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I'm running BNR stage 2's, a PFC and 2x MAC solenoids for wastegate and precontrol. The problem is that the BNRs never seem to want to boost past about 16-17psi in primary-only mode, and immediately at transition the manifold pressure abruptly drops and only slowly builds back to about 8-10psi by redline.
Before the BNRs, on stock twins, the system was working beautifully for a time. Then a few months ago the AWS blockoff plate fell off (thanks to the one and only mechanic who has ever worked on my car for putting it there without asking, and then apparently not fastening it down well enough!). The missing block-off plate caused a large boost leak which caused the car to obviously not boost right, however I never captured any logs of the car in that state. At the same time I fixed the AWS leak I also installed the BNRs -- point being that I really don't know if the problem I am experiencing now has anything specific to do with the BNRs or if it's something else that started during the same timeframe as the AWS leak, and unfortunately I have no logs to compare now and then.
Here is a 2nd gear pull followed by a 3rd gear pull:
You can clearly see the sudden drop in pressure at 4,200rpm.
Note that both primary and secondary boost targets are set to 1.4kg/cm2 (~20psi) in the PFC and both duty cycles are set to 255; and from the chart it looks like the solenoids are behaving properly.
I have thoroughly pressure tested everything for boost leaks, and at this time believe the system is very tight.
So what is doing on? I have spent literally hours staring at the vacuum diagram, as well as studying various information found here including @arghx 's "Why is this engine so damn complicated??" thread (https://www.rx7club.com/3rd-generati...tified-841821/) and I have come up with a list of things I think may be going on:
One of the Turbo Control actuator vacuum lines is leaking, causing it to not fully transition
The Turbo Control actuator is seized
One of the two Turbo Control solenoids is stuck open or closed
The vacuum or pressure chamber is leaking
One of the vacuum or pressure chamber check valves has failed or is installed backwards (they are Dale's valves and I believe they are all installed correctly)
The wastegate actuator rod is improperly adjusted (I shortened it to the point where it didn't want to easily shorten anymore before installing the new turbos)
The Charge Control butterfly is gunked up/not opening properly (stuck solenoid?)
The CRV or ABV is leaking/not closing all the way
Some other random vacuum line is plumbed incorrectly (always a possibility but I am VERY careful about vacuum routing)
The ACV check valve is not installed? -- I don't know what affect this might have but I don't recall installing it last time the ACV was off (does it just stick into the inside of the UIM and stay in place when the ACV is off?)
I'm going to pull the UIM off again shortly and test all of the cases above, but I wanted to post here to see if anybody had any other ideas or suggestions.
As always, much appreciate the knowledge and help here!
I dont have any experience tuning sequential operation with PFC controlling WG and Pre Contr solenoids, but I do have experience with Hallman Pro RX MBC on instead of WG and Pre Contr solenoids and I will tell you what it sounds like to me.
1) Wastegate is being pushed and held open by exhaust manifold pressure and unable to reach desired 20psi.
Solution, add preload WG actuator an/or decrease exhaust and/or intake restrictions.
2) You dont seem to have precontrol spinning the 2nd turbo up while on 1st turbo.
This is probably because your primary turbo boost level is being able to be attained 100% by WG. I mean, actually desired boost isnt even being met.
The WG exhaust flap and Pre Contr exhaust flap have to both be working together to keep 1st turbo on target boost for proper transition. If just the WG can control boost, there is no exhaust flow for Pre Contr function (spinning 2nd turbo up before transition).
3) Low post transition boost. See # 1) WG being pushed open.
Check the preload on WG actuator (and might as well set Pre Contr actuator by the book while you are under there with the lower heat shield off).
Get your sequential operation working before you go trying to raise the boost all the way to 20psi.
Try 10psi first since that is what the factory hardware is sized for and get sequential operation working.
Once you can get steady 10psi sequential operation try raising it to 14psi and get it running steady through transition at 14psi.
Then you can try higher, but what you will find is that the stock sequential hardware (actuators, exhaust housing and manifild design) are all sized for 10psi and you might have to compromise for higher boost.
Usually this means a lower target boost for steady sequential transition and then let boost creep with 2nd turbo going to allow higher boost after transition.
The fact that you dont already have boost creep on 2nd turbo indicates to me you may have boost leaks or restrictive intake and/or exhaust.
I dont have any experience tuning sequential operation with PFC controlling WG and Pre Contr solenoids, but I do have experience with Hallman Pro RX MBC on instead of WG and Pre Contr solenoids and I will tell you what it sounds like to me.
