I have a 13b blow through (carb) turbo config. in a 1st gen RX7. The turbo is a t4 garrison, what should I be using for the wastegate?

 

Well, with an aftermarket manifold, you'll need to be running an external wastegate. 38mm & 40mm are common sizes.

 

The manifold is a new factory Mazda part from I believe from an 88 year model. should I be using a factory wastegate? if an aftermarket wastegate is required with the OEM Mazda manifold should I use a 38mm or 40mm? And what's the difference between the two?

 

A T4 turbo will require an aftermarket manifold, so if that's what you really have, it's not going to be using the stock exhaust manifold off of an FC. If that's the case, you should already have an external wastegate.

If you really have a stock FC turbo or a hybrid turbo (stock exhaust side, upgraded compressor), then yes, you could still have the stock manifold on there. If that's the case, your wastegate is internal, and will be 13mm (S4) or 31mm equivalent (S5).

Take a picture of your manifold and both sides of the turbo, and I can tell you what it is.

 

Tial 40-50mm is your friend.

Too expensive?

Go on ebay and buy a no-name. They work just the same. I've taken apart a turbonetics evo 38mm gate and one of the chinese 38mm gates and they are basically identical. Shouldn't have anything to worry about. If the supra forum guys trust them and guys use them for years without problems on their civics and whatnot, it should be fine for you.

 

Ebay is your friend.

 

View my public profile, I was able to upload a picture. Let me know if this help you determine what I have.

 

That's a S5 hybrid turbo. The compressor side is definitely not stock, but it's not huge either. The wastegate flapper door is on the turbine side, right on the bottom. You've got 2 wastegate ports: one is 18.5mm & the other is 23mm (eq. to 31mm total). This is decent, but porting them larger will eliminate boost creep. Here's a link on how to do that:
http://www.fc3spro.com/TECH/HOWTO/KWG/kwg.html

 

Okay, so do I need a wastegate? What am I missing that connects to the wastegate flapper door? Can you send me pics or refer me to a site that illustrates what I need to move forward?

 

There are lot of pictures of the internal wastegate in the link I provided. The wastegate is there, but you're missing the wastegate actuator. It would normally be attached to the compressor housing and have a linkage attached to the wastegate arm. Buy a stock FC turbo and take it off of there. I doubt someone will sell you the actuator by itself.

 

Here's a picture to help you see which piece you're missing. Talk to whoever built your turbo. They would have been the ones to have not replaced the actuator when they swapped the compressor housing. It bolts onto the back of it (backing plate).