turbotoaster

Ok maybe mr howard coleman can input on this or someone with a long standing idea on rotarys.

say you have a predicted output 750bhp which is roughly 100lbs of air, or 1000bhp in piston terms


you have looked at 2 turbo chargers, both claiming 1000bhp, ill list the specs below


Borgwarner s475 with 96mm turbine wheel on 1.32 turbine housing
Borgwarner s478 with 83mm turbine wheel on 1.1 turbine housing

as can see, they are different in there approaches to making power,

one buy decreasing backpressure to increase VE, which in theory is great for a rotary to reduce overlap of exhaust gas in the intake stroke.

the other runs a smaller turbine wheel which in theory means more backpressure but makes its power by running a larger comp wheel to 'in theory' make more lbs of air at the same boost.


now spool is effected by trim, comp and turbine wheel sizing but say you had to choose between the two, which would be your choice and why?

for example, which do you believe would spool sooner, make more power on a rotary and be better overal turbo.

to give you more reference
s475 with 83mm on 1.1 housing is claimed 950bhp(piston)
s478 with 96mm on 1.32 housing is claimed 1050bhp(piston)

as you can see there isnt alot in it.

my thoughts are the s478 due to the smaller wheel and turbine housing will allow it to spool enough to make it reasonable to someone with a 8.5-9krpm limit
where as the s475 with the big rear end are useful for guys running e85/meth or running a big bridge and a decently high rev limit


it would be really great for everyone to jump on board this conversation because ive never really seen a thread on here about what overall is best for a rotary and this place is where alot of people come to learn