Ladies and gentleman....
I've been driving my new set-up for about two weeks now. I'd never owned a sequential car, so I decided to go with a "premium OEM" concept when modifying my car over the last couple years. I sold an Apexi RX6 turbo I had that was running with a junk manifold that always seemed to leak. Once the car was hot the leak would seal, but it irked me so I parted with it. I picked up a set of BNR III's from ebay. I rewired my Rywire harness to include sequential solenoid control and connected it to a Fabco-Air solenoid rack. I upgraded from a PFC to the more recent Modular Adaptronic ECU because it's 2020. Plus, I like having the wide-band wired directly to the ECU with the internal lambda module. I took it slow and was very meticulous. Shortly after rebuild I drove the car from Minnesota to Virginia on a rich and power conservative tune. No breaks along the way and I could plainly observe proper sequential operation. Id get 8lbs, drop to 6 at transition, and then back to 8lbs. At this stage, I recognize my turbos are working harder than my boost rating and I associate it with my intentionally low boost pressure and the ease of which small turbos spool. I am now at a stage where I am turning up the boost incrementally... or... I should say, I am attempting. I'm realizing that building more than 6-8lbs of boost is far too difficult. I also picked up a another 7 that has a stock seq system and that system builds faster... so the little anxious voice in the back of my head that suggested "boost leak" or "waste gate leak" is beginning to sound more legitimate. I search the club and I find many have had the same issue, specifically, with BNR's. In all my research about these turbos, I never came across this complaint before... looks like Aaron Cake had the exact same problem, as did a few others... Supposedly, the BNR twins ship with a 6lb spring. Pretty retarded, but the wastegate is a dual port.... so, shouldn't native spring pressure be negated by electronic boost control and proper plumbing to both ports? Folks are resorting to "helper springs," which I want to avoid... RotaryEvolution mentions swapping the WG with a universal unit from Kinugawa. Not an awful solution, but it's more money and messing around. The fact of the matter is, the WG on the twins is a dual port. If I'm generating 8lbs of boost then the spring pressure should help the gate remain closed with 14lbs of force. I don't know how many pounds of force its taking to generate the 8lbs boost. Ideally its 8, but machines are never so efficient. lets say 10lbs of exh pressure is pressing against the WG... I still have 40% more force holding it closed... So, what am I missing?

Fuel system
Prim 1000's Sec 2200's. CJ rails with dampener. FPR set to 43.

Breathing
Blitz Carbon Power intake, BNR III, Custom SMIC w/ 10x12x3in Spearco core.
Petit DP, resonated mid, and Racing Beat Exhaust.

Control
Adaptronic modular PnP.
Fabco-Air solenoid rack (six, not four, solenoids. To include the WG(I) and PC(J))
All vacuum hoses are silicone and I retained the 'pills.'

Ignition:
AEM Igna1 coil kit.

Any help brain storming would be great.

 

I think you are misunderstanding how boost control works a little bit.

First off, the OEM wastegate actuators are rated at 7psi. If you hook a vacuum line straight to them you will run 7psi of boost. Stock, there are the 2 wastegate and precotnrol solenoids that up the boost (with the pills) to 10psi.

BNR uses the stock wastegate actuators, nothing fancy there.

What are you trying to use to control boost? Do you have boost control in the ECU? What solenoid is plumbed into the wastegate for boost control?

Right now it doesn't sound like you have a boost leak and the sequential system is working more or less properly if you are getting 8psi, then short dip to 6 then 8 to redline.

You just need some proper boost control.

Also do you have a stock main cat or mid pipe or something else? You didn't say in the list of mods.

Dale

 

WG control (I) is wired into the harness. The ECU is controlling the solenoid. The solenoid is a Fabco-Air type like the ones found in the AzeKnight solenoid rack.

Resonated midpipe.

 

If you call Brian he'll tell you exactly what the wastegate actuator is rated for. He's a straight forward dude to deal with.

