Wastegate Battle: 38mm vs 44mm vs 60mm

There is always constant discussion about what is the proper diameter wastegate to get. Some say, "38's always work." Some say,"44 is the shit." And even some just say, "Hell, toss a 60mm on and you'll never have to worry!" Regardless of what they say, there's a reason behind it all. The proper wastegate size is all determined by how well your manifold is build, where your wastegate is located, and how it is placed.

First off, the point of a wastegate is to take exhaust flow away from the turbine. When you have a wastegate at a straight 90* angle, the exhaust flow tends to pass it by, and very little exhaust gases actually flow towards your wastegate. There are manifolds with 90* wastegate angles, but they have made it so there is more flow towards the wastegate by "tear dropping" the entry. Here is a Full-Race manifold for example:
http://i86.photobucket.com/albums/k8...s/IMG_5226.jpg

The exhaust flow gets brought into the wastegate in a very smooth flow. Without this, the exhaust gases just pass by and create boost creep. The following photos, thanks to Full-Race, show this perfectly:
http://www.full-race.com/prototype/06SI/boostcreep1.jpg
http://www.full-race.com/prototype/06SI/boostcreep2.jpg
http://www.full-race.com/prototype/06SI/boostcreep3.jpg

Even Precision knows their stuff (although their journal bearing turbos leak like a siv :tap:). Here is what they have in their manual:
http://i86.photobucket.com/albums/k8...sionManual.jpg

Hope this information was helpful :turbohug:

Manifold companies need to focus on this stuff more. This is great info, I'm surprised I missed it.

This is very valuable for anyone fabricating there own turbo manifold or are looking for a proper manifold for there build. Though I have always been a big advocate for running the largest wastegate that you can fit. :)

Definitely good information and definitely something most builders and fabricators miss or don't think of

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I'm glad you guys find this to be a good read. I really enjoyed reading this, so I had to post it.

Loved reading this. I never even thought about the angle of my WG. Great info! I'm still pretty noob to turbo technicalities, so this will surely be a facepalm question, but....what do the spring ratings mean? Saybi have a 38mm WG with a 10 lb spring. Does that mean the WG opens at 10psi?

Pretty much exactly so it will open and dump exhaust once it reaches the springs psi /pressure rating and it is also the least amount of boost you will be able to run unless you get a 4 port I think with a 4 port boost solenoid you can cut the boost level in half to say 5 psi .I don't have one as of yet but am looking into them so I can run less boost in 1st and second and not have to back pedal so often .I run a twin scroll set up with 2 gates both have 7 psi springs in them and I love having twin gates as it doesn't creep at all up top and it spools insanely fast down low .

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Originally Posted by vdubkilla

Pretty much exactly so it will open and dump exhaust once it reaches the springs psi /pressure rating and it is also the least amount of boost you will be able to run unless you get a 4 port I think with a 4 port boost solenoid you can cut the boost level in half to say 5 psi .I don't have one as of yet but am looking into them so I can run less boost in 1st and second and not have to back pedal so often .I run a twin scroll set up with 2 gates both have 7 psi springs in them and I love having twin gates as it doesn't creep at all up top and it spools insanely fast down low .

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You are right, kinda. The spring pressure is the LOWEST boost you can run, no questions asked. A 4 port solenoid, or any solenoid/boost controller can never cause boost to be less than the spring pressure, it can only raise it. The nice thing about the 4 port, is that it can raise it a LOT above spring pressure. Generally a 3 port is good for like 2.5x spring pressure, so a 3 psi spring will top out at (on the high side) 10-12 psi, whereas the 4 port can make probably over 30 psi with that 3 psi spring.

Well I've actually been discussing running 2 three port solenoids to reduce the boost pressure and was pretty certain it was possible and thought a 4 port can do the same but I have yet to delve into this aspect of my build so I'm not certain yet .I am sure in the near future I'll have a good education on the exact workings of either (2) 3 ports or one 4 port but I hope it can be done .What you say does make sense though I guess I'll just have to do a little more research on it .I will say this I've def made over 30 psi with a 3 port and a 7 lb spring in the gates

trying to find it but on CRSX there was a manifold that was designed more for wastegate than turbo. Was a sick manifold.

