wonder if anybody could tell me how to take my twin turbo legacy jdm subaru engine and do a parallel conversion. It seems im not finding any how to or info on how to do this. if somebody knows from experience , let me know.. cheers. mate

you'll find all the info you want here


http://www.rslibertyclub.org/forums/register.php 

The answer to your question is
(1) remove the changeover valve from the exhaust - this valve directs exhaust air from the first turbo to also power up the second turbo
(2) make both turbos the same - stock there is a small turbo (vf13 or 18 depending on year) with a wastegate. The second turbo is larger (vf14 or 19) and doesn't have a wastegate. So you need to fit 2 x turbos that are the same and preferable both have wastegates. This ensures even air flow in your turbo system.
(3) Remove the valve at the entry to the intercooler that opens up when the seond turbo is creating boost. This way your intercooler can accept airflow from both turbos all the time.

That's it.

Question is, why would you want to do it? It makes it slower to spool up since the stock sequential system creates boost down low and then keeps boost on all the way till redline. Even easier/better to change to a single turbo a-la WRX style. If you buy one of the newer turbos like a VF23 with ball bearing centre it will boost up down low and take you all the way to redline.

How do I know? I've got a twin turbo motor here myself for my Manx project and have gone through all the possibilities of going single, twin sequential or twin parrallel. I've got all the hoses, solenoids and vacuum canisters to go with it (if you don't have these you can't really control the sequential) I am going to stay twin sequential just to be different but once I want to start chasing real power I'll just move to single turbo like a WRX.