RX-7 FC Injectors OK to use with Greddy Kit? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-15-2007, 02:00 PM   #1
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Default RX-7 FC Injectors OK to use with Greddy Kit?

Contemplating purchasing a Greddy Kit - I was given 440CC injectors from a 91 RX-7. Is this overkill or exactly what I should be using?
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Old 10-15-2007, 02:01 PM   #2
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its overkill if you have no way to idle and control them
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Old 10-15-2007, 02:32 PM   #3
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Somebody hasn't read the FAQ. There's some slight math to be done, and you can do it here in the third post: https://www.miataturbo.net/forums/showthread.php?t=4288

The short version is that (although some have managed) the stock ECU won't idle injectors above 330cc very well. And that's OK because with the Vortech AFPR and a fuel pump capable of over 100psi you can fuel enough for over 200whp+ with 330's... which is probably a good goal for an initial Greddy upgrade.

Just what do you hope to accomplish by upgrading the injectors? The Greddy kit with it's base boost output of 4.5-5psi is designed to work with the stock injectors and fuel pump and the supplied disc in the AFPR. As you turn up the boost, the AFPR will raise fuel pressure to the max of the stock pump at 80psi... which is why guys usually upgrade the fuel pump along with larger injectors (but 440's are too big to idle) which will give A LOT of headroom for fuel. But you can't turn the boost up without some way of getting intake temps down no matter how much fuel you dump in... so now you need an intercooler... then you get to a point in turning up the boost that an intercooler isn't enough to keep your engine from pinging at the Greddy mandated 6* of timing advance, so you need someting to manage your timing (a Bipes).

Or you could skip all that crap, keep the 440's and get a Megasquirt and Devils' Own Water Injection Setup and run 15psi on the Greddy for about 240-250whp... don't forget a clutch... might want a BOV and an upgraded crossover pipe too... and new tires... and better brakes... and maybe a rollbar... and since your girlfriend is gonna dump you cause you spend all your time working on the car, a new one of those (blondes tolerate more).
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Old 10-15-2007, 04:45 PM   #4
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Sam, do I understand you correctly- the 330 injectors will let through enough fuel for up to around 230 rwhp? at what point is the horse power high enough to require some sort of timing advance above the Greddy recomendation--how much safe power can be produced using the 330 injectors and the Vortech AFPR along with a basic fuel pump upgrade?
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Old 10-15-2007, 04:58 PM   #5
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Sorry for jumping in here, Sam, but...
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Originally Posted by USMCDriver View Post
Sam, do I understand you correctly- the 330 injectors will let through enough fuel for up to around 230 rwhp?
All by themselves, no. With the addition of an adjustable FPR, yes, with room to spare.

Quote:
at what point is the horse power high enough to require some sort of timing advance above the Greddy recomendation--how much safe power can be produced using the 330 injectors and the Vortech AFPR along with a basic fuel pump upgrade?
Before you start doing anything, you'll want an intercooler or a water-injection system. Or both.

It's unlikely that you'll need to upgrade the fuel pump. With 330cc injectors you'll have enough fueling for your stated HP goal without needing 125PSI of fuel.

The Vortech FPR is probably going to cause problems with 330s. You need something adjustable. That unit was designed for the stock injectors at 5 to 6 PSI of boost.

However it's quite likely that you will need some dynamic ignition retard. The Bipes ACU is one option, though for the cost of that plus a good FPR, you're in EMU territory, price-wise.
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Old 10-16-2007, 01:17 PM   #6
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Thanks so much guys; I've been reading as much as possible.

I was given a set of RX-7 Injectors in exchange for other parts I had with someone. I knew they were P&P, but now I see they aren't suitable for my application.

I'm thinking of leaning towards a Greddy kit, with intercooler, and running 6-8 lbs. I want to build a reliable, daily driveable setup that focuses on quick spool and low down torque as opposed to big numbers and highend HP.

Thanks all for the guidance so far. Much more research to do.
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Old 10-16-2007, 01:19 PM   #7
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yea- i can see a increase in my expendatures comming up... ha. I just got done reading braineaks FYI post on everything. thats gonna help me get an idea of my required fuel system set up.
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Old 10-16-2007, 01:22 PM   #8
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Quote:
Originally Posted by JrodNJ View Post
I'm thinking of leaning towards a Greddy kit, with intercooler, and running 6-8 lbs. I want to build a reliable, daily driveable setup that focuses on quick spool and low down torque as opposed to big numbers and highend HP.

then the biggest thing with a GReddy kit will be to