How to tune a wastegate

[DIESEL SHOP LLC.]

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?

very good explanation thank you:thumbup:

 

[Hotrodtractor]

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:

I know your trying - but please take a step back for a moment and breathe. Then take a moment to take a look at the post you made and see if you make it so its a bit harder to read. I had to FORCE myself to read it - normally posts like this just get skipped and ignored because of the difficulty. For instance it could be something like this:

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:

See how just a couple off taps of the "ENTER" key can make it so much more readable?

 

[Charles]

I always run a super soft spring with a dual port gate so that I can use manifold pressure to easily alter the spring rate by adjusting how much additional manifold pressure I let impact the diaphragm through the top port.

This way you're not out there swapping springs a zillion times for no reason. The spring should be strong enough to hold the gate shut until manifold pressure begins to climb. That is all. As soon as you have manifold pressure you have force to hold the gate closed, so why dick around with a mechanical spring when you have an infinitely variable air spring at your disposal???


Aside from this, there is one other point I would like to make. And that is the concept of failSAFE operation and design.

If you set your system so that manifold signal must be present to OPEN the gate, and you blow that line... you will overboost, which could be devastating depending on the system capabilities.

This for instance would be the case if a person ran a lot of spring and then had a signal line to the bottom port oppose the spring as manifold pressure rose, and lift the valve open. Well.... if/when you rupture that signal line you now have no wastegate signal. The engine will then run boost right up to the mechanical spring force. You're "on spring" at that point. Could be a nightmare, especially on a compounded truck. I know.... I've done it, a FEW times. Snapping a 100psi gauge when you're set for 70psi isn't my idea of a good time.

Contrary to that methodology... if you instead were to say, set the spring so that it would NOT achieve desired boost, and then regulated the pressure to the top port then you could control boost without issue. The difference being.... if/when you rupture the signal line you LOSE boost and drop off like crazy. Truck drops power and starts smoking.

That's FailSAFE operation. Something that tends to keep the coolant IN the degas bottle and the rods IN the block on a truck that gets driven enough to see hose failures from time to time, which is any daily driver.

Last point..... seriously consider using very high quality signal lines, preferably braided stainless rubber lines with AN type fittings. Signal lines blow OFTEN in my experience. There is a lot of sh*t going on under the hood, and with the heat and time, plus relatively high pressure at relatively high heat, it's a rough environment for a hose. Most hose that comes with controllers and gates is IMO insufficient.

 

[Vader's Fury]

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.

K i got it now. For some reason I was thinking that the back pressure pushing on the bottom of the wastegate would open it up.

So by using a heavier spring you basically slow down the rate that the wg opens giving you an easier transient instead of a on/off feel to it correct.

 

[907DAVE]

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.

In my mind, this seems like the best way to setup a wastegate.

What would be the best way to set the spring pre-load, should you just set it loose and let the boost reference do most of the work?

 

[Charles]

In my mind, this seems like the best way to setup a wastegate.

What would be the best way to set the spring pre-load, should you just set it loose and let the boost reference do most of the work?

That's been my mode of operation ever since I got tired of taking wastegates apart for tuning and just let the air do the work.


I've been using 4 port solenoids to control my gates for a few years now. Manifold pressure is directed 100% to the top port until boost begins to rise and then the PCS slowly shifts the duty cycle away from the top port toward the bottom port. In this way I can actively hold the gate totally shut until I'm ready and then start progressively opening it up as boost rises. It has proven to be very responsive on my truck.

 

[907DAVE]

PCS would be nice to have!

 

[V-Ref]

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.

Thanks! :thumbup:

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.

Thanks! :thumbup:

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?

Sticky worthy post right here. In regards to WG port plumbing...What advantages/characteristics should you consider when deciding to either to plumb using atmosphere/reg boost pressure vs unreg/reg boost pressure on the two ports.

Thanks for you smart guys patience...but I'm just not seeing what advantages there are to running boost pressure to one side of the gate vs. venting it to atmosphere. No matter the goals/application/spring/boost level it would seem venting one side of the gate to atmosphere would always be simpler.

I guess my question is what advantage does running reg boost press on one side of the gate and unreg boost press on the other side of the gate, have over the reg boost press/vented to atmosphere WG plumbing scenario.

Thanks!

I always run a super soft spring with a dual port gate so that I can use manifold pressure to easily alter the spring rate by adjusting how much additional manifold pressure I let impact the diaphragm through the top port.

This way you're not out there swapping springs a zillion times for no reason. The spring should be strong enough to hold the gate shut until manifold pressure begins to climb. That is all. As soon as you have manifold pressure you have force to hold the gate closed, so why dick around with a mechanical spring when you have an infinitely variable air spring at your disposal???


Aside from this, there is one other point I would like to make. And that is the concept of failSAFE operation and design.

If you set your system so that manifold signal must be present to OPEN the gate, and you blow that line... you will overboost, which could be devastating depending on the system capabilities.

This for instance would be the case if a person ran a lot of spring and then had a signal line to the bottom port oppose the spring as manifold pressure rose, and lift the valve open. Well.... if/when you rupture that signal line you now have no wastegate signal. The engine will then run boost right up to the mechanical spring force. You're "on spring" at that point. Could be a nightmare, especially on a compounded truck. I know.... I've done it, a FEW times. Snapping a 100psi gauge when you're set for 70psi isn't my idea of a good time.

Contrary to that methodology... if you instead were to say, set the spring so that it would NOT achieve desired boost, and then regulated the pressure to the top port then you could control boost without issue. The difference being.... if/when you rupture the signal line you LOSE boost and drop off like crazy. Truck drops power and starts smoking.

