Rb26, -5 Turbos, Boost Creep - Common?

[black bnr32]

Morning ladies and gents,

I'm troubleshooting some massive boost creep on my rb26 with -5s. I have not finished testing, but I am curious if others have experienced boost creep on a -5 setup. Is it common? Are we near the mechanical limits of boost control on this setup? I do not see many posts on this topic, so I suspect we are not near the limits.

Edited June 23, 2013 by black bnr32

[DVS JEZ]

Explain the boost creep.

[scotty nm35]

Too much preload on the actuators perhaps?

[R31Nismoid]

A setup properly ... Setup... There should be no creep at all.

[black bnr32]

this is with no preload, ported gates, boost controller off, verified working actuators and flappers, verified working datalogit signal for boost, and verified working signal lines

[scotty nm35]

So what's the problem? Just run 20psi and have a nice flat boost curve.

[black bnr32]

ha, I wish. I bet I'd see 30psi if I kept going.

[scotty nm35]

I doubt it, you are close enough to maximum best torque anyway, perhaps 24-25psi...

Do you have split dumps or something? Any porting done in the manifold or turbo opening?

Is the top end tuned? A lack of timing and excess fuel can raise boost like that.

[OoskylineoO]

I doubt it, you are close enough to maximum best torque anyway, perhaps 24-25psi...

Do you have split dumps or something? Any porting done in the manifold or turbo opening?

Is the top end tuned? A lack of timing and excess fuel can raise boost like that.

^ +1 on dump set up.

Actuators will not be the cause for boost creep, you get boost creep (generally at higher RPMs) because the flow of exhaust gas entering the turbine housing can not physically exit quick enough for whatever reason, i.e, turbine housing too small/restrictive, wastegate outlet port too small/restrictive, bad dump pipes or tune.

I would be looking into the tune or dump pipes, had a mate with similar issues on his XR6 where he tried everything to fix the boost creep, turns out he overlooked the dump pipe, even with the larger port and flapper upgrade, the problem was a poorly designed dump pipe causing it, WG flap could only travel a short distance before it hit the divider. Changed his dump and fixed his problem straight up.

[black bnr32]

My head, stock manifolds, turbine housings, flapper ports, and tomei bellmouth dumps are all gasket matched. My top end definitely could use some tuning. I was surprised how little the flappers move when testing them. Like 25 degrees at 20 psi