1) Wastegate is being pushed and held open by exhaust manifold pressure and unable to reach desired 20psi.
Solution, add preload WG actuator an/or decrease exhaust and/or intake restrictions.
Preload would be added by shortening the rod, correct? I did shorten it a bit before installation, just enough to where the nut stopped moving freely without much resistance. Maybe I need to tighten it a bit past the point of resistance?
Originally Posted by BLUE TII
2) You dont seem to have precontrol spinning the 2nd turbo up while on 1st turbo.
This is probably because your primary turbo boost level is being able to be attained 100% by WG. I mean, actually desired boost isnt even being met.
The WG exhaust flap and Pre Contr exhaust flap have to both be working together to keep 1st turbo on target boost for proper transition. If just the WG can control boost, there is no exhaust flow for Pre Contr function (spinning 2nd turbo up before transition).
That's an interesting idea. So you're saying that until target boost is met, the WG stays open, which doesn't create any exhaust pressure to be diverted to the precontrol? You have to hit a point of restriction via the WG closing at target boost on primary before the precontrol starts to work?
Originally Posted by BLUE TII
3) Low post transition boost. See # 1) WG being pushed open.
Check the preload on WG actuator (and might as well set Pre Contr actuator by the book while you are under there with the lower heat shield off).
This again makes me wonder if the CRV is leaking, and some of the air from the primary is getting past the charge control butterfly and out the CRV, and then when the butterfly actually opens at transition tons of pressure is getting dumped through the CRV.
Originally Posted by BLUE TII
Get your sequential operation working before you go trying to raise the boost all the way to 20psi.
Try 10psi first since that is what the factory hardware is sized for and get sequential operation working.
I will try a target of 10psi -- maybe that will prove #2 correct at least in terms of why pre-spool doesn't appear to be working correctly.
Originally Posted by BLUE TII
Once you can get steady 10psi sequential operation try raising it to 14psi and get it running steady through transition at 14psi.
Then you can try higher, but what you will find is that the stock sequential hardware (actuators, exhaust housing and manifild design) are all sized for 10psi and you might have to compromise for higher boost.
Usually this means a lower target boost for steady sequential transition and then let boost creep with 2nd turbo going to allow higher boost after transition.
The fact that you dont already have boost creep on 2nd turbo indicates to me you may have boost leaks or restrictive intake and/or exhaust.
BNR uses heavier springs in the actuators (they say 3lb over stock, so 11lb?). He also ports the wastegate to 30mm.
For the record the intake consists of Autoexe + SuperU-style IC, and consists of DP, Bonez cat, and RB dual tip.
Just logged a few pulls @ 10psi target with varying secondary duty cycles. It looks like, and feels like, increased secondary duty cycle is helping the transition to not dip quite so much. However there is still clearly an issue building boost after transition.
Primary builds to about 10.6psi, then drops to about 2.8psi at transition, then builds to about 7psi by 6,300rpms.
It's hard to tell by comparing the graphs because the timescaling is a little different between each, but with a higher secondary duty cycle the transition definitely feels quicker and smoother. So the secondary turbo is prespooling at least somewhat. Is this was only a wastegate preload misadjustment, I would expect the primary turbo to be able to keep up at least a little better by 6300.
If I'm not mistaken, the wastegate can bleed exhaust to bypass both the primary and the secondary turbines. In other words, a wastegate problem should affect the primary boost as well. Try changing the wastegate duty cycle to 30%, and I suspect you'll see low boost when only the primary turbo is operating.
Low boost on the secondary makes me suspect either the Charge Control Valve, Charge Relief Valve, or their related plumbing /wiring/etc. I don't remember how either of those would act if their vacuum solenoid control lines were disconnected, but I think it's worth looking into.
I'm assuming you successfully tracked down all the boost leaks per your post. What's the status of your solenoid valves? Have you replaced them all? You really shouldn't have original solenoid valves. Brand new OEM ones basically eliminate a failure point. As I mentioned in a dedicated thread, the turbo solenoids (charge control, turbo control, charge relief) should be treated as wear items.
The secondary turbo builds boost before transition by the precontrol valve being open. So in the process of controlling primary boost, the secondary turbo spools. It looks like in the first run you posted, both precontrol and wastegate are completely shut. Precontrol is shut because the boost control system is trying to get as much exhaust flow to the primary turbo as it can. There just isn't enough "turbine power" to build boost. This is likely the result of restriction on the intake and/or exhaust side. If the primary turbo spooled better, it would crack the precontrol open earlier and start prespooling the secondary turbo.
