What is the max. “allowable” boost pressure for 12 valve engines?
The HX-35 and HY-35 turbochargers are rated for a maximum boost of 44 PSI. To safely reach 44 PSI, the turbine housing MUST be sized to keep the choke point above 40 PSI. The 12 cm2 housing chokes at about 32 PSI and the 9 cm2 single port housing chokes at somewhere below 30 PSI, so be careful about pushing the stock turbocharger beyond 30 PSI! From: Drdonnelly@aol.com Well, Cummins used to say 30 psi was max, but no one running 35-40 has experienced failures related to the amount of boost, so now they seem to say 35 psi or so is OK! Of course, the turbo is spinning at or over 200,000 rpm. At any rate, the Rams don’t see the upper boost levels and turbo rpm for much of a duty cycle. From Dave F: 1 pound of boost for every 10hp is the maximum engine requirement. Overboost does not increase power. Excessive overboost increases the manifold EGT and reduces fuel economy due to the increased exhaust pumping losses. The “choke point” of a turbo charger is defined as the maximum exhaust volum
