I am having problems with boost and transitioning to the secondary turbo. I have had the same issue with a stock ECU and suspect a mechnical issue, but with the PFC and PFC-Connect logging I can now apply another level of analysis. I am, however, confused about the PFC’s wastegate response to the symptoms.

Run to run, symptoms vary a bit but these two logging segments are typical. Both runs were 3rd gear pulls up a 1:20 grade; Stock 99 RS; FC-Tweak default settings for a stock configuration; PFC-Connect logging.




Zone 1: is as expected – Wastegate and Pre-control both shut

Zone 2: Pre-control opens up. Boost never reaches target.

Zone 3: Transition. Wastegate falls to 64% as per PFC settings, stays there for about 0.3 seconds before compensating for the fact that the **** has dropped out of boost.

Zone 4: Wastegate slams shut and boost starts to build.

Zone5: At about 4kg/cm^2 the wastegate duty cycle starts up. Why? It is only just over halfway to target boost.

Next run: Boost Targets raised 0.1 Kg/cm^2:



Similar boost profile but a different Pre-control response through Zone 2.

Wastegate response through zone 4 was as expected given how far short of targets actual boost was, then around 6720 rpm it decides to start opening the wastegate. Why?

I know I have bigger problems than the PFC but is there any explanation to the PFC response?

 

Have you adjusted the wastegate actuator rod?

 

Good advice and definitely worth another look. https://robrobinette.com/boost_note.htm has a bit of advice for setting the pre-control actuator:This probably equally applies to the wastegate actuator as well. Maybe the wastegate actuator can handle a little more preload.

This is a re-appearance of a long running issue. It first appeared with the stock ECU about a year back. Typically, the first pull was OK then things went down hill as heat soak set in. After a lot of testing including testing the solenoids at temperature and the actuators, in desperation, I tried a dose of Penrite Cat & EGR Clean+ and the problem disappeared – at least as measured on my butt dyno and the stock 99RS boost gauge.

Since then, the car and I have had a 6-month layoff. On re-acquaintance I installed the PFC and the problem is back worse than ever. On gut feel the problem is something sticking.

And I still don’t understand the why the PFC responds the way it does.

 

You did not give a description of the mods done to your car or how it’s currently set up. Without this it’s hard to know what variables you’ve induced. Before you go down the rabbit hole, I would check that your cat isn’t clogged.


~ GW

 

I am running a stock 1999 JDM RS. Stock Cat, Stock Muffler.
I have had an endoscope in from both ends to check out the ceramic matrices. They are complete, no cracks and a nice dusted mid grey colour. Not a clogged cell to be seen. I have been running with the airpump, only disconnected it for the tuning runs.

 

So you’re running a totally stock car other than a Power Fc. Let me ask a few questions before I walk you thru the testing process. How are you recording boost pressure? Do you have a mechanical / electric boost gauge other than the map sensor is telling the ecu and the gauge on the cluster? Also, if you can, post your map and log file here and I can take a peek at it. Will need both .dat and .txt


~ GW

 

I have no other boost gauges other than the PFC and the electrical gauge which both run off the MAP sensor. I don't need a gauge to tell me that it is a bit sluggish on primary boost, dies on transition and never fully recovers.
The dat and TXT are attached. The segment in the first screen grab in the OP occurs around 780 seconds. If you are not using PFC-Connect, the size of the log file might be an issue but you should be able to manually extract the segment in question if you are using FC-Edit.
The MAP offset has been corrected to sea level. The runs were done at 1300 feet, so the air is 5% thinner and the turbos have to work a little harder to reach target.
As stated in the OP, I know that I have an issue that I am pretty sure is mechanical. The real question here, and the thing I'm not on top of is why is the PFC appears to be trying to open the wastegate while well sort of the target boost

 

maybe sticking solenoids? worth a test. I know nothing, just the random thought popped in my head...

 

I’m sure you can feel something. The map sensor reading for boost will be lower than “actual” if you have not calibrated it to your gauge.

I have the ability to see the log file for that size. I’m pretty familiar with all of Xavier’s stuff. Will take a peek and report back.


~ GW

 

I checked out the log you attached. All the settings are correct. The car is calling for pre control and wasegate correctly and all the electronic boost controls appear to be working correctly.

As you’re running in vacuum and rolled into the throttle, I see primary pressure building up to its target, pre-control varying its feedback to maintain until its blending. I do see it switching over from pre-control to wastegate when it reaches the designated rpm. I can see that when it transitions from primary operation to parallel, it falls flat on its face. It does try to claw its way back during parallel operation, but falls short.

Unfortunately, I cannot check to see if the ECU is calling for the charge control/charge relief switch since the file size is too large to open on FC edit and PC connect does not have an option to see those.


I’m relatively sure you have a mechanical issue. Since primary operation seems to work great, you need to start by testing the charge control, charge relief and turbo control actuator. In the US 93 workshop manual, start at page “F84” and you will see how to do those. Also verify that your double throttle is in fact, opening up and working. With the car warmed up at idle, it should be in the open position. Make sure your vacuum tank is also holding vac.

Start there and report back.


~ GW

 

Yep, I have a lot of methodical troubleshooting ahead. I am just hoping that I don't finish up having to remove the UIM; again , or worse still, the exhaust housing.
I will post back when resolved.

