Efini Y-pipe....
 

replace the stock y-pipe with efini y-pipe produce hp increments? ....many people said 10 hp.... is true?

From what I've been told, it does lead to an increase in hp, but primarily b/c of increased boost, not necessarily flow. When I made 421 rwhp on BNR twins (see the link in my sig) I was still running the stock y-pipe :)

The main benefit of the latter Y-pipe is that it doesn't use a coupler to connect the crossover pipe. Due to the heat generated in that area from the turbos, that coupler is notorious for splitting and causing boost problems. Other benefits, it looks damn nice when polished! ;)

More like 1 or 2. Whatever it is it isn't enough to be dectable by the butt dyno.

Maybe your butt dyno should be recalibrated. :lol:

Word. Of course, the BNRs run cooler than stock twins, so my coupler never gave me any problems, even at 19 psi ;)

Too lazy to search right now, but I could have sworn that I read a thread here from a couple of years ago that verified about 1 psi > at WOT....all else being equal. Credited to better flowing at the 'Y' because of the design. I don't know what that would translate into hp. I confess though, I bought mine because the cross-over was polished and my coupler was getting crispy. ;)
Still... FWIW, I opened my intake from stock, but still had no problems with spike until I added an efini 'Y'.

FWIW, I was just surfing the MAZDAMOTORSPORTS site and ran across this for the efini 'Y' pipe. Ten (10) hp (I assume at the crank) sounds a little ambitious, but.........
"This kit is a worthwhile addition. Includes two new aluminum pipes. One replaces the longer Y-Pipe coming off the turbo and now has a flange fitting instead of slip fitting at the top. Also, the plastic pipe that used to attach to this pipe with a slip coupler is replaced with aluminum, also with a flange fitting. This eliminates the possibilities of the slip coupling popping off under high boost, or the plastic pipe breaking. Smoother airflow brings the added benifit of 10 additional horsepower. From the 1996 Japanese Efini RX-7. Includes all necessary hardware."

Does the coupler in the stock y pipe actually reduce flow? Has anyone found a legit link to the efini y pipe proven advantages or hp numbers?

Read the post directly above yours. Mazda claims 10 hp increase.

I had one on my other wise stock FD back in 1999, don't think 10hp is valid. Mazda did bump up the HP rating of the FD by 10 hp (iirc) in '96 but they changed ALL the intake and IC piping. The later stuff all looks much smoother.

To get all 10hp I think you need all of the intake and IC piping.

I also was thinking 10hp seems like a lot! Adam, i seen the post, but when i went to the mazda motorsports website, i couldn't find anything about it, so i assume its been removed.

the JDM cars were 265hp from the start i think, they of course have no precat... i also had an efini Y pipe and duct set in 99, and its better, but i don't think 10hp is valid either

Early cars were 255, then 265 and the autos were still @ 255, post updates...so short answer no, won't give ya 10hp!

Yes it does reduce flow , any bend , any material , anything at all that diverts , directs , air will reduce flow thats just how things work (thats why its recomended to have as gradual, and smoothest the bends possible)this is why some exhausts are better then others.

The big question is which one reduces flow the least apparently the Efini Y pipe makes a difference in power better smoother flow means the turbos need to work less to achieve the same ammount of flow / boost . which means better spool , which means better VE , which means better power , or the illusion of better power from the extra spool .


10 HP is pretty big claim for a small pipe . But saying the car will gain some torque and power is not a lie .

Also the fact that that rubber coupler is a problem point is no lie , Ive had mine pop off numerous times , had to replace it with a silicone one since I dont have the stock IC my setup so I couldnt run the Efini Y pipe. otherwise I would of gone that route .

I don't have a picture of them for comparison, but IIRC, in addition to smoothing the connection to the cross-over, the large nipple at the 'Y' junction is pulled out of the air flow.