Just removed the vacuum chamber and saw this pipe with no hose. Anyone know what hose goes here???
Can this affect your second turbo operation? I lose boost after 4500 rpms and read on a search to look under the blck vacuum chamber to see if it blew a hose off. Didn't see any but I found a hose or perhaps a cap missing here. Any help appreciated.
Thanks, Rob.

 

2nd pic

 

That's the infamous empty pipe, it's supposed to be like that. Only us elite automatic transmission users get to harness its awesome double-throttle actuating power!

 

Thanks Jonski, any idea why my second turbo doesn't come on? Boost is exellent till 4500 rpms and then it just drops to zero. I replaced couplings and 1' hoses. I have great vacuum just no 2nd turbo funtion.
Thanks, Rob

 

It could be a couple of things.

I think the most likely culprit would by if your Charge Releif Valve is staying open. This can be caused by a bad CRV solenoid, a bad CRV, or a cracked vacuum tube (there are three to check between the CRV and the CRV solenoid).

 

Jonski can you put that in laymans terms???
What and where are these items?
Thanks, Rob

 

http://www.scuderiaciriani.com/rx7/v...e_diagram2.jpg


The CRV (Charge Releif Valve) releases the pressure of the secondary (rear) turbo during pre-spool. At 4500 the boost from both the primary and secondary turbos are combined and the CRV is supposed to close, otherwise it lets out all of your boost. It's like a BOV (Blow-Off Valve) for the secondary turbo that stays open between 0rpm and 4500rpm.

The CRV solenoid is responsible for operating the CRV. If it is broken, then the CRV will be stuck on one position. It's labeled (H) in the diagram.

There are three hoses between the solenoid and the valve. One small upside-down U-shaped one from the solenoid to the metal tube. Then one from the metal tube to the third nipple from the top on the LIM (Lower Intake Manifold). Then the last one goes from the LIM to the Valve.

 

JONSKI
I replaced the hose behind the CRV today. It was VERY hard and brittle from heat I suppose. It comes from the turbo to the CRV then to the intake,right?
How can I test this CRV. It sounds like the problem. Feels like it is is just venting out, but how can I be sure?
Thanks, Rob

 

Take the CRV in your hand. If you can blow through either of the two big nipples then the CRV is bad.

 

I found a vacuum hose just right of the infamous empty vacuum line. It is u-shaped (3' long) and it was kinked. I blew in it but no air, comletely stopped up. I think the black box, pressure chamber pushed down on it and caused it to kink. Plus I put a nipple cover on the empty line and now I have 2ndary boost, WOO,HOO. What does the u-shaped hose go to?
Thanks, Rob

 

I think the kinked hose went to the CRV solenoid and that's why I had no second boost !!!
Sometimes it is the obvious after I replaced so many other things, oh well I guess I learned a lot!
thanks, Rob

QUOTE:_______________________________________The CRV solenoid is responsible for operating the CRV. If it is broken, then the CRV will be stuck on one position. It's labeled (H) in the diagram.
_____________________________________________

 

Check that check valve that comes off of the pressure chamber. It can cause no boost above 4500 as well.

 

I like happy endings.

 

what would cause no boost on the low end and boost after 4500 rpms?

 

Probably the Charge Control Valve is stuck open. Do you have a 0-8-10 boost pattern or something similar?