What's the point of a 3" DP...
 

I finally got the last of the parts back to reassemble my turbo ('91 TII engine). Looking at the outlet of the turbo, I can't help but wonder what the point is of the Racing Beat 80mm DP and 80mm exhaust when the outlet of the turbo plate is only 58mm?? My 80mm exhaust parts came on the '91 "organ donor", so it's not like I paid extra for it. ;) With the Fuel Cut Controller, RB claims "a 59 HP increase on a 1987 Turbo II RX-7". How much of that is free flow mufflers and no CATs? I wonder what impact modifying the rear turbo plate & DP for a "divorced" DP (seperate outlet for wastegate fed back in further downstream) would do to those HP figures? For reference "divorced DPs" are alledgely worth 20% HP gain on the Audi twin turbo V6...

Sounds like a future experiment... :D

Air becomes more dense the colder it gets. So you need more space to retain the high flow. A full, progressive exhaust would probably work best. But this is my thoughts.

Do some searching and/or asking in the FC section, NZConvertable made a divided DP and another guy (who's name I can't remember) make a custom DP for a hybrid turbo where the wastegate had a seperate tube coming from the wastegate and joining later.

My coworder who is turbo'ing his subie 2.5rs with a 04wrx turbo did this. Eventualy hes going to seperate the wastegate running internaly so there is less turbulance