External wastegate mounting options

[DSMNerd6889]

Hey guys, I've searched, but haven't really come up with the answer I was looking for... I know that some people mount their wastegates on their O2 housings and some people mount them on their exhaust manifolds. What I would like to know is:
1) What are the pros and cons of either set up and;
2) How is it possible to mount the external wastegate on the 02 housing (i.e. after the turbo)?

Thanks in advance.

[crunchymilk55]

if you mount it at the 02 housing, you'll still have issues with boost creep.

Most go with the manifold, for good reason.

[slugsgomoo]

Originally Posted by crunchymilk55

if you mount it at the 02 housing, you'll still have issues with boost creep.

Most go with the manifold, for good reason.

You are absolutely incorrect, at least without stating all of the facts. Gross generalizations are bad.

O2 mounted wastegates *can* still boost creep, however not if they are mounted properly.

If you are using a turbo that was originally set up for an internal gate, you should remove the flapper, and then remove almost all of the material around where it sat. The easiest way is to have a machinist do it, the cheapest way is to pull out your air tools and a carbide bit.

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I don't like manifold mounted gates for a couple reasons.

When they're mounted on the #1 runner they don't sound good (IMO) and it's a major PITA to mount them to the collector- where they should be, if you're not mounting it on the o2.

Not to mention that welding to a cast manifold collector is a bitch (to have last), and welding the flapper door shut brings it's own fun problems.

Of course, having an o2 mounted gate, on a 14b no less, and having zero creep with a full 3" turboback & o2 eliminator *may* have biased my opinions on this subject.

[kjewer1]

The biggest factor will be what size is the turbo and what is the lowest boost you intend to run on it. For someone looking to run 20 psi on a 16g all day long any external gate setup will work. Someone with a 56 trim running 15 psi might have trouble with an O2 mounted setup. Even with all of the flapper seat material removed the exhaust gases still have to take a bunch of 90s at an awkward place. I do agree that the number one runner approach is less than ideal, but I feel it is more ideal than an O2 mounted setup. The only justification I can see for an O2 mounted solution is ease of install, such housings are readily available from many sources and are simple bolt ons. One other advantage is that they are very easy to return to the exhaust, if noise is a concern, which is certainly valid.

That being said, my main personal experience is with an old FP built 2g manifold with a deltagate off the collector (would run spring pressure of 13 psi on a 56 trim), another variety of collector mounted gate (ran with a 16g, no brainer there, it worked fine), and a Tial mounted to a South Florida Performance tubular manifold that had a nice angle on the pickup (ran 15 psi on a T67/stroker before upgrading to a 21 psi spring). I just tack weld the internal, or order my turbo with the flapper sealed. So naturally I'm a big fan of the manifold mounted setups, but there are compelling reasons to go with an O2 mounted gate in certain situations.

And I should also note that mounting the gate on the O2 is not mounting it "after the turbo." It's still before the turbine wheel, of course; otherwise it wouldn't do anything at all.

Edit> slugsgomoo, it seems you and I tend to think and post alike, welcome to the site

[Thor06]

What about internal gates? When is it a good idea to convert to external?

[kjewer1]

I really hate internals, so perhaps I shouldn't be the one answering this But the correct answer is that you can use an internal up until the point that you no longer get the range of boost you need. There will always be a compromise between flow (low boost) and holding power (maximum boost). Larger flappers help with getting boost lower when combined with the appropriate porting, but remmeber that force equals area times pressure, so larger flappers are easier to blow open. Once I went over 16g sized turbos I had an impossible time of getting the internals to work. Tried all kinds of flapper/actuator configurations, and could never get over about 23-25 psi. There are many variables... After I stopped wasting time and went to the external, there was no going back. I Also ran an internal and external at the same time for a while so I could do some experimentation, and learned a thing or two to say the least. But it's too much to get into. The end result is that I hate internals I would say convert to an external as soon as the budget allows, but not so soon that the money would be better spent elsewhere on the basic mods. And consider it an ivestment, since you can use it with future turbos as well.