How to tune a wastegate

[Vader's Fury]

I thought we could get a thread going on how to tune in a wastegate. Lets try to limit this to people that actually have hands on experience with running one. I know that wastegating a single is being done more and more (I am installing one right now) and it can be confusing.

If we get enough good responces, hopefully we can make it a sticky.

 

[PowerstrokeJunkie]

I have read to have backpressure about 10psi higher than boost, so on my setup I put a 10.5psi spring in it (to help close the valve) and referenced the top of the diaphragm to manifold pressure... so for every pound of drive pressure pushing the valve open there's another on top holding it closed.. once the drive overcomes the spring the wastegate will open.

 

[Vader's Fury]

In your setup the drive will have to overcome boost by 10.5# before the wastegate will open up correct?

 

[RedSmokey]

I have read to have backpressure about 10psi higher than boost, so on my setup I put a 10.5psi spring in it (to help close the valve) and referenced the top of the diaphragm to manifold pressure... so for every pound of drive pressure pushing the valve open there's another on top holding it closed.. once the drive overcomes the spring the wastegate will open.

Is this "tuned" more for nitrous or is that a pretty normal setup? What size injectors and what kind of boost are you making along with HP?

In your setup the drive will have to overcome boost by 10.5# before the wastegate will open up correct?

:whs: Thats what I gathered from it. Also why I was asking if that is aimed more for the giggle gas or just a high boost/hp truck?

 

[DIESEL SHOP LLC.]

i have a controller to adjust the waste gate, forgot what size spring think a 25. I am running mine because i have a d66 turbo and 238s on 100s, so my drive psi is very hi at the end of a hard pull and i have it on giggle gas haha i like that one. i have mine set at like 37 psi of boost and 37 drive psi, and knocks off the rest to atmosphere.

 

[DIESEL SHOP LLC.]

my total drive psi is around 48 to 50. i have a flange between the collector and turbo i will try to post some pics not the best at it. There might be some in my gallery if u want to check it out

 

[CSIPSD]

i have a controller to adjust the waste gate, forgot what size spring think a 25. I am running mine because i have a d66 turbo and 238s on 100s, so my drive psi is very hi at the end of a hard pull and i have it on giggle gas haha i like that one. i have mine set at like 37 psi of boost and 37 drive psi, and knocks off the rest to atmosphere.

wow...

 

[DIESEL SHOP LLC.]

wow...

did i do something wrong ????

 

[Wackerjr]

did i do something wrong ????

Nope most competent post in this thread.....

 

[Hotrodtractor]

I need to come back and elaborate a little bit on this.

I like to have about 5-10psi more back pressure than boost on the pulling track - this allows me to continue putting enough power into the turbo to keep the turbo "lit" at the big end of the track.

For street driving I tend to put the heaviest spring in the waste gate I can get - then put regulated boost to the top of the gate and put unregulated boost to the bottom of the gate. By adjusting the amount of regulated boost I can control when the waste gate opens. By changing springs to a softer spring, or decreasing the pre-load on the spring you can adjust how "hard" the boost hits - by going to a softer spring the waste gate will open just a bit during large increases in back pressure that occur when you stab the throttle - I like mine a bit more hard hitting than some.

Another option that is more associated with competition is to build a back pressure blow off valve - basically use a waste gate and install a spring with enough force to hold the gate closed until the back pressure reached your desired goal - for instance through testing you might know you will have 55-60psi of back pressure at 50psi of boost - then you just adjust the spring pressure and pre-load until the waste gate blows itself open at 55-60psi of back pressure - once it gets there it opens - no matter what boost is doing.

 

[Vader's Fury]

I need to come back and elaborate a little bit on this.

I like to have about 5-10psi more back pressure than boost on the pulling track - this allows me to continue putting enough power into the turbo to keep the turbo "lit" at the big end of the track.

For street driving I tend to put the heaviest spring in the waste gate I can get - then put regulated boost to the top of the gate and put unregulated boost to the bottom of the gate. By adjusting the amount of regulated boost I can control when the waste gate opens. By changing springs to a softer spring, or decreasing the pre-load on the spring you can adjust how "hard" the boost hits - by going to a softer spring the waste gate will open just a bit during large increases in back pressure that occur when you stab the throttle - I like mine a bit more hard hitting than some.

Another option that is more associated with competition is to build a back pressure blow off valve - basically use a waste gate and install a spring with enough force to hold the gate closed until the back pressure reached your desired goal - for instance through testing you might know you will have 55-60psi of back pressure at 50psi of boost - then you just adjust the spring pressure and pre-load until the waste gate blows itself open at 55-60psi of back pressure - once it gets there it opens - no matter what boost is doing.