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Originally Posted by vdubkilla

Well I've actually been discussing running 2 three port solenoids to reduce the boost pressure and was pretty certain it was possible and thought a 4 port can do the same but I have yet to delve into this aspect of my build so I'm not certain yet .I am sure in the near future I'll have a good education on the exact workings of either (2) 3 ports or one 4 port but I hope it can be done .What you say does make sense though I guess I'll just have to do a little more research on it .I will say this I've def made over 30 psi with a 3 port and a 7 lb spring in the gates

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I agree with Almk, i am not certain where you read that you can reduce spring pressure but i also do not believe it is possible. Essentially you can't run a boost pressure lower than the spring pressure. A boost controller is only used to increase the total boost you want to run but adding pressure to the top of the WG. Would be beneficial if there was a way to reduce it but with the range a 4 port can operate in, just running a lower psi spring is also a reasonable option.

I think a 44mm wg is perfect for almost every application on this site. some people run twin scrolls and 2 44's might even be overkill but when it comes to preventing creep overkill is best lol. A 60mm wg unless your running some 800hp monster is unnecessary.

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Originally Posted by snizzletoff

I agree with Almk, i am not certain where you read that you can reduce spring pressure but i also do not believe it is possible. Essentially you can't run a boost pressure lower than the spring pressure. A boost controller is only used to increase the total boost you want to run but adding pressure to the top of the WG. Would be beneficial if there was a way to reduce it but with the range a 4 port can operate in, just running a lower psi spring is also a reasonable option.

I think a 44mm wg is perfect for almost every application on this site. some people run twin scrolls and 2 44's might even be overkill but when it comes to preventing creep overkill is best lol. A 60mm wg unless your running some 800hp monster is unnecessary.

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I didn't read it anywhere apparently I was given the wrong info or misunderstood the guy that I was discussing it with last week at Cecil .As I said this is my first time exploring with 3 and 4 ports but you can bet when I'm done I'll know it well and have it perfected .I'll be making the change to reduce the amount of boost I can run if it means changing my wg springs then that's what I'm gonna do as I'd like to lower it to a few lbs in first and second on the street so I don't have to back pedal so much .I do indeed love the twin 44 mvrs they control boost so good up top it holds rock steady and you know I'm always one for overkill lol

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Originally Posted by 1JZ_Type-S

Loved reading this. I never even thought about the angle of my WG. Great info! I'm still pretty noob to turbo technicalities, so this will surely be a facepalm question, but....what do the spring ratings mean? Saybi have a 38mm WG with a 10 lb spring. Does that mean the WG opens at 10psi?

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From what I have read the spring will open when it sees 10lbs but that is a big spring. I have a four port boost solenoid and my 3lb spring is holding find up to way over that. No creep at all :D

If I change out my spring, I assume I'll need a new tune, correct? Due to the variation of boost pressures at different rpm

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Originally Posted by 1JZ_Type-S

If I change out my spring, I assume I'll need a new tune, correct? Due to the variation of boost pressures at different rpm

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What size spring you got?

10 pound. I've only creeped a handful of times with it. My confliction is that I'm running a journal bearing turbo, so I need the wastegate to open as late as possible to allow for the quickest spool

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Originally Posted by 1JZ_Type-S

10 pound. I've only creeped a handful of times with it. My confliction is that I'm running a journal bearing turbo, so I need the wastegate to open as late as possible to allow for the quickest spool

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I am on journal too and I spool pretty fast on four port. Do you know the difference between them?

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Originally Posted by ksboi

I am on journal too and I spool pretty fast on four port. Do you know the difference between them?

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I don't. Ive never heard of port differences until I joined thid site

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Originally Posted by 1JZ_Type-S

I don't. Ive never heard of port differences until I joined thid site

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From what I was told the boost solenoid has four ports, ie four port, two run to the gate which put increased pressure on the top of the gate which will allow no air to seap out which allows you to build boost faster and go way over the spring rate.

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Originally Posted by Spaz

trying to find it but on CRSX there was a manifold that was designed more for wastegate than turbo. Was a sick manifold.

