Loosing all boost,could it be the tune???
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Loosing all boost,could it be the tune??? I just finished up my forged ls1 with single turbo on my ws6. Everything is going great,i have about 1000 miles on the setup running off the mass air just to break it in. I bring it to the dyno and at 4800 all 14psi goes to 0 for the remainder of the run.
I have a post in the FI section and have done everything to verify any leaks,wastegate,bov or anyother mechanical problems i can think of.
Could there be any problem with a tune that would maybe shut off injectors or spark at a certain boost level or rpm. Its a sd 2 bar tune with hp tuners. With a 5lbs spring it will pull to6500rpm. Its only with the 14lbs spring that at about 10lbs it will all of a sudden drop to 0psi and make very low power. Car runs clean at 0psi,no mis or anything. Only thing is it goes dangerously lean as soon as it hits 0psi.
Any ideas?
I have a post in the FI section and have done everything to verify any leaks,wastegate,bov or anyother mechanical problems i can think of.
Could there be any problem with a tune that would maybe shut off injectors or spark at a certain boost level or rpm. Its a sd 2 bar tune with hp tuners. With a 5lbs spring it will pull to6500rpm. Its only with the 14lbs spring that at about 10lbs it will all of a sudden drop to 0psi and make very low power. Car runs clean at 0psi,no mis or anything. Only thing is it goes dangerously lean as soon as it hits 0psi.
Any ideas?
I'd lean towards a mechanical failure, really dont' see a "tune" reason for it dropping boost. On my S/C car i lose boost with a vacuum leak, different i know, but whenever boost drops it always seems to be mechanical.
Maybe 10PSI is just more than the particular turbine can make
all the way across the band? Though it should not go to 0PSI,
you'd think. If something goes way wrong like the wheels get
unstable the exhaust might "stack up" (not a turbo guy, but
I've seen electric motors that can get into a shaft-wobble
mode and sort of "bind up at speed" (speed well lower than
normal). You ought to hear ugly sounds from something like
that.
Can you get another pressure reading (maybe both turbine
and impeller) to verify that it isn't an instrument problem, a
ground problem etc.?
Is this a purely mechanical control or is there an electronic
boost control gizmo in the mix?
all the way across the band? Though it should not go to 0PSI,
you'd think. If something goes way wrong like the wheels get
unstable the exhaust might "stack up" (not a turbo guy, but
I've seen electric motors that can get into a shaft-wobble
mode and sort of "bind up at speed" (speed well lower than
normal). You ought to hear ugly sounds from something like
that.
Can you get another pressure reading (maybe both turbine
and impeller) to verify that it isn't an instrument problem, a
ground problem etc.?
Is this a purely mechanical control or is there an electronic
boost control gizmo in the mix?
I dont see why Tune would cause a sudden drop in boost.
If you're boosting 14psi up untill you reach a certain RPM then it has nothing to do with how much fuel or timing is added.
I'd guess it's eigther your boost guage reading incorrectly, you have a leak somewhere, or your wastegate is suddenly giving out.
I've never had a forced induction car, but thats what I would assume it is.
If you're boosting 14psi up untill you reach a certain RPM then it has nothing to do with how much fuel or timing is added.
I'd guess it's eigther your boost guage reading incorrectly, you have a leak somewhere, or your wastegate is suddenly giving out.
I've never had a forced induction car, but thats what I would assume it is.
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The gaugle is fine. Its not that its only reading 0psi,it loses all power along with it indicating no boost. I have tested everything mechanically. There are no leaks,the waste gate is closed. I was thinking something like its cutting the injectors off all together and thats why it goes insanly lean when it drops to 0psi. With no fuel at all there wont be exhaust to spin the turbo. My question is,is that anything in the tune that i could have checked that could possibly do something like that.
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Could be 14psi is the weak point in your intercooler piping/connections, it hits that psi and the connection that held up until then pops out all your boost. Maybe re-tighten everything up just to be sure ?
Just a thought - at least that's usually what it is when I lose boost...
Rob (Bad30th)
Just a thought - at least that's usually what it is when I lose boost...
Rob (Bad30th)
what are you talking about? the engine doesn't cut off when the MAF is maxxed and you can't change the MAF frequency.... you can use an intermediate device that alters the signal but the MAF's output is fixed.
Last edited by Frost; Oct 13, 2007 at 02:28 PM.
It's peculiar that it's described as a dead cut and not just
hanging on at some lower level of output / boost. Would be
good to know if this is something where, on the street, if
you backed down to (say) 4000 and boost came back up
or if it's stuck off until restart etc.
I did encounter something like this years ago when I was
playing around with transmission torque management. I
had tried to make a "flat torque" limit by messing around the
% torque reduction table, and under some specific street
driving circumstances I would get a "hang" with very reduced
power, stuck until I let out the pedal. So I think you do
want to review a dyno log for signs of unexpected spark
retard (who knows, maybe heinous knock or false knock is
there and your loss-of-boost is really saving something (or
just an overreaction). Or there's some torque management
threshold that you just crossed, that never bothered you
before but now oversteps and kills torque where it should
just roll it back. Like on my car there's a hard 640 max
value and maybe you stepped over the line with 10#, and
need to zero-squash it instead.
hanging on at some lower level of output / boost. Would be
good to know if this is something where, on the street, if
you backed down to (say) 4000 and boost came back up
or if it's stuck off until restart etc.
I did encounter something like this years ago when I was
playing around with transmission torque management. I
had tried to make a "flat torque" limit by messing around the
% torque reduction table, and under some specific street
driving circumstances I would get a "hang" with very reduced
power, stuck until I let out the pedal. So I think you do
want to review a dyno log for signs of unexpected spark
retard (who knows, maybe heinous knock or false knock is
there and your loss-of-boost is really saving something (or
just an overreaction). Or there's some torque management
threshold that you just crossed, that never bothered you
before but now oversteps and kills torque where it should
just roll it back. Like on my car there's a hard 640 max
value and maybe you stepped over the line with 10#, and
need to zero-squash it instead.
Bov leak ... Or a boost leak somewhere. One of my dsms when i first bought it had a bad boost leak it would build up to12psi where the boost guage was set then it would leak it out back down to like 2psi during a 3rd gear pull.
same thing happen to me... It was valve springs.... if you have 14psi in the intake you have at least double that on the exhaust... big cam.918 springs and big boost .. I bet its holding them open....
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I dont think it is the valve springs. We arnt talking about boost that leaves slowly,this thing pulls like a beast up to 10psi then right at ten it goes to 0 and actuall starts pulling a vacum at full throttle. I have brand new patriot golds on the new motor. I performed a boost leak test at the inlet of the turbo and there was nothing. It held up 30psi with no leaks anywhere. Im at the point were its either the tune some how or the turbo.
does your boost controller have overboost protection?
if your wastegate vented to atmosphere and it all the sudden got really loud you would know that the gate was being opened to the max
but to make vaccum.. i would have to say your tb is getting closed on you... have somebody watch to see if it stays in the wot position
if your wastegate vented to atmosphere and it all the sudden got really loud you would know that the gate was being opened to the max
but to make vaccum.. i would have to say your tb is getting closed on you... have somebody watch to see if it stays in the wot position
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I do have it vented to atmosphere for testing purposes and it does not get loud. It would make perfect sense that the tb was closing. Im going back on the dyno tomorrow so im going to check the tb blade. If thats fine im going to stick something in the bottom of the wastegate to feel the valve. Just to make sure that its not opening. If its not any of those 2. Its either a bad turbo in a wierd way, or some wierd tuning problem.