NefMoto

Car has the Giac recommended setup (K04, FMIC, 315cc, DP) an AFPR.
Initially, fuel pressure was set low (forgot, but lower than 2.7 bar), I now set it to 43.5 psi (3.0 bar) with vac line disconnected (Giac specification).

With lower and now 'stock' fuel pressure, the car runs ok under WOT logs.

But part throttle (very little with the lower FP setting, a bit more with 3 bar), the car goes berserk and boost to 25 psi or more.
If getting out of throttle during such berserk runs, a massive jolt occurs.

What might be causing this behavior. First to0 lean, now too rich.

Some suggested 2.7, 2.8 bar; will try 40.5 psi.

Can coil packs or spark plugs cause such weird behavior?

 

Don't guess, log

CAn only log with VAGcom, slow.
Did a throttle  body alignment, seemed to help.

Will run more logs.
What parameters suggested?

Seems to run at 40 psi on the AFPR (vac disconnected).
With this setting:
- still some jerking when getting off PART THROTTLE boost (not so WOT).
- still boosting much higher at 40-50 degree throttle (up to 25 psi) vs. WOT (15 psi)
- NO codes/misfires
- looking at the logs, it seems clear that under part throttle, the N75 is not doing anything !!!! (numerical values zero).
- WOT N75 kicks in (high numerical values, until fading out at higher RPM)

I am trying to attach the excel file (complete run, several part and WOT runs)

Can someone clarify for me:
zero showing in log for N75 duty cycle means: N75 closed, not bleeding off boost. Spring holds wastegate shut closed.
99% showing in log for N75 duty cycle means: ECU tries to bleed off boost. N75 as open as possible, trying to push wastegate open to limit boost?

Still no progress in finding out what is going on.

Why is N75 NOT trying to limit boost, showing all zero 'waste gate duty cycle' under partial throttle (and boost going through the roof up to 25 psi), while cutting boost to 16 psi (and showing up to 99% duty cycle for the N75)?

N75 0% duty = wastegate spring only = ECU wants low/no boost
N75 95% duty = closed wastegate = ECU wants high/more boost

Something tells me your wastegate is stuck shut.

Thanks. If wastegate is stuck shut, why boosting 16 psi under WOT, and 25 psi under partial throttle?
Would it boost 25 psi all the time?

I see if I can reach down there and manually move the wastegate actuator.

Depends on your turbos, exhaust set up, and waste gate spring rate.

At some point, exhaust gas pressure will open your waste gates for you.

Also, just because a turbo can reach 25 psi @ 3500 RPM doesn't mean it can hold that psi to redline.

A stock K03 on a 1.8t can spike 25 @ ~ 3000 with a closed wastegate, but then dies down to ~14 psi @ redline, still with a closed wastegate. The turbo just can't flow enough to feed the engine and maintain that pressure. Again with wastegate completely shut.

Not 100% sure if a K04 can hold 25psi @ redline.

The point is (just to clarify again):
N75 shows values at WOT, boost 16psi
N75 shows ZERO at part throttle, boosting (not spiking) 25 psi

Has someone logged his PC16 with WOT and partial throttle?

Stuck wastegate should be stuck at WOT or partial throttle.
Bad N75 should not work WOT and partial throttle
Leak/hose etc should be same for WOT and partial

I will look for another N75 to swap in.
I will try to move the wastegate by hand (hard to reach)
At next opportunity, I plan to swap ECU with other Giac (also PC16) I run in different car.

If I disconnect N75 (remove plug), what boost should I see?

If no solution can be found: put MBC in parallel to prevent high boost.

If you disconnect N75 you will see spring boost.
Do this first before removing the wastegate or doing other things.

Then you will see if it's an electronical problem or physical.

Will do that, thx.

Two can't on a 2.7t :)

Not the point here what the turbo can do.

N75 electrical plug off: boosting 25 psi, part throttle or WOT.
Is that the expected result (N75 not anymore able to bleed off boost during WOT)?

Not unless you have a 25psi spring?

You have a mechanical issue.

N75 bleeds off the pressure going to the lower chamber of the wastegate.
Not boost.

N75 can only ADD boost above what you get with it disconnected.

No. When disconnected electrically, the N75 should send all boost to the wg line, which should cause boost to bleed off when the pressure overcomes spring tension.

The N75 DOES NOT BLEED OFF BOOST AS YOU SUGGESTED IN YOUR POST.

I can't stress this enough. It bleeds off boost AWAY from the wastegate, which is a very different thing.

