The Flying Kiwi (another build thread)

[anyonebutme]

Ah, so it would be quite close to perfect if you ran the 9B's at waste gate boost and the boost controller just on the T04.

I don't think it'll work like that without enlarging the wastegate hole, but it might. The compressor size actually has little to do with how well the turbos interact with each other. Having the other turbo will increase the deltaP across the turbine of the 9b's, which would require even more gating than stock. The mechanics behind it are mind boggling complex. In my diesel forums guys who have been building compound setups for years will tell you they learn something new everyday, lol. Case in point: If you lower the boost of the 9b's, you'll end up having to mess with the gate on the T04 because it will be receiving higher thermal energy now that it's bypassing the 9b's, and they play off each other constantly so finding the sweet spot can sometimes end up to be a chore on some setups.

Looked it up, total boost is the product of the absolute pressure ratios of each stage, then converted back to gauge pressure. Example: Say a symmetrical PR, each stage of 2.25, so each turbo thinks it's boosting ~18 psig, final manifold pressure will be a hair under 60 psig.

When you add in intercooling, especially interstage, then it starts getting nuts in the mass airflow front.