I agree that you are asking too much of the turbos with so much restriction. You didn't post a current mod list but previous post says Racing Beat exhaust and cat (which I don't blame you for, I myself like that setup). If you like the "liveability" and legality of the quieter exhaust and cleaner smell, you will have to accept lower power. Exhaust restriction's biggest impact is on peak power. Backpressure increases exponentially with rpm. That's why a 2.3 liter Ecoboost Mustang makes something like 40 horsepower less in Europe than in the US for recent models. In Europe a gasoline particulate filter is required to meet Euro 6c emission standards. The mid range torque is basically the same though, because restrictive exhaust matter more at higher rpm and for spool. Restriction tends to result in a torquey mid range powerband (at least if you don't have to worry about turbo transition).
That being said, another thing you can try is to raise your turbo transition RPM. Increase it by say 500 or 1000rpm rpm. The engine will have more exhaust to spool the secondary turbo.
I agree that getting things dialed in at 10-12 psi is a good idea to start with. Get your transition ironed out then go for the gold.
Is your exhaust loud enough that you can hear the turbo control door open up?
You can also, to verify things, get a long piece of vacuum line and a brass T. Tee your boost controller into the control lines for various items - the vacuum and boost lines to the TCA, the CCV, etc. Make sure they are getting the right vacuum/boost when they should be. Also check for dumb stuff - bad check valves, pressure tank holds pressure, etc.
What's the status of your solenoid valves? Have you replaced them all?
I replaced all the solenoids last year. I think I'll put a 10psi regulator on the pressure tank just to be safe. I've heard of people here doing that, and I know Chris Ott likes to do it for customers.
Originally Posted by arghx
The secondary turbo builds boost before transition by the precontrol valve being open. So in the process of controlling primary boost, the secondary turbo spools. It looks like in the first run you posted, both precontrol and wastegate are completely shut. Precontrol is shut because the boost control system is trying to get as much exhaust flow to the primary turbo as it can. There just isn't enough "turbine power" to build boost. This is likely the result of restriction on the intake and/or exhaust side. If the primary turbo spooled better, it would crack the precontrol open earlier and start prespooling the secondary turbo.
Isn't this hypothesis disproved in post #4, where both primary&secondary boost is limited to 10 psi? You can see that the WG starts to open when 10 psi is met on the primary, and that the secondary does indeed prespool. The is the same with stock twins/boost level only difference being the +3lbs WG spring.
But even in the 10psi case, you see that after transition the system cannot build back to 10 psi, which makes no sense given that the primary alone was just able to build 10.
Originally Posted by DaleClark
Is your exhaust loud enough that you can hear the turbo control door open up?
Unfortunately I cannot.
Originally Posted by DaleClark
You can also, to verify things, get a long piece of vacuum line and a brass T. Tee your boost controller into the control lines for various items - the vacuum and boost lines to the TCA, the CCV, etc. Make sure they are getting the right vacuum/boost when they should be. Also check for dumb stuff - bad check valves, pressure tank holds pressure, etc.
You mean "tee your boost gauge" right? I read this suggestion in another one of your posts and LOVE the idea. Waiting for a few 5/32 brass tees to show up in the mail... I think @alexdimen said he just leaves them in his system with a cap on the 3rd port.. lol these cars...
Just got off the phone with Brian @ BNR and his suggestions overlap with several of my bullet points from post #1 -- mainly he suspects the Turbo Control actuator is not working properly. But more importantly he didn't think I should have problems building 18-20lbs on my setup when working correctly.
I'm just going to have to tear everything down again and check for boost leaks, check the CRV/ABV, turbo related solenoids, vacuum routing, pressure+vacuum tanks....
Before you tear deep into things, start with T'ing in and checking things out. This can be done without much take apart.
BTW Wal-Mart used to sell really nice barbed brass T's in the aquarium section that fit great and worked like a champ for 99 cents. Now it's all plastic. Sucks because that was my easy go-to if you needed a tee.
I replaced all the solenoids last year. I think I'll put a 10psi regulator on the pressure tank just to be safe. I've heard of people here doing that, and I know Chris Ott likes to do it for customers.
Isn't this hypothesis disproved in post #4, where both primary&secondary boost is limited to 10 psi? You can see that the WG starts to open when 10 psi is met on the primary, and that the secondary does indeed prespool. The is the same with stock twins/boost level only difference being the +3lbs WG spring.
