Probably just a bad gasket on the CHRA oil drain tube. Or possibly a crush washer was re-used on the oil banjo bolt above. Either way it doesn't indicate a bad turbo. It's an external leak.

Do the o-ring. Probably not the fix, but it is obviously bad.

You have primary boost. That's good and means a number of things are working.

If it were me I'd honestly put a tube coming of the CRV into the cabin and see if it's still blowing off boost after transition. It may be hot air so be smart and do this at your own risk.

Post up a photo of your entire intake system. I had limited boost after transition before and my intake was closing up. Not the hoses, but the actual ducting coming off the air box was closing up.

Here's the intake system.
https://cimg0.ibsrv.net/gimg/www.rx7...ead65bfb8.jpeg
https://cimg2.ibsrv.net/gimg/www.rx7...44a79a5b8.jpeg

What's up with that y-pipe to crossover pipe cooupler? Looks stock. Those things blow out all the time. Like, they look intact but have cracks that open up under boost.

Also, you have a straight shot from the y pipe to the vmount inlet. That bend around the thermostat housing is just added resistance/pressure drop.

Yes my y-pipe to intercooler is janky. I got the V-mount setup second hand and it didn't come with those pipes. I don't have any fabrication tools so I got it to work with what I have. I'll get it straightened but right now it's not the highest on the list. The boost leak is. The coupler is rubber but it's not very old. I've taken it off and checked it out and it's fine. It also doesn't leak when the primary turbo is working.

I put the car back together and went for a drive. It's not magically fixed I'm afraid. But it is a little different. It will hold some boost after 4500, more then it used to but then bleeds off to around 1psi. Is this just a bad O-ring on the y-pipe? I wiped the underside of the pipe after the drive but it is dry. I'm thinking of letting it cool and then wrapping it in DEI thermal wrap and going for a drive to see if it blows it off. I'm just worried about getting off the adhesive after the drive. Any other ideas?

Thanks again!

Looking at the picture, where does the vacuum hose for the blowoff valve (the one that's right by the intake filters) go to? that should go to the nipple on the upper intake manifold, not one on the lower.

The vacuum line looks different which made me question that.

Dale

That's where it goes. Under the intake pipe and then up to it. It's right behind the most aft clamp for that intake pipe.

Replace the o-ring. Run a hose off the CRV and see if air goes thru it after transition.

Also, your primary turbo inlet looks like it has a silicone elbow. There's a chance that could collapse at high revs if it's not rigid enough. Honestly the primary filter looks like it has been collapsing too.

Silicone hoses are meant for pressure, not vacuum. That's why people have used the wire reinforced mcmaster hose for turbo inlets in the past.

The way I diagnosed my collapsing inlet was to take ALL the hoses off and just run open hard inlet pipes to both turbos during the test drive.

Don't underestimate the vacuum generated at the turbo inlets.

I don't think the silicone elbow is collapsing because wouldn't it do that before the transition? I thought it fed the drive turbine of the secondary turbo after the transition so it wouldn't see any more vacuum. I'd love to be wrong. The filter is a little bent do to a previous set up when it had to bend around the hot pipe.

I went up to Home Depot to try and get some pipe for the intake. Of course they didn't have what I wanted. Drove home and put the car up. I checked the bottom of the y-pipe and it had fresh wetness on it. So I'm clearly losing some boost there. I ordered a new one. I'll be at work thre next few days but hopefully I'll be back to the car on Monday.

Dude. You can search youtube and find a dozen underhood go-pro videos of silicone turbo inlets collapsing on various cars at high rpms. Why do you think it couldn't happen to yours?

Is it definitely the cause? I have no clue. Is it possible and have others experienced the exact same thing? Yes.

At higher RPMs the engine consumes more air per unit time. To keep the same boost pressure at a higher flow rate you have to flow more... more vacuum at the turbo inlet.

#3 from the RX-7 specific troubleshooting guide I linked to early in this thread...

"Primary Turbo Inlet:
Typically collapses under high volume air through air cleaner into Primary Turbocharger. When the engine is cold the rubber is less prone to collapsing. Typical symptoms are having boost at lower RPMs and then a loss of boost at higher RPMs, this is agravated when engine warms-up softening the rubber allowing for easier and more complete colaspe of the hose. Typically costs about U$90 at dealer."

Typically the collapsing intake problem happens with the restrictive stock intake. A good intake system should see ZERO vacuum before the throttle body - this is a misconception a lot of people have. The intake to the turbos should have very little pressure drop through the filter.

The only way you can create a vacuum is with a drop in air pressure with a restriction.