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I think it's the AFI manifold. The manifold Vit has on his black civic is also designed like that. Maybe he can post a picture here [MENTION=789]VitViper[/MENTION]

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Originally Posted by snizzletoff

I agree with Almk, i am not certain where you read that you can reduce spring pressure but i also do not believe it is possible. Essentially you can't run a boost pressure lower than the spring pressure. A boost controller is only used to increase the total boost you want to run but adding pressure to the top of the WG. Would be beneficial if there was a way to reduce it but with the range a 4 port can operate in, just running a lower psi spring is also a reasonable option.

I think a 44mm wg is perfect for almost every application on this site. some people run twin scrolls and 2 44's might even be overkill but when it comes to preventing creep overkill is best lol. A 60mm wg unless your running some 800hp monster is unnecessary.

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I like all of what you said, but in a way a high horsepower build can probably be just fine on a small gate, since it never really needs to run low boost anyways, who cares if most of the exhaust can't go out the gate when you need to make 30+ psi :giggle:

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Originally Posted by vdubkilla

I didn't read it anywhere apparently I was given the wrong info or misunderstood the guy that I was discussing it with last week at Cecil .As I said this is my first time exploring with 3 and 4 ports but you can bet when I'm done I'll know it well and have it perfected .I'll be making the change to reduce the amount of boost I can run if it means changing my wg springs then that's what I'm gonna do as I'd like to lower it to a few lbs in first and second on the street so I don't have to back pedal so much .I do indeed love the twin 44 mvrs they control boost so good up top it holds rock steady and you know I'm always one for overkill lol

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Ya I would put the 3 psi spring in both your mvrs and use a single 4 port (unless using 2 3 ports is better, which I doubt it is, but I don't know for sure) as this will allow you to run as much boost as you'll ever want/need in the higher gears, but should make just about 3 psi on wastegate pressure.

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Originally Posted by 1JZ_Type-S

If I change out my spring, I assume I'll need a new tune, correct? Due to the variation of boost pressures at different rpm

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Who is your tuner? If the tune was done correctly, it really shouldn't need to be retuned. I mean turbos are not superchargers, they make boost at all different kinds of rpms since it is load based. So your tune should have the fuel compensation necessary for a lower boost level.

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Originally Posted by 1JZ_Type-S

10 pound. I've only creeped a handful of times with it. My confliction is that I'm running a journal bearing turbo, so I need the wastegate to open as late as possible to allow for the quickest spool

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What are you using for tuning? If you have k-pro or flashpro you can forget about this old school thought. With the quick spool feature hondata now has, a 4 port solenoid will hold your wastegate shut even more effectively than a larger spring would, ie it will keep a 3 psi spring gate shut till 3 psi comes and you will see much quicker spool because of it. Oddly enough just posted this in another thread, but Vit a while back showed a 1200 rpm improvement in spool time on a GTX3076 just by turning on quick spool.

I never really thought about it til today and you guys are right it's not gonna happen 1/2 ing the spring pressure of 7 psi .He must have been talking about running (2) 3 port boost control solenoids and 1/2 the solenoid duty cycle on them .I am probably just gonna bite the bullet and buy a 4 port rather than fool with 2 solenoids .Snizz your gonna have to fill me in on it this weekend when I meet up with ya .

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Originally Posted by vdubkilla

I never really thought about it til today and you guys are right it's not gonna happen 1/2 ing the spring pressure of 7 psi .He must have been talking about running (2) 3 port boost control solenoids and 1/2 the solenoid duty cycle on them .I am probably just gonna bite the bullet and buy a 4 port rather than fool with 2 solenoids .Snizz your gonna have to fill me in on it this weekend when I meet up with ya .

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You can get one from Vit for just $60, fairly cheap in the boost world. As for you using two wastegates, I think you can just put a T in both the lines coming out the side of the solenoid that go to the wastegate, and run a line to each gate.

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Originally Posted by aLmk

You can get one from Vit for just $60, fairly cheap in the boost world. As for you using two wastegates, I think you can just put a T in both the lines coming out the side of the solenoid that go to the wastegate, and run a line to each gate.

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Just ordered a 4 port from him :thumb: thanks fellas for clearing me up on that ish

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Originally Posted by vdubkilla

Just ordered a 4 port from him :thumb: thanks fellas for clearing me up on that ish

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Nice, what are you using now for boost control? I'd like to hear your impressions after you get it in and tuned.

