Welding wastegate to turbo exhaust housing
 

Hy there,


I was browsing through Speedhunters' website and found the article on Frederik Aasbro's new car. A picture of the engine bay shows that (or so it seems) dual wastegates welded on the turbo exhaust housing.

in theory it's possible to weld it, apart from the fact that the housing is cast and unless you really know how the get the welding tension out, it will crack.


any opinions?

There is a 20b swap on the forum that has his wastegate on the EX housing. Its pretty common.

Its also not that hard to weld over cast, you have to slowly bring down the temperature on the welds with a torch and stuff. Hope that helps

Thanks for the info. It was interesting as my custom manifold doesn't leave much space for the wastegate so this migh be an option.

Just a bit afraid that the housing would crack (costly)

That's a BW turbo with a stainless exhaust housing right? Probably holds up better than cast steel.

as long as you preheat the housing, and bring the temp down slowly once the weld is completed, you shouldnt have any cracking. same thing you have to do when welding an internal wastegate closed.

ATP actually makes turbine housings with wastegate flanges cast in. You may consider checking it out. They are for vehicle specific applications now, but they may be interested to know people are interested for normal housings.

me lickeeee.... gonna run this idea by my fab guy

Seztep had it done, Enzo 250 did the welding for him. Seztep's manifold had a horrible wastegate placement, and after moving the wastegate to the turbine housing, he had solid boost, wherever he set it up.

I also want to say that Elliot at Turboblown had done one for Node, on a stock T2 turbo.

Unfortunately, I can't find the posts for either one lol

This is truly the best place for a wastegate, Too many people think that the wastegate needs to have some magical angle and be close the motor. When in fact right at the turbo is by far the best place for a wastegate, having it where it has good flow is stupid and only done by people who do not understand how they actually function. The wastegate is venting the backpressure in the manifold to control the boost not the exh gases. This is why right at the turbo is the best placement for them because that is where you will have the highest emap in the system. This is also why having a dumptube re-routed through the downpipe will make a wg more efficient due to the scavenging effect it has.

If you dont beleive me place some pressure transducers in your manifold at the block flange and then at the turbo flange..

^You are only half right and I think you are misconstruing some ideas and Principles.

A wastegate can only make the exhaust pressure drop if there is a volume flow going through it. When it's opened, it is part of a performance exhaust system. Wastegate flow not important? Why do huge 60mm wastegates exist?
Not saying that welding a wastegate to the turbo is a bad idea, I like the idea of it, should work fine and be nice and compact, but volume flow though a wastegate does matter.

^ Exactly. You want the wastegate in the path of exhaust flow so it can vent the exhaust gas. Wastegate placement is a very important part of a turbo manifold design. And from what I have read about wastegate placement.... Having the wastegate on the exhaust housing is the best place for it.


BTW, rxspeed7, can you explain to me what causes back pressure in a manifold......Oh wait, It is exhaust gas. So how can you say that there needs to be no consideration for exhaust flow out of the wastegate.... Hint: You cant.

^ i've been reading up on this for the past 3-4 hours on different forums. I'm no expert but there seems to be a reoccuring problem with slightly higher hp cars. When I say that I'm talking about inline 6's, honda's etc around 6-700whp. Some people are experiencing turbulence caused by the angle of the wastegates on the turbine exhaust housing. This is due to the angle at which the wastegate vent is placed. It seems like angle of the placement on this application is VERY important. You want about 50/50 flow to the wast-gate and to the actual turbo. If you get this wrong.. either or will suffer..(spool or the ability to hold boost/regulate boost) My eyes hurt from reading. it may or may not be more beneficial to get the gates as close to the manifold/turbo flange as possible in the long run. A well placed wastegate on a manifold can function just as well as one on a turbo exhaust housing. But if you need to alter the set up..you may be looking at replacing the exhaust housing on the turbo, and the v-bands for the wastegates. definitely a rad idea...still looking into this for my un finished long-runner top mount =-)

I'm just going off what we have seen with all of our race cars and manifolds we have built. Everytime we have tried to have "good" wastegate placement we have had horrible boost control after 30psi.

After having this problem more than a few times we started logging emap to see what was going on and decided to start building the wastegate runners as close to the turbo as possible because that's were we saw the highest emap. After doing this haven't had a single issue.

Not trying to stir shit up but I speak from experience not Internet readings or theories. May sound good on paper but don't always work as good as they sound.

No one is denying your experience but it seems that you have certain misunderstanding in what you have experienced.

You can't have pressure drop without flow drop or temperature drop and unless the wastegate is some extremely efficient cooling device that would control manifold pressure via temperature it is what it is - flow device.

Reason why you experienced best boost control in the place where is highest EMAP could be pretty simple, highest pressure delta, best flow towards the wastegate.

There are too many variables, wastegate is venting up to 50% of total mass flow through the system in some applications, and exhaust gasses, despite under pressure, have its own inertia and they don't like to change direction.

It seems that it goes down to application, for example Turbo F1's had wastegate runners at right angle from the collector, on the other hand some low boost race cars have manifold design which prefers wastegate flow.

Is anyone currently running this style of wastegate setup? What were the results like?

I see you're in Sydney. You'll find heaps of examples people running this style setup on hybrid/hiflow Hitachi turbo setups in Australia with great success. On AusRotary.com there are examples hitting 350rwhp+. (Dyno Dynamics figures, which usually translates to 380-400rwhp in terms of Dynojet dynos typically used in the US)

see eg

Series 5 Hi Flow turbo - AusRotary
Hi Flow Turbos - AusRotary

Actually, Aaron who did a few posts on this thread back 6yrs ago (you Necro-bumper!) ended up with dual EWG on his turbine housing. You can see it in this video here:

Pretty common in the v8 world these days. Seems to work well as long as you heat up the housing before welding. Saw someone on Youtube heat the housing with the burner from a turkey fryer haha.

The EFRs are like mentioned before stainless steel cast, which IMO should be able to weld just like other stainless steel
Cast iron on the other side needs to be welded with MME carbon shielded electrodes, otherwise the iron will loose to much carbon and get brittle.

Dont actually know if the Garrett housings are cast steel or iron, maybe steel but just not stainless steel like the EFRs

https://en.wikipedia.org/wiki/Steel_casting

Just remember to make sure you're running a high nickel content rod (though your welder should know this if he's confident he can weld cast)

Well, if the downside to an external wastegate on a rotary is failure due to heat on track (and it is), I can't imaging plopping it directly on the turbine housing is going to do it much good.

Short of the local dragcars, there was a guy in Tassie running this set-up on his FD a few years ago. Local specialist who had all the proper heat treat ovens to ensure a long life weld on something like a street car, passed away a few years back. There's supposedly someone down in Minto/Ingleburn area who might be ok for this work, but no personal experience using him.