I was trying to search why the Efini y-pipe flows better, but came up with no results. All I could find was you can get 10hp more, and about 1 more psi, not sure if that was up 1psi or 1psi less drop, or maybe thats the same.

Anyways, can anyone explain "WHY and HOW" it flows better? From my under standing the design is the same, just one uses nuts and one uses clamps.

 

I've never heard of anyone gaining 10hp, and i'm pretty damn sure I didn't gain 10 hp. lol Anywho, the efini y-pipe attaches to the crossover pipe via flanges instead of by a crappy coupler like the USDM rx7's use. Since it's a better seal they'll be less pressure drop. It's also more reliable then the USDM crossover pipe due to it being made from aluminum instead of plastic, wich is known to crack.

-Alex

 

I estimate the gain from 1-2 hp and less than 1 psi boost. It looks better and is more reliable.

 

Mazda Comp "claims" a 10hp, besides that is what I also read here onthe forum.

Yeah I know about how it connects, but "assuming" the y-pipe is pefect, the seal should be the same either way. I just do not see nor can figure out the "why and how"

 

They wont be the same even if they are in "perfect" condition and what not. The coupler on the USDM y-pipe SUCKS, and will leak no matter what from my experiences. The efini y-pipe bolts together keeping constant pressure between the 2, with a flat surface to seal.

As far as a 10hp gain, I'd have to see a dyno graph and provided proof that was the only mod. I just don't see ANY way you could gain even close to 10hp. I don't think people really do it for the hp, but more for the reliability.

-Alex

 

I also don't see how you would gain HP.. Like everyone said.. its made so that it doesn't pop off..

 

I am not saying its a 10hp gain, I am just restating what others and Mazda comp said.... how baout we forget about the whole 10hp gain

I just do not see what you are saying with the bolts v couplers, how it seals better as long as it is "perfect" and straped tight. Then I guess if you were to bolt together the intercooler piping you will see the same gains..... I am just searching here......

 

I personally don't think it gains you any hp if your stock ypipe wasn't leaking. I also don't agree ttrex when he says that the US versions always leak...I think thats crap. Mine didn't leak.
If the us version did leak and caused a 1 lb of boost drop that would be about 10 hp right there. I was actually under the assumption that it has a slightly different shape, which allows for a smoother flow, plus the flange. I've never had one so I really don't know. If its just the flange difference the only way it would give you hp gains would be if yours was leaking.

 

Mazda claims a 10 hp gain with this mod. I would bet that they have done extensive testing to back that up........... but I guess you all know better

 

I never said they leaked enough to have a pressure drop of 1 lb. You can think whatever you'd like, but the fact is the stock coupler is a POS, and doesnt clamp properly. Theres a reason why you see less pressure drop with the efini y-pipe!

-Alex

 

IIRC there was a 10hp uprating on the 96 FD. I believe Mazda did get 10hp more out of all the IC piping changes including the Efini y-pipe.

The IC pipes are smoother and should flow better along with the Efini y-pipe. The crossover pipe is larger than the stock plastic pipe in part because it does not have that cheesy mounting flange that intrudes on the cross section on the stock plastic pipe. The BOV nipple looks to be of a better design also, I'm sure someone mentioned that already

 

Negative, the design is not the same. The flange for the hose leading to the blowoff valve on the stock Y-pipe protrudes quite a bit into the collector for both turbo outlets; the Efini Y-pipe's flange is recessed, opening up and smoothing the overall airflow in that area. The crossover pipe not only is bolted and uses a gasket (doing away with the crack-prone rubber coupler, a major failure area), the bend from the Y-pipe is smoother, and the internal volume is slightly larger.

 

i am in the process of modifying my y-pipe in a similar manner. here are some pics of it. it is now has a metal flange using the efini y-pipe gaskets and has the BOV tube moved out of the way for more airlow just like the real efini y-pipe. here are some pics. definitely not as pretty as the one before but fully functional. i was inspired by seeing the previous garfinke pics plus my desire to do something else to the car.

the second pic shows how the turbo inlets are more free flowing than the original.

alex

 

here is a little something from the Japanese rx7 magazine, "I love FD3S RX-7".

In 1996, rx7 obtained 265hp.

-Boost was increased from 400mm/hg to 470mm/hg.
-Mazda has increased the size of air intake valve and improved the pipings.
-ECU was upgraded from 8bit to 16bit.

It's not the Y-pipe that made the car to obtain 260hp. Because of the Y-pipe and other pipe improvement, they were able to raise the boost safely.

 

Could someone just go dyno the damn thing so we can get this settled? The design is better, but whether it does anything other than look nicer and stay sealed better is arguable. We're talking about 1 and 2 HP here.. is that even noticeable?

 

When you hold an Efini Y-pipe (the name is a HUGE misnomer, BTW) and the stock Y-pipe, you'll understand .

I think the advantages have been fully covered - flange instead of the coupler, BOV pipe pushed "out" so the flange for the BOV bung isn't in the air path, and the crossover pipe is larger, better designed, and flows better. Not to mention it's aluminum and you can polish it if you so desire .

I think Corksport actually has it for like $215 - that's a DARN good deal. Even if you only gain 1hp from it, the difference in quality is well worth it. I think looking at it as a horsepower upgrade or bang-for-the-buck isn't the right idea - it's best to see it as upgrading the car with one of the refinements they made in '96 that we didn't get.

And, yes, they did add the new Y-pipe in '96 in Japan - not '99.

Dale

Dale

 

Has anyone successfuly converted to the 16-bit ECU ? Is it even worth it, with the PowerFC as an option ?

Neil

 

I made this one several years ago for my intercooler project.

 

I've had so many intake/intercooler combinations on this stupid car I can't even count them... I've had both the stock pipe and the newer one and noticed no difference besides asthetics. Only time I really noticed a difference is when I turned the TO4R up over 15psi..

 

Since stock boost control is not a very precise closed loop sys, I did see about a 1 psi gain with it. This means less pressure drop at high flow. With no boot, about 3" of strait length are freed up, and the transitions from each turbo's feed pipe are less severly kinked. Can be seen here.

http://robrobinette.com/efini.htm

If you are trying to get the most hp _per_psi-boost from the stock or BNR twins, every step to eliminate drop in the intake system helps.

 

The thing I noticed when I changed the y-pipe was the transition at 3000 rpm and 4500 rpm was cleaner / smoother.

 

Like I've mentioned, they made alot of improvements especially the Y-pipe. It should allow the air to flow better. Because of the improvements, they were able to bring up the boost reliably, raising the hp from 255hp to 265hp. 10hp did not just come out the efini y-pipe.

 

Didn't they also remove the precat in that same year?

Thanks for all the info, I apppreciate it. I was going to get them either way, I was just curious as to what made it better.

 

I'm not sure about the pre-cat. All it said on the magazine was that they "improved the pipings". (1996 and above)

Yea, I got the efini Y-pipe to prevent from cracking the stock Y-pipe causing it to boost leak, since my car is running higher boost than the stock 10psi.

 

the complete project. i just test fitted it and it clears the strut bar by about 3/4" and reaches the ic just right. now i just need to put it back in the car!