Good morning all you terribly beautiful people!
I have a question
I've got a stock block evo 8, hks 272 cams, Ams 3.5" interfooler, Muse charge piping, straight 3" exhaust, a tdo6sl2r/20g turbo in an evo 8 chra, MBC, E85 on 27 lbs and speed density.
Here's my issue, I get compressor surge mildly in 3rd but pretty bad low down in 4th and 5th.
What would be the best way to fox the issue?
1. EBCS and tune down the duty cycle in affected gears so it doesn't build enough boost to cause surge
2. Cam gears
3. Upgrade to an evo 9 chra and get a antisurge compressor housing.
The compressor housing on the turbo now is stock intake size with the ETS 3" SD intake.

Any opinions?

 

This may sound too simple but worth noting. What bov are you using and what spring? I've found too stiff of a spring can also cause surge. Also what rpm is it surging?

 

Does it happen if you turn your boost down?

 

Tial qr with an 11lb spring. Car runs 16ish vacuum at idle. The 11lb spring is what's rated for my vacuum level. I can keep it from surging by just not giving it full pedal.
At wot in 4th it surges from about 4k till 5500, in 5th its pretty close to the same as far as surge starting tho it stops sooner.

 

While it was getting tuned it didn't surge when the boost target was 24psi. It still surged in 5th, but not in 4th.

 

just to verify, you are getting:
If so, you should stay under the boost before that happens. With a 3-port, your tuner can program the boost for each gear and avoid this. Other option is to find an antisurge compressor housing (if anyone makes it for your turbo).

 

Yes. Compressor surge due to too much boost too soon, not bov flutter.
There is no antisurge housing for the evo 8 chra, there is one for the 9 chra. So one of the options I posted in the OP was to upgrade to a 9 chra with antisurge housing.
Was considering the 3 port tho as it'd be cheaper and I could use it for keeping torque down.
Setup now is limited to 27 lbs due to torque peak of 429 at 29 lbs. At 27 lbs it's right around 400