Last year with the stock turbos and 1bar tune I pinched the hoses going to the wastegate actuators and the car still made only 1bar of boost when in theory it should have overboosted like crazy.

This year I installed a set of K24/20G turbos and was only making 1 bar of boost. So this is what Ihave done…

1- Boost leak

Boost leak test at the intake of the turbo and blocked off intake of other turbo. (Car held 25psi)

2- Divereter valves

a)Made sure they were not leaking. (they were finebut replaced anyway)

b)Thought the N249 valve might be bad so Ibypassed it and took boost/vacuum right from intake manifold. (No change)

3- Wastegate Actuators and N75

a)Thought the N75 was bad so I bypassed it which should make me over boost like crazy since the actuators are getting no signal(Made no difference)

b)Thought exhaust backpressure was opening up the internal wastegate flap so I set out to find new wastegate actuators. 32Krazy! Saw my post and sent me a set of 1bar actuators for free!!!! He wouldn’t eventell me the shipping costs for me to pay that!! To say the least I was very thankful. I put those on yesterday. (madeno difference L)

c)Wired the wastegate actuators shut so theyphysically cannot open. Made a small difference. I now see 1.1bar and sometimes 1.2bar. I do not think this has anything to do with my issue though. I think I just see more boost because the turbos are working like crazy to meet commanded boost so with the wastegate flaps not able to open at all it helped build a bit more boost. That’s my theory anyway.


4- Clogged cats

Removed exhaust and cats are OK. Tested exhaust pressure before the cats andit was well under 1psi so it is within spec.


So the only things I can think of left to do is:

1- Remove the turbo intake pipes and replace them with ashort hard tube with a screen on it to prevent crap from going into the turbosduring test drive. This would eliminatethe possibility that the intake tubes are collapsing in on themselves. I don’t think this is happening but at thispoint I have to check it.

2- Bypass the diverter valve system completely to test if for some reason they are bleeding off the boost (even though I confirmed theyare physically good and the issue has nothing to do with the N249 that controls them.

3- Set the car on fire

Thanks for any help!

 

when you say you bypassed the N75, did you just unplug the connector?...edit, sorry reread, capped hose... hmmmm
have you tried putting a manual boost gauge on to confirm what you are seeing on the dash/log is correct? maybe a bad MAP sensor...

 

Hey, thank for the input. I dont think it is a gauge problem because when I wire the wastegate flappers shut it only makes a .1 bar difference. Even if the gauge were not accurate it would go up much more that .1bar. I would also feel the difference for sure.

 

at this point I'd give some serious weight/thought to "how does the car RUN, regardless of what the boost gauge is reading". since often times we are not in ambient conditions that will allow for 1.3 ( which is pretty normally seen in MY car )


but it still freaks me out since I know I SHOULD be seeing 1.3 regularly..all this even when the car RUNS perfectly. you could be falling prey to the boost gauge not being accurate. while your car in fact IS running properly!?


just a thought....

 

To be honest the car doesnt feel any faster than it did last year with the stock turbos at 1bar. I would have thought K24/20G billets would be a considerable butt dyno increase. lol Im actually running the car right now with the wastegate actuators dissabled so I have no form of boost control. Even now I can only make 1.1 and maybe 1.2 bar when it should boost to the moon without the actuators being able to do their job.

 

Are there other supporting mods or just k24/20 ?
Injectors ? upgraded IC ?

 

verify the throttle body is opening fully? exhaust leaks before/in the turbo hot side

 

72lbs injectors, stage 3 CM clutch, modified stock catback exhaust. Other thanthat pretty much stock.

 

Checked for exhaust leaks yes.

I didnt check to see if the TB is opening fully but I did the TB re-learn procedure. Maybe I will physically check though.

Thanks!

 

is the car pulling timing?

i would definitely get another boost gauge to see what is going on.

could put it on a dyno, and remove the inlet pipes and see what the car is doing
have you datalogged the car?

 

^+1, I'd say we need datalogs at this point

 

My tuner has been working with me to try and solve this as well. I've sent him a couple of logs but they had mostly to do with A/F and boost I think. The things logged were..

RPM
Load
B1 Lamda
Boost Pressure
Set point boost

 

I'd be careful running around with the W/G unhooked! Check for an issue on the intake side and the exhaust side aka unhook the intake pipes and make sure the exhaust breathes - pretty much what you're thinking. Check with another boost gauge, a bad sensor could be causing lots of issues. You've swapped turbos already and saw no change so that should be ruled out now. You've done a million boost leak checks too so that should be fine. Got to be the sensor misleading, the intake, or the exhaust. Could also get crazy and swap those turbo onto another 996 but I just can't see how your luck would be so bad as to get two sets of turbo with issues! Runs smooth? No missing? A real mystery and I look forward to you finding it and sharing!

 

i'm also highly dubious about your wastegate non fix. i'm not sure that's a great idea, but understand your frustration. i would not leave those inoperable though, at all. good luck man.. this sucks, but logs will have to help! no??

 

Ya I know I shouldn't run with the wastegates disabled in case it decides to all of a sudden make boost normally. I hooked them back up to be safe.


I will try the things mentioned and if no change I will do some logs and post them up.


Thanks guys!!