 

That’s why I want to walk you thru the stuff you can access first before having to pull the uim. It could very well be a misbehaving solenoid, but we start with “A-B-C” and work thru in a process.

You will need a vac/ pressure hand pump to do the testing. Also, I don’t know the mileage of your setup but it may be worth pulling the rear turbo air tube off and just checking that the secondary turbo is in fact still good. Start with the simpler stuff.


~ GW

 

check for boost leaks in the intake system with a smoke tester or pressurize it with caps and use soapy water and a stethescope, primary boost doesn't push a lot of air but sequentially they do, and that could be causing a blowout like say in the crossover charge air boot feeding the IC which is a common place for issues. i've seen tears in that boot allow the primary to build just enough pressure to run normally then open up a tear for the turbos to fall on their face once sequential transition is activated.


often times the simplest answer is the one most overlooked.

 

Additionally, I would recommend that the OP search on and read up (if he hasn’t already done so) on transition problems/solutions involving the Turbo control solenoid “E”, a known trouble spot for sequential control.

 

Likely unrelated, but if you have a '99, make sure your coil harness and plug wires are hooked up correctly. Coil positions were changed for version 4 and later cars.

One of the vacuum lines to the wastegate actuator should have a hidden check valve in it., if I am not mistaken. Sometimes that hose gets replaced without the check valve.

Map sensor filter facing the right direction?

You have the correct PFC for your model year?

The correct MAP sensor?

Replace the entire wastegate actuator?

 

If the op “ RGF” jumps around with all the suggestions, it’s easy to miss something and have to re test. Understanding how the sequential turbo control works, it can only be a handful of things that cause the issue. Troubleshooting a problem starts at the beginning. Working thru the steps, A-B-C. Not A-J-Z-B-C. It could very well be one of the suggestions, but proper troubleshooting is important. After testing the things suggested, I do agree with a smoke test. That’s one test everyone should be doing with their cars.


“One of the vacuum lines to the wastegate actuator should have a hidden check valve in it., if I am not mistaken. Sometimes that hose gets replaced without the check valve.”

I do not know if his 98 model has the black box, but I would think that being a 98 it will have the pills pressed into the nipples of the primary turbo and only a few lines that come off the vacuum block. I did see that the OP already pulled the uim and did some testing.

“You have the correct PFC for your model year?”

His car did the same issue with both the stock ecu and the power Fc. The Ecu plugs are different in the newer models that should work with his model year.

“Additionally, I would recommend that the OP search on and read up (if he hasn’t already done so) on transition problems/solutions involving the Turbo control solenoid “E”, a known trouble spot for sequential control.”

This is more than likely where the problem stems. Charge control, charge relief and turbo control actuator which is driven by “E” all work together. You have to pull the uim to check this unfortunately.


I’m hoping that the “Op” reports back about findings on the charge control, charge relief and turbo control actuator testing so we can move on to the next steps.


~ GW

 

Magic Box N3F1-13-4B0 starts in 1996.

 

I don't know if it is too late to put the original ecu back in and do a code read?

 

Somewhere there is a list of which Power Fc match which model years. I believe Apexi did a more recent update, and may have dropped the older models from their list on their site (in Japan).

There is a Version IV and Version V Power FC corresponding to Version 4 ('96-98) and Version 5/6 ('99-'02). cars.

Both of those would have the 16 bit ecu plugs.

 

The wastegate actuator does not seem to be closing as much as it should at a duty of 64%. One can see that even when the PFC makes its desperate move and decides to bump up the WG duty from the programmed value of 64% to 90% (step from zone 3 to 4), boost is still not able to reach its target. As already suggested by others, check the WG actuator rod setting and troubleshot backward starting from the WG actuator itself.
By the way, you can now also log and playback switches and solenoid status on PFC Connect v7.5 using the DL-340XB. So you can also verify whether your ECU is sending the correct instructions to the solenoids, which most probably is.

 

Rather than trying to troubleshoot a 30 year old actuator, why not replace it with a new one?

BTW: I could not find evidence * to support my hearsay that there may be check valve in one of the vacuum/pressure hoses to the actuator. Might have to take one hose apart.

(*The parts catalogue shows a little double line on one of the vacuum hoses to the "big" actuator. I don't know what that signifies.)



The smaller turbo vacuum lines don't seem to have the same marking.

 

“Rather than trying to troubleshoot a 30 year old actuator, why not replace it with a new one?”.

Just replacing parts for the heck of it may cause further issues and is an unnecessary expense. For instance, on numerous occasions, individuals have bought brand new solenoids for them only to be faulty out of the box.


I believe the check valve you’re referring to is the one that’s tucked underneath the pressure chamber. It is sort of hidden. It’s job is to hold pressure in the pressure chamber supplied from the ypipe.

The lines to the turbo control actuator are the vacuum and pressure that switches back-and-forth to push and pull the door open. There are no check valves in those lines. Consequently, that’s controlled by the solenoid “E “that gives us trouble.


~ GW

 

Do the springs in the actuators fatigue? Over 30 years, how many reps does the actuator spring make?

 

I would be more worried about the old diaphragm cracking than a spring. Let’s be honest most of these cars sit around for extended periods and are not driven very often. If it passes the test, we move on.


~ GW

 

its relatively easy to test it, and see if it works, and then move on to something that is more likely to be bad, like a check valve or the Magic Box