bigdgsr

iTrader: (1)

Yesterday the car went on the dyno to do some ignition tuning and to up the boost. The car is healthy and from what we can tell, there are no boost leaks. The car holds 10-12 psi steady. It was tuned on a mustang dyno and at 10 psi it said 252 HP and 208 Torque. We starting turning up the boost and what would happen is that at 4500rpms the turbo would hit 19 psi but then just fall down to 10 psi by redline. Its a Garrett T3/T4 60 Trim .63 AR turbo. Both housings are Shodan Coated and the backhousing on the turbo has been port matched. We were not making any more power. Boost is controlled by a Greddy Profec B Spec II boost controller. We turned up the boost controller and played with the gain but 3 consecutive runs the dyno boost plot showed exactly the same thing happening. The boost just fell off after 4500rpms. The boost controller changes made no difference. I have a 8.7lb spring in my Tial 38mm wastegate. We were thinking the the manifold pressure was just blowing the wastegate open as the RPM's climbed. Maybe the Greddy Boost solenoid has gone bad, but it seems to hold about 10-12 psi okay. I didn't have access to a bigger spring, but I am thinking of putting a 1 bar in and seeing what happens. Any ideas?

Set-Up:
-B18C1 .20 over
-Wiseco 9.5:1 Pistons
-Eagle Rods
-Ported GSR Head with ITR cams and valvetrain
-Skunk2 Cam Gears
-ITR TB & Skunk2 IM
-SFP Street Manifold
-Garrett T3/T4 60 Trim .63 AR
-Tial 38mm Wastegate with dump routed under oil pan
-2.5" DP flared to 3"
-3" Kteller Exhaust
-Endyn Catch Can
-Cometic HG & ARP Headstuds

PrecisionH23a

Is the boost controller hooked up properly? Everytime I have seen a boost controller spike like this it has been installation error.

bigdgsr

iTrader: (1)

Yes it ran last year with no problems when I was running 10 pounds with a 3 psi spring. It really wasn't spiking. We wanted to run 19 psi. It would go to 19 psi and then just fall right off after 4500rpms.

PrecisionH23a

Try setting the gain and low boost turned all the way down and do a run. See if it holds a steady boost pressure.

Also, were you doing the 19psi run on the low or high boost setting? I always set the high boost dial higher than the position of the low boost dial.

bigdgsr

iTrader: (1)

It was under the low boost setting for the 19 psi run. Right now its holding about 12 psi steady. Really anything much higher I think the wastegate spring can't handle it and you can see the boost dropping.

turbotime

how old is the turbo? WIth that ebc the spring pressure shouldnt matter the profec should be able to hold way more than 12psi, seems like you need to tweak your settings if boost is falling off, have u played with anything other than the gain? like set boost, and all that other crap

PrecisionH23a

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bigdgsr &raquo;</TD></TR><TR><TD CLASS="quote">It was under the low boost setting for the 19 psi run. Right now its holding about 12 psi steady. Really anything much higher I think the wastegate spring can't handle it and you can see the boost dropping.</TD></TR></TABLE>

Run high boost for the 19psi setting and see what that does.

bigdgsr

iTrader: (1)

Thanks for the responses. I decided to just tear out the boost controller and start from scratch. I think one of my vacuum lines had a tiny tiny hole in it. Re-installed the boost controller with new lines and right now it seems to be holding about 16 to 16.5 psi just fine. I ran it few times just to make sure it was holding correctly. Gonna hook up the wideband and laptop this weekend and make sure everything is OK.