NefMoto

Hello
I have a problem with air pressure dropping after 4000rpm
so its only
16psi @4700 (requested 18psi) and drops down more with 95% WDC (((

turbo is K04 hybrid (K04-022 CHRA with machined K03 hot side and K04 cold) maybe problem with that?
no leaks detected in system
fueling is ok

another way - stock cat-back after 3" downpipe
and there is stock 710n bypass valve, checked it - all ok
engine is 1.8t me7.5
little log attached

thanks

I have similar issue with customer, but his pressure drops till near 5psi.

in you case: Look channel 114 RPM = 4680 and 5120.

Note Spec load < spec load correc < Actual load

And 183Kg/s is a good mark without inlet and upgraded intercooler

Try raising kfdimx if you haven't already.

Other than that it might be your wastegate, if it's an old or weak one it might be struggling to keep the wastegate closed under high rpm/boost.

unplug the wg completely and see what you get.

if you can't build boost, you have a WG issue or BPV issue, or a boost leak.

if you don't see fueling problems, you either have bypass valve problems, or you don't have a boost leak..
usually this kind of stuff is trivial to diagnose because it likely doesn't have anything to do with the tune.

overspeed, car have a fmic and AEM  intake with tt maf housing. need moar!!

littco, yep kfldimx is stock, i will try to playing with it. but if WGDC = 95% is there any reason to touch it? i see that is not accurately with  some overboost @3000 still no time and knowledge to fine tune it.
wastegate are pretty new come with turbocharger (~halfyear). how can i check it? by opening pressure test?

nyet, i will try to accurately unplug WG.. scaring to blow something..
checked BPV by standart vacuum test - ok, trying to boost it by mouth to high pressure hole - ok (idont know how many psi i can build by myself)))

fueling is ok, actual lambda is 0.75 in WOT same as specified
try to find some leaks.. btw there is strange sound in part throttle when pressure at 0 psi (doesnt appear at negative and positive in any conditions)
sound like poooo (not poo :)) going from engine bay, i know its stupid but maybe someone know what it an be. ive checked all piping with no luck

thanks guys
sorry for my english

First boost leak due bad crankcase ventilation hose under intake manifold . Its hard to diagnose because its too soft and when on idle vacuum close it and idle is good , when on boost you have massive boost leak from there.
Second one is bad DV valve (blow off) , bad solenoid that control DV (I dont know what version is the car).
And most of 1.8T Ive seen are with bad wastegate actuators due high temps and many km on them.

If you have normal maf readings then I bet on your wastegate.
Make like Nyet says to you but dont full throttle on 2000 rpm the car , just soft and wot uptop. If there is no diff in your boost then just short wastegate actuator rod.

i ve replaced all breather hoses and valves

thanks for detailed advice, i will check DV solenoid and try to run with unplugged WG

maf doesnt look faulty, its 1y old bosch unit

Unplug the n75 - you wont blow anything , it will run off WG pressure - this will give you a good idea where the boost is for PID control.

You can check the crack pressure as well , if this is low then its possible for the WG to open at high rpm with high exhaust flow .

As I understand , KFLDIMX can be what it is and yet you will still get max WGDC , KFLDIMX feeds into the PID controller . So in this sense you can adjust KFLDIMX up in certain areas for a higher base WGDC

Correct ?

so today im checked N249 solenoid - its ok, no leaks, open & closes correctly.
checked WG - ok, no leaks. but can not give specified pressure to it. so i dont know minimum opening pressure.

still cant drive without WG because have no time or heavy snow :(

Pressure drop from ineffective charge system flow, or your turbo intake pipe may not be up to the job to flow the v

I had a lot of problems with used K03 after 4000 Rpm. Dead turbocharger was the problem. Though 18 psi for K04 gybrid is not so much, but I believe its either problem with turbo or with your file.

there is only one restrictive place - turbo inlet. pipe is silicone from frankenturbo with TT maf housing and AEM dryflow filter.
so if typical K03/K04 can rich more, than <i think> mine too


as i can understand file cannot be a problem because WGDC = 95% (max) so WG must be closed
turbo.. maybe. this is hybrid and who knows how it works, but this is not old one.

I saw 22 psi on K03 turbo with standart pipes. Though its not ok for K03, but I mean pipes are not so important.
I installed K04 and made a holl into air filter box (like RS4 box now but without flap  :)).

You can check catalyst also (if its still installed) and N75.

But I think the problem with the turbocharger.

Rule 1: before you tune ANY turbocharged car, you pressurized the entire system with a compressor at the MAF->Turbo hose (preferrably bypassing PCV).
You have not done this yet? GTFO the forum and make sure Rule 1 is checked correctly.

Any time you skip Rule 1 on a mass-flow ECU you will just waste your time and your tune will be worthless.

as i said in 1st post - system have no leaks

no cat
N75 works fine, but i will try friends one thanks

Your wastegate spring is soft and wastegate opens under backpressure , replace or short the wastegate arm lenght.
You have big compressor side turbo and small K03 exhaust housing , its normal to see high backpressure with this type of turbo.
And Im sure you still use your K03 wastegate actuator.

im using wastegate actuator coming with this hybrid. btw im trying to compare spring strength by pull actuator arm (by my hand) on friend`s K03 car and it looks ~~ the same. i will try to pull K04 car actuator to make a sense
so if i tighten spring by shorten arm it will give me a good result (without overboost in mid-range RPM where wastegate opens) or better buy K04 actuator?

I use K03 actuator with K04 turbos and everything is ok - 22 psi when I need it. 

How did you check for leaks?

we used empty fuel filter housing installed on a TIP in maf place
and set 1 bar (~15psi) pressure to it then listen to air noise

only one leak from oil level hose. we plug this hole and there is quite and pressure holds

didnt check with bypassed PCV

Pressure testing only finds leaks PRE throttle body. There are a lot of potential failure points POST throttle body as well.

i ve replaced ALL PCV with vacuum pump
yesterday we`ve checked vacuum line from N249 to BV (with vagcom output test) and N75 to WG with same pressure test. also we`ve checked brake booster line going from side of manifold. they all ok

we have no time to check PCV vacuum pump line going from downside of mani, so i will try to made it. but as i said - they are all new..

Chinese gybrid? Just interesting. :)

This is not the correct way to test.
The correct way is to use a tire inflator, and add 1 bar of pressure, after that let go, and see how long it takes for the pressure to drop.
It should be more than 1 minute.
If it drops as soon as you let go of the trigger, you have a leak.

dont know who did it
have a photo

(http://i60.fastpic.ru/thumb/2013/1209/bc/fdac65dc44afab251ca00b8fc511f9bc.jpeg) (http://fastpic.ru/view/60/2013/1209/fdac65dc44afab251ca00b8fc511f9bc.jpg.html)

so im shortened actuator arm and car drives more agressive. im slightly lowering LDRXN after 1st post of this topic. so actual pressure now same as specified and its the same that i have previously
but WGDC curve now look right for me and it reach 95% only @5600.
maf are 199 g/s now vs 182.. im very surprized at this value. but dont know how can be different values at the same pressure.. is it possible?

here is comparing picture with 1st post log and im attached new logs

(http://i60.fastpic.ru/thumb/2013/1209/2d/18f053ce647e3f558e003313039de52d.jpeg) (http://fastpic.ru/view/60/2013/1209/18f053ce647e3f558e003313039de52d.png.html)

prj, im pushing off the compressor trigger and pressure holds.. unfortunaly we do not waiting for a minute, but ~30 sec it holds

Looks like chinese crap. Good luck with this turbo  ;)