This is how I was planning to set mine up to begin with and then play with it a bit to try to get it dialed in where I feel comfortable with it.

In a situation like you are describing, by putting a 10# spring in the wastegate, Once boost reaches 10# the gate will start to open and bypass exhaust around the turbo. By adjusting the regulated boost to the top of the gate I in effect increase the pressure required to open the wastegate correct?

 

[Hotrodtractor]

This is how I was planning to set mine up to begin with and then play with it a bit to try to get it dialed in where I feel comfortable with it.

In a situation like you are describing, by putting a 10# spring in the wastegate, Once boost reaches 10# the gate will start to open and bypass exhaust around the turbo. By adjusting the regulated boost to the top of the gate I in effect increase the pressure required to open the wastegate correct?

No - at 10psi of boost - you likely have 10psi both above and below the diaphragm keeping it "balanced" - so the spring is just holding back the pressure on the waste gate valve trying to keep it closed - depending on how much force that is - it may or may not be successful.

 

[V-Ref]

No - at 10psi of boost - you likely have 10psi both above and below the diaphragm keeping it "balanced" - so the spring is just holding back the pressure on the waste gate valve trying to keep it closed - depending on how much force that is - it may or may not be successful.

You have me confused here (that's easily done though)....could you clarify how you have the controller plumbed in the scenario you mention above.

 

[V-Ref]

FWIW- The setup I'm learning on...

PTE 46mm gate w/25.5 psi spring pack
Turbosmart Diesel Boost tee
76mm inducer/200% nozzles
ZF6
street driven truck
Controller plumbing-Boost reference port on turbo compressor housing->Turbosmart Boost Tee->Bottom of WG. Top of WG vented to atmosphere.

I blab all that, because I think it's key to realize how you set the gate up, is probably somewhat application dependent, and how the WG is plumbed.

It's embarrassing to admit...but after installing a new boost tee with proper fittings, my BP to Boost ratio is much more in line with what I observed/read from other folks setups, as am 1:1 to nearly 40 psi now in a non transient/stabilized state. Chasing boost leaks is a rookie move I know, but the basic stuff just keeps biting me in the azz over and over again with my turbo/wg. Hopefully that'll put the exclamation mark on this issue for someone else.

Back to the OPs question though...my two main concerns were transient turbo response with a large turbo/street driven/manual trans truck. So the heaviest possible spring pack went into the gate (too be perfectly honest, it's the one Jake put in the gate, so he's the genius/dummy...and I just rocked it 'cause I knew he was smarter than me on this issue, as it's the first time I ever ran a gate). When the truck was run without a boost ref tee, and the turbo compressor housing boost ref port was plumbed direct to the top of the gate, the turbo was extremely light switchy...either off or on. Nearly impossible to see boost between 15-45 psi...it was either all in or not.

After installing the boost tee as plumbed above...I dialed it in (unknowingly but suspecting a leak), and found that now transient response was down some, but I could at least operate in the 15-45psi range. I was disappointed in Boost vs BP ratios though.

Just got the new TS Diesel Tee in that has 1/4" barbed fittings...and it's an all new truck all over again. Better transient response, and BP vs Boost is much more favorable than previous. I know some might be looking at this post crosseyed like I'm crazy...but I'm adamant that boost leaks will make or break your setup...and drive you in circles chasing "other stuff" in attempt to fix 'em.

A slight sidetrack to the OPs original question in the thread...I've read on other platforms, specifically the 6.4 fellas are seeing WG diaphragm failures..presumably from excessive pressures/heat. Is this a point worthy to consider when deciding how to spring/plumb your gate(s)?

PSJs setup could in theory expose the top of the WG diaphragm to the maximum boost pressure his turbo could generate...which could be 40-50 psi (PSJ I'm not sharpshooting your setup at all, just listed it as an example my question...as I'm here to learn too)....where as the other extreme is a scenario like the one I listed above...where the bottom of the WG diaphragm is exposed to a minimal amount of boost...ie..the controller decides how much boost the WG sees to assist in opening it. Kind of leads into the question I posted for HRT above...this balanced deal he mentions...my feeble mind can't grasp it though.

