MiniRotary

I have a 1992 FD3S Type R. OEM motor, ECU and turbos. The rear turbo does not seem to be working. I believe the boost range should be something like 10-8-10 but mine is more like 10-5-3 and from 5k rpm to redline, it just stays at 3psi. There is oil leaking from the compressor of the rear turbo as well. So I just thought it was a blown turbo. Yet sometimes in first gear when it pulls hard, I get full 10-8-10psi of boost, but then shift to 2nd and it drops back down to 3psi. People have been telling me blown turbo, others have been telling me boost leak, others have been telling me vacuum lines or hoses, etc. I would like to hear some of you're guys' input. I was planning to just swap the turbos and see where that gets me. Thanks.

DaleClark

iTrader: (55)

Probably not bad turbos, it's most likely the control system. Especially if it does work some times. There's plenty of stuff out there documenting turbo control troubleshooting, step through and test.

The oil could point to them being leaky, but they're probably not bad as far as them working.

Dale

alexdimen

iTrader: (13)

Yep. You will spend $500 on a good set of used turbos and spend a weekend swapping them over. All that and it is not likely the turbos themselves are the problem.

Bad secondary boost means one of these probably isn't working or has a bad solenoid/line:
- turbo control actuator (vacuum and pressure)
- charge control actuator (pressure)
- charge relief valve (pressure)

I would start by pulling off and checking the small and large hoses on the secondary side attached to the charge relief valve. You could just have a cracked charge relief hose.

MiniRotary

So, just remove the Y pipe and check for cracked hoses? How do I know which hoses are which? I'm pretty new to owning an FD so I'm not too sure on what to actually look for. I also have a few minor mods under the hood(HKS Twin Power, Blitz 1st Gen BOV, HKS Twin Intake), if that changes anything. Thank you for the quick reply.

AE_Racer

iTrader: (1)

Check this thread out, there is a diagram showing all of the turbo control parts https://www.rx7club.com/3rd-generati...tified-841821/

alexdimen

iTrader: (13)

Nah. You won't know without a diagram. The factory service manual is available for download in the FAQ section or with a quick google search. If you're going to work on this car you need the manual.

DocHoliday89

iTrader: (10)

Hey, but if that rear turbo DOES so happen to be toast, I know I saw one for sale in the 3rd gen classifieds

MiniRotary

So the JDM Models like mine use a different vacuum line setup than USDM. And my buddy pointed out my engine has an S8 Rats nest. I also changed all the vacuum hoses for the rats nest and still no boost. So it is either an actuator or solenoid. And after seeing the rats nest, it would be nice to simplify it as well.

alexdimen

iTrader: (13)

I would check for boost leaks on the secondary side as suggested in post 3 before doing anything else. If that doesn't give you anything, then tee into your TCA pressure and vac lines with a boost gauge and see if it's getting both signals at transition. Same with your charge control and charge relief pressure lines. Test those driving with a gauge teed on them.