Not really interresting for others than me, but anyway.....

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Std. engine T4 - 2L 4 cyl. 110bhp.

Max. RPM: 6000

VE: 90%

L: 2

Pr1: 1,8

CFM = 2*6000*90*1,8 / 5660 = 343,5 = 24 lb/min @ 20deg and 981mB

Half that to each compressor: 12lb/min

According to maps inside 72% isle: 2x T3 trim 40:

50% flow is 6lb/min

20% flow is 2,4lb/min

Thus surge-problem...

T3 trim 45:

Inside 74% isle

Same surge-problem.

T3 trim 50:

Inside 75% isle

Again surge-problem.

Hmmm. maybe instead opt for a smaller T2 as problem apparently worsens with higher trim ?

more to come