has anyone done this to a s4? i kno the basics and it looks fairly simple...thought about it some and going by the bnr site they port their turbos to 60mm. i have a drill press and was planning on using small bits and going up larger till 60mm in small incriments. then welding on new ss washer then reassemble. i kno its not that simple but for the main points is that about it...its prob what shops do anyway...

 

http://www.aaroncake.net/rx-7/s4wastegate.htm

Should about cover it.

 

thanks great article looks easy enough

 

Any opinions on adding a dumptube to the stock turbo? Basically blocking off the inside where the wastegate normally vents to, cutting a hole through the back plate and welding a dumptube in place. There is a rare backplate available from Japan that accomplishes this without fabricating it, but it just sems that this would allow much better flow (no more 90* turn), as well as letting the wastegate open much, much further.

 

I am intrigued.... please tell more...

 

Here's what the aforementioned piece looks like.

 

Hmm, Ive never seen that before.

 

no kidding..wild looking stuff...now that plate and tube would bolt in place of the plate on the back of the turbo now. instead of diverting the exh gas straight down it would be staight out down the tranny tunnel correct? that heat that close to the tunnel cant be good. major heat shielding required..fill me in further on this jdm plate veedubbed

 

You can also use an s5 hotside and turbo manifold. The design is better. Finding a blown turbo could be cheap. Just join the hotside to your s4 turbo.

 

60mm? Er, no... There'd be nothing left of the housing. The BNR website says 35mm, but that's the flap as opposed to the actual port. I welded a 32mm washer to the stock flap to cover a 28mm port with heavy back-cutting, and never had any boost control problems.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/serious-s4-wastegate-porting%85-343788/ (scroll down to post #15 for reposted pics)

The wastegate flap can only open as far as the actuator will allow, i.e. until the spring is fully compressed. Even though the flap does hit the backplate in stock form, the actuator is already nearly at full extension. Backplate mods make very little difference to how far the flap opens.

The wastegate only opens under boost when the car has plenty of speed, usually only for short periods at a time, and the exhaust gases are aimed down at the road. No need for any heat shielding.