I've had my car down for about a year while I tore out alot of crap and replaced with some new stuff (mostly electrical components, nothing that would affect the engine/turbo). I did replace the craptech w/ an SFMU and new SS lines, but other than that... everything is the same.

So anyways, I took it to the dyno last night to tune, and for the life of me could not get the car to push more than 10psi. It would raise up to around 12psi then fall back down and hold at around 10psi. The turbo is being way overworked, and I've never heard the bov so loud before, but it just doesn't seem to be getting into the engine. Completely took off the mbc and opened the wastegate with no change.

Outside of leaks in IC pipes and vacuum lines, should I be checking anything else out? I couldn't find any leaks last night while I was there and I'm going to tear into it, but I'm here wondering if it could also be the wastegate or bov? Any suggestions?

DSM Registry:
http://www.dsmregistry.com/137

Setup in a nutshell:
8.8:1 block, 3 angle valve, port/polish
440cc injectors, Vortech SFMU, Walbro Pump
Apexi SAFC, Missing Link, FFWD mbc (got Hallman mbc on the way)
HRC S16g, Greddy Type-S Bov, Starion FMIC

Should be running 16psi,
- J

Well if it did with the MBC and without it, then its definitely not a MBC issue. If the wastegate was stuck shut, you'd definitely know.. you'd be building a shit-ton of boost, you wouldn't be able to control it. If it was stuck open, well, you wouldn't be building any at all. I think it's safe to put your MBC back on, all that does is delay the signal from getting to the wastegate until you reach your desired boost level.

It could possibly be a leaky BOV. I see you're using a Greddy Type-S. I know Greddy valves are known to leak over time, thats why I decided to go with an HKS SSQV. Another idea I had was throttle body; are you sure the throttle plate is opening all the way? On second thought, even if a very small opening was made (ie, the throttle plate only opened 5% of its max) the manifold will pressurize just the same. So that can't be it.

My money is on a leak somewhere between the turbo and TB. Triple check your connections. Check your intercooler endtanks for any hairline cracks (it happens, rarely), and definitely check the BOV. A trick I always used for diagnosing boost leaks is your average can of carb cleaner. With the engine idling, spray all possible leak areas and if the engine revs, you've found your leak.

Btw, on my 1.8T Jetta I had a massive leak from one of the connections on my intake manifold and the car behaved just like yours is. I just remembered this. The rubber in a 1/2" hose coming off the manifold had deteriorated over time and eventually broken off. It made me HATE my life until I finally figured it out.

pressurize the system and look for boost leaks.

The couple of times this happened to me, I had a rip in an intercooler pipe coupler or a pipe that looked like it was in it's coupler (but wasn't). Everything looked OK, but leaked heavily under boost. With the boost controller reading from the manifold, the turbo was running wide open to make boost. In one case, I overspun the turbo and tore up the seals. Once I said "What's that high pitched squeal", it was too late.

Corbin
'95 ESI-T

Now with more power and fewer leaks



Humble servant of the Wiki

lol, well... I've got some brand spanking new couplers & t-bolts from Xtremepsi that should arrive on Monday. I'm fully hoping that all 'these issues' will be gone come Tuesday :twitch

- J

How high were you boosting before? May have a restricted exhaust, a weak EGR (if you still have it), or even a bad wastegate spring.

Was running 16psi before w/ no EGR and same 2.5" exhaust.

- J

Im having the same issues but i think i got mine narrowed down to a bad spring.

some days ill build 15# of boost and some days it will jump to 8 then drop to 5...lol

iv checded everything, the only thing i havnt done is phisicly take the wg apart and check the spring and diaphram.