0.4 bar probably limp mode. I had wg stuck open and still got over 1 bar of boost. How long since you changed plugs?

 

Does sound like limp mode. Easy thing to try is to disconnect the negative battery terminal for 15 minutes, then reconnect and drive 15-20 minutes without boost to remap the ecu.

Good luck.

 

http://www.brockwayengineering.com/codes.html ? is this what you are looking for?

 

I had the same problem with my 02 996 turbo. There was also a fuel smell at high rpms. After many hours of labor at the Porsche dealership, they finally determined that the hose between the intake and block was loose and would only leak under high pressure. mods are GIAC tune, Fabspeed exhaust, Agency power diverter valves and K+N filter. Runs great now. Hope this helps. Gordo

 

thanks for everyone's comments.

no but thanks though. Have got zero DTC's read out on the brockway.
what i meant to ask was whether limp mode would show up on the brockway.

No dash indicators present.

is there anything other than 0.4bar that would indicate limp mode activation?

if the car is in fact in limp mode, i presume this process should clear it? after driving 15-20mins, hit the throttle and if I still have 0.4bar, could "limp mode as cause" be eliminated?

plugs changed less than 1000 miles ago...

Did a search on limp mode and found this thread. similar symptoms. couple posters suggested a "frequency valve". Is this the same as the N67 valve? Could either of these valves cause problems described?
http://www.pistonheads.com/gassing/t...t%20to%20check?

Enough internet research, time to get hands dirty. Ghetto rigged a tool. It looks retarded, but it works...




put the car on the lift and checked the WG arms. These were in one piece no play, and gates aren't stuck open.

I tried to adjust the WGs. First time i've done this myself. Thought i in theory, i knew how these things worked. i don't really, lol.

Didn't have the cats off so all I could see was the WG lever arm. first off i thought 1bar actuators aren't supposed to move until 1bar was applied. Took only 0.4bar to get it to start moving. Ah ha I thought! OK... let's adjust the bolts back towards the actuators. this should keep the arm still/WG shut at higher pressure. but no, as I went towards the actuator, the arm was more sensitive, for example it started moving at 0.2bar now instead of 0.4bar. (however i do realize due to physics of leverage, the gate inside is moving less)

moved it yet farther towards the actuators again, and found there is a point at which the arm does not budge, even with 1.2bar pressure. I guess this is where the spring's maxed out. At this point, I decided to play it safe and moved the adjustments back away from actuator. Last thing i wanted to do was to over boost on a stuck shut WG...




I thought if i test drove the car on a (safe) range of 3 different WG adjustments, and found a difference, then the issue is the WG.

1. Original setting arm moving at 0.4bar (5mm from end of arm to nut)
2. farthest out from actuator moves at 0.4bar (3mm from end of arm to nut)
3. closer to actuator arm moves at 0.2bar (14mm end of arm to nut)

To my suprise, all three settings yielded similar results. Setting 2 with nut closest to the end of the arm had marginally less boost at 0.3bar on avg.

My big question now, is do I need to adjust the arm back towards the actuator until which point, the arm starts to move at 0.8bar? Or was the range adjustment test above enough to conclude WG adjustment is not the issue?

Sorry for the long post... thanks.

 

Check where the Wgs start opening up... if at 13 psi then they are 1 bar springs... if at 6psi or so they are stock...
those look like rebuilt turbos... not new.

if you have any pics of the compressor wheel that would help....

 

photos are correct. these are the "newly" rebuilt k2418gs pictured ... i was suspecting this cos actuators look the same as the stockers, but figured internals were different. am i missing something here... cos even still, with stock actuators, shouldn't it be boosting at least same as stock?

Mark, the wastegate/actuator arm starts to move with less than with 0.5bar regulated pressure from aircompressor. can't see movement on actual gate cos exhaust still on.

By "Wgs" - do you mean the actuator arm or the gate inside the housing itself? i noticed degree of movement between the arm and gate vary depending on WG arm setting when bench testing the stock turbos/actuators.

attached photos of rebuilt turbos.

thanks guys...

 

hmmm... ok that makes sense cos both actuators on my stock k16 and this set broke open same time on regulated compressed air.

that's easy, just swap to the correct ones but...

even stock, wouldn't it hold more than 0.4bar? thank you

 

YOu can turn them and see what happens... lets say 3 turns...

 

I have been following with interest.

If I use the following terminology:

a.Wastgate is the Ceramic Flap Valve in the turbo Housing
b.Wastgate Arm is the 90 deg crank coming off the Turbo Housing
c.Actuator Rod is the threaded arm coming from the Wastegate Actuator
d.The Wastgate Actuator is the Canister at the end of the rod.

