Compound Turbo Setup and New Rubber

I was trying to get an idea of where I would put the large turbo in my compound arrangement. I think this will be the basic layout. I need to verify that this will all fit with the thermostat housing assembled. The Top turbo is a Borg Warner s300sx3 66mm/91mm compressor & 79mm/73mm turbine with custom 1.10 a/r housing from full-race. On its own is good for ~775whp. The lower turbo is a Borg Warner S400sx4 80mm/110mm compressor & 96mm/88mm turbine w/ 1.32 a/r housing. This turbo is good for about 1175whp currently. I'm looking at 3 or 4 different compressor wheel upgrades. I will likely go with a compressor with the dimensions 88mm/118mm. The goal is to get it to support ~1250-1300whp at a pressure ratio of 2:1.

The whole reason for doing a twin turbo compound configuration is for more area under the curve. The small turbo will spool to ~30psi initially. This added exhaust energy will allow the larger turbo to spool up sooner. It will also only be spooling to 15psi, instead of 45psi. This all equates to a system that will come up on full boost 1500-2000rpm faster then the big turbo would by itself. This will then allow me to not have to rev the engine beyond 7500 rpm, increasing durability. The added benefit is the turbos are each only running at pressure ratios of 2:1. They will barely be breaking a sweat when I'm running 45psi and making 1200+whp :)

The engine is being solid mounted to the tube frame. I do have lots sheet metal to cut away to make room for all of the new piping. The down pipe from the small turbo will feed into the turbine housing of the large turbo. The compressor outlet of the large turbo will feed into the compressor inlet of the small turbo. The compressor outlet of the small turbo will go to the intercooler.











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