Car wont make commanded Boost. I give up!!!!
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how is the boost command being done ? I assume thru the ECU since u say the n75 valve is hooked up?Or through a boost controller?
As somebody else mentioned throttle could be closing....
Caution!!Also do not check by disabling the actuators or the n75 valve cause if it does boost it will see 30+ lbs and pop a head gasket or bend a rod!
As somebody else mentioned throttle could be closing....
Caution!!Also do not check by disabling the actuators or the n75 valve cause if it does boost it will see 30+ lbs and pop a head gasket or bend a rod!
Last edited by joetwint; Jun 17, 2015 at 07:20 PM.
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how is the boost command being done ? I assume thru the ECU since u say the n75 valve is hooked up?Or through a boost controller?
As somebody else mentioned throttle could be closing....
Caution!!Also do not check by disabling the actuators or the n75 valve cause if it does boost it will see 30+ lbs and pop a head gasket or bend a rod!
As somebody else mentioned throttle could be closing....
Caution!!Also do not check by disabling the actuators or the n75 valve cause if it does boost it will see 30+ lbs and pop a head gasket or bend a rod!
When I disabled the wastegate actuator I was very careful to lean in slowly as to not over boost like crazy. It was only after dooing a few part throttle tests that I discovered even at WOT I not only dont over boost I still dont even reach commanded boost.
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I disconnected the hose that goes to the actuators not the electrical connection.
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He should be making a pile of boost, my N75 is removed and when I removed the EBC solenoid I made a mistake recently. Saw 1.4 briefly and realized the error quite quickly lol.
It's got to be the throttle, something is blocking airflow and since it's an electronic throttle that really makes sense in this case. Gotta' check and see if it's opening fully, pedal maybe? I'd expect codes though
It's got to be the throttle, something is blocking airflow and since it's an electronic throttle that really makes sense in this case. Gotta' check and see if it's opening fully, pedal maybe? I'd expect codes though
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i think this is close to where your problem lies. And i believe the logic here is backwards.
The n75s function is to increase (not decrease) boost pressure. That is, without the n75 in play either electronically or plumbed in, the turbos can only run base pressure as determined by the wastegate spring pressure. This is typical logic of wastegates as the failure mode is base boost rather than to overboost.
The n75, as it cycles, will regulate the amount of boost pressure to the wastegate, adding to the holding pressure of the wastegate and scales as boost builds. I know you said you wired them shut at one point to test, but you'd be surprised how much force it takes to keep them shut.
Few thoughts:
- did you pressure test the line from the n75 to the two turbos?
- replace the n75 valve as they have been known to fail
- zip tie the little elbow pressure line from the y-pipe to the n75 (just before the thottle body)
- replace this little pressure elbow? They have been known to pop off or even leak
here's a diagram i found to help understand the n75/wastegate circuit better. It's not specific to the 996t, but it's typical.
The n75s function is to increase (not decrease) boost pressure. That is, without the n75 in play either electronically or plumbed in, the turbos can only run base pressure as determined by the wastegate spring pressure. This is typical logic of wastegates as the failure mode is base boost rather than to overboost.
The n75, as it cycles, will regulate the amount of boost pressure to the wastegate, adding to the holding pressure of the wastegate and scales as boost builds. I know you said you wired them shut at one point to test, but you'd be surprised how much force it takes to keep them shut.
Few thoughts:
- did you pressure test the line from the n75 to the two turbos?
- replace the n75 valve as they have been known to fail
- zip tie the little elbow pressure line from the y-pipe to the n75 (just before the thottle body)
- replace this little pressure elbow? They have been known to pop off or even leak
here's a diagram i found to help understand the n75/wastegate circuit better. It's not specific to the 996t, but it's typical.
Last edited by pteck; Jun 18, 2015 at 09:13 PM.
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You're misunderstanding, not only has he tried wiring the W/G closed but he has disconnected the vac lines running to them. He has NO boost control and still see low boost...
Oh, he also has 1BAR W/G! It's a real mystery...
Oh, he also has 1BAR W/G! It's a real mystery...
Last edited by BLKMGK; Jun 18, 2015 at 06:45 PM.
Car wont make commanded Boost. I give up!!!!
What if the wg bars are too long?
Like what if they aren't holding the flaps tight enough from the beginning?
