boost still dropping at RPM.

[summit]

Went to the track last night after opening up the valve lash per Billy Anderson's suggestion to try and solve a boost drop problem. Still doing it. Boost starts dropping at about 6500 rpm and will lose almost 4 pounds by 7300.

HKS GT wastegate--adjusted tight as possible with stock(?) spring
4 bolt 88 turbo
274 Stage II with Stage II heads
70mm throttle body on a Hemco intake mated to a stage II intake
750 pounds of pressure over the nose, 280 closed
Using an innovative boost controller
MSD DIS--have not tried to bypass it yet
CAS front mount
3.5 downpipe

Car ran best being short shifted at 6500 rpm.
Went consistant 6.02 @ 117 1/8 mile last night.
If I tried to stretch it out to 7300 times dropped to 6.3 @ 112
Boost controller had no problem holding a 12 or 14 pound launch boost setting, and boost would peak wherever I set it at (25-27 pounds). I guess next step is to use an old school bleeder for boost control and/or bypass MSD box. 70mm throttle body shouldn't be a restriction at this level? Suggestions?


Greg Kring
Arlington, Texas

 

[Otto J]

You may try setting up your innovative controller with a c02 setup for better control, It has worked for me
Do a search there are a few thread on it here

 

[EightSecV6]

What is the lobe sep. on the cam?

 

[summit]

Cam specs

intake .635 lift 248 @ .050 duration
exhaust .609 lift with 242 @ .050 duration

lobe seperation is 110
110 intake centerline

lash speced at .016 from comp cams, now set at .024--no change
street roller grind

Maybe run straight wastegate and bypass Innovative controller for now? Car seems to take the boost fine as long as I don't try to leave with more than 12-14 PSI of boost.

Greg Kring

 

[ijames]

Is this a new combination that has never not done this, or is this a problem that appeared on a previously okay setup?