If you are still seeing boost, either the N75 is broken (it is incorrectly bleeding off boost from the wastegate line) or you have torn wastegate lines.

Pressure test your wastegate lines.

Alternately, you can crimp off the hose from the bleed leg (longest leg) of the N75 and retest.

(http://s4wiki.com/images/d/d1/N75.jpg)

The one you want is the leg pointing to the left above.

Of course it is relevant. If the turbo can't make 16psi at redline, then no, there is nothing wrong with it doing 16psi at redline, and much more at lower RPMs

Peak boost occurs around 4k rpm, both WOT (N75 in the 90%) and part throttle (N75 is always at zero %).
Both tapering down at higher rpm.
Under WOT, max boost is 16 psi , while part throttle going to 25 psi.
With N75 electrical connector pulled off, both WOT and part throttle go 25 psi (possibly higher; didn't dare).

If mechanical issue, what mechanical issue could cause the different behavior of the N75/ECU (throttle position dependent) and boost?

I will check the N75 / wastegate lines first.

You have a sticking wastegate, problems with the lines or similar.
Put the ECU away and fix your car.

If WGDC is 0 and your boost is doing all sorts of crazy stuff it's a purely mechanical issue. Nothing to do with electronics.

Personally I think your N75 is hooked up wrong.
You have the long port (bleed off) going to the wastegate and the short port going to the bleed off.
So it's doing the reverse.

That's why when the ECU wants to request boost it reduces it and when it wants to reduce boost it requests it.
You ought to look over other schoolboy errors as well and pressure test the car before going into the ECU :)

Very much looks like it. Friend brought the car in for timing belt and radiator work; he only mentioned some suddeness during part throttle.
Furthermore, previous owner told him the car has "Giac PC16 X" (does not exist) and 330 injectors. Car has DV relocation.

I take the front off today and go through the connectings (needs new fan blade anyways). While accessible, will move the WG actuator, and measure the N75.

i will report back afterwards.

if you have a mityvac pump or equivalent you can check wg requried crack pressure which will confirm if the actuators leaking, stuck, and what psi it takes to start to push open.
N75 wise.. std valves long leg goes to TIP, centre is charge pipe boost feed and the other goes to the actuator.

"long leg" of N75 was connected to actuator, short leg to TIP!

Thanks for all the help.

Will put together tomorrow, but may be end of the week by the time i can take her out for test drive and log run (car is on stands again for more work).

Exactly as I thought then.

Yes, you were right on the money. Only surprised that under WOT, the boost was 'only' 16 psi, and weird pressure (for Giac PC16 anyways) of 25 psi only occurred during partial throttle. Any explanation for that?

As I wrote above:

You had it plugged the opposite way around, so it also worked the opposite way.
100% duty cycle would give 0 boost and 0% duty cycle would give max boost.
So on part throttle the ECU had a low duty cycle, and that gave a lot of boost, and on WOT it gave more duty cycle, and got less boost.

Now that you have it in the correct way, it will fall into place, and 0% duty cycle will mean no boost and 100% duty will mean full boost.

First test drive today after correcting the N75. Boost not anymore going through the roof.
But I have what I call 'boost pumping': boost swings between 10-15 psi at mid range rpm.

bad video here.

http://s853.beta.photobucket.com/user/vtraudt/media/1998%20Passat%20Big%20Guy%20John/1998PassatBigGuyboostpumping_zpsc21422ad.mp4.html


I will attach VAGcom log later.

I set the fuel pressure to 43 psi (3.0 bar as per Giac).
I ran a 5th gear log WOT for the mid RPM range where the boost pumping occurs (slow enough to get at least some data points with VAGcom).

Attached is the excel file. I don't see anything weird there. Can someone take a look and see if there is anything that points to the culprit for the boost swings?

1) please do not upload excel files. Stick with the plain csv.
2) consider using ecuxplot

Reason?

Thought its for Me7.
Works on AEB ecu for data logging? If so, will certainly try.

Thought its for Me7.
It works on AEB ecu for data logging? If so, will certainly try.
NYET: can you send me the ecux definition file for 1998 AEB ECU 8D0 907 557 P?

should work with ecux and vagcom/vcds. If it doesn't send me the log and ill patch it up so it does.



sorry, dont have that :( you'll have to talk to APR about it... which means you're boned heh.

I have log parsers that parse .csv

When people post excel files, they save it off in various unparseable (and proprietary) excel formats. Even exporting it back to .cvs generally ends up with something not even close to what the original was.