It would build boost slowly right? And make leak enough by that you don't teach the correct boost level.
Like what if they aren't holding the flaps tight enough from the beginning?
It would build boost slowly right? And make leak enough by that you don't teach the correct boost level.
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no misunderstanding on my part. I believe the misunderstanding here is the logic on how the wg works.
- the vac (boost) lines are there to increase boost pressure above base pressure
- the n75s purpose is to increase boost pressure above base pressure
without the n75/vacuum line in place and functioning, the ecu has no control over increasing boost pressure which is the problem here.
I know he wired the w/g closed...but i think he underestimated how much tension there needs to be to keep the w/gs really closed.
- the vac (boost) lines are there to increase boost pressure above base pressure
- the n75s purpose is to increase boost pressure above base pressure
without the n75/vacuum line in place and functioning, the ecu has no control over increasing boost pressure which is the problem here.
I know he wired the w/g closed...but i think he underestimated how much tension there needs to be to keep the w/gs really closed.
Last edited by pteck; Jun 18, 2015 at 09:13 PM.
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I've never seen a single turbo car that was using a solenoid to control boost who's solenoid wasn't used to INCREASE boost by bleeding off pressure to the W/G can. The Porsche is no different in this case. If you remove the vac hose from the N75 you have ZERO W/G control and boost will skyrocket because ALL pressure is bled off. Been there, done that - once!
So far he has leak tested, swapped turbos, removed all W/G vac control, wired the W/G shut, swapped W/G mechanisms, checked his catalytics - he may have even run it open exhaust I'm not sure. I'm dying to know what's going on with the car, throttle body or some sort of truly jacked up intercooler is all I can think of!
So far he has leak tested, swapped turbos, removed all W/G vac control, wired the W/G shut, swapped W/G mechanisms, checked his catalytics - he may have even run it open exhaust I'm not sure. I'm dying to know what's going on with the car, throttle body or some sort of truly jacked up intercooler is all I can think of!
Last edited by BLKMGK; Jun 18, 2015 at 10:51 PM.
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in this case: base boost correct adjusted ? boost leak? defect check valves? no boost pressure on top of the bov? defec bov? turbo def?
dont drive the car with a pressure loss....turbos overspin
Car wont make commanded Boost. I give up!!!!
But let's say he install the wastegates and has the wrong tension amount on the wastegates bars... In this example, not enough.
Or even if he underestimated how tight wiring them needs to be... In fact I can't even visualize what that looks like.
Then, he would be losing exhaust pressure with or without the n75 solenoid.
Isn't that plausible? When I fitted my 1bar wg, I had to tighten the rod significantly.
Or even if he underestimated how tight wiring them needs to be... In fact I can't even visualize what that looks like.
Then, he would be losing exhaust pressure with or without the n75 solenoid.
Isn't that plausible? When I fitted my 1bar wg, I had to tighten the rod significantly.
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best advice I've read here yet was check valves. replace them if ya haven't. at least you'll eliminate a COMMON yet often overlooked source of BOOST LOSS.
for what? 25 bucks? if that? my tech gave me mine ( 2 ) for free. cured ALL boost issues along with a new n75.
for what? 25 bucks? if that? my tech gave me mine ( 2 ) for free. cured ALL boost issues along with a new n75.
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Possibly he has the W/G cracked open by having too much tension on the rod however this isn't his first set of W/G. counting what was likely on the orginal set he swapped back in I think he's had 3? W/G on here? I know he got a set of 1BAR W/G from Krazy in an attempt to rule out W/G issues. I'm not sure how he wired them closed but I know it's doable and can be done if the vac is disconnected but if tension is too high it might leak. He's done multiple boost leak tests and I believe the DVs were replaced. Not sure about the check valves but he's had that system torn completely apart I think - this is his third thread about the problem :-(
^can't believe I 'missed' wastegate adjustment...if the rod/flap tension is too loose the turbo's will never hit desired boost pressure(unless a permanent vacuum is applied)...hook up the N75/hoses/etc and tighten down the rods a 1/4turn or so each try(leave the clips off and the jamnuts just 'snugged') until you find desired pressure-assuming its the issue. 1bar wastegate should begin to loosen/crack rod tension at 1bar/~14.5psi