Hallo there. I just need some of your help cause I don't have much knowledge on the details of how a seq. setup works. I have an FD with BNR stage 3s, Power FC, HKS front-stock mount I/C, 3inch exhaust from start to finish (no cat.), MSD 10A, etc.

The problem I have is that I can't seem to be able to regulate boost.

When I finally got around to tuning the car (with the "ring" on the wastegate actuator in the position I got it out from the box) the primary turbo goes up to 11 psi and when the secondary turbo kicks in it wants to go up to 12 or even to 14psi.
The thing is I have an old engine (hi mileage-no porting) and I don't want to run this kind of boost at the moment. I would prefer to run it at about 9-10psi.The car seems to be able to make good hp numbers even with this amount of boost.
So my mechanic turned both the actuators fooly loose and now the car's not boosting at all until 4-4,5k RPM (at 4K the reading of boost on the PFC commander reaches "Zero" then boost gradually-sloowly starts to build up until it reaches about 9-10psi but at high rpm)
If he tries to tighten the actuators just a little bit again we go to the pattern that I mentioned earlier. He also tried all sorts of combinations between the two actuators and still nothing. He said the spring on the actuators is very hard that's why it is so difficult to run stock boost.
I haven't put a restrictor before the "pressure chamber" (as many people with BNRs do) but I think that doesn't affect the two solenoids that control the actuators. Is it possible that some other solenoids are responsible for this pattern? All the solenoids were checked prior to the installation of the BNR's a few months ago. Maybe some of them don't work as they should?
I don't have a boost controller-will that help at all? (personaly I don't think so)

Bare in mind that the turbos have only 1000miles on them and I see a couple of drops of oil on the wastegate actuators on the part where the "rods" get connected to the black "puffs". Also a drop of oil on each "intake" part of the turbos.

 

While adjusting the rods is part of setting boost, I would have begun by adjusting my boost controller.

The PFC with stock solenoids has some adjustment and may work fine for handling BNR's, but I would consider the aftermarket boost control solenoid option for the PFC or some other boost control setup.

The pressure regulator is needed when running above 10psi, since pressure above 10psi can cause some of the other solenoids to stick. That should not be of concern until you are intentionally running your boost higher.

Dave

 

You need to begin by collecting a lot of data. Do you have a Datalogit? You need to see how different wastegate preload adjustments affect the boost curve, both with and without the solenoids plugged in.

What I would do is this: Unplug the two solenoids so that there is an uninterrupted pressure signal to both precontrol and wastegate. Do a 3rd gear pull, logging "Advance" in the Datalogit as well as Sensor/SW TCN (turbo control solenoids) and Sensor/SW CCN (charge control solenoids). Check the PIM curve ("Advance PIM" , basically boost in terms of absolute pressure) to see what's happening as the secondary turbo comes online. Repeat with the two boost control solenoids plugged in. Try different amounts of tension/preload in the rod. Post the logs here.

The whole goal is to find an appropriate combination of solenoid duty cycles and actuator tension to achieve your target boost levels. Hopefully Sandro will get in on this thread, he's done a lot of extensive logging/testing but with stock turbos and an unported wastegate.

 

An easy way to control boost is to re-install a cat (stock or high flow). It can be difficult to control boost spike and more importantly boost creep on a full open exhaust.

An electronic boost controller sometimes helps as well as the stock boost control solenoids often don't respond quickly enough on a car with an unrestricted exhaust.

 

I don't have much to add but to arghx comments and recommendations.

You need to start testing with no active boost control first, trying to understand how much is due to rod regulation and how much is due to boost creep. Boost control through solenoids valves, only can make boost higher - not lower.

You may want to look at my tests https://www.rx7club.com/3rd-generation-specific-1993-2002-16/testing-mac-vs-oe-solenoid-valves-other-boost-control-strategies-874031/ The first pull is with no control system (solenoids unplugged). You can clearly see the boost creep.

You can avoid boost creep by restricting the exhaust, as generally suggested, in which case you loose some of the benefits of an open exhaust (quicker turbo spoolup and more energy to the turbine). Or you can stop boost creep the way I do - by retarding ignition advance in the rows (PIM) you don't want to hit. Quite unorthodox but very effective. I started doing this for safety. But it works so well that my current boost control strategy actively use it.

You realize you really need a Datalogit, right?

