone had the spring pop off or snap due to heat cycling? I'm a bit concerned about that happening.

Actually... I wasn't going to do this but yep... Imma unload my thesis now:
If the spring is a linear spring (which is most common) then foce doesn't increas dramatically with deflection. This means that adjusting the eyelet on the WGA arm adds pretention to the spring which assures initial cracking pressure is adiquate, but does not actually increase force put on the arm. Adjusting the eyelet also decreases the flapper stroke, which means the maximum boost limiting ability is decreased. This isn't a problem unless it is over-adjusted. The only real advantage that might come from adjusting the eyelet (WGA arm length) would be cracking pressure, which means higher boost spike. The decreased flapper stroke gives the turbo the ability to hold higher boost... because less exhaust gasses escape. Adding the external spring actually sounds quite genius to me because it basically increases the spring's entire curve.. not just an initial pressure.

On a normal WOT pull this is how the WG is working:
During the spool, the WG remains closed.
As boost approaches the target (max) the WGA spring does its deal and allows the WG to open linearly until its open all the way at target boost.
At higher RPM the engine "eats" the boost faster so the boost decreases. This is where the WGA should start to close the WG again. I believe the problem is that when the WGA tries to close the WG at this time the exhaust velocity/pressure is so high that it overcomes the spring pressure. Increasing the pretention will not help in this and decreasing the maximum flapper stroke doesn't help either. The only thing that would help is increased force. This can only come from a stiffer spring or added springs to increase return force.

In summary:
-Adjusting the eylet (WGA arm length) increases pretention which increses boost spike value and may result in higher possible boost values due to decreased flapper stroke.
-Adding another spring or increasing spring stiffness prevents taper and premature opening, all while slightly modifying the boost curve.

So I will test this out tomorrow to see what this single change results in. I'm hoping to maintain 20-21 by redline, while keeping my normal 24-25 at peak torque.

Did this mod on my jetta and found I was able to uncrank my wastegate from what I had it and still able to hold a good amount of boost to redline. Also uncranking the wastegate allowed the car to drive much more civilized around town. Overall I have found using this mod to increase wastegate spring pressure is much more suitable then changing the wastegate arm because of the fact that changing the wastegate arm also begins to limit the ability for the car to control boost. This mod doesn't have that downside, you car can still fully control boost yet it has the increase spring tension.

[Marcus_Aurelius]

Cryser, I'm glad the mod helped and I see that you found the thread even before I got a chance to finish the how to and link you to it.

To add to what you are saying, cranking the adjustable rod not only screw up the ability to control boost spikes but it has a much more negative effect. With flap stroke or travel reduced, when there is actually a pressure signal from the N75 or boost controller asking the flap to open in order to reach a boost target, the flap only opens at a reduced percentage (less volume bypassed) and create high EGTs. Steve AKA Spartiati documented this in one of the technical forum thread, and having an EGT probe housing, he registered the issue and also power loss.

I don't want to make this thread about cranking rods adjustment as it is highly undesirable IMO. The spring mod however, allows you to retain full flap travel but also increase the ability to fight premature wastegate creep and make more boost/power efficiently.

The only warning I have with the spring mod is that it should not be used a way to control boost. Upper boost limit should be controlled by a boost controller. Besides that there are only positives and most people don't know how much stronger their car can get with this simple mod, until they tried it. I'm hoping this will help others that will follow the lead

[Cryser]

yeah I'm still messing with uncranking my wastegate because of the mod. But so far I have uncranked it a significant amount and still hold more boost in the top end then I ever did with it basically fully cranked. At the moment I'm still having problems with partial throttle boost at above 50% pedal I get a big spike and some "surging/bouncing" off boost but that has been going down as I slowly uncrank the gate more and more.

I'm almost back to stock location and still holding more boost in the top end then I ever did with my WG almost fully cranked. I'm just trying to find that delicate balance between un cranking and allowing the ECU to adjust for boost

[RabbitGTDguy]

going to chim in on this here as Max and I have talked about things many times before and this indeed does work and achieve what most are after as long as you know what you are getting into and the implications for doing it.