Now, if the K&N filters on those aluminum intake pipes were badly clogged or something I could see this happening.

OP, you should be able to re-create the "whooshing" noise parked in the driveway. You'll have to rev the engine past 4500 RPM to have the sequential system engaged, though. May be able to see/feel the air escaping.

It may make the neighbors mad, though :).

Dale

If you don't want to upset the neighbors, you can use a boost leak tester to zero in on where the air is getting out like this one:


There are cheaper ones available on other sites too, and its not super difficult to build your own with some stuff from home depot. Its basically just a PVC end-cap with an air inlet and a pressure gauge.

Might not catch every potential leak, but should make anything large very obvious, especially if you spray the suspect area with some soapy water.

Dag Nab-it!

Okay, new y-pipe o-ring didn't help. Removing the silicone coupler and filter didn't help. Reving to and over 4500rpm in the driveway(church parking lot) didn't cause my venting/leaking. I need to rent a real air compressor to do a boost leak test. I'm grasping at straws here. Is there a way to test if my wastegate is stuck open? I don't have the normal symptoms of a sticking E solenoid but I think I'll try that fix too. Anything else?

Thanks again!

Just FYI, Amazon Warehouse sometimes has some fairly affordable compressors that can do good enough to get your engine up to 8 or 9 psi. Mine was ~$60 delivered.

Just a 5 gallon compressor, it's nothing fancy and its fairly loud. Helped me track down at least 10 leaks/issues I wasn't able to completely zero in on by revving the car up though.

You can test the wastage by applying vaccume or pressure to the nipples. An open waste gate should still give around 7 psi through redline. It also wouldn't cause the sound as far as I can tell.

I thought you already tried, but if not, cap the BOV and CRV outlets and go for a quick drive. A pull or two won't hurt anything and you can 100% rule those items out as the cause of the leak and or sound. You can also pull off the primary intake tube and run open air to rule that out too. Again just for a pull or two.

I capped then both, again, today just to make sure, again. Still didn't help.

When you start hearing the "whooshing" when driving, are you sure it happens at the transition point (4500 RPM or so) or does it steadily build and get louder as RPM's go up?

Dale

I did the sticking "E" solonoid fix, didn't help.

It definitely starts at 4500rpm. It sounds like both turbos are just blowing air out of a big hole. It's not a whistle or a high pitched sound. It sounds like if you took a deep breath, opened your mouth all the way, and exhaled all at once. But continually. Boost immediately drops to about 2-3 and then bleeds down to around 1 if you stay on it.

I'm down to my last, and dangerous idea. Put the car up and rev it in gear and maybe find it.

Anybody else have an idea?

Thanks!

I'd still recommend a pressure test. If the boost leak is that big you'll find it in a few minutes.

Dizzel... what kind of cat do you have? Can you drop the exhaust to inspect it? Could be clogged / breaking down.

I live in the Dirty South, no cat.

So this problem started while we were tuning the car. Dale asked if the sequential turbos we turned off and I said no, but I don't really know. I don't know how to tune the car and just have to take the word of my tuner. It's possible he made a mistake and didn't catch it. Is there a way for me to check myself without a Datalogit? Also, if the ECU is telling the car to vent and it's not the CRV or the BOV isn't my only option the wastegate?

In the Commander on the PowerFC, you can go to Settings and there's a menu item (can't remember what it's called) that you can turn on and off a number of things - O2 feedback, Idle IG control, and sequential control is there. The yes/no is in Japanese but you can typically figure it out.

Dale

Phooey.
https://cimg5.ibsrv.net/gimg/www.rx7...541e511fc.jpeg

Hey, worth checking the stupid stuff!

Forgot the new EL commander got rid of the kanji for the yes/no, that makes it much easier.

If you have the car over 4500, can you get off the gas then back on the gas and it still whooshes? Staying over 4500 the whole time?

Dale

Dale, I think it whooshes but don't remember for sure right now. I'll try tomorrow and let you know. Other than that, I'm totally out of ideas. I was planning on pulling off the turbos to see if I had broken something there only because I don't know what else to do. I'll test to see if I can build boost after 4500 when I lose it. I know if I stay on it it doesn't build back. I'll go over 4500 and let it drop but only to 5k and see.

Thanks!

I went driving this morning and when I try to build boost after the transition it momentarily goes up to 2-3 and then drops down to 0-1. So, yeah...


Now that my turbos are nice and hot I'm going to try and take them off to see if I can findanything wrong with them. I'm sure someone will come up with a test I have to have the car put together to do but that's life.

As always, thanks for the help! And keep those ideas coming!