Have an R53 with Borla sport exhaust, Madness intake and a 15% pulley. Have been thinking about changing the injectors and doing an RMW tune on the ecu. so I have a few questions. 1. Which size injectors work best? Been looking at 400 or 440. 2. Can I run the engine on the new injectors while I'm waiting for the ecu retune? And #3. Is the RMW retune the better way to go or is their someone else or something else better?

 

380's / 440's / 550's
You can not run anything larger than the 380's without tuning Immediately.
If you're not going to mod any further the 380's would be fine.

As far as tuning, the 2 front runners are RMW & Mynes/Bytetronic, everyone will have their own opinions and they will work differently, you'll have to just do some research .

My choice is in my sig.

 

When I was doing research for which injectors to go with I came across people experiencing problems with the 440 injectors. Stick with 380s or 550s I would say, unless the tuner that you use has a specific preference.

 

Yup....ditto on blown away...
One question....
To tune at this point kinds finishes your car...generally tunes are less tolerant to future mods...and if you are ready to spend $1000 ish....and kinda freeze your build mechanicly....unless you get a retune...so be sure you are where you want to be.
do not get me wrong, my tuned car runs better, smoother, with more tq and power....i am happy, just be sure you are where you want to be...tune it now, then want a cam means a retune...
Tuners have their favorites, just buy quality, with the right spraypattern...this has been coveted a million times,
At this point it sounds like jcws are fine, and CAN be run ok (you will loose hp due to too rich) if you looses a tune from a dealer reflash, no adaptors(pigtails) needed, but i would check with the tuner of your choice....

 

This is as far as i plan on going. No more mods after this. Just trying to keep a slight lead on my younger brother who drives a miata. And his pockets are now as empty as mine.

 

Then yes 380's, will work without a tune, will work better with & no worries about accidently loosing your tune. (people have taken their cars to the dealer & forgot to tell them NOT to download updates).

 

I do plan on tuning it. Are 380's still the best way to go?

 

With your mods yes, covers all the bases & takes the "need" out of having to have a tune should something go wrong down the road.

 

So 380's with an RMW tune will do it. How much HP and torque should I hope to gain. Gotta stay ahead of my little brother

 

What is done to your brothers Miata that you can not keep up and pass him?

 

He's installed a turbo, injectors, exhaust, intake and tuned the ecu. It's not a matter of keeping up with him, that is no problem. It's a matter of staying ahead of him and being irritating as hell to him. He is now looking to installing a supercharger as well

 

Yup...
imo, while you COULD run them no tune with a 15%, your car will run way too rich, shorten the life of the cats, losse mpg...but like said, you can install them at home, a couple weeks before the tune, and drive to the tun, no longterm issues.
the jcw380's (only sold with cars with the jcw210 package, or jcws upgraded to this level from 2005 on)...when you look at them they have blue on them...folks smetimes try to sell used injectors from older jcw's....those are the same as on the S....have kinda a yellowish tan, not blue.
Stock s injectors on the JCW were good for 200 hp to the crank....jcw380's 210 to the crank...so they do not add a HUGE amount of fuel, but a bit more to keep the afr's safe, and make a bit more power st higher rpms....

 

So the 380's are preferred over the 400's? When I do this the car probably won't run more than bot 25 miles before the re-tune. And I'm considering using RMW for that.

 

380's are oem quality, no pigtail adaptors needed...look stock, cause they are, and have the right spray pattern...a dualcone.
Different places have come and gone offering other injectors....jcw's are a safe bet.
Not sure which ones you are talking about....

 

380's it is. With a RMW tune. I'll install the 380's and then contact RMW for the tune. Thanks for all the input. You have to remember your dealing with an old gray headed fart that grew up around carburetors , coils and distributors. Haven't spent a lot of time over the years staying up with the stuff. Thanks for all the input guys.