I have been searching the forum for info on some minor mods I am planning for my stock '86 turbo converted (j-spec I suppose) rx7. All I want to do is get the boost up from the 5.5psi it runs stock to around 10psi which I hear is OK for the stock turbo.Yes I will need to tackle the fuel cut issue (FCD?) but that is not what I am asking here. My mate has offered to make me a full 3" exhaust but I have it on good authority (RETed) that this will create over 12psi of boost. I'm confused because I thought maybe a boost controller could bring the boost back down but I was told that it doesn't lower boost, it raises it. I have been told that a ported wastegate will control the boost.
Now, my real question is: why can't I forget the exhaust and simply get a boost controller and crank it up to 10psi? Sounds too simple so this is probably a dumb question but I'd love to know the explanaition! Thanks in advance.

 

As far as I know you could just purchase a boost contoler and raise the boost up that way. I don't see any problem with that.

 

Howdy from Osaka right now. Yes, the only way to lower the boost is to vent more of the gasses hitting the turbo, porting the wastegate. You can do a partial exhaust and see how high your boost goes or you could leave it stock and just get a boost controller to raise it. When you run higher boost on the stock exhaust the heat under the hood will get higher and boost spikes may become a problem but it should be fine. Just make sure everything is working right, especially the voltage to the fuel pump and the injectors are clean.

My 2 centavos.