Boost tests are a staple in the DSM world. Cap off the turbo inlet and apply pressure. If you're lucky nothing will start making noise till you've got 15 or 20 psi in the whole system.

I wanted to check my stock twins for any leaks so I capped off both turbo inlets. Whether I apply pressure directly to the UIM or to the Y-pipe, I can't build ANY pressure in the system at all. It's all going somewhere too quickly to even register on the gauge. I sprayed soapy water around, listened everywhere, etc. and I couldn't find any obvious leaks. Is this "just the way it is" with a rotary or am I missing something obvious?

Thanks!

 

That happens to me too. Someone said to stuff a rag in the muffler tip because it can actually go through the motor. I think if the engine is warm it would be better too. I will try this one day too.

 

I listened at my exhaust while my g/f fed air into the system and I didn't hear a sound. It almost seems like it's not getting that far even.

 

I've boost tested a number of FD's, the pressure usually does fade away after a few seconds, but it will build up pressure.

I usually set my air compressor to 20psi or so then feed air in.

That is a mystery. Is the car making boost in general?

Dale

 

Yea I set my compressor to 20 psi as well and am feeding the system via a tire valve. I am unable to build any pressure at all. I tried feeding air while turning the eccentric shaft to see if there was any position of the rotors that wouldn't leak all the air straight out but couldn't find one. Not convinced the pressure is even getting that far.

The stock twins boost great. I'm chasing down a boost control issue (sometimes on 3rd/4th gear pulls it spikes beyond what I've got it set for) so I thought maybe I had a vacuum leak in/around the wastegate actuator/solenoid which I was trying to find with the pressure testing in the first place.

 

Where are you piping in the air pressure, and where are you reading boost from? If one or either is after the throttle plates, that could be blocking the pressure. Open the throttle plates up during the boost test.

Dale

 

At first I tried introducing air through one of the top nipples (where my BOV is normally sourced from) on the UIM. Then I tried on the other side of the throttle at the y-pipe. I also opened and closed the throttle by hand and nothing seemed to make any difference.

 

I've never attempted to pressure test the stock sequential twins, but when you pressure test a single turbo Rx-7 it's no different than a piston engine.

 

Figured it out. I hadn't turned the motor over far enough. Having someone watch the gauge while you simultaneously inject pressure and turn the e-shaft to tell you when it starts registering helps a lot. Found 3 minor leaks and fixed them