When I was setting up my Stg 3 WMI with Max here...we went this route. I need to pull more sustained boost at higher RPM's and overall. To accomplish this, I did it a bit differently than Max but did have a good result from it. Instead of using the above springs I remember that I had some long return/assist springs from a recent rear drum/brake job I had done on my own Jeep (though, this type of spring is common to most drum setups). It has a "eyelit" at one end and a hook at the other. To use. I simply slightly heated that eyelit end so that I could bend the eyelit to 90 degrees and fit it around the acuator rod end and then the hook end easily grabbled the acutator mount itself. Pretty slick. It worked flawlessly...

Then came the FORGE acutator...I bought one this winter...installed this spring. After the nightmarish install (it wasn't really that bad...just a pain for such an small part). I am currently running the "yellow" spring which is the next up from the stock green one they put in it.

I have to say, I can attest to the preloading of the spring and the associated consequences of doing so recently as well.

I set the acuator as you should (and many don't) but closing the flapper, applying 7psi or so to the acuator, and then setting the "preload" on the acuator from there. There truly is a "sweet spot" to this acutator and it is NOT by adding preload. I had it slightly in too much and I had surging everywhere. It was horrible. boost would sky rocket so fast and made things spooky scary and also that couldn't have been healthy for the turbo either. While it was exihilarating...it was also useless.

I made a few adjustments the other night and took ALL the preload off the flapper and it feels SO much better. As a matter of fact, since I'm pushing near the levels of boost as Max discusses, I believe that with proper tuning that I could handle the blue spring or the red one to achieve my goals for now (before a BT or FT build). The wategate spring really SHOULD be the end all when it comes to adjustment at the wastegate itself because it really should match the level of boost you are wanting to run...think about how the stock acutator settings work. The same thinking should be applied on the aftermarket approach as well. This isn't to be done by "cranking" the wastegate though.

What you achieve through the spring mod is more linear and smooth in action. Easily achieveable with the stock acutator as mentioned above or through the ability to "tune" an acutator like the FORGE unit. (I didn't buy mine new...trust me...wouldn't have thought it worth it if that was the case...was "like new" though....but not "like new price" ). I'm really edging towards trying to source a blue spring and giving it a go because this is what the car really needs to hold all the boost as long as you can. Set correctly....no surge...just smooth power/good build with better top end hold and as long as you have the mods and the know how to hold it...your golden.

Max, you'll find this interesting. Bought the "Road and Track" buyer's guide for the original TT where they discuss the K04 in part of it. Now...whether it is fact or fiction...but they claimed at the time that the TT with the K04 was capable of producing a max of 29psi with the K04. Makes me want to talk to the engineers and still keeps me playing with this unit. I still can't make that jump to the other side of the fence do to the less laggy/low end fun/torque and driveability that the K04 gives. I wouldn't want to lose that!

By the way...emailed you. Package should arrive soon. You decide what its worth to you and we can work from there. I emailed you info about things though.

Joe

[1.8 skeet skeet]

Where do you buy the springs? Im going to give this thing a try

[Marcus_Aurelius]

Where do you buy the springs? Im going to give this thing a try

Home depot - autoparts store - hardware store etc.

The autoparts store have an assortment under the Help brand, use the heaviest spring. The home depot carries an assortment too that has two springs that are perfect. I like going to a local Ace hardware because they have a big spring selection and the rates and other specs are available.



The home depot one, the two big springs are perfect for the job

[Cryser]

^

using those exact springs I'm using. Think it ended up being 6 bucks from home depot.

Although I'm using the 2 smaller ones rather then the 2 bigger ones as I didn't want to add that much more spring tension. Although I have the smaller one stretched pretty far to reach, I'm wondering if using the bigger ones, not stretched as far might work better.

only time and testing will tell =)

[1.8 skeet skeet]

Home depot - autoparts store - hardware store etc.

