I was watching Aaroncake's video on making his turbo manifold for his cosmo project and I noticed he was using garret gt3076r internal wastegate. I thought this was a great idea to keep costs down on my single turbo project.

I have a s4 13bt with a street port running 91 octane in CA, so 15lb boost at most.

I know he got the turbo mainly for response, but what kind of peak hp numbers would I be looking at?

Do you think I would have any issues with the wastegate being too small?

I did some research, read the "sticky" posts. I get a great deal on Garrett turbos, so I am not in the market for one, but I am having a hell of a time deciding. I want 300-350hp range, my car will be driven on the street. I was looking at the journal bearing, ball bearing to4e, but then saw there was a to4r, and s, and z, etc etc. I'm getting a headache. I saw aaron running the gt30 internal gated turbo and thinking the money saved on an external wastegate, and fabrication could go into a ball bearing turbo. Help me, help me!

 

If you're ok with an external wastegate on a small ebay turbo, check out this thread where 7dust shows off his setup. I have the same small turbo and got it for response in a rotary truck which is should do based on its small size. It's just a tad bigger than an S5 turbo. And when they go bad, they're cheap to replace.

https://www.rx7club.com/build-thread...-good-1045260/

 

It will be interesting to see if the small hotside holds aaron cakes setup back, and if the IW can keep boost down to civilised levels.
Anyway here is something with more conventional sizing a quick search turned up GT35 GT3582R Internal Wastegate 1 06 50 A R Turbo 5 Bolt T3 Water Turbocharger | eBay

I certainly cant speak for the quality, but the price is right!

 

Most of the older design internal wastegate turbos available to the aftermarket don't have a particularly high flowing design. The Borg Warner EFR's offer a more modern high flowing wastegate.

 

My setup is for a VERY specific application and it wouldn't be a good idea to use it as an example.

After all, when is a T3 .82 turbine housing EVER used on a rotary?

The turbo setup for the Cosmo is all about maximizing boost in the low and mid range. The goal is to have instant boost at any RPM without worrying about power/boost tapering off in the high RPM range. This car is a cruiser, not a high RPM corner carver so it's powerband is totally different than most RX-7 setups.

It's also important to recognize that my exhaust system is far more restrictive than most. A cat, resonator, muffler and another muffler. All 2.5" after the downpipe (3" cat used, 3" downpipe to give volume for the turbo to surge into). Additionally there will be a fully enclosed airbox.

 

I am actually not after a ton of power either, I was looking more for response. I've had too many problems with used turbos so I am really thinking about doing a complete upgrade, but only looking for around 300hp, little more or less is fine.

I was also debating on saving money on the external wastegate, and using that money towards a ball bearing turbo. Decisions decisions. I really wish there were more good used stock turbos out there.