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Originally Posted by aLmk

Nice, what are you using now for boost control? I'd like to hear your impressions after you get it in and tuned.

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Currently running a 3 port mac valve .I now need to order springs for the waste gates and change them out the only thing is by the time I get them and get them in it's likely gonna be a little cool outside .I did a full pull this afternoon on 20 psi and man was that fun but traction is on the brink in 4 th gear up top I can feel it's about to cut loose but didn't yet haha

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Originally Posted by vdubkilla

Currently running a 3 port mac valve .I now need to order springs for the waste gates and change them out the only thing is by the time I get them and get them in it's likely gonna be a little cool outside .I did a full pull this afternoon on 20 psi and man was that fun but traction is on the brink in 4 th gear up top I can feel it's about to cut loose but didn't yet haha

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Gotcha. I'm really curious how much an improvement you will get out of the 4 port in terms of spool time with your GT35 and twin scroll. I would think it could improve the spool quite a bit, but I could be mistaken.

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Originally Posted by aLmk

Gotcha. I'm really curious how much an improvement you will get out of the 4 port in terms of spool time with your GT35 and twin scroll. I would think it could improve the spool quite a bit, but I could be mistaken.

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I really don't have much lag now though so I am not sure it's gonna make a huge difference other than blowing the tires off but I guess I'll see I really wanna be able to run less boost with the lower wg springs for traction in 1 st and second and still be able to make big boost say 25 lbs or so on c16 .My turbo spools pretty quickly now I love that old school 35r in twin scroll :turbohug:

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Originally Posted by vdubkilla

I really don't have much lag now though so I am not sure it's gonna make a huge difference other than blowing the tires off but I guess I'll see I really wanna be able to run less boost with the lower wg springs for traction in 1 st and second and still be able to make big boost say 25 lbs or so on c16 .My turbo spools pretty quickly now I love that old school 35r in twin scroll :turbohug:

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Ya it may not help your spool as much because you're twin scroll. But will definitely give you the other benefit. Now I highly doubt Vit will even use quick spool in 1st and 2nd because of traction. He didn't on my setup.

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Originally Posted by 1JZ_Type-S

I don't. Ive never heard of port differences until I joined thid site

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Welcome to BoostedK20. Lmao

OK the 4 port solenoid and two new wg springs are ordered the lowest spring they make for the Tial MVRs is a 0.3 bar 4.35 psi but that's better than the 8.7 lb springs I currently have .

here is the manifold

https://www.k20tuned.com/xcartv2/ima...iesmaninew.jpg

[MENTION=83]vdubkilla[/MENTION] if you are running twin gate then run dual fort port boost solenoid.

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Originally Posted by ksboi

[MENTION=83]vdubkilla[/MENTION] if you are running twin gate then run dual fort port boost solenoid.

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I asked VIt and he said no need I will just T the boost source

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Originally Posted by vdubkilla

I asked VIt and he said no need I will just T the boost source

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I'm running twin gates with 1 4 port solenoid and it works perfectly

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Originally Posted by 1SLOWFG2

I'm running twin gates with 1 4 port solenoid and it works perfectly

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Cool the 4 port is new to me as I have always run the 3 port and hell for some reason I thought you were supercharged maybe you were and changed up ?

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Originally Posted by vdubkilla

Cool the 4 port is new to me as I have always run the 3 port and hell for some reason I thought you were supercharged maybe you were and changed up ?

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The 4 port with quick spool is pretty awesome, I am turbo and always have been lol

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Originally Posted by 1SLOWFG2

The 4 port with quick spool is pretty awesome, I am turbo and always have been lol

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I have heard that a lot and guess it cant hurt if we can keep traction my twin scroll 35r spools pretty friggin fast as it is though.I am excited to get it and install it and see how it works out. I can't keep track of everybody these days I know so many people on the forums and ya gotta remember I'm old haha .You would think I would have figured out your turbo by looking at your avatar :oops:

The sound the 4 port makes with quick spool is fucking sweet too. That's probably the only thing I miss about open dump, with my gate recirculated you no longer hear it. It's like a gurgling noise.