Some basics.

There are 3 pressures involved with the Turbo.

1. The pressure built up in side the Turbine exhaust housing by the exhaust Gasses, it presses on the Wasgate inside the turbo
2. The Spring pressure in the actuator
3. The air pressure applied to the wastegate actuator for control.

All things being equal, the spring pressure in the actuator has to be greater than the pressure of the gasses behind the Wastgate or it would pop open every time the exhaust gas pressure increased. This equilibrium is changed when pressure is applied to the top of the actuator changing the balance between the Wastgate and the Actuator spring.

Shorten the distance between the Wastgate arm and the actuator and the boost will go up. Lengthen the effective length of the rod and the boost will fall.
It does not matter what type of actuator you have the rule still apply. The standard actuator will have a spring inside designed to balance off the exhaust gasses and control pressure on the top of the actuator to give the factory .65 bar.
If you shorten the rod length in stages and the boost should go up. You will get the the point where the rod can not be shortened ( assuming you still have threads left) any more " CAUTION" this is locking the wastgate shut, it will not open as the spring inside the actuator has bottomed out ie no longer a spring no matter what air pressure is applied to the top of the actuator the boost will not decrease, However with caution this A a good test. I say again with "caution" drive the car and slowly bring the car into boost, as soon as you have satisfied your self that it is indeed boosting , if you see the gauge climb .4 .5.6 .7 .8.9 stop You will be able to massively over boost if you are not careful. You don't have to floor it in fact " DO NOT FLOOR IT. Use 4th gear ( its best to load the car down and is more controllable) at 2000 rpm make the process a scientific test. Do not use 1st 2nd or 3rd. "If a turbo makes boost it makes boost".
If you don't get boost and you are sure the system pressure test you have done has shown no leaks then perhaps you have a crack in one of the ceramic Wastgate flap Valves or is bent or the seat for the valve is damaged etc. It might be best to take the exhaust off and have a look.Could also be an internal Turbo problem Compressor wheel not connected to the shaft, spinning freely etc. Is a Turbo seized???

If the actuator rod is so short that the wastgates can not open then you can rule out the boost control valve as it will be incapable of opening the wastgate. Remember this will give the Max boost the turbos are capable of making. Never use WOT.

If you are not a disciplined level headed guy that can control the boost with the gas peddle then don't try. However if you are capable then make enough boost to satisfy you that the Turbos are fine . Stop testing and drive home in a restrained manner. Never use WOT." Softly Softly catch the Monkey"

If you do get boost, then start looking at the actuators or the boost control valve. Remember wind out the rods again!!!!

These are all routine tests I have used on my Gp A Cosworth Rally car. 120 Cui producing 500 BHP. Might not sound much but it's only 120 Cui !!! 4 cylinder. Stress a standard 996tt can only dream about.

I hope this is of use to you. You don't have to take any notice of this but it works for me. That's the point, for me. Use caution.

Good luck, I am really interested in problems like this. These are ones you print off the answers to once found and keep for the future.
Sory for the long post but its too complicated to trivialise.
Frank

 

Sorry "explode" meaning take off.

Like Markski said, tighten the wastegate actuator rod until the wastegates start to crack open at 12-13 psi. Basically you're connecting a vacuum host to the wastegate and applying boost pressure to fine tune when the wasetgates start to open. make sense?

 

Ari,
Totally agree that is the correct way to set up boost, but I think this has already been done and didn't work ( I might have misunderstood however) As I see it there seems to be an unexplained lack of boost and most avenues have been tried??. My way is a good way if, careful ,to check Turbo output. It wont go bang ( explode) because you don't allow full boost. Built up the boost using load and throttle control. Stop when you are convinced that the Turbos are working. I mean stop long before max Boost. No Gun ho. Nice and easy. As I said treat it scientifically.
But to reiterate, under normal circumstances your method of setting up the wastegate actuator for boost is correct. I did see a picture on page 2 of a setup being used for this purpose.
Frank

 

Frank, thanks for the 101. Markski, thanks for the late night phone call and thank you to everyone whose taken the time to help. after a couple of nights trying this and that... i can make sense of frank's 101 and suspect the waste gate is the cause of low boost issue.

more or less certain the actuators on the rebuilt turbos are infact stock (though I ordered 1bar... dan's kindly offered to ship the right set)
Dan advised one way to check is to plum the actuators direct to a manifold souce. But not sure I understand what this test is supposed to show outside of what's already been tried (and closed the msn box by accident and can't recall what he said). would appreciate of if you guys could chime in here. Something I can test tomorrow as well.

