Diameter?
 

anyone know what size pipe is uses for 1987 Mazda rx 7 ? I'm removing the front cat and need to know what size pipe to fab . I also need to know what kind of steak is used for an exhaust . I would like to use something stronger but yet lighter then what's on there ? One more thing if I replace the front cat with pipe will I need to get my car tuned ? It's non turbo and there aren't any upgrades other then the parts I have hanged to get it road worthy and safe this year for me to enjoy and see what's going to fail from driving it . Thanks guys

the Ecu on the car can't be tuned so Forget that aspect of it.
(Unless you get an after market ECU that has that Capability).

I think the sizes are 2.25 and 1.75 for pipes.Y pipe and mufller respectfully.

Steak?.T-bone..(chuckle!)

the FC is 50mm I.D. pipe until the Y and it splits to 2x 40mm pipes (from memory).

for the front pipe, the stock diameter is pretty ideal, although going to a 60mm ID is fine too, going smaller is bad.

the Y pipe could be 2x50mm ID

Racing beat makes off the shelf stuff if you feel like it.

for the steak try reverse sear, Cooking Temps: When To Cook Hot & Fast, When To Cook Low & Slow, And When To Do Both (Reverse Sear)

my friends are nerds, so we use 2 thermocouples, and it plugs into a bluetooth thing, so you can read temps on your phone.

You can do hot dogs with a 2 wire electrical cord!...wrap a nail with the stripped ends and then place the nails in each end of the hot dog and then plug in the Cord!
Booyah..hot dogs in 30 seconds!