diagnose my low boost plz

[08_ms3_gt]

my setup = stock BPV, HKS SRI, AP 1.03 Stage1+SF 93oct map, 1 step colder NGK plugs gapped to 0.027"

the problem = LOW boost. generally around 14-16PSI, while the AP map specifies 18+/-1.5PSI. BUT it does still peak to ~20PSI before dropping. it does not seem to hold; instead, it continually drops.

what i've tried =
-swapped to the stock BPV from a Forge BPV+blue spring
-changed the spark plugs; seemed to smooth out the boost curve
-tightened all clamps except the [IC tube-->intake manifold]
-logged in a number of temperatures

any ideas as to what i can/should try? i've read that the stock map lowers boost in cold temp.'s due to the greater air density, but i've also read that the Cobb maps are supposed to make the same boost no matter what.

i've attached my latest maps. they were in 38*F temp.'s. my other maps are on page 7 of the "103 finals are out" thread in the Cobb ECU forum, which i can't attach here.

NOTES on the maps = WGDC is divided by 10 to fit with the boost/AFR/etc. scaling. thus 4 = 40%, 5=50%, etc.; the hiccup near 6k RPM on the 4th gear WOT log has not happened to me before, so it is probably an anomaly.

OTHER NOTE = my spark advance goes in the mid 40's when off the throttle - should i be worried?

please help!!!

[08_ms3_gt]

does anyone have ideas/input???

possible issues that have occurred to me:

1) both the stock and Forge BPV (w/ blue spring) leak
2) the intake does not flow properly for the map
3) a loose clamp/connection.. i don't know where

i've read other 'low boost' threads, but they all seem to include stock maps, which DO 'detune' the car in cold weather. i've been told that the Cobb map does NOT detune/reduce boost in cold weather. am i wrong? and is 38*F really that cold?


or am i just full of it and nothing's wrong???

[babcockxmx]

im having the same problem.it happened right after i installed an inlet pipe. i used tobe holding 18.5-19 psi and now its 15. tried stock and my hks bpv.

[08_ms3_gt]

Originally Posted by babcockxmx im having the same problem.it happened right after i installed an inlet pipe. i used tobe holding 18.5-19 psi and now its 15. tried stock and my hks bpv.

so your issue is probably related to the inlet.

are you sure that you tightened the clamps properly? i've already tried tightening mine, but there could be further issues.

what 'stock' did you try?

[danesti]

he tried stock BPV and HKS and the problem was present in both tests...

babs...
we were sufficiently high during this install.. i might have pussed out on a clamp or something (doubtful).
we gotta get your shit figured out though..

[08_ms3_gt]

i tightened everything down over the weekend - intake, inlet pipe, intercooler clamps, etc. it doesn't seem like anything changed. i can't 100% verify that everything was 100% attached properly, but it sure looked OK.

if your issue was NOT there prior to the inlet, then it seems that the issue is inlet-related.

that said, we might not have the same problem.

is the wastegate somehow tied/piped to the inlet?

[babcockxmx]

i have tightened everything down to the point of about to strip the clamps.

what else besides boost leak can cause low boost. because even when my stock inlet was leaking i was getting shit tons of kr but still help 18-19 psi.

[Haltech]

You did re-attach the vac line to the nipple for the WDC, correct? We installed the inlet on Lenny's car and his boost did not fall, it holds 19psi.

[mark2ooo]

What boost do you get if you put the stock map back on? When I used the cobb ap the maps never worked like they said they would and we got higher boost with the stock map.

[08_ms3_gt]

Originally Posted by Haltech You did re-attach the vac line to the nipple for the WDC, correct? We installed the inlet on Lenny's car and his boost did not fall, it holds 19psi.

i'll have to check that vac line - is it a common failure point? does the wastegate use this line as a reference to get the boost pressure in PSIG?

and about the inlet - i know that they get loose, and i tightened mine a few days ago. i had trouble seeing the inlet-->turbo connection, though - do i need to confirm that the inlet is properly seated on the turbo?

Originally Posted by mark2ooo What boost do you get if you put the stock map back on? When I used the cobb ap the maps never worked like they said they would and we got higher boost with the stock map.

i haven't tried the stock map recently, and i didn't have boost monitoring ability until i got my AP. i was thinking about trying the 91 octane map in case the car is running poorly on 'winter blend' 93 octane.

[babcockxmx]

08 id definately check the inlet on the turbo cus mine fell right off. u can tighten it baqck there with out taking anything out but u will be a lonngg extention

[babcockxmx]

and my WDC vac line is kinda of pulled to reach the new inlets nipple. if its bent at all would that have anything to do with it?

