Blown turbo? Popped pipe? Popped intake seal? Dump valve open?

[Howstar]

3rd Gen RX-7 FD
 
Scene;
Driving on motorway at fd motorway speeds, 70% throttle, and \'pop\' like a back fire pop and turbo pressure drops down from 0.9bar max to 0.4bar and won\'t go any higher.
Also with loud whistling/hissing sound from turbo/dump valve area of engine whenever in +ve pressure
First thought was that turbos has gone bang, so limped it home.
 
 
Confusion;
Been out for couple of short drives since.
- Car idles like normal 0.9k - 1k rpm no problem
- Pulls away no problem
- Drives no problem
- No smoke at all from exhaust (straight thru)
- No bad smells
- No oil leaking
- Oil level not gone down at all
 
Only difference is can only get 0.4bar out of turbos, loud whistling/hissing sound and no dump valve.
 
All things lead to popped pipe in my opinion, no obvious pipes have come off but i need to check properly.
Just wanted outside opinions and recommendations from proper rotary guys.
 
 
Running;
Apexi intake,
HKS twin turbo pack (sequential)
HKS dump valve
Mapped to 0.9bar boost max

[shaunwil]

Sounds like one of the many vac pipes in the rats nest has either split or come off.

Shaun

[omgj]

I would say it is a boost leak if youve lost 0.5 bar of boost!? or maybe hose to dump valve has come off?
get a boost leak checker on it.

[Grant Monkhouse]

Vac hoses, either split  or broken, especially if they have never been replaced

[Howstar]

Cheers for replies,


Managed to have a listen and it does sound like a hissing in the rats nest near the back.
Difficult to gauge where as the car is so loud and :censored:es off neighbors :p.

[mpk490p]

Get some 3mm silocone pipe and get the UIM off and replace it all, it\'s worth doing as peace of mind anyway but it does sound like you have a problem there. do you still have the air pump? I\'m over MK a fair bit if you want a hand