But even in the 10psi case, you see that after transition the system cannot build back to 10 psi, which makes no sense given that the primary alone was just able to build 10.
Unfortunately I cannot.
You mean "tee your boost gauge" right? I read this suggestion in another one of your posts and LOVE the idea. Waiting for a few 5/32 brass tees to show up in the mail... I think @alexdimen said he just leaves them in his system with a cap on the 3rd port.. lol these cars...
The ironic thing is my original problem was a collapsing intake extension I had made imitating the cheap bastard snorkel. Boost has been rock solid for years so I haven't had to use them since but it is nice to have the option and I learned a lot about how the system operates in the process.
Isn't this hypothesis disproved in post #4, where both primary&secondary boost is limited to 10 psi? You can see that the WG starts to open when 10 psi is met on the primary, and that the secondary does indeed prespool.
The is the same with stock twins/boost level only difference being the +3lbs WG spring.
But even in the 10psi case, you see that after transition the system cannot build back to 10 psi, which makes no sense given that the primary alone was just able to build 10.
So here is where it gets difficult to understand what's going on because you don't have two very useful sets of instrumentation: string potentiometer (basically position sensors that can be used on precontrol/wastegate and turbo control valve), and turbo speed sensors. That's how I troubleshoot these things in my day job. So there's a lot of guess work here. We know the Wastegate duty cycle, but we do not know the position of the valve. In post 4, the last image, the wastegate duty drops very slightly at transition. Is the valve even opening? We don't know, because we don't know the valve position and we don't know the turbo speed.
The fact that you can't "hear" the turbo transition in the exhaust tells me there's something up OR you just don't have a trained ear for it. I can hear the transition in the exhaust even on my basically stock FD (stock except RB catback).
Putting a T in there to read pressures helps.
If you really want to diagnose what the valves are doing, get a string potentiometer. This one is similar to what we use at work although that model probably has too small of a string:
Basically feed it 5 volts, attach it to the precontrol/wastegate/turbo control (you can sort of tie it on there as a temporary test set up, don't want to have this installed long term), and voltage will change as the valve moves. If it's not moving, or moving too much, there's something not adjusted/tuned right (either physically, or pneumatically). That's assuming you can fit it in there. Lab-grade turbo speed sensors would be a budgetary and fitment/packaging no-go for road testing I think.
Just a note about #7 on your list of things possibly wrong, If you stand on the passenger side, look down, grab the throttle and give it a rip you'll see the charge control valve actuate If you don't, you know it's sticking.
I wish I could help more, I too am running these turbos, but letting the haltech do the controlling. I am getting a good sequential pattern 10-8-10 out of it, working on different issues (compression ) at the moment...
Your wastegate shouldn't be opening on primary operation, just the precontrol. The wastegate solenoid should be 100% duty so it doesn't open and the PC is some duty less than 100%.
I think a simpler way to check the secondary transition system is to bench test everything on the secondary side with a mityvac (or test in the car if you can access). Mainly the TCA (pressure and vac) and the charge control actuator. Then tee into those lines and see if they're being sent a vac or pressure signal when they should. You will have both pieces of the puzzle at that point - do those components function and are they being sent pressure or vac to operate.
As far as the pressure regulator that's a great idea. You might also want to look into a solution proposed by speedoflight which stops the tca solenoid from sticking. I have used it with great results... https://www.rx7club.com/3rd-generati...ctive-1120259/
FWIW the only solenoid i have ever replaced was the TCA vacuum attached to the uim. The rest of my solenoids are antiques with 160k miles on them haha. No problems at 13 psi.
I tried switching the WG & precontrol electrical connectors today and surprisingly had very similar results.
Although I thoroughly tested for pressure leaks a few weeks ago and found/fixed two (a leaking INTERCOOLER from FD Motorsports in Sydney / Sasha Apostolov / "T H E D O C T O R" on here -- luckily fixed with JB Weld..., and a bad PCV check valve) I still feel like I'm I hearing a leak...kind of a whistle noise that comes on shortly after throttle, and dies off on decel -- but it's difficult to tell since I don't know if that's just how BNRs themselves sound.
At any rate, this weekend it's UIM off and everything tested... I'll plan to install all the T's for the boost gauge test, too.
So I was driving today, trying to diagnose a different issue (of course), and at one point I pulled over, turned on MapRef in the Datalogtc, and got back to the road. Low and behold, all of a sudden my < 4500rpm exhaust note had changed considerably to a much louder and more drone-y sound, and I could suddenly hit 20psi on the top-end (!)
