Injector Size?!? (Greddy 10-14psi) - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-25-2009, 07:12 PM   #21
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With a strong fuel system, I was able to max out the td04 compressor before maxing out RC 440 injectors.

Spray pattern is important. Nozzle injectors are leaps and bounds better than old pintle injectors.

RX7 injectors FTL.
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Old 01-26-2009, 12:09 AM   #22
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I've seen the stock FPR on the 1.6 "stick" at 50 PSI with the stock pump, with 15PSI in the manifold, so would be wary... But if yours is staying 1:1 then you are doing great.
Here's the math:

320HPx (.55)/(4)= 44lb-min= 440cc @100% duty= [email protected]%

So your FPR is increasing pressure reliably 1:1
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Old 01-26-2009, 05:49 AM   #23
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Running a RRFPR with a much smaller than normal disc to raise fuel pressure somewhat in conjunction with larger injectors is a fantastic idea when getting into the range where you may need such large injectors that idling /af's will get uncontrollable but that is not the case with 460's.. Aiming for 15+ psi I would probably do so, but personally I would like to keep the pressure in the fuel lines as low as possible so as to require the least amount of work from the pump and to exert the least amount of pressure on the lines. I'm not preaching against the suggestion, after all, I'm currently running my MS in conjunction with the Vortech FPR and have it tuned in quite well for my 6.5 psi. Aside from the fuel map looking strange becauase it drops back off once there is positive pressure in the engine, it works great (so far though I'd like to not push 100+ psi through my system any longer than I must), but I'm saying optimally I'd like to keep pressure low low low... 460's are on my desk waiting for my BEGI downpipe to arrive.
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Old 01-26-2009, 11:02 AM   #24
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^^^ i agree with a lot of this, if you haven't upgraded your fuel system. I also don't feel that it is a good Idea to go over 100lbs of fuel pressure as most injectors( from my experience) don't tolerate it very well. In our little niche of the automotive world we are pretty lucky. The high impedence injectors that a miata uses seem to put up with it pretty well. for most people I would only suggest maybe a max of 75-80 lbs, but you damn sure better have a healthy fuel system. ie good and fresh rubber lines. In my case I have all steel braided and a/n fittings on the pressure side as well as a big walboro pump.
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Old 01-26-2009, 04:38 PM   #25
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i think the issue may be more the stock pump not liking the higher pressures, more so than the FPR having issues. i am running a walbro 255, but the FPR is stock escort

i'm running rx7 injectors but i;d like to upgrade to something more "modern" eventually.
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Old 01-26-2009, 05:04 PM   #26
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Quote:
Originally Posted by ThePass View Post
Running a RRFPR with a much smaller than normal disc to raise fuel pressure somewhat in conjunction with larger injectors is a fantastic idea when getting into the range where you may need such large injectors that idling /af's will get uncontrollable but that is not the case with 460's.. Aiming for 15+ psi I would probably do so, but personally I would like to keep the pressure in the fuel lines as low as possible so as to require the least amount of work from the pump and to exert the least amount of pressure on the lines. I'm not preaching against the suggestion, after all, I'm currently running my MS in conjunction with the Vortech FPR and have it tuned in quite well for my 6.5 psi. Aside from the fuel map looking strange becauase it drops back off once there is positive pressure in the engine, it works great (so far though I'd like to not push 100+ psi through my system any longer than I must), but I'm saying optimally I'd like to keep pressure low low low... 460's are on my desk waiting for my BEGI downpipe to arrive.
It wouldnt matter because most people with the rrfprs raising pressure in the rail use highflow walbros. racing pumps are meant to handle that type of pressure, it doesnt even strain anything. The lines are fine as long as they're not rotted or anything too. fuel hose can take that beating too, especially the braided ones. Only downfall really is probably bad gas mileage.
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Old 01-26-2009, 05:20 PM   #27
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bad mileage? if I keep my foot out of it I get 30ish mpg. I think that is pretty good no?
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Old 01-26-2009, 05:34 PM   #28
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Quote:
Originally Posted by dynokiller90 View Post
bad mileage? if I keep my foot out of it I get 30ish mpg. I think that is pretty good no?
You know that **** is tempting lol. I am constantly in boost but my turbo spool is pretty damn good so its hard to stay out of it. Or maybe i just have a lead foot. That is pretty good, but so many variables can affect gas mileage on turbo cars. You must not be boosting very high though even when in boost. All turbo cars will boost when you drive them, unless you're a super grandma. Most people boost alittle even unconsciously
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Old 01-26-2009, 06:55 PM   #29
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this will help RC Fuel Injection
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Old 01-26-2009, 10:20 PM   #30
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^^^ according a calculator on that page my 305s that actualy flow 315 on avg. at 100lbs of pressure have an approximate flow rate of 477cc/min at 80% duty cycle.

fun days I run 14lbs, normal days I run 12lbs. that's not exactly low for stock internals. I actualy saw an improvement in fuel milage when I put the turbo on. the added torque made it require less throttle for shorter times to do things like merge onto a highway. I'm sure that others have probably had similar experiences. don't get me wrong though, if I put the boot to her, she's a thirsty bitch.
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Old 01-26-2009, 10:44 PM   #31
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well i would get good gas mileage when i stay off out of boost, but i dont really take gas logs as much. And most of the time i drive the car, im testing for things so im always on it. Once I actually watched my fuel gauge drop lol. But by that calculator i am running well over 500cc. Actually with this setup, I have enough fuel to run any amount of hp I want that the engine can take, which is roughly 15psi and I still could support over that in fuel
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Old 01-29-2009, 07:10 PM   #32
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There is a fuel Calculator on our site, Deatschwerks
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Old 03-03-2009, 09:19 PM   #33
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a bit off topic but will subaru blue injectors fit a 1990 miata?
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Old 03-03-2009, 09:21 PM   #34
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I think the STi injectors were in the FAQ but they were removed because they are just slightly too short.
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Old 03-03-2009, 09:28 PM   #35
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they are still there and wrx injectors are there too.
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Old 03-04-2009, 09:14 AM   #36
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Quote:
Originally Posted by Ben View Post
With a strong fuel system, I was able to max out the td04 compressor before maxing out RC 440 injectors.
+1.

Example:



That's 71% duty cycle at 185 kPa (12.4 PSI) at 7,000 RPM on 440cc injectors, maintaining AFRs in the mid to low 12s. Fuel system is stock, apart from the fact that when the stock fuel pump died I replaced it with a Walbro 190.



edit: Wow- didn't realize this was an old thread. Oh well.
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