Wolf_Tm250 wrote:
Ok....
what do you suggest ?
1) Controlling the boost rpm-based ?
Yes that will work, Motec would provide it, but tuning the boost curve on the Motec is a major job to get it just right.
2) Or... just an idea... given that I reached in track EGT 950 deg. C., and given that I know for sure it was available a bigger a/r turbine for that turbo, could I change to the bigger one a/r turbine, to decrease the backpressure ( less EGTs ? ), and to make the turbo build boost later (less surging ) ?
That should work by increasing the flow, and it should give you better top end, at the expense of bottom end power, which is probably not a bad thing considering thep power you have down low. One thing though, it may push the surge further up the rev range if the boost is raised any higher, I think 2.0Bar is probably more than enough anyway.
3) Any other method to avoid surging ?
Bigger air filter ? Now I'm using an A'pex Power Intake... maybe not so big at those values...
No, increasing airflow to the turbo will just make the problem worse, you need to improve flow from the turbo onwards. Changing the A/R of the exhaust turbine is probably the best option you have. Your cams should provide more than enough flow for this HP level, but you may be able to eliminate surge by changing the overlap, though that a "try it and see" option, and may not do anything, or could even make it worse.
So, in conclusion...
a) correct the surging problem
Yes
b) weld the wg feed pipe, flexi and brace on the wg exhaust, SILENCING the wg exhaust
no need to silence the WG exhaust if you don't have/want to, but it does need a brace and a flexi pipe to control expansion.
c) lower the EGTs
Yes 950 is far too high, should be around 850 or lower, especially if you're using a wideband O2 sensor, as that will not like those temperatures.