- Sandro

 

The whole thing sounds like a combination of improperly tensioned actuator and poor tuning with the EBC. I am assuming the BNR's have an adjustable nut like this pic I found off goggle? I am not familiar with every detail of the BNR Stage 3's, so enlighten me if necessary.



Any boost creep due to insufficient wastegate flow may be due to the pretension in the wastegate actuator. The BNR turbos have ported wastegates passageways. If the arm tension is set properly, there should be enough flow capability especially since this isn't even a ported engine we're talking about here.

If the actuator is too long (too much preload), the wastegate won't open fully. If the actuator is too short (too little preload), it may be open partially. Single turbo BNR setups (FC BNR turbo, Rx-8 BNR turbo) have to deal with this as well. Every car is different so some experimentation may be required.

The preload needs to be "close enough" first, without any boost control. That's why I suggested that the boost controller be disconnected electrically or removed from the plumbing altogether.

 

your getting boost creep because there is no back pressure, even tho the wastegate was ported it still flows way to much for the wg to handle.... a boost controller wont help i have mine on the lowest setting and it will creep to about 14 if i go wot in 4th, i never tried as i release it when i see it get over 11-12, what i was tuned at before... now im going to be getting tuned for higher psi so the creep to 14-15psi wont matter... but I had the stock cat in the car for about 5 months and the creep stopped. but took it out and put the mid back in because im getting tuned. so if you want it gone, you need to create some back pressure

 

thanx for everyone's replies
argx what you show in the picture is about the same in the BNR's. I will convey you advice to my mechanic.
As for putting back the cat it is a practical idea but at least here in Greece we had many cars with aftermarket cats been "sTuffed" or destroyed from heat. Even a couple of cars with Knightsports cats(!) and only 300-320hp to the wheels had their cats destroyed. I had an aftermarket Magnaflow-type which worked pretty well with the stock turbos but failed in more powerfull cars so I took it out-don't want to cause any damage to my BNR's.

Sandro the tuning of the car has been done with datalogit of course!

 

use the Datalogit to create logs of the boost curve with the boost controller disabled, while testing different wastegate pretension settings

 

Then you didn't do it right, I have ZERO creep with my BNR set-up, and I'm running a resonated midpipe and Pettit cat-back. I have a Hallman cockpit mounted manual boost controller and wouldn't use anything else, it's works great.

 

Mark, your BNRs are the old style with oem factory turbine wheels.... you basically have oem turbos with larger compressor wheels being the only difference.

The newer iteration have substantially larger turbine wheels (among other changes), so you cant compare apples to oranges.

 

As far as I know, boost creep is related to restriction in the wastegate and/or the manifold itself, I'm not sure the size of the turbine wheels has anything to do with it (assuming you're running the same boost range)....correct me if I'm wrong.

David Garfinkle really hogs out the stock manifold and wg, which is why it flows so well

 

Boost creep should not be an issue. I believe Bryan ports the wastegate when he makes a Stage III.

Dave

 

i got the bnr 3 and yes he does port the wastegate, but i still get creep with a dp, magnaflow mid and racing beat duel tip cat... it will go to 15+ psi if i am in a long enough gear. (4th/5th) 3rd goes up to about 12-13psi.. He needs to restrict the exhaust a little if he wants to get rid of the creep.

 

It has to do with the amount of flow and what the wastegate can regulate. If the wastegate is open 100% and it still cannot regulate the boost, there is nothing more it can do. Therefore, enlarging the wastegate to handle the increased flow or reducing the overall flow (i.e. less boost or more restriction in the intake or exhaust) is the only means to bring the boost under control.

Since the entire airflow system comes into play, there are a lot of variables which can determine whether someone will or will not experience boost creep; as well as whether simple porting will actually cure it.

Unless Bryan uses a different wastegate door, then there is only so much he can do. There are many reports of the stock wastegate size not being large enough and needing to port more thus requiring a different wastegate door. The quick fix for most is using the pre-control door since it's larger and not used for non-seq (which most BNR owners choose to do).

 

Take the manifold off and send it to Garfinkle, he'll take care of it. Putting exhaust restrictors in is the candy *** "solution". David uses an oversize, stainless steel door.

Let it breathe...let it RIP....tree huggers and global warming conspiracy theorists be gone!

 

I haven't looked at the BNR stage 3's. But I can tell you that improperly tensioned wastegate actuators will restrict the travel of the flapper.