Wastegates Explained

[abaddon_baliel]

Ha! You probably thought I was going to actually give info here. Sorry, I'm a newb, so this is a question, but I want all the knowledgeable people out there that actually know what they're talking about to explain it here. I've searched and searched, tried every variation of wastegate I could think of to get the information I wanted. I read some other sites, including this one.

That site goes a little into what wastegates are and how they help the turbo cut off boost for preservation and spool. I got that. I'm just confused on how they apply to my (read: our) car. I've heard of people venting the wastegate to the atmosphere because it's not as restrictive and frees up HP, so I'm confused about that because this thread is talking about dumping o2 to the atmosphere, and I feel like it has a similar tone to the reasoning. I don't know if they're doing it for HP or for sound. It seems to me the o2 dump and wastegate are the same thing, since they're talking about it "opening up" at a certain boost level, which is what the wastegate does.

I am getting a 68HTA turbo from FP. All supporting mods, yada yada. I can post my list if you'd like, but search my "building a cruiser" thread and you will see a constantly updated list of my parts.

I'm going to probably be running 21-25psi on this setup. I can't tell if the FP68HTA comes with a wastegate already attached (I think that's what that silver thing with the tube is?) and if it does, is that one sufficient or do I have to buy an aftermarket wastegate? If I do, what is a good inexpensive one?

What does the xxmm have to do with the wastegate and its performance? Is it just a greater amount of gas it can release or what? What mm would I need, since I believe the 68HTA is just a 16G.

Also, does it come automatically with the recirculation parts so I don't have to dump it? And if I wanted to dump it, do I have to buy something special for that? I looked on PR's site and found the o2 recirculated and dump tubes. Now I'm sure the wastegate is what people talk about when their talking about o2 dumping, since scrolling down PR sells the wastegate/recir/dump combo kit. So that's one question out of the way, but I'll leave it on here for people to see anyways.

Thanks in advance for the information, pictures would be amazing (especially pics of both the recirculated and/or dumped wastegates on your car, from different angles).

 

[VETTE_50_TH]

A wastegate is a bypass for exhaust gases around the exhaust wheel. Basically is helps in control of boost of the turbo. If turbos didnt have wastegates, at least on modern gas operated engines, there wouldnt be any control of how much boost you run.

So the wastegate, is a valve(externally gated) or flapper(internally gated) vacuum operated that allows the gases another route out. The reason why externals are better is because they can react to drops in boost faster than internal gates.

You can tell if a car is external or internal very easily. The link to the fp 68hta is an internal gate. Its actuator is the round silver object attached to the compressor cover. The actuator arm then connects to the flapper inside the exhaust housing. An external will be mounted on the exhaust housing it self in one contained unit or on the exhaust manifold.

 

[abaddon_baliel]

When choosing an external wastegate, you are given options in the form of "bar". Here is an example of that, and the corresponding PSI value for each bar:

BAR PSI
0.7 10.5
0.8 11.6
0.9 13
1.0 14.5
1.1 15.95
1.2 17.4
1.3 18.85
1.4 20.3
1.5 21.75
1.6 23.2
1.7 24.6



My max psi would be 25, and it exceeds those BAR specifications. Does this mean I cannot use the Tial 38mm wastegate? And if so, what wastegate would you recommend? OR am I confusing psi values, and this means something completely different?

 

[mike96]

yes you can still use that waste gate (or any waste gate for that matter) to attain the desired boost above whatever spring rate the waste gate is set at, you just need some way of controlling how much pressure reaches it. for example a manual boost controller. there normally is a tube that goes between the compressor cover and the waste gate (WG), if that tube were left alone then the WG would open at the whatever pressure the WG was set at, this is the spring rate you are asking about. when you install a manual boost controller it goes in between the compressor and the WG and set it for your desired boost (usually by trial and error) and it will completely block boost from reaching the WG. for something like that Tial external WG you would want to pick something around the middle range then if you are having issues with the WG being blown open by to much exhaust pressure you go up as needed.

 

[JusMX141]

The 68HTA comes with an internal wastegate configuration which has held boost in the high 20's on many different cars. If your target boost is below 25psi, you should be fine with the turbo as-is.

 

[DGajre777]

The HTA68 comes with an internal wastegate (as mentioned above).

