whats the main defference between the old twin turbos and the new one from 99 and up ?

 

The "high output" turbos (sometimes called 99 spec) have a special compressor housing design that increases efficiency a little bit. Mazda increased the power on cars with this turbo model by slightly increasing the boost level.

These turbos were quite popular because they were actually cheaper than buying a new set of original turbos. IMO the performance advantage of the 99 spec turbos is greatly exaggerated. They really don't handle much more boost or spool a whole lot faster or whatever. They're just a little better all around, which means they really make sense only for stock applications.

If you want to really make a difference, get BNR stage 3s, Knightsports twins, or just go single.

Dave

 

There aren't many differences between the 93-95 turbos and the 99 turbos. The turbines in the 99's have a very minor turbine clip(clipping the HT12 turbine doesn't gain any benifits). Compressor wheels are the same part and are the exact same. Compressor housings, the 99 has the abradable nylon insert which helps with spool, but hinders power up top by around 20 RWHP. Thrust sections are smaller in overall diameter but are the same 270 degree design. 99 turbine shafts are left hand thread which is better than RH thread. Really the only benifit to the 99's over the stock twins is the left hand thread shaft nut. Thats it. 99's are great for a stock car with just intake and exhaust. But if you are planning on more than that just let me know!

Bryan@BNR
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