The autoparts store have an assortment under the Help brand, use the heaviest spring. The home depot carries an assortment too that has two springs that are perfect. I like going to a local Ace hardware because they have a big spring selection and the rates and other specs are available

Thanks man I really appreciate it! Im going to home depot tomorrow

[Cryser]

so I backed off my wastegate arm even more today, I think I have it at stock location(based on the patina on the actuator arm rod). Reset my ecu boost adaptations and everything(removed the battery for 10 mins) and I can tell ya, damn what a difference. The ability for the car to actually control boost is fully restored. Yet I can still hit 22-23PSI going up hill. Drove the car around in all sorts of loads and it's adapting nicely, still giving me a bit of surging at about 50%-70% throttle but it's nothing you can feel, just see it bouncing on the boost gauge and that is starting to target in. I'm gonna log tomorrow because the car feels a lot more powerful in the lower boost regions and my thoughts are that the ecu isn't pulling as much timing because of the reduced EGTS. The sound of the turbo also is MUCH better so I'm excited to get some logs and see if my estimations are true.

This truly is a MUCH better way to increase spring tension over cranking the **** out of the wastegate. A mod like this allows increased tension while still allowing the ecu to control boost properly. Spool up isn't as violent and because of that the car doesn't fight itself to control boost, before with my cranked wastegate I was basically limited to 10-25% throttle and full throttle. It's nice to be able to take off from a light at an "aggressive" pace without having to go full throttle and not look like a 16yr ricer trying to impress everyone around me.

[1.8 skeet skeet]

Just installed the springs! But its so hot and humid out I don't feel like taking her out of the garage I will let you guys know how it goes

[Cryser]

I was right, a lot less timing pull a negligible loss in airflow(-1g/s). There was actually more airflow past 5500 because of boost being held longer and the ecu has adapted quite nicely to the car returning a full pedal range. Much better way to hold boost longer

[20psi now]

I know this is off topic and NOT to thread jack, but you 225 guys might want to check your EGT probe at the turbo. Every time i get down there it back out a few threads and need to be tighted back up. I Would like to try this spring mod but I hold 14psi from 2500-6500 .

[warranty225cpe]

I wonder how much spring tension I would need since I have the stiffer forge already.

[Marcus_Aurelius]

^

using those exact springs I'm using. Think it ended up being 6 bucks from home depot.

Although I'm using the 2 smaller ones rather then the 2 bigger ones as I didn't want to add that much more spring tension. Although I have the smaller one stretched pretty far to reach, I'm wondering if using the bigger ones, not stretched as far might work better.

only time and testing will tell =)

The two smaller ones might be better than the bigger ones if they are short enough to be under tension at rest. I haven't used this assortment with the TT but did so once with an EVO. If you test both just report your results but for the time being I will update the second post to recommend the springs you are using. Thanks for the contribution!

[Marcus_Aurelius]

Just installed the springs! But its so hot and humid out I don't feel like taking her out of the garage I will let you guys know how it goes

let us know your results

[Marcus_Aurelius]

I wonder how much spring tension I would need since I have the stiffer forge already.

You may or may not need any... only testing can determine that since you already have uprated spring rate. It all going to depend on the amount of boost that you run, more boost = more pressure in the hot side to prematurely crack the flap open. You can test your initial cracking pressure with the Forge unit and internal spring installed. That will tell if the color spring you run is enough or appropriate for the boost you're running. Just make sure you don't have excessive preload on that actuator rod, I still believe that it played a major role on your turbo failing. Preload and reduced flap travel is evil IMO because of the heat and stress that's put on components (much higher EGT indicates it).

[1.8 skeet skeet]

let us know your results

I think it feels great!! You can totally feel a difference at the end of gears. The turbo doesn't fall on it face at upper RPM's like it use too

[jason bouchard]

wow , nicely done. . . I think I will be trying this soon. . .