If you want to run an external gated turbo WITHOUT a boost controller at 25 psi, you could use springs for 1.7 Bar (which according to the chart below would hold boost at 24.5). You can run twice the boost pressure of the spring. The common/ideal way is to go with a 1.0 Bar spring and then using a boost controller to hold boost till 30 PSI (14.5 x 2). If you turn your boost controller all the way down, using this spring, the turbo will hold a MIN of 14.5 PSI. With the 1.7 bar spring above, 25 PSI is the minimum boost the turbo will hold, so you have no way of turning it down (if you need to for any reason) without taking one of the springs out.

 

[TSi Kid]

You can run twice the boost pressure of the spring.

What happens if you boost more then twice the pressure of the spring? A 0.7 bar spring on 25lbs of boost for example.

 

[Jankenshank]

What happens if you boost more then twice the pressure of the spring? A 0.7 bar spring on 25lbs of boost for example.

the springs are rated at a spec pressure...

10.5 psi spring compresses at 10.6psi and releases to the best of its capability any other boost created out and around the turbine wheel...

the only reason you would boost more than the spring is rated is if the turbo is flowing more air than the Waste gate can deal with.

 

[talonDSMerr]

The wastegate will open at twice the pressure of the spring meaning you won't be able to reach more than that.

 

[laserspeeddemon]

What happens if you boost more then twice the pressure of the spring? A 0.7 bar spring on 25lbs of boost for example.

A lot of people don't understand that when the air/fuel combination leaves the combustion chamber(s) it is still under pressure. How much the pressure is debatable. I've heard everything from 1:1 (meaning the boost goes in at 20 psi and leaves at 20 psi) to 1:2 (in at 20 psi, out at 40 psi) to 1:0.5 (in at 20 psi, out 10 psi) and everything in between. Personally I think there are too many factors; such as exhaust size, length, intercooler size, piping size/length, etc.; to accurately formulate a ratio.

The point to understand that there is boost pressure in your exhaust/turbine hosing. If the pressure of the spring in the wastegate (or wastegate actuator) is too light. The boost pressure in the exhaust can force open the wastegate.

 

[Zdrummer15]

As was said above, if you plan to run 25 psi DO NOT run a wastegate with a spring rated at 24.5 psi because that will be the minimum amount of boost you can run. If you ran your car with that wastegate and no boost controller your car would run at 24.5 psi. A boost controller allows you to run more boost then the wastegate spring would, but not more. All the boost controller does is bypass the wastegate until you reach the desired pressure. For example, a wastegate with a spring rated at 15 psi will obviously blow open at 25 psi.

 

[abaddon_baliel]

OK.. I have an mbc installed on the car, and was pretty

confused on how to use it at first (still may be)... mine has an

arrow pointing down on the body of the MBC, so I figured turn

the knob in that direction for more boost. So I have the knob

turned out on this long scew, and another knob at the base

holding it flush against the mbc body (i'm guessing so the

pressure doesn't fluctuate). I can take a picture of it if you like

how I have it.

And that's awesome that the 68's wastegate is plenty for my

needs, because I really didn't want to spend $300 on a 3"

piece of hardware. I'm already kicking myself for having to

spend $200 on a decent BOV.

Does the 68's wastegate come already as recirculated? That's

what I would prefer to run it as.

 

[JusMX141]

I'm already kicking myself for having to spend $200 on a decent BOV.

Why'd you do that? Used 1G valves are $30, new 1G valves are $100.

Does the 68's wastegate come already as recirculated? That's what I would prefer to run it as.

That's entirely up to you....the turbo itself does not determine whether the wastegate is recirculated or vented.

 

[abaddon_baliel]

Why'd you do that? Used 1G valves are $30, new 1G valves are $100.

That's entirely up to you....the turbo itself does not determine whether the wastegate is recirculated or vented.

I know the turbo doesn't determine that, but I don't know if you need anything special to make it recirc. so I was asking if it came ready to recirc. (ie had all necessary parts in order to make it recirc.) or if I had to buy something extra for that.

And I haven't paid for anything yet, I'm buying all my parts in bulk. I'm thinking about getting the Synapse BOV because I've heard it's really durable, doesn't have flutter and can hold more psi than I'll ever run.

And I read for 1g BOVs, in order for them to be able to do any amount of psi over 18 you have to crush it, and I'm not into ghetto rigging my parts. There are too many variables after you "modify" that part and the exact amount of psi it can hold isn't known, and while there aren't a whole lot of reports of it going bad, would you report it after you crushed your perfectly good bov? Most people would not. So I decided I'd just go with a bov that I know can hold the pressure, I don't have to "hack" to make it work for me at my desired psi levels, and pretty much for peace of mind. It just blows me away that bovs and the like cost so much, considering how little they do. It's just a pressure-operated valve.

