Hi guys. As stated in the title, I've searched a lot, but have not quite found a solution for my particular issue. I'll begin with a list of mods, listed in order of relevance:

DP/resonated midpipe/RB catback
Rebuilt twins (converted from non-sequential, back to sequential)
Upgraded solenoid kit (AzEKnightz)
Greddy ProfecB Boost controller
Mild Streetport
Power FC
550/1300 injectors

The issue:

Since replacing the turbos (myself, with the help of the friend who sold them to me); the primary works perfectly, and boosts instantly to whatever pressure it is set for.

Once it hits the 4500 rpm transition point though, I get a loud "SHHHHHHHHHHH" type of sound, coming from the turbo area, again ONLY once the secondary has come online. There is a definite extra "kick" as the secondary comes online, so I can only assume that the transition is "working", and it is consistent, coming on at 4500 rpm, every time. It certainly isn't as crisp as it should be, and was, with the previous turbos however, and the boost pressure does bleed off.

What has me baffled though is the fact that, from my understanding, it is nearly impossible to have a leak on the secondary ONLY, which does not also affect the primary...? Can anyone give me some direction on where to begin looking for the cause of this issue? It's extremely frustrating, mainly because the turbos were operating PERFECTLY, with the same solenoid system, before my last engine rebuild, and turbo replacement.

Any help and/or direction would be extremely appreciated.

Thanks in advance, guys.

 

Most likely it's a small air leak on the back side of the Y-pipe. I would check the charge relief valve 90 deg. 3/4" hose, the O-ring that seals the two halves of the Y-pipe, and the charge relief valve itself.

Also, the gasket between the Y-pipe and secondary turbo could be a culprit too.

May want to pressure test the system if you have access to an air compressor, makes finding small leaks like that so much easier.

Dale

 

Did you have this issue before the turbo replacement? Is your Charge control actuator just not even bolted to the turbos? That could cause a definite secondary turbo leak. :P most secondary issues are linked to the actuation of the turbo control actuator or the charge control actuator

 

Thanks for the quick replies, and suggestions guys! Mrmatt3465, I did not have this problem before the turbo replacement. I'll definitely check into
all of your suggestions and report back.

Thanks again guys.

 

When my first car was stock twins I had a hairline crack in the Y pipe that would only expand and leak boost when the secondary turbo would come on. I ended up switching to a single turbo when it was found.
If I had known at the time I may have just replaced the Y pipe with the Efini metal replacement. The stock one is plastic and should be replaced with the updated Mazda Efini unit anyway as its a common and well known failure point.

 

Yep, check the pipes, couplers and clamps. May be as simple as a loose clamp especially that lower Y pipe clamp and coupler.

 

I'd say a boost leak from either the y pipe oring, the ypipe to compressor connection, or one of the charge relief valve or hose. If you can rotate the 1" diameter hoses coming off the airbox to the ypipe they are too loose.

 

Thanks for the added input, guys. Also, my apologies for forgetting to mention the Efini Y-Pipe in my list of mods...