That's FailSAFE operation. Something that tends to keep the coolant IN the degas bottle and the rods IN the block on a truck that gets driven enough to see hose failures from time to time, which is any daily driver.

Last point..... seriously consider using very high quality signal lines, preferably braided stainless rubber lines with AN type fittings. Signal lines blow OFTEN in my experience. There is a lot of sh*t going on under the hood, and with the heat and time, plus relatively high pressure at relatively high heat, it's a rough environment for a hose. Most hose that comes with controllers and gates is IMO insufficient.

Great point on FAILSAFE, and emphasis on the basics regarding plumbing.

I think I know my answer to this next question...cost. But Aviation applications use electromechanical blow off valves/bypass valves...that would seem to push WG adjustment/tuning out of the witchcraft spectrum and more towards a science...are there electromechanical WGs available/in use in automotive applications?

 

[TARM]

Charles,

I understand your theory on setting up the wastegate and using "air spring" as the main control component. But with a single turbo system when you first jump on the throttle your drive pressure tends to spike somewhat first with boost catching up and evening out as it builds. Would not going with a lower tension spring possibly allow the drive pressure to over come the spring enough to crack open the valve thus blunting the rate boost builds? Obviously this could be a positive or a negative I would think depending on what you are after.

If I understood Jason, this is what he was speaking of in his comments about how hard hitting you want boost to come in??

I am thinking depending on the turbine setup and how fast spool and boost ramps up would dictate if some slight bypass initially is or is not wanted. Yes ? No?

 

[PowerstrokeJunkie]

Charles my thinking is similar to yours as in having a variable air spring on the top and using a light spring to hold the gate closed off boost. I do not see the reasoning clearly why you would nee regulators and a clusterfucuk of hoses to combat a heavy spring in the wastegate on a single turbo setup..

I started out not knowing what my setup would run and put a 10.5psi spring in.. next time I have access to the gate im going to put in a 5 psi spring and see what happens

 

[TARM]

Charles my thinking is similar to yours as in having a variable air spring on the top and using a light spring to hold the gate closed off boost. I do not see the reasoning clearly why you would nee regulators and a clusterfucuk of hoses to combat a heavy spring in the wastegate on a single turbo setup..

I started out not knowing what my setup would run and put a 10.5psi spring in.. next time I have access to the gate im going to put in a 5 psi spring and see what happens

Maybe I am not reading it correctly but the way I read it his method still uses the same top and bottom manifold pressure hoses with the top one being regulated to control.




BTW Charles,

I re-read what you wrote and it accounts for the drive spike so disregard my last posted question.

 

[PowerstrokeJunkie]

No I am running nothing on the bottom side of the diaphragm and a manifold reference above the diaphragm. I am assuming the surface area of the diaphragm is equal to the area that acts on the bottom of the valve. Also. That a 10.5 psi spring will open at 10.5psi of backpressure and not 10.5 psi total force on the stem

 

[907DAVE]

Can anyone verify that if a spring is rated for ___LBS, that is the amount of backpressure required to overcome this spring?

 

[PowerstrokeJunkie]

:whs:

 

[V-Ref]

Can anyone verify that if a spring is rated for ___LBS, that is the amount of backpressure required to overcome this spring?

That is what Precision told me. xx.x spring requires xx.x drive pressure to overcome. That would tell me the spring pack (color and number of springs) psi rating is defined by gate size. Didn't write the fella's name down.

FWIW-My gate "sounds" different as it opens when you apply shop air to it now, as it did when I first installed it....hmmm, probably time to pull it apart and see what's up :doh:

 

[TARM]

That is what Precision told me. xx.x spring requires xx.x drive pressure to overcome. That would tell me the spring pack (color and number of springs) psi rating is defined by gate size. Didn't write the fella's name down.

FWIW-My gate "sounds" different as it opens when you apply shop air to it now, as it did when I first installed it....hmmm, probably time to pull it apart and see what's up :doh:

Makes sense to me otherwise it would have to be pressure against the valve itself.

 

[Big Bore]

That is what Precision told me. xx.x spring requires xx.x drive pressure to overcome. That would tell me the spring pack (color and number of springs) psi rating is defined by gate size. Didn't write the fella's name down.

FWIW-My gate "sounds" different as it opens when you apply shop air to it now, as it did when I first installed it....hmmm, probably time to pull it apart and see what's up :doh:

So in a compound setup where you are running very low boost pressures you would have to use boost signal to operate the gate and the spring is basically a fail safe?

 

[Chvyrkr]

Good thread...

 

[907DAVE]

So in a compound setup where you are running very low boost pressures you would have to use boost signal to operate the gate and the spring is basically a fail safe?

I have tried running the boost reference to the bottom of the gate with a heavy spring in my setup, and it does not work well. You have little control over the gate because how fast and far it opens. Recently I loosened the preload (using the same spring) and used the top port on the gate with much better results. I get a touch more smoke on a snap throttle, but once boost rises its much more responsive.

 

[a_moore]

Why can a simple pneumatic cylinder not be used to make the tuning a little easier.

If you want slightly more backpressure hook the boost up to the rod side (as it has a smaller surface area on the piston based on rod diameter) and the backpressure to the piston side (assuming that you set it up with the cylinder and gate normally closed). Wala, a self regulated gate control. It may be necessary to add regulator to the air, or say a 20 psi check valve to get things lit.

This (in my head anyway) would regulate itself to near optimal p/r and keep the controls and extra tuning and adjustments out of the equation. As anyone knows who has played with turbos....they run good and pull hard to a certian point, then they start to fall off in power as they are pushed out of theit map and start to create hot boost and high parasitic loss via backpressure.

I will try it someday.