Wastegate question

Malak · #1 10-12-2004, 02:34 AM

Im piecing together a turbo for my car because my buddy upgraded his stock T-25 to a T3/T4 hybrid so he has no use for the T-25 anymore.

Anyways, the T-25 is internally gated but with my setup, I have an up pipe and a down pipe. On the up pipe is a flange for a 35mm external wastegate. So there are two obvious options. One is to cut a piece of metal that would just bolt over the hole onto the flange. The other option is to weld the internal wastegate shut.

I would prefer to do the latter because when I go to upgrade my turbo, I can get one cheaper (maybe?) because it doesnt have an internal wastegate. And also because the flange is already there!

So my question is, if I weld the wastegate shutter closed, how does the external wastegate work? I was having a hard time Googling this topic. Like am I supposed to connect some vac hoses from the external gate to my turbo? Or do I simply bolt the external gate on to the flange and let it be to do its exhaust dump?

Another small bit of info, on my downpipe, it doesnt have an opening like other downpipes have for the internal wastegate to flow the exhaust gasses through to the exhaust system. Since its like this, I probably dont even have to bother with welding the shutter closed, right?

If anyone wants pics of the up pipe and down pipe, ill upload some. Just ask and ill go hunting for my digi cam.

Thanks in advance,

~Malak

nissanfanatic · #2 10-12-2004, 10:14 PM

Weld the shutter closed. The external will operate by teeing into a vaccum line and running a hose from that line to the wastegate. The wastegate operates according to manifold pressure. If it has a 5psi spring installed in it, then it will open when the manifold reaches 5psi. If you are using a boost controller, it gets a little more complicated. Good luck.

Malak · #3 10-13-2004, 02:52 AM

By manifold you mean, turbo manifold, or intake manifold? Stupid question I know but the whole external wastegate thing just confuses me haha.

And I do plan on going with a boost controller.

~Malak

nissanfanatic · #4 10-13-2004, 06:56 PM

Yes turbo manifold. The external bypasses exhaust gas to control the turbine speed. What kind of boost controller?

Malak · #5 10-14-2004, 02:57 AM

Not sure of the brand yet but I plan on getting a cheap manual boost controller. Something that gets the job done without screaming "STEAL ME PLZ!"

Any idea where on the T-25 the vac line is supposed to go? I dont have it infront of me so I cant really tell.

~Malak

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