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Old 03-22-2014, 12:52 PM   #1
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Default RX8 injectors differences

I've searched around both here and on the interwebs, and cannot find the answer.

What's the difference between #195500-4450 and #842-12332 yellow injectors?

Size? Brand? I think the 195500s are Denso, is this preferred though?

Part two of my question, is that I'm planning on ordering from Rockauto. Remanufactured injectors are $38 each, should I trust these or still send them to RC engineering? If that's the case, they'd be $62 each and the wife will be less happy.

And what size are the red primary injectors? Cause those are only $3 more from rock auto.
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Old 03-22-2014, 01:29 PM   #2
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IIRC, RX8 reds are around 300cc, yellows are in the 400cc range, and blues are around 500cc. All that matters is the color, the part #'s are completely interchangeable. But that's just off the top of my head.

Good luck, Curly.
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Old 03-22-2014, 01:47 PM   #3
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And as I think about it, go for the 09+ - the 09+ are superior to the earlier injectors.
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Old 03-22-2014, 02:02 PM   #4
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When I was injector shopping, I couldn't find yellow rx8 injectors anywhere but Asia with the part numbers 195500-4450. When you look up RX8 injectors on rock auto, the part number is 84212332. I couldn't actually find flow for those. But I came across a post on a Rx8 forum saying their yellow injectors are 390cc. Not the 425s we generally want.
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Old 03-22-2014, 04:28 PM   #5
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RX8 rail fuel pressure, like all rotaries, is lower than what we run in the Miata Tekel. They are rated at typically 2.5bar.
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Old 03-22-2014, 06:43 PM   #6
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My 195500-4450 yellows were flowed by WitchHunter at 426, 420, 420 and 428 cc/min at 43.5psi.
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Old 03-22-2014, 10:08 PM   #7
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Yellows are 425, blues are 540.
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Old 03-23-2014, 02:51 PM   #8
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Thank you all, $38 yellows are on their way. It was also pretty easy to find a 5% coupon for rock auto if you search "rockauto coupon" in google. So ended up being $155 shipped for four.

Sadly, I don't have the funds for $300 Fuel Injector Clinic 525 or Deatschwerks 450 injectors.
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Old 03-23-2014, 02:52 PM   #9
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I'm somewhat surprised you didn't go for the blues then Curly, as they were close to the same cost as the yellows (within a few bucks IIRC) and offer higher flow.
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Old 03-23-2014, 04:06 PM   #10
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Uhhhh....because I forgot.

I'm not too close to maxing out my 460s, which supposedly can do about 235hp at the crank, where as the RX-8 ones can do 215. That's at a safe 80% duty cycle, so I have some wiggle room.

I'm currently at 185whp, with plans to possibly go to 200, but probably not any time soon.
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Old 03-23-2014, 09:57 PM   #11
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The yellows can do more than that.

We're somewhere between 220-240whp at the moment, tuned rich, duty cycle 80-85%. Wally 255, stock fpr.
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Old 03-23-2014, 10:21 PM   #12
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That's good to hear. What is fuel pressure at full boost? My '99 is limited on fuel pressure, and I don't want my top power to be determined by injectors.
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Old 03-23-2014, 10:26 PM   #13
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Dunno. Whatever a 95 fpr would give at 12-13psi.
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Old 03-23-2014, 10:28 PM   #14
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Upgrade to a walbro 255 and you'll have 60 psi (I think it is) to redline.
Curly, 460's only give 235 crank hp? I made 225whp with 460's and I hope to make an easy 240whp with rx8 425's!
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Old 03-23-2014, 11:17 PM   #15
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That's what RC engineering's calculator said for .6 BSFC and maximum 80% duty cycle.

With my Walbro 190, I thought my FPR was regulated to 43.5psi, but I could have forgotten a thing or two.
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Old 03-24-2014, 12:04 AM   #16
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RC Engineering's calculator is very conservative. It's not a surprise to hear it claimed only 235 crank hp on RX8 injectors. Think of it this way, Curly, the stock injectors are what, 260cc or so? But people make 160rwhp on them or so somewhat regularly I believe.

Call 235 crank hp 210 rwhp. You are telling me that increasing the injector size by 165cc (A ~60% increase) is only going to net a 50 horsepower gain (A ~30% increase)?
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Old 03-24-2014, 12:49 AM   #17
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I'm making ~300 whp on RX8 yellows and a Walbro 255

15 pounds of boost and 3 gallons of E85 per full tank of 93 on a stock '03 VVT motor, you'll have no problem reaching your goals.
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Old 03-29-2014, 07:11 PM   #18
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I am using a set of #195500-4450's in my Miata. Before installing them I had them cleaned and flow tested. At standard 3 Bar test pressure (43.5 psi) they flowed 428, 426, 424, and 424 after cleaning at WitchHunter.

Hope this helps,

Keith
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Old 03-29-2014, 11:17 PM   #19
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Mine are in and running. And after a brief moment of "WTF?", I changed injector opening time from 1.0 to 1.3, and holy hell throttle response is much better than before. They're also much quieter. I used to have the injectors battling the lifters for loudest clicking. The injectors have no chance now. And yes, they're blindingly yellow.

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Old 03-31-2014, 01:55 AM   #20
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What is Max WHP we can expect on these injectors? I hit 200 wheel HP on my m45 with them on E85 and I was pig rich doing it. I am wondering if I can reach 250 at the wheels on E85, or if will need to go bigger.

Keith
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