More testing showed that < 4500rpms seemed to want to spool more slowly, and that the transition was still really bad.
In the last couple days I had pretty much convinced myself that the problem I've been having is that the TCA rod was physically stuck or that the actuator c-clip had come off. When I park the car, facing downhill, sometimes after killing l the engine I hear a kind of rusty-door closing sound. So I thought maybe that was the secondary turbo control door sliding open once the idle exhaust pressure had stopped, and that during running the exhaust pressure was holding it closed, hence the boost face-plant after transition.
Now I'm thinking that the TCA actuator rod is is stuck open, or at least mostly open. I also see now what Dale had mentioned about hearing the secondary control door open. It's been a while since this car ran right (6 months) that I forgot all about that. I can now in fact hear that "deep drone" exhaust note suddenly get louder at transition, but it's also present to a lesser degree under transition as well (it was not present at all until today). I think what may be happening, since I do still get a transition dip, and an exhaust note change, is that the previously-stuck TCA is now moving, but not in its full range, and perhaps moving slowly at that (bad press. or vac. side TCA solenoid, leaking pressure or vac tank?) I actually tested that the system was indeed holding pressure and vac a few days ago, as well as did press. and vac. leakdown tests on both sides of the TCA, which both held fine.
More excitingly, I was able to hit 22.5psi on secondary !
This was with target boost set to 1.6kg/mm2 (22.8psi). I actually swear it hit 23+ at one point, but I seem to have lost that log . I'll try for a higher target later, but need to re-scale my map first (a good problem to have!).
Here is another run, starting before transition, showing per-transition peak boost at about 20psi and post-transition at about 21.2psi. This was done with a target boost of 1.4kg/cm2 (19.9psi). Note the huge drop in pressure at transition, and that the pre-control is working, and the wastegate is bleeding exhaust a after transition.
And one more run where I tried a target of 1.1kg/cm2 (15.6psi) and saw again that the target was being met on primary and that exhaust was being bled off for pre-control.
I will need to try more with lower boost, 10-12psi to see if that helps transition, but again I feel like the TCA is probably sticking and/or moving slowly.
For references, my relevant mods are:
AutoExe intake, Y-pipe, U-type intercooler (similar to Knight Sports), IGN-1A, 550/2200, RP pump+bulkhead wiring+10ga ground+IGN switch bypass+1.5Ohm low-speed resistor, stock ports, DP, Bonez high-flow cat, and RB dual tip. Also running 250cc/min of water.
My AFRs are pretty close to target at high boost, and I still get a little ignition breakup at the top on high-gear pulls, so not sure what that is about.
Transition issues aside, 20-22 psi twins on a pretty tame build... my face looks like my profile picture right now. Need new tires soon.
The turbo control door is normally closed with nothing acting on it. It opens when vacuum is applied to one side of the diaphragm and boost on the other, that pulls against the spring that holds it shut.
You should be able to easily get to it under the car and push the rod in with your finger. Rod out = door closed, rod pushed into actuator = door open.
The door should be tight against the manifold and not rattling. If you remove the rod from the peg that goes to the door, it should overlap by half of the hole in the rod - in other words, you should just BARELY have to pull the rod onto the peg. There is an E-clip that keeps the rod in place.
If you disconnect the hoses on the actuator, you can push the rod in and put your finger on either hole - the rod should move but stop, and then continue when you remove your finger. This should hold true for both vacuum and boost sides. If the rod goes all the way back out with your finger on the hole you've got a torn diaphragm.
I can’t get the car off the ground where I live so unfortunately all the fun things have to wait for the weekend when I can take it back to the folks’s place. But what you describe about disconnecting the lines and moving it manually is what I plan to do first thing. I suspect it’s going to be gritty ans difficult to move. If that’s the case, hopefully some Blaster followed by lithium grease and manually moving it around a bit will free it up. I have an ebay extra on hand, too. Those actuators are getting hard to find... I've seen some thready with people speculating about using aftermarket push/pull wastegate actuators in it's place but don't know if anybody has tried that yet.
To your comment about adjustment, check out the sound from this video I took yesterday. Could that be a turbo control door loosely
closed/rattling against the manifold? Its hard to tell in the video but it sounds like something rattling from inside the exhaust.
02-20-21, 02:29 AM
) at the moment...
. I'll try for a higher target later, but need to re-scale my map first (a good problem to have!).
