RalliSpec.com is selling a Type RA spec C motor.
But it says "add $2400 for a twin-entry turbo"
what's that and what's good about it?

- ben

 

A twin-entry turbo is a very trick turbo. Its turbine housing is split into two "channels" through which the exhuats gases are flowing from 2 matched pairs of cylinders.

"Multi-cylinder engines have ranges in which there is some overlap in the exhaust valve opening timing of one cylinder and its sequent cylinder. This can cause interference to the exhaust gas flow where the exhaust gases from the two cylinders join and results in exhaust energy loss in the turbocharged engine. Also, cylinders which have just finished the exhaust process are
affected by the high back pressure of the exhaust initial process, so that high pressure gas remains behind more easily. This hinders smooth intake flow to the engine. This design
increases the engine's low-speed performance and acceleration response." -- Turbo Magazine, 1990

Here is a pic of a typical twin-entry turbo.



Such turbos are used on a varienty of JDM cars such as MR2's, later EVO's and many others.

 

Basically, it is called a twin-scroll turbo, which is what the Evolution 8 is using.