[08_ms3_gt]

Originally Posted by babcockxmx 08 id definately check the inlet on the turbo cus mine fell right off. u can tighten it baqck there with out taking anything out but u will be a lonngg extention

already did... it was definitely loose.

i can't be 100% certain that it was on properly, though. couldn't see shit back there. i assumed it was seated on the turbo and just tightened the clamp.

have you resolved your boost issue?

[08_ms3_gt]

Originally Posted by babcockxmx and my WDC vac line is kinda of pulled to reach the new inlets nipple. if its bent at all would that have anything to do with it?

if it's bent enough for the line to collapse under vacuum, then possibly. it depends on what the line is rated for.

a pretty quick (potential) fix would be to get a new, longer line for that. just make sure it's rated for vacuum pressures.

[arcticms3]

so i notice the map is rated for 93 oct, are you actually running 93 oct?

[08_ms3_gt]

Originally Posted by arcticms3 so i notice the map is rated for 93 oct, are you actually running 93 oct?

of course. it's just possible that gas companies throw extra ethanol or whatever into fuel in the winter to avoid any potential cold-weather issues. i'm not really sure what issues they're trying to avoid, though.

[08_ms3_gt]

UPDATE:

i spent awhile trying to get the inlet tightened down REALLY tight and seemed to have picked up more PSI aka like 1. maybe it's still loose...? anyone have personal experience with what it takes to get the inlet properly attached?

observations:
-the boost still drops as before, only seems to be scaled up a bit.
-i get more boost in 4th than third, probably due to engine load.
-the logs won't indicate it, but the car feels more responsive. power/boost comes on faster but still drops.

i'm still stumped. have you fixed your boost, babcock?

anything relevant with these values?
-->WGDC is around 40-60% for WOT runs.
-->Relative throttle is around 71-73% at WOT.

is it possible/likely that i have a bad turbo???

[danesti]

babs` boost is still a boo boo....

[babcockxmx]

those vlaues are fine 08. what are u using to read boost?

[08_ms3_gt]

Originally Posted by babcockxmx those vlaues are fine 08. what are u using to read boost?

i'm reading boost using the AP. i'd love a legit boost gauge but have been told they void warranties.

i'm really hoping you figure out what's causing your low boost so that i can apply the same fix for mine

today, i took a few steps towards troubleshooting:
1) tightened the throttle body hose clamp
2) swapped in the forge BPV with blue spring+1 shim for shits n giggles
3) reset the ECU
4) tightened other hose clamps

aaaaand
5) fucked up the inlet clamp. tightened it too much, i think, because it's now 'slipping'. not sure what to do about that one since it *might* be tight enough and swapping clamps would prolly be a PITA.

[babcockxmx]

clamp would be easy to swap. just take out the inlet and do it.
the wierd thing that i just found out is its only showing lower boost on my boost guage. my AP still says im spiking 21 holding 18.5. my guage used to be the same as AP then i installed my inlet

[08_ms3_gt]

Originally Posted by babcockxmx clamp would be easy to swap. just take out the inlet and do it. the wierd thing that i just found out is its only showing lower boost on my boost guage. my AP still says im spiking 21 holding 18.5. my guage used to be the same as AP then i installed my inlet

i suppose it wouldn't take long to actually take the inlet out. i almost feel stupid doing so, though, without putting an aftermarket one in...

do you mean to tell me that your gauge indicates lower boost while the AP does not?!?!?!? hmmmm. well, in that case, it would appear as though i'm the only one with a problem.

that said, i'm curious why there's a discrepancy b/w your MAP sensor and boost gauge. they should be reading the pressure off the exact same system.

do you notice a power loss with the 'low' boost?

i also find it interesting that my car is still spiking to 20.x PSI but doesn't hold the pressure. the turbo is delivering yet the boost doesn't sustain. maybe the boost drops because the stock exhaust doesn't deliver enough flow..?

[08_ms3_gt]

per dread's recommendation, i tried the MSCAI map instead of the Cobb SF, given that he mentioned having low boost with the CAI using an SF map.

the results are good - i'm holding ~17psi at WOT, which isn't quite 18 but within the map's specification. this would indicate that i can either
1) get a custom map from Cobb
2) tweak the map when ATR comes out
3) order a new intake, either Cobb or MSCAI
if i was hell-bent on making 18.5psi.

otherwise, the logs look OK. a little more KR than before, but enough to worry about?