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.

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.

And as I think about it, go for the 09+ - the 09+ are superior to the earlier injectors.

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.

RX8 rail fuel pressure, like all rotaries, is lower than what we run in the Miata Tekel. They are rated at typically 2.5bar.

My 195500-4450 yellows were flowed by WitchHunter at 426, 420, 420 and 428 cc/min at 43.5psi.

Yellows are 425, blues are 540.

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.

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.

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.

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.

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.

Dunno. Whatever a 95 fpr would give at 12-13psi.

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!

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.

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)?

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.

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

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.

https://www.miataturbo.net/attachmen...ine=1396145826

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

I'm pretty certain I hit 200whp on my stock 99 injectors.

Both begi and flyin miata say the stock 99
Injectors Max out there. If that is the case the RX8 425cc injectors should Max out at around 325 on gasoline or 250 on E85.

Thanks,

Keith

I'd kinda worry about 250 with e85. After hearing some testimonies on these injectors, I think they'd be fine with pump gas. I've never tuned with E85, but I hear it requires a LOT of gas. Might wanna consider an adjustable fuel pressure regulator, or larger injectors.

That's way above what RX-8 injectors can do. I'm capped at ~200 hp at crank (!), running around 90% duty cycle @ AFR 12.2. And yeah, that's E85 with stock fuel pressure.

What fuel pump are you using and is this on an NB running 60 psi of fuel pressure? Last dyno session I made 200whp and I was running pig rich. That was on "winter blend" E85 though (E70).

Keith

Nope, it's NA with 43psi (?) referenced fuel pressure regulator. NB 60 psi regulator is not referenced to manifold so i guess they are effectively the same at 7 psi of boost i'm running.

hi, all

Since there was only one person that has replied on a topic that has experience with these injectors i will ask again

Today i picked up a couple of yellow 4450 ones. And a few hours later i got a mail that some has a couple of purple 4460.. At first i was looking for this one but the rx-8 model that has these injector where never imported to the netherlands. So i gave up searching and picked up de the yellow ones.



Does anyone more has experience with these 4460 purple ones?

Nope.

I was shooting for around 260whp, glad to see I picked injectors that will be suffice.

Is your FPR a 1:1 ratio? That is what I am used to on turbo mitsubishi's. Yeah, at 7 psi of boost you would have around 50 psi fuel pressure, keeping the differential pressure between the fuel rail and intake manifold at 43 psi. Since mine is not referenced to manifold pressure I would still have 60 psi of fuel pressure, and the differential pressure between my fuel rail and the intake manifold would be 53 psi. It may not be a huge amount, but a 10 psi pressure difference will make a difference in how much power you can make.

Keith

Bringing this back to get some input on my build. See Se Post 102

I would think I should be at those kind of power levels at 80% DC on these injectors. I know both @Savington and Emilio have also used them in the past.

Note that I have gone to a return-style fuel system.

Should I be looking at the DW100 or DW200 to replace my fuel pump?

I ran an experiment this morning. Nice and cold, so already 1% more fuel requested due to MAT Corr. Then I changed the target AFR from 11.7 to 11.4 (Fueling is "Incorporate AFR")

Ran full pedal. IDC went to 108%. At that point, Target AFR was 11.4, but Measured AFR was 11.9. I'm pretty sure I'm no longer controlling fuel.

So, for now, I'm backing down max boost at high RPM so that I'm at least below 100% IDC.

Question remains: Would this be helped by a new pump or not? Or am I at the limit of the Yellows with 3-bar, MAP referenced fuel system.

What pump are you running? I can tell you I'm seeing fuel pressure drop at 6 to 7psi or roughly 175whp. I'm throwing in a walbro 190.

Original Stock with 95k miles.

I've pretty much decided to back down from 194 to 188kPa, which gives me 96% Inj Duty Cycle until I have the car properly dyno'ed, which will be who knows when.

I guarantee you that your fuel pressure is dropping off substantialy. You are out of fuel pump capacity by a large margin. To complicate things it's not like your fuel pressure will drop off consistently every time you go WOT, battery voltage, temperature, ECT. Will all affect how much the pressure drops off so you will see large variations in pressure. I wouldn't​ continue to run the car at these boost levels until you get a pump.

From what I've read you'll get so.e pressure creep at idle with any pump larger than a walbro 190. The 190 will easily support 300whp, so there isn't a good reason to run anything bigger.

I don't know if "substantially", but that does seem like root cause. Following is an un-tuned pull after putting in a DW100. Looks like I have about 10% more fuel available at the top end.


https://cimg5.ibsrv.net/gimg/www.mia...7b2cb13f60.png

Also, idle and cruise did not change, so that indicates that indeed, the DW100 does not over-power the FPR (1999 European MAP referenced).

10% is a nearly a full AFR point, so tOmato / tomAto.....It was quite a bit.

Considering the dw100 flows 165 lph it won't over power the regulator. I just swapped pumps to a walbro 190 because I was loosing pressure at WOT and found a 255 walbro in the tank, I'm running a fuel pressure sending unit and saw a 12 psi drop in pressure at high flow conditions. It was rocking up to 74psi at low flow and dropping back to the NB 62psi at wot. I just thought my sending unit wasn't calibrated, but ends up I had the opposite issue that you did.

Glad you got it fixed.

Good Point. 10% at that level is another 20 HP, potentially. And yes, it was a full AFR (10.7 vs 11.7) and at 90% DC while achieving that.