Low or no boost on primary

[Guest]

Hi, got a problem with my rsk B4. this problem doesnt happen all the time but it happens more than it doesnt if you know what i mean.

when i take off from stand still i get primary and secondary turbos kicking in no worries but then when it changes to second gear i get no boost at all on the primary until i pass the VOD and get a massive kick of boost from the secondary. instead of the usual engine sound i also get this deep groaning sound. and it will keep doing this each gear change. i dont have a boost guage but i can tell theres no boost because i can probably run faster :.

bit of background its auto, no mods, just a rear dif back exhuast (fujitsubo)

any ideas or help will be much appreciated, cheers

[neodowd]

Are you changing gear in the VOD period? if you are the boost does some funny stuff unless you change down a gear.

[telemekas]

You may be experiencing Drop In.

The TT has what I call two distinct VODs

1. Transition:

This is the one noted on the Dynographs as the RPMs climb to max (same gear).

Usually with a noted boost drop of approx 8 psi @ 4100-4200 (BE5 Rev E)

This void is usually not "FELT" as much especially post tune.

To improve this and get to boost drop to approx 2 psi. The AICV can been replaced with a passive one way valve and the SPRV removed. Therefore no dumping to the intake.This is similar to that used in the Toyota Seq TT System

2.Drop In:

This is where th ECV (4100-4200 rpm) has just opened and then you up shift ie 1st --> 2nd before the secondary turbo has fully boosted.RPM then drops to ie 3500. However the ECV will not close until 3300 RPM (return point BE5 Rev E). Essentially in twin turbo mode in low rpm and trying to boost.

To improve/remove this move the transition RPM points ie ECV open @4600rpm and the return/close @ 3900-4000 rpm. this can be done via ECU reflash if you have DENSO ECU or via Zerosports Sequential controller for the earlier TTs

[Guest]

 neodowd said:

Are you changing gear in the VOD period? if you are the boost does some funny stuff unless you change down a gear.

Ill have to test that one out and see if that is when it does it, but because its an auto i just go flat down and let it change at the red line. Ill have a play around in tiptronic. cheers!

[Guest]

 telemekas said:

You may be experiencing Drop In.

The TT has what I call two distinct VODs

1. Transition:

This is the one noted on the Dynographs as the RPMs climb to max (same gear).

Usually with a noted boost drop of approx 8 psi @ 4100-4200 (BE5 Rev E)

This void is usually not "FELT" as much especially post tune.

To improve this and get to boost drop to approx 2 psi. The AICV can been replaced with a passive one way valve and the SPRV removed. Therefore no dumping to the intake.This is similar to that used in the Toyota Seq TT System

2.Drop In:

This is where th ECV (4100-4200 rpm) has just opened and then you up shift ie 1st --> 2nd before the secondary turbo has fully boosted.RPM then drops to ie 3500. However the ECV will not close until 3300 RPM (return point BE5 Rev E). Essentially in twin turbo mode in low rpm and trying to boost.

To improve/remove this move the transition RPM points ie ECV open @4600rpm and the return/close @ 3900-4000 rpm. this can be done via ECU reflash if you have DENSO ECU or via Zerosports Sequential controller for the earlier TTs

i think i may have to invest in the second option, mines a 2000 so ive got one of the earlier B4's. cheers!