I am having problems with my wastegate holding pressure (checked line)
I think its the canister

[nuff said]

I am wondering how to test the wastegate cracking pressure. Please chime in anyone .I assume
I would tap into the wastegate line, with a gauge ,and under the car,slowly pressurise the line,keeping a close eye on both pressure,and the wastegate,when the car is not running. Does this sound correct? Also,should the cracking pressure be about the samne as the max boost you run?

[Marcus_Aurelius]

I am wondering how to test the wastegate cracking pressure. Please chime in anyone .I assume
I would tap into the wastegate line, with a gauge ,and under the car,slowly pressurise the line,keeping a close eye on both pressure,and the wastegate,when the car is not running. Does this sound correct? Also,should the cracking pressure be about the samne as the max boost you run?

To test the cracking pressure, simply hook the hose going to the actuator to a regulated air compressor with a gauge hooked up. While watching the gauge, slowly increase the pressure with the regulator until the rod start to move and you have your cracking pressure. The old bike hand pump trick would work also, just use one with built in pressure gauge.

As far as ideal spring tension or cracking pressure, you want it to be a few psi under the Max boost that you run. Your goal is to eliminate the wastegate being blown open too much without a N75 or MBC actuation signal. If you put your cracking pressure at the boost you're running, you're basically running at wastegate pressure and have no real control over boost. For example, when I ran 33 psi, I had 20 psi cracking pressure and also tried 25 psi cracking pressure, had plenty of control over boost with both but 25 psi cracking pressure offered the best performance.

Think of it this way, the OEM actuator naturally cracks at 5-6 psi and that's conservatively designed to work in concert with a stock boost of 13 psi; increase the boost x psi over stock calls for at least x psi more actuator tension

[nuff said]

Thanks for your reply Marcus Aurelius. I got under the car and installed some springs ,testing as I went along. I ended up trying 18 psi cracking pressure. My boost was running at 22 psi. I have set everything up previously for quickest boost response. After driving today and testing it these
are the results;
My wastegate takes much longer to open once cracking pressure is met, so say I want to pass someone,there is now that hesitation before it gets going. The good side is I am now boosting 25 psi,a 3 psi improvement. I got on it ,on the freeway in 5th gear and after the slight hesitation ,the car accelerated like a rocket ship. It actually surprised me. It felt like it was accelerating expotentially faster.Even though I only got on it for a few seconds ,the boost gauge seemed to be super glued at 25 psi and felt as if I could go to redline(set at 7200rpm) and have nearly no drop off. I cannot decide which I prefer. Without the springs ,the car feels like it pulls harder ,immediately,but a few seconds later ,would not keep up with the car if the springs were in. I wish there was a way to have both the instant response and the improved acceleration at the top end......Thanks for your write up on this mod..

[Cryser]

Wanted to post an update. Currently I am using 3 of the smaller springs with the wastegate rod actually looser then stock. My cracking pressure is around 15PSI, this has allowed me to run a stage 2 eurodyne map(only edit on my side is swapped to using LAMFA map(power enrichment) rather then LAMBTS(full load lambda) other then that completely off the shelf tune. Everything runs great, getting my eurodyne cable back this week and I'm throwing my stroker bottom end on with the stock turbo for now, so I'll get to see how just a displacement increase effects things before the PPT .72 A/R 71r goes on =)

Again to sum up the thread, THIS is the PROPER way to increase wastegate spring tension while still allowing your ecu to actually control boost, better MPG, better response, better power then just cranking the actuator rod and effectively limiting you ability to control boost. My car now has a nice full range of power, still holds 21PSI around max boost, 14PSI at redline. Rubberbandness of the car is gone a lot more fun to drive around town.

