SPRAYED 01

iTrader: (22)

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?

SPRAYED 01

iTrader: (22)

anyone???

BanditTA

iTrader: (3)

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.

jimmyblue

iTrader: (11)

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?

exit

iTrader: (1)

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.

SPRAYED 01

iTrader: (22)

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.

jimmyblue

iTrader: (11)

The log files should show an injector pulse width cut,
an electric throttle angle being pulled, gross advance
pullback etc. Fuel, air or spark has to show.

trickeng

if it was only the turbo it would go way rich. since your is going lean, i'd look at your guage. its cheap enough to replace.

Bad30th

iTrader: (13)

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)

SPRAYED 01

iTrader: (22)

I had it on the dyno so i could watch all the piping and feel and leaks and nothing. Every thing is tight. Im totally stumped here.

moehorsepower

iTrader: (3)

If you are saying that the engine is just cutting off, then you could be maxing out the maf, did you change the frequency of the maf?

Frost

iTrader: (45)

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.

jimmyblue

iTrader: (11)

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.

217zenki

iTrader: (4)

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.

SPRAYED 01

iTrader: (22)

ill have the tuner look at the torque managment

Moparnos (The SLP Guy)

iTrader: (55)

are you still having issues? perhaps i can help

Casey2323

iTrader: (14)

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....

SPRAYED 01

iTrader: (22)

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.

MIGHTYMOUSE

iTrader: (59)

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

SPRAYED 01

iTrader: (22)

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.