 

[V-Ref]

i have a controller to adjust the waste gate, forgot what size spring think a 25. I am running mine because i have a d66 turbo and 238s on 100s, so my drive psi is very hi at the end of a hard pull and i have it on giggle gas haha i like that one. i have mine set at like 37 psi of boost and 37 drive psi, and knocks off the rest to atmosphere.

Can you describe how your controller/WG are plumbed? Do you use regulated boost pressure to assist in opening or closing the gate?

 

[strokin'_tatsch]

On my brothers old pulling truck we set up the gate as HRT describe. Heaviest spring we could get in the WG with regulated boost to the top and unregulated boost to the bottom. We used a compressor regulator to regulate boost to the top of the WG. We started with the regulator all the way out, so that the top of the WG saw the same amount of boost as the bottom, and the gate stayed closed allowing as much boost as we could get. We then dialed in the regulator in(less boost to the top of the WG) allowing the gate to open sooner, until boost was where we felt comfortable to keep the turbo happy. We never checked drive pressure even though I would have liked to see what it was doing.

You have me confused here (that's easily done though)....could you clarify how you have the controller plumbed in the scenario you mention above.

Think of it this way.. You have one boost line with a TEE on it. One side of the tee goes to the bottom of the gate and is NOT regulated. The other side of the tee goes to the top of the gate and has a regulator inline after the tee. Hope that makes sense.

 

[PowerstrokeJunkie]

I am not using nitrous, i have 250/80 injectors, and im probably somewhere around 500 horsepower, if that. I chose a wastegate because i have a nice responsive small turbine and knew i was going to over drive it on the second half of the throttle

 

[Short Bus]

on my twins i measured the total bp then tuned the gate so that at X boost the gate would open and let the h2e only see 40 psi of bp.

 

[DIESEL SHOP LLC.]

Can you describe how your controller/WG are plumbed? Do you use regulated boost pressure to assist in opening or closing the gate?

i have the controller assiting wg to open its connected to bottom port on wg and is connected to the tee for my boost gauge and controller for nos.i have a plate or block between turbo and collector on up pipes, it has a tube that runs between exhaust housing and center section on turbo then comes up to the side of intake spyder with a tube and has wg bolted to it. This is all new to me also the set up was made by steve at BDP,so when i turn my controller to the + side i get more boost bf wg blows off , if i want less boost i turn it to -, hope i am explaing right, i am not a expert, just a guy always trying to learn and i know my spelling sucks and all that good stuff. Also not sure why this happens but some days it needs a lil adjustment to make it blow off some days its a bit high on boost sometimes a bit low any ideas why it does this would be great, no boost leakes or exhaust leaks checked an double checked. ITS FRIDAY YAAAAAAA think i am closein shop for weekend need a day off :fordoval:

 

[Hotrodtractor]

You have me confused here (that's easily done though)....could you clarify how you have the controller plumbed in the scenario you mention above.

Variables in waste gate setup:

Spring rate
Spring preload
Valve face diameter
Pressure above the diaphragm
Pressure below the diaphragm.

How those variable effect waste gate tuning:

Spring rate is mostly used to set up initial spring preload to keep the waste gate shut - but can have some effect on how far the gate opens at any given waste gate condition (the higher the rate - the harder the gate is to move the farther open it becomes).

Spring preload - some waste gates have adjustable spring preload that allows further tweaking of the initial seat pressure of the waste gate.

Valve face diameter - Exhaust pressure is pushing against the valve face - the larger the face - the more surface area that pressure can push against trying to open the gate.

The diaphragm has ports above and below the diaphragm - and there are LOTS of ways to set these up depending on what results you might be looking for. BUT no matter how you set them up - having more pressure on one side versus the other will want to make the unit want to either try and open or try and close. I've seen both ports open to atmosphere, regulated boost to either one with the other one open to atmosphere, unregulated boost to either one with the other one open to atmosphere, regulated boost to one with unregulated boost to the opposite, etc.....

I prefer a heavy spring - with a good sized gate - with unregulated boost below the diaphragm - and regulated boost tot he top of the diaphragm as a good starting point for most setups - but depending on the application and desired outcome all of those items could change for any given setup. For instance - my Dmax usually has a heavy spring with regulated boost to the top of the diaphragm and the lower open to atmosphere - this allows the wastegate to slightly open when I suddenly go WOT - then the boost begins to hold it closed until the backpressure is strong enough to overcome the combination of the spring's seat pressure with the added force of the boost on top and it starts bleeding exhaust gases around the charger.

There are DOZENS of ways of setting up a wastegate - and they are all good for certain things and several different ways can be used to achieve the same basic thing.

Confused yet?