Boost Spikes And Then Falls Below Preset Boost Setting

[denisonnd]

Hi all

I recently took my a car to a track and noticed some unexpected boost issues

SO

-RB25DET + boltons inc turbo, external wastegate, plenum and more

-Link 4g Extreme

-Car was tuned 4 years ago, done 20000k, 10 track days or so

-300KW

-Boost 1.07 Bar

-When I floor it on a 3rd boost spikes up to 1.2-1.3 and then dropps off to 0.65 or so

-I originally had wastegate plumbed back into the exhaust, now I have it open

I've checked peak boost with open wastegate on the street and it seemed fine but when I took it on a race track and car was properly loaded up (drifting) boost went higher

My mechanics suggested that possibly could be a because car was tuned with wastegate plumbed into the exhaust and it has less pressure so it has a boost spike, boost comes back because link ECU would have some fail safe function to cut boost (or bring it to "safe" level once it a lot higher then it should

Another posiblility boost curve needs to be checked

What do you guys think?

[GTSBoy]

Reduced back pressure on the wastegate outlet is allowing the manifold pressure to blow it open. Probably need more pre-load. And set the boost controller up again to suit.

Edited September 16, 2015 by GTSBoy

[scotty nm35]

Wastegate springs soften with heat which exacerbates the manifold pressure issue. Slap some stiffer springs in it and see how you go. Sounds like the Link is working overtime to try and hold boost.

[Dose Pipe Sutututu]

Sound like too much base duty cycle before it comes on noise.

If you have a laptop, try reducing the base duty cycle

[STATUS]

will need the boost control tables changed n the Link to reflect the physical changes you just made.

[denisonnd]

Ok, so if I plumb it back it the way it was it should go back to normal right?