 

[JusMX141]

And I read for 1g BOVs, in order for them to be able to do any amount of psi over 18 you have to crush it, and I'm not into ghetto rigging my parts. There are too many variables after you "modify" that part and the exact amount of psi it can hold isn't known, and while there aren't a whole lot of reports of it going bad, would you report it after you crushed your perfectly good bov?

You can read all you want about whatever brand, I'll take my $30 1G BOV that has been crushed and / or Dodge Garage Modded. In the end you will have spent $200 on a valve that does the same as mine, yet mine does not require yearly diaphragm changes like some aftermarket valves do.

This exact valve setup held 32psi with a HX35 on TalonDave's old setup and would probably still be on the car today but the piping he bought for this season's HX40 setup was flanged for a TiAL BOV.

 

[abaddon_baliel]

You can read all you want about whatever brand, I'll take my $30 1G BOV that has been crushed and / or Dodge Garage Modded. In the end you will have spent $200 on a valve that does the same as mine, yet mine does not require yearly diaphragm changes like some aftermarket valves do.

This exact valve setup held 32psi with a HX35 on TalonDave's old setup and would probably still be on the car today but the piping he bought for this season's HX40 setup was flanged for a TiAL BOV.

As I said before, I'm not into modding things myself for 2 reasons: 1) I'm not adept at that sort of thing, I will #### it up, and I don't have a ton of money to keep replacing parts. 2) There isn't a whole lot of proof to backup that anything actually works how it's supposed to. It's chance. (ie "crushing"... not talking about the garage mod)

That being said, could I buy a 1g bov that has already had the garage mod done to it? If so, where?

I've also read good things about the new NGR Type-S bov, that they've strengthened the diaphragm and no leaks. Do I still have to replace the diaphragm yearly with this bov?

From what I've read all over the forums, Synapse, TiAL, NGR Type-S, and 1g bovs (modded) are the best. I'd love to get a 1g that's been garage modded, but not crushed. And if I don't, I'll just get the Synapse.

 

[rlacasse1]

It's really simple to mod, you won't #### it up.

Not unless you are blind and missing your arms at least.

 

[JusMX141]

That being said, could I buy a 1g bov that has already had the garage mod done to it? If so, where?

You can buy a brand new 1G BOV and send it to me....I'd be more than happy to do the Dodge Garage Mod at a very reasonable price, and you'd have a brand new valve priced cheaper and proven more reliable than any overpriced NGR, Greddy, Synapse, or HKS garbage available today- proven by 20+ years of use.

 

[abaddon_baliel]

I may not #### it up, but I don't have the equipment needed to do that. Not everyone is into tools. How much would you do it for? I'll go pick up a 1G at a junkyard and send it to you when I have some spare cash. You can PM me if you like.

 

[VETTE_50_TH]

You should never go more than 1.5 times the spring pressure for a wastegate. Ive personally had my wastegate open/crack trying to run more than 1.5 times of boost at it. Always get a spring pressure within a few psi of what you want to run. 80% or so

 

[abaddon_baliel]

You should never go more than 1.5 times the spring pressure for a wastegate. Ive personally had my wastegate open/crack trying to run more than 1.5 times of boost at it. Always get a spring pressure within a few psi of what you want to run. 80% or so

That's good to know (not that yours cracked, that sucks) but it's nice to have people with first hand experience on things like this.

I contacted FP and they verified that the internal wastegate that the 68HTA comes with is sufficient for 25psi. I didn't get an exact rating for it, but they said there would be room to grow even over 25.

 

[JusMX141]

FP can't give you an exact number because the amount of peak boost the turbo can make / hold will vary by things like elevation and barometric pressure as well as your supporting mods....hell even the amount of holding pressure between two identical wastegate actuators will differ slightly; although for the most part FP can get within the ballpark on a good guess from all of the feedback from their users.

 

[abaddon_baliel]

How would I set the PSI on the internal wastegate? (Set the amount of psi I'd want it to go off on)

 

[rlacasse1]

You would use a boost controller.

 

[VETTE_50_TH]

That's good to know (not that yours cracked, that sucks) but it's nice to have people with first hand experience on things like this.

I contacted FP and they verified that the internal wastegate that the 68HTA comes with is sufficient for 25psi. I didn't get an exact rating for it, but they said there would be room to grow even over 25.

Im not talking about the wastegate cracking. Im talking about the wastegate valve cracking, as in, opening early. Not it physically cracking.