Do I Need The Injector Diffuser?
 

Searched a bit, found some answers, but got to clarify some more.
Have a built S5 T2, 720/1600cc injector. 15psi, 350rwhp. just realized that I still have the fuel injector diffuser still in there. my question is, should I completely remove them or just ground there legs? does the injector need the top portion of the diffuser for sealing or alignment? below are the primary and secondaries look like on a s5 t2. Can I leave the primaries alone and probably worry about the secondaries?
http://i58.tinypic.com/18ggi1.jpg
http://i61.tinypic.com/beegkj.jpg

With a modern type of injector, such as injector dynamics/bosch ev14 you can just remove the crap and install injector spacer s instead, Full functional engineering sells them for next to nothing.
With old school injectors i would recommend to keep them and keep them in stock shape. They help fuel atomisation at low revs and thereby emissions and idle quality.

Would you still keep the ones for secondaries?

They don't hurt you might as well leave them in.

If you notice,that little plastic piece on the bottom (holes..diffuser) can be just nicked off(the 3 little thin legs) and you still have the necessary seal and spacer to install an injector.
The newer injectors have a better spray pattern than the old stock injector.
Some Guys like to take that off just as a precaution so to not worry about it breaking off and causing damage to their "highly modded Rebuilt turbo engine"...
Others usually break it when they remove the diffuser/spacer..heh.!

So really,it's your choice.

I kept the legs/mixing plate on the primary injectors (720cc), but removed the legs and mixing plate on my 2ndaries (1600cc).

I kept the diffuser upper portion and the injector air bleed lines to a non vacuum intake source in both cases as it just make sense to me that equalizing intake pressure above/below the injector spray would help with the pattern/output with boost and there is really no downside.

Others have disabled the injector air bleeds and counted on the rising rate fuel regulator and that seems to work fine for them as well.

Have a built S5 T2, 720/1600cc injector. 15psi, 350rwhp.

My S5 TII with stock hybrid 720/1600 @ 15psi was 380rwhp, so taking out the 2ndary diffuser must be good for 30rwhp!:lol:

Just kidding- results may vary.

Thanks Man, you answered my questions :icon_tup:

This thread got me thinking about the newer style injectors so I checked the price. I'm interested in getting some for my next engine build. Maybe 2 primaries at first to be low budget

I'm curious how much better the combustion is since the rotary is a pretty basic engine. Isn't that why a lot of people just throw carbs on their Na builds? I wonder if anyone had made dyno comparisons. Is throttle response better? I'm sure idle is better

Mazda spent an extra few dollars per car to put them there. I doubt they would have spent a few hundred thousand extra total on something that doesn't have a benefit.

That's how I see it, anyway.

That was also for the original injectors that shot out stream vs a must

As far as I'm aware, all "denso-style" injectors operate by spraying a fine mist, including the stock ones. It's likely that the diffusers were there to alter the direction of the atomized mixture, not necessarily to enhance it. Note that diffusers on some rotary applications are flat, while some are angled. Some have holes in the bottom, some do not. The differences in design are linked to different intake manifold designs, not different injector types.

The injectors FC's use are a fairly run of the mill type that most Japanese cars of the same era used as well, nothing unusual about them. However, the diffusers are fairly unique to the rotary engine so I'd imagine there's a use for them.

From the FD "service highlights" book



Attachment 557269

Cool, thanks! I'll just leave them in

I hope it comes off easy for me. lol

The secondary bleeds are far less important than the primary as the secondaries are up high in the manifold in a strong air stream.

But the primaries are VERY important and regardless of injector type I'd suggest keeping them.

Sure, modern injectors spray far better than old injectors but the geometry of our primaries kind of sucks. Blowing straight down into the port. Part of the job of the bleeds is to encourage that flow towards the port.

I have tuned and FD where the bleeds were removed and it is was telling. Compared to other cars, it needed about 20% more fuel to idle and richer ratios. It was also very difficult to achieve a smooth idle with a solid AFR because fuel would puddle in the runner.

The RX-8 has the bleeds and Mazda takes it even a step further. There is a little pipe poking up from the bottom of the runner that blows directly on the injector nozzle.

my tuner told me even if it breaks its should just go out through the exhaust.

..not before going through the engine first.
A piece of shop towel gave me Zero Compression..try a piece of plastic diffuser and see how it fairs out!

Do the Rx8's ones fit the early 13b engines?

Nope. :( They are actually part of the iron. Would take some work to modify the FC iron in the same way.