boost issue question
 

Ok so I've got my car in the garage right now doing some stuff to it. Hopefully solving a vacuum leak by replacing the upper to lower intake manifold gasket.

But now I'm tackling the issue of my boost. One day after starting up the car and getting ready to head home, hopped on the freeway and immediately my friend and I both noticed that we were definitely not a full power. did a couple pulls and monitored the boost guage. primary turbo ok, but secondary was netting about 6-7 psi on average. stopped and checked out under the hood for loose hoses etc and noticed that my crossover pipe was getting pushed up pretty far when I revved it up. Tightened that up when I got home but still the same. drove it a couple times just to putts around town on rainy days (my DD is a motorcycle lol) and just before puttin it into the garage noticed that now my primary was getting only about 7 psi and varied from 5-7 above 4500 rpm.

Ok so thats the long story over with. Immediately this observation was not made, but after a couple more times of driving it trying to diagnose, we noticed a loud whooshing noise coming from under the hood. of course everyone is saying that its the wastegate and thats what I thought myself, until I read this tonight:

http://robrobinette.com/efini.htm

Saying: "The black plastic crossover tube has a tendency to crack on both ends and the rubber connector between the Y-pipe and crossover tube has a tendency to split. These cracks can be the source of hard-to-solve boost problems. The cracks can't be seen unless you remove the tube and pry it open, and yet under boost pressure the cracks open up and vent your boost (which is sometimes accompanied by a loud whooshing sound from under the hood)."

so then I decided to inspect the crossover pipe and that connector. the crossover pipe has no apparent cracks, and neither does the connector. though it is hard to tell on the connector and I'm wondering if a small crack that I couldn't see would be enough to cause this? also the connector looks and feels like its a bit stretched out, not that I know what a new one would look or feel like =/

So is this a better possibility than a wastegate, and should I spend the money to get my hands on an efini y-pipe and crossover? if not, I'm not quite sure how to inspect the wastegate. that crap is buried deep down there lol. not to keen on taking that out.

sorry for the essay :blush:

Did you remove the cross-over tube while changing the gaskets?
If not I would definitely check all vacuum hoses, check valves and other stuff that were removed during the change first. A reverse check valve could mess up the control system.

Even if you did remove the cross over tube it's wise to check some cheaper stuff first.

I believe it's time to replace all of your vacuum hoses/check valves with Silicone if you haven't already done so :) There are too many things that can cause that and it's almost impossible to pointpoint one problem. It's better to replace them all and be done with it. There are MANY other things that can cause vacuum leaks besides just hoses, this should have all the info you need
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/im-ready-do-full-vacuum-hose-job-need-pointers-868621/

if you can hear your turbos pushing air into the engine bay then the first place to look at is your Y-pipe coupler. hoping you removed it to inspect it, you can't thoroughly inspect it while it's still on the car.

get an efini y-pipe, best solution to fix/prevent ^that problem

All my vacuum hoses are already silicone. no offense but theres no way a check valve could just get reversed one day without me taking it apart. Though I did break one while taking stuff apart so now I need a new one =/

I've got some parts on order right now. waiting for my gasket and some silicone hose connectors. I think I'll throw a silicone connector on the crossover pipe to check to see if that is in fact the problem. If so then I'll spring for the efini setup. and I did in fact remove the coupler to inspect it. Didn't see anything, though I'm wondering/hoping that maybe it was something I couldn't see with the naked eye.

the check valves can fail, and so can silicone vacuum hoses

When you did your vacuum hoses last time did you check all of your solenoid valves for proper operation before you put it all back together, and replace all of the check valves at the same time? When I did my vacuum hose job, 3/8 solenoid valves were bad and needed replacement. The Turbo Control Actuator and Wastegate Control Actuator can also cause boost leaks. You need to buy the Fighters Garage FD boost pressure tester to pressurize the entire system and listen for air leaks.

If your boost is good on the primary turbo then its not the y-pipe. Think about it, the primary also boosts through it and op is seing boost ok. I would trace the secondary boost leak from the secondary turbo itself. Start with a visible inspection of the CRV and associated lines comming from the secondary turbo. If they pass then check the y-pipe to secondary turbo outlet.

Testing the pressure tank
https://www.rx7club.com/showthread.p...+issues+solved

Testing the CRV
http://www.autosportracetech.com/RX-...leshooting.htm

Also look at what I found at my secondary turbo outlet to y-pipe connection: The bolts had worked their way off over time