So here the setup.

Setup:

1992 1.6 5spd
150K stock motor
Greddy kit with the only remaining part not upgraded being the turbo
ETD manifold
Tony's 2.5" DP to 3" cat to 2.5" exhaust straight through muffler
Stripes intercooler kit
460cc inj
Braineack MS with EBC boomslang
CLutchnet 3X PP and 4 puck sprung disk
Godspeed rad


Here the question...as we all know the greddy WG needs springs and still has issues on any boost level over about 8psi. Being I have the ETD manifold and there is a ton of room under it what do you think of the idea of welding on a WG to the bottom of the manifold under where the turbo mounts? I think there is plenty of room and hopefully that will let us close the internal WG for ever and regulate boost accurately with the underside WG?

OK, lets hear it......good idea or bad?

 

uh no that is plane silly.

 

Expensive, much more epensive than 30 minutes with a die grinder to port the internal WG hole and add a helper spring. It would work great though. Add the external WG and tack weld the WG flap closed. Or drill and tap a hole in the current DP flange and use a bolt through that hole to hold the flap closed.

 

seen it done on evo stock turbo worked nice but imo not worth the cost

 

May as well sell the ETD, buy a BEGi S5, and build a DP.

 

You could add the external wastegate as mentioned and have solid boost control. Not really that big of a deal. The greddy is a good turbo with great top end!

 

You could also simply replace the wastegate actuator with a more stout unit.
Details at post # 18 of this thread: https://www.miataturbo.net/forum/showthread.php?t=21069
and # 35 in this thread: https://www.miataturbo.net/forum/showthread.php?t=13351

Additionally, I moved my WG reference from the stock location at the outlet of the compressor to a nipple which I screwed into the pipe between the intercooler and the throttle body. Abe suggested that to me, and it worked wonders.

Between these two changes, my boost is quite stable at ~13 PSI all the way to redline. Apart from the fact that I'm still using an MBC, my setup is basically identical to yours- unported TD04H-15G, no helper spring, Tony 2.5" DP, 2.5" cat, 2.5" straight-through exhaust.

 

The EBC with the helper spring (or improved actuator) would give you everything you want. It did exactly that for my t3.

 

bottom mounted wg sucks for maintenance.