BNR Stage 3 Slow Spool Issue
 

My tuner and I are trying to troubleshoot a "lazy turbo" issue.

Symptoms
1. 10 PSI by ~5k RPM
2. 16 PSI by ~7k RPM

Observations
1. No smoke. First set that BNR sent leaked oil from the moment they were installed. BNR sent us a new version with upgraded oil seals that also have lower rotational friction.
2. Pulling off the vacuum lines and running the wastegates at spring pressure yields the same very slow spool.

Hardware
1. Freshly rebuilt motor with street port from Garage Life (Garage Life is also the tuner)
2. BNR Stage 3 turbos (new) with stock pills in the vacuum lines
3. HKS RS reloaded intakes
4. Trust SMIC
5. Efini y-pipe
6. Greddy TB elbow
7. HKS ceramic coated downpipe
8. SMB 80mm mid-pipe with high-flow metallic substrate cat and mini muffler (new)
9. Tenabe 80mm Medallion exhaust
10. AEZKnights solenoid upgrade kit with new silicon vacuum lines. Turbos are configured for sequential operation.

ECU
1. Apex'i PFC (boost control also through PFC)


Theories
1. Wastegate may not be fully closed. Although the wastegate arms are adjustable on the BNR Stage 3 twins, we assumed that no adjustment was necessary to ensure that the wastegate was fully closed. Perhaps this was a bad assumption? Would love to know if others had to adjust their BNR Stage 3 wastegate actuator arms to ensure that they were fully closed when the turbos are below target boost pressure.

2. Boost leak? Seems unlikely because we're still able to hit 16 PSI, albeit at a very late RPM.


Thoughts or suggestions to aid troubleshooting would be much appreciated. Thanks!

Is it running sequential or non-seq?

Running sequential with the AEZKnights solenoid upgrade kit from the groupbuy section of this forum.

How is your boost controlled? With the PFC? Don't think BNR's have pills in the lines. No pills will result in slower boost I do believe. It will also result in lower boost. Is everything plumbed like factory for the pre control and waste gate?

Matt

Pills in the vacuum lines. PFC controlling boost pressure. Vacuum lines are routed per AEZKnights diagram.

My first thought would have been solenoids. I had a similar issue (10psi on primary, 16psi on secondary) way back when and it turned out to be dodgy solenoids. Fixed/replaced them and it was a dramatic change!!

I'd test the solenoids just to be sure??? :dunno:

We suspected that it may have been the solenoid upgrade kit. However, we pulled the vacuum lines off of the wastegates to troubleshoot and observed the same extremely slow spool.

I would crank the pre-load up on the wastegate actuator rod.

I have seen this same issue resolved several times on this forum for FCs with the BNR singles as well.

The ported wastegate has more surface area and the exhaust manifold pressure pushes them open easier AND they don't boost creep like smaller stock wastegate does.

Just because it makes a certain boost pressure does not mean you can't have a boost leak.
I'd recommend compressing the pipes and checking for leaks just to be safe.

We adjusted the wastegate and added preload. Seemed to help a little. With the vacuum hoses disconnected, we're now making 5 PSI by ~3,500 RPM, 10 PSI by ~5,000 RPM, and 15 PSI by ~6,000 RPM.

Tuner suspects that the brand new SMB catted mid pipe may be the culprit. Anyone nearby South El Monte with a good mid pipe that we can use to troubleshoot? :)

I have the resonated SMB midpipe as well and it did help lower my boost creep compared to just a resonated midpipe (meaning it does flow significantly less).

Still...

Your boost is so slow I would suspect that there is something up with the sequential switching system or a giant boost leak.

Since you have the vacuum line off the primary turbo wastegate (and pre-control?) actuators and still have the problem, I would suspect the switching actuator isn't sucked in shut as it should be (so it is sending exhaust to both turbos always).

The mid pipe is no longer the leading suspect. The tuner discovered that the BPV is bleeding substantial amounts of air. However, this is not the only issue as the symptoms are still present. Charge pipes and couplers will be taken apart, inspected, and reinstalled tomorrow. Hoping that this helps...

No offense to you or the tuner but that seems like a lot of billable hours for something that could be inspected by pressurizing the system with shop air...

No offense taken. Garage Life has been a great resource and has earned my trust. The tuner is adamant that there are no leaks and he is by no means "milking" the situation. However, this issue remains very elusive. I've wrenched on turbo platforms for over 10 years and its not like we're not aware of how to troubleshoot a boost leak. Our first-hand intuition pointed in other directions, but at this point we're not going to rule out the possibility that we missed something along the way. So we're now systematically going through all components.

I'll update as we know more.

I dont see how you can have a boost leak when you are making 16 psi at high rpm.

That's all well and good but there exists a test that actually tests all of those components without spending hours doing it and if a problem is found can help narrow the placement of it to individual components. Hence my comment as well as others in this thread. Regardless, good luck.

We confirmed no boost leak. The secondary turbo BPV was not holding pressure. We're now making ~19 PSI by 5,000 RPM. However, the slow spool persists.

The new Exedy "Stage 1" clutch exploded during troubleshooting on the street. We're waiting for a new clutch before continuing with troubleshooting.

Are you sure that the flapper in the Ypipe isn't ajar, its controlled both by boost and vacuum and if its not completely shut, turbo 1 would bleed into turbo2, which is vented into the air cleaner until 4500 rpm. You would have some boost below 4500rpm as turbo1 tries to overcome the the leak and as turbo 2 comes online at 4500 rpm boost would raise dramatically. Check all hoses around the actuator on the Ypipe, and make sure the rod pulls in at key on, 6 times without starting the engine, you may have a vacuum leak. Don't assume that the problem is in a region that you have just worked on, rx7´s like the cozy environment of the garage and once in they will often develop new and never before seen issues just to keep themselves in there!

Out of curiosity, has the problem been solved?

Strange but true! :egrin:

I've gotten 10 psi by 2500 rpm with the BNR stage 3s. Something isn't right. Make your crv isn't leaking or the manifold flapper bad.