I have the oem k16turbo/actuator set so tested those tonight as well. these are on the OEM setting, roughly 10mm from outer nut edge to rod end. Using regulated pressure at the actuator nipple: The arms/wastegates start moving at 0.35bar. and the gate cracks wide open ar around 0.7bar. These turbos on the old set up (flash,DVs and exhaust) made 1.0bar, peaking at 1.2bar.

With the same rod setting, the actuators on the rebuilt k24 turbos did exactly the same. From this, is it fair to say that these actuators are stock and working properly.

What I don't completly get is how the car on it's old set up was able to make 1bar boost when the wastegates/arm/rod begin to crack at 0.35bar... my guess is boost is still made with the wastegates partially open and that's why 13psi (approx 0.8bar) was the suggested starting setting to achieve stable 1.2bar.

If the above assumption is correct, even though the k2418g set up is running on a stock acutuator, it should still be making reasonable boost, may be not same levels as with old set up cos bigger turbos are moving more air and opening wastegates sooner, but as seen in the video, there's no boost build up and peak boost holds only at 0.4bar.

Limp mode. Did as suggested, unplugged battery, 15mins, drove 50kms with out boosting. Tried boosting, same issues. Hoping that rules out limp mode.

After using up 1 full tank of gas. What I did notice was boost hits 0.6bar under certain load/rpm when half throttle but never at WOT. At WOT, boost drops to 0.4~0.3bar. in 3rd and 4th gears.

I could try as frank's suggested and adjust rods so wastegates are always shut and see if car boosts but want to reserve this for last.

Couple questions related to TB: following photos are (A) from a post on how to install the AP TB kit. and (B) one from my car.
Notice in (A) left bottom quadrant, there's an additional check valve (white color). On my engine, photo (B) this doesn't show. I asked the mechs to put it on as per the photo (A), but not sure if they had done so. Will check. What's this for, cos the stock system doesn't have it and if they forgot to install it, could this be a reason for lack of boost?
(A)

(B)


As mentioned earlier, one of the shop guys shot full aircompressor pressure thru the system. (i should explain a bit here) the car was at a paint shop that does maintenance work on standard cars but not mods. Dealer mechs moonlight here and basically agreed to do the standard work ie removing/reinstalling the engine, standard parts, and after market parts were installed as per my instruction. things like boost test, fabbing etc I was on my own... along with some of the non P mech shop employees.

Here's a photo of a valve that blew apart, and replaced with a new one. Shop said the unit was already loose, probably damaged while disconnecting during parts disassembly. We tested the system again after. pressurized 1.4bar into leak test tool, then connected the system via MAF location. if there was a leak, I pressumed the gauge would read lower than 1.4bar. But it was steady. But after thinking about it, there's a bunch of check valves all around the system, is it possible while the system still holds pressure, that some of these valves could have gotten blown out creating a low boost issue? The car idles smoothly and drives fine.


the diaphrams in the diverters are "valves". I thought with pressure at the MAF, pressure is applied on both sides of the diaphram and thus a torn diaphram was unlikely. But not sure about this, please let me know your thoughts. Using the AP units for less than 1000miles, and working fine prior. At this point, given what's been tried so far, hoping to single this out to be the problem. If the valve above was cracked open, may be the diaphrams are torn? would this explain higher boost at lower load and lower throttle positions versus WOT? May drop engine and inspect these tomorrow, have an aftermarket pair I can borrow to test but don't want to go there if chances are slim.

(borrowed from audi tt forum)

Lastly, just grabbing at anything that may give clues. Irrespective whether the car's warm or cold. sometimes it starts with out hesitations, other times takes 2-3 tries. Engine stutters to a start. Have a heavily modified NSX that does this after it hasn't been started for a while or cold, but once warm, starts and idles fine so not sure if this is normal for the 996tt. here's a few videos of start ups. high revs on initial cold starts appear normal. once warmed, idle is steady and consistant, no bogging or bobbing as rpm falls to idle.

(not sure why youtube's embedded double, sorry not able to fix)

cold start, starts immediately - seems normal
http://www.youtube.com/watch?v=dKKO3EwksL4

cont. of above cold start, initial up high revs, then settles - seems normal
http://www.youtube.com/watch?v=JS9hNaYQEyI

cold start, hesitation and slow ramp up of rpms, bit of bobbing - problem?
http://www.youtube.com/watch?v=H4oMID0IgRU

sorry for the long post again...TIA

 

something is not right... what injectors did you use?
You need to pressure test it from the turbos... and go thru the car...

 

60lb RC injectors. AFR 0.4bar WOT mid-low 12s, Idling mid 14s

yes will give that a try, need to collect hardware to make the plugs first. thanks