[Marcus_Aurelius]

Thanks for your reply Marcus Aurelius. I got under the car and installed some springs ,testing as I went along. I ended up trying 18 psi cracking pressure. My boost was running at 22 psi. I have set everything up previously for quickest boost response. After driving today and testing it these
are the results;
My wastegate takes much longer to open once cracking pressure is met, so say I want to pass someone,there is now that hesitation before it gets going. The good side is I am now boosting 25 psi,a 3 psi improvement. I got on it ,on the freeway in 5th gear and after the slight hesitation ,the car accelerated like a rocket ship. It actually surprised me. It felt like it was accelerating expotentially faster.Even though I only got on it for a few seconds ,the boost gauge seemed to be super glued at 25 psi and felt as if I could go to redline(set at 7200rpm) and have nearly no drop off. I cannot decide which I prefer. Without the springs ,the car feels like it pulls harder ,immediately,but a few seconds later ,would not keep up with the car if the springs were in. I wish there was a way to have both the instant response and the improved acceleration at the top end......Thanks for your write up on this mod..

With everything else in check, you should not have any hesitation resulting from the spring mod. All you're really doing is increase the wastegate actuator pressure holding capacity to reduce the wastegate being blown open under loaded exhaust pressure. The increase in boost achieved and sustained should be the only things that you get from doing this.

I am pretty sure your hesitation or flat feeling right at onset (peak boost) is from something else. Maybe the ecu is dumping timing due to heat from the extra boost pressure; it could also be something else but definitely not a result of the mod. I would look at AFR, IAT, timing corrections, and even misfires to see what's causing the flat spot.

[Marcus_Aurelius]

Wanted to post an update. Currently I am using 3 of the smaller springs with the wastegate rod actually looser then stock. My cracking pressure is around 15PSI, this has allowed me to run a stage 2 eurodyne map(only edit on my side is swapped to using LAMFA map(power enrichment) rather then LAMBTS(full load lambda) other then that completely off the shelf tune. Everything runs great, getting my eurodyne cable back this week and I'm throwing my stroker bottom end on with the stock turbo for now, so I'll get to see how just a displacement increase effects things before the PPT .72 A/R 71r goes on =)

Again to sum up the thread, THIS is the PROPER way to increase wastegate spring tension while still allowing your ecu to actually control boost, better MPG, better response, better power then just cranking the actuator rod and effectively limiting you ability to control boost. My car now has a nice full range of power, still holds 21PSI around max boost, 14PSI at redline. Rubberbandness of the car is gone a lot more fun to drive around town.

Thanks for the update!

Switching to LAMFA over LAMBTS sounds interesting, I remember asking my buddy DougLoBue for the reason for the preference for full load lambda in the community. What are your findings?

I also can't wait to hear your thoughts on the increased displacement on a stock snail, keep us posted

[RoTTirocket]

Wow great read. Will def have to do this since I found out my whole waste gate is literally loose, just wiggling around back there. Thread jack: Any tips for getting back there to remove the waste gate and install the new one? So tight!

[Marcus_Aurelius]

Wow great read. Will def have to do this since I found out my whole waste gate is literally loose, just wiggling around back there. Thread jack: Any tips for getting back there to remove the waste gate and install the new one? So tight!

Remove the turbo outlet pipe, hose and strut tower bar and the metal shield behind the valve cover. Then bear hug the motor from the top so you could reach everything. It's not that bad with everything out of the way.

[nuff said]

I have now had the wastegate spring mod in for 2 weeks.I experimented with a few different spring tensions to find the best combination. One of the good results was uncranking my
previously cranked wg.It is now back to stock position.I now have better drivability,less flutter,and 3 psi more power. All for a couple bucks....Excellent mod thanks to Marcus A.

[Marcus_Aurelius]

I have now had the wastegate spring mod in for 2 weeks.I experimented with a few different spring tensions to find the best combination. One of the good results was uncranking my previously cranked wg.It is now back to stock position.I now have better drivability,less flutter,and 3 psi more power. All for a couple bucks....Excellent mod thanks to Marcus A.