After racing a 911 Carrera last night (which I spanked ) I'm getting just about 0 boost all the way through the rev range. If the car is decently cool I'll get 1 or 2 psi, but nothing above that. Because this happened so suddenly, and right after I brought my car out of storage from the winter, I assumed it'd be an IC coupling, or one of the hoses. I can hear a nice whooshing sound as soon as I should be seeing some boost, so I know the turbos are spinning away just fine. The engine idles solidly, makes great vacuum, and normal rotary N/A power, so I know the engine is fine.

So I took a look through my intake track this afternoon. Working from the intake elbow back, the hose that goes into the top of the IC was fine, and attached quite well. The hose that comes out of the bottom of the IC and up to the coupling with the crossover pipe was fine. The coupling between the IC hose and the crossover pipe looked good, and the crossover pipe itself looked fine.

The coupling between the crossover pipe and the y-pipe looked ok. And heres where my question is. How is the y-pipe attached to the turbos? Are there 2 more couplings? I didn't have enough time to keep digging this afternoon, so I didn't get to check that.

I also took a look at the BOV, and it's functioning fine, holding pressure until vacuum is applied.

And if anyone thinks my issue could be something other than a coupling or pipe, feel free to chime in.

Thanks for any help.

 

The Y-pipe (stock) is actually a two piece affair. There is an "elbow" that attaches to the output of the primary turbo via a metal to metal bolted interface, with a metal gasket. This elbow also contains the combined output connection (Y-pipe to crossover) and the blow off valve connection. BTW, did you remove the coupler for the Y-pipe to crossover and fold it inside out? Or just visual? Splits in this coupler can be difficult to see.

Anyway, the other half of the Y-pipe is an elbow that mounts to the output of the secindary turbo, again with a gasketed metal to metal bolted interface. the rear elbow has the connection for the charge releif hose. Since you have no primery boost, I wouldn't suspect a torn CRV connection.

The two elbows meet on the secondary side of the combined output, but before the carge control valve. You can see where the one pipe is larger than the other (I forget which). They mate together with a simple O-ring. If the O-ring is blown, this could also be a culprit. You will need to pull the y-pipe to check this out.

 

I removed it and stretched it and flattened it out some. Didn't think of turning it inside out, but I've read many a time on this forum about how hard splits can be to see, so I gave it good thorough lookover.

I'm non-seq though. Would it still not be an issue?

I was afraid of that. Well looks like I know how I'm spending my free time this weekend. Thanks for the help spurvo, keep it coming.

 

The other day I was spiritedly driving with some friends and all the sudden I had no boost and had all the same symptoms you have. My problem was a split in the IC piping coming off the bottom. It was really hard to see but once I found it it was pretty large and easy to see.



Double check the IC piping before you start taking other things apart.

 

Also check to make sure your AWS hose is still firmly connected to intake elbow.

 

that piece was my problem saturday. although it was just sucked in on itself.

 

Check the lines going to the BOV and CRV. The CRV should not be functioning if you're running NS.

In a sequential setup the CRV enables the secondary turbo to prespool, by providing an alternate path for the turbo's output, when the turbo's main output pipe is blocked by the Charge Control Valve

When the system switches from primary only to primary/secondary mode the CRV closes and the door between the two sections of the Y-pipe opens. The secondary turbo's output is diverted from the CRV valve to the Intercooler.

If you still had the CRV hooked up to the solenoid you would get no boost below the turbo transition point. However if the valve is still physically attached to the Y-pipe, but stuck closed then it should be fine.

The CRV connects to the section of the Y-pipe closest to the firewall. The BOV connects at the center of the pipe. Regardless of what is attached to them, I would check both connections. However, if you're getting ZERO boost I tend to think the cause of your problem is more than a loose hose.

I agree with Rynberg re the AWS hose.

 

bro where have you been this has been discussed so many times
stick to what azaka said. you either blew the coupler holding the crossoverpipe onto the y pipe, the lower intercooler pipe, or the upper intercooler hose. Simple, its there 100%. great idea on the AWS hose as well thats the only other place I forgot.

 

Oooo, good call rynberg. I didn't think of that one. I'll check it out tomorrow.

I looked, but I'll look again. I really gave them a good bending/inspection, but I'll give it another shot. Thanks.

I really didn't think the CRV could be causing any issues, just wanted to make sure. KDR did the non-seq setup when they had my car last summer, so I really don't know if they left the CRV attached or not. I'll check that out this weekend too hopefully.

 

the crv closes a tad bit later than the bov does so it will let out a very small amount of air that could be going to the engine. you are non seq on twins. you only need one bov cap the crv run a line from the bov to manifold and be done with it. yur the one who wants simplicity why would you keep something you totally dont need

 

Did ya read my answer at all? KDR did my non-seq, I assumed they were competent, and I didn't check it over. I have no idea if the CRV is there at all. I'll check it out though, thanks for the input.

 

im not trying to be an *** you just seem like you are avoiding learning some easy things because someone else did the work. Id sure hope they could figure it out being a 3d gen shop but most are still pathetic.

heres a diagram I made for dummies like myself who finally learned
http://plaza.ufl.edu/yanni25/mynonseqsetup.jpg

 

Thanks for the diagram. It's a little off for my setup, because I still have all emmisions related crap, stupid massachusetts. But it'll be helpful.

 

I'm not too familiar with non-seq setups, so this may not be helpfull. I had a similar problem last year, and it was just a hose that had popped off under the black pressure tank in front of the UIM. If you are still using this part of the vacuum system, its an easy spot to check. Just remove the pressure tank and take a look around.

It does not sound like a bad intake hose to me.

 

How are you holding the 2 flappers? Did you weld them ? The two under the turbo area. If both (or even one maybe) got loose then that is your problem. I forgot to hold them open and I finished the non-seq and with the wastegate closed I could only get 3 psi pushing it 5! So just imagine Im pretty sure that could be your problem.

 

thats rigthwhere mine was but 2 times the size. got maybe 5 psi then it would be 0 when it got hot under the hood.
joel

 

All the hoses are brand new silicon, and zip-tied on. I've only driven the car like ~6k miles since I got it back from KDR, so I'd imagine it's not a vacuum hose. I didn't have time to take a good look, but I will.

Not sure what KDR did with the flappers, I'd assume they welded them, because I know I talked to Dave about that. But then again, I also talked to Dave about street-porting the motor before he put it in, which he conveniently forgot... So I have no idea what went on in regards to the non-seq.

It's funny, the fact that I'm getting a tiny bit of boost when the engine bay is still cool made me think it'd be an IC hose, but after inspecting them and not finding anything, I decided to move on to other things. But you've had very similar symptoms with an IC hose problem. I'll have to double check those.

 

LOL. That is so so sad. I wonder if they actually rebuilt your motor or just middle manned a Malloy reman. How much did they charge you?

 

Well I hope they did, because otherwise it took them 6 weeks to R&R a motor!

 

911GT2
Check the flappers, this IS your problem if he wired them shut or even if he did a bad job on the weld. All you have to do is get under where the turbo area is and just take a look and the flappers try to move them. If they open and close with your hand then their lose and will close under exhaust pressure.

 

I found the cause of my boost leak this afternoon. I decided to do a quick check to see if rynberg and others were right with the AWS hose, but unfortunately it was still firmly connected.

I took one more look at the y-pipe and bingo, the 3/4" nipple previously used for the CRV had only the remains of a vacuum cap on it. Over heat cycling I guess the cap cracked, and the first good long in boost run to redline I had this spring blew it right off. So I stuck a new cap on, and viola! No more boost leak

Thanks to all for the help as usual.