 

What are you actually using for boost control? The fabco solenoid rack (i assume that's what you're referring to), like the ones azeknightz puts together, control where the pressure/vacuum go to support the sequential operation of the turbos, but does not control how much boost you make. That's handled by a separate solenoid (wastegate control valve) in the stock system. If you're using a Modular ECU, you can just use a MAC valve... this basically bleeds off boost so less boost makes it to the wastegate actuator so it stays closed longer. https://www.rx7club.com/3rd-generati...l-help-840313/

EDIT: Opened this earlier before there were replies.. you've answered what I was asking in your later post.

 

I didn't have the factory wastegate and turbo precontrol solenoids. I sold my mac valve with a kit of parts. I have extra Fabco-Air solenoids so I wired two of them up as my wastegate and turbo precontrol solenoids.
My boost control is plumbed exactly as illustrated in the FSM diagrams.

 

Hmmm... I may have figured it out. Looking at the duty cycle map in Eugene (the software for the Adaptronic), it appears my WG may be programmed to function opposite as intended. I.E. duty cycle is 100% (open) when it should be zero...

 

Figure it out? It's been awhile but I believe the boost control solenoid control in eugene, the higher it is, the more boost you should be running. Are you able to toggle the solenoid manually in eugene and check that it is operating as expected?

 

It's still not clear how you have your boost control plumbed. Draw us a diagram of the pre control and wastegates and the solenoids controlling them. Even though they are two port actuators they don't work like a normal two port actuator. The ports are on the same side of the diaphragm. They are functionally single port actuators, which is why when using a 3 port boost control solenoid you cap off one of the ports.

You really should have two solenoids, and they should be PWM capable solenoids, and you need to have the frequency set right. Are the ones you using meant for PWM control or just ON/OFF ? Did you notice the stock vacuum rack solenoids are different than the stock boost control ones?

What is your sequential staging point in terms of ON and OFF ?
Post screenshots of your precontrol and wastegate PWM duty maps. You should have separate maps, and they need to be adjusted according to the staging rpm.

 

also please read about sequential turbo control systems. since you aren't using a Power FC you need to have a pretty detailed understanding of how this works. The Power FC basically just handles all this stuff in the background, controlling two different boost control solenoids, and throttle based hysteresis control of staging. Sequential turbos on a non Power FC standalone is basically turbocharging on hard mode.

Article on the Rx-7 sequential turbo system:

https://www.rx7club.com/3rd-generati...tified-841821/

Article on the Rx-7 system vs the Mark IV Supra system, which controls turbos very differently:

https://www.rx7club.com/3rd-generati...turbos-960727/

 

Wastegate control : Using the stock actuator. One port is connected to the nearby compressor outlet. The other port is connected to the 'in' of a two-way solenoid (I). The 'out' of the two-way solenoid (I) is connected to the intake tract before the turbos. The solenoid is normally closed.

Turbo Precontrol: Stock actuator. One port is connected to the nearby compressor outlet. The other port is connected to the 'in' of a two-way solenoid (J). The 'out' of the two-way solenoid (J) is connected to the intake tract before the turbos. The solenoid is normally closed.

Turbo Control: Stock actuator. There is a port on the end (A) and a port on the side (B). The turbo control actuator is controlled by both pressure and vacuum utilizing a pair of two-way solenoids. The pair of solenoids is know as (E) and share the same output on the ECU. Port (A) is connected to 1/2 two-way solenoid (E), which is connected to the vacuum tank. Port (B) is connected to 2/2 two-way solenoid (E), which is connected to the pressure tank.


I have two solenoids, but from what I can tell they are not PWM capable. They are on/off type. I did notice the stock solenoids were different, I didn't know why exactly, and I didn't own a set. I used what I had on the shelf. So, this could be a source of the problem.

AFAIK, the Adaptronic ECU doesn't control transition this way. You don't get a duty cycle map for the precontrol solenoid. You input the desired RPM and a designated number of seconds from which the ECU will begin the transition. The point transition begins is interpolated based on rate of change in TPS% and engine speed.


I recognize a transition point of 4000 is lower than OEM. The settings were being experimented with in order to smooth out this sensation of modulation during transition, which may be a result of the solenoid type I'm got wired in. Currently limited to 9.5lbs boost.

 

That appears to be the case, which causes confusion. You would think that a normally closed solenoid that is triggered by ground signal at the ECU would be increasing boost with a lower duty cycle and decreasing boost with a higher duty cycle. Idk. I'm still learning, which is why I'm here asking questions, lol.

I'm pretty sure I can operate it manually. I plan to fiddle with it and test to verify what the solenoids are actually doing.

 

Well, that's not going to work... MAC valves are like $40 on Amazon last time I checked. Get a couple of the correct type of solenoids plumbed in and I bet your issues disappear.

 

If you want to use two way valves, just get a set of used stock precontrol and wastegate solenoids. They don't typically fail. If you want 3 way valves, use the MAC solenoids that are common on many aftermarket boost control systems. With either type of solenoid , higher duty reduces pressure in the actuator diaphragm (bleeds/vents pressure). That keeps the actuator closed and should raise boost.

I don't have the instructions for the Eugene software, but from that screenshot, it looks like it uses maybe the same duty cycle map to control both solenoids?

Can you post a datalog of you doing a WOT pull in some kind of Excel compatible format, and make sure to include rpm, boost, pre control and wasteg gate duty, and TPS % ? It will make more sense if we can see that. Either way you need to get the right kind of solenoids.

 

*Havent forgotten, just been busy. I’ll get the logs for you.

 

PM'd

 

Ok, now that I've received this log I think I understand what's going on here. It keeps the pre control OPEN (duty cycle 0, limiting boost) in its normal state, unless it enters "pre control mode." For whatever reason the pre control mode is staged by time, which i guess is back calculated from when it thinks it will hit the other criteria. So what you see here is the pre control is open (duty is 0, lower number is lower boost) before transition and before "pre control" mode. Then it attempts to control the precontrol valve for a second or two, then transition mode flips and it sets precontrol back to 0 which opens the precontrol valve to flow into the turbos.

Here's what I would try next. You need to do more WOT runs, and you need to do them at lower rpm, like 1500 rpm. First you need to get some PWM solenoids and install them to control precontrol and wastegate. Try 3 port solenoids for both. Then here's what you should do:

With the same settings, do a WOT pull starting at 1500rpm (TPS should be 100% by 2000rpm), in say 3rd gear if you can do it safely (I'm assuming you are tuned safely AFR/spark wise, if not, ease into it and don't do anything risky/stupid), otherwise 2nd gear.

Do another WOT pull with the boost limit calibrated out, so set that from 2psi gauge to like -8 or whatever. Get rid of that lower limit for staging so it activates the precontrol valve sooner.
Do another WOT pull with boost limit calibrated out, and precontrol time lengthened a lot, to like 20 seconds or something. Basically ditch that timer as it's not clear why you would want to run around with an open precontrol valve during low rpm acceleration.
Do another WOT pull with the duty cycle set the same for all TPS values (all cells in a column the same).

Post the results here. If you're lucky you can tweak the duty cycle map and precontrol will be useful if you lengthen the time to whatever it needs to be. In what I suggested above, you are effectively having it always in precontrol mode to get an understanding of how it would behave. You may end up adjusting those boost and precontrol timer limits to a number where it is actually doing something. Worst case scenario, you will have to ditch the existing sequential staging logic if you can find other outputs that will do the job. Use the boost control logic to run the wastegate and precontrol together, or maybe do something separate with the precontrol. Can the ECU just do an open loop PWM map that you could do for precontrol? Then use a nitrous output logic to control the turbo/charge control valve. That's only if you can't get the existing logic to work though.

When you're tuning a system that has so many degrees of freedom and domains like TPS, timer, rpm, duty cycle, you need to dumb down the control first. You have to try and turn off the sophisticated stuff and just get basic functionality, and then tweak it for better driveability/failsafe/etc later.

 

Another trick you can think about doing later, and this is somewhat similar to tuning a variable valve timing system on a piston engine, is to force it into non sequential mode (set transition to 1000rpm or whatever). Then tune the duty cycle to achieve the desired boost. Then force it into primary only turbo mode (transition is 8000rpm or whatever) and do a pull up to say 4500 rpm, and have the wastegate output control the precontrol. Do pulls and measure what duty cycle it takes to achieve the boost you want. Once you've collected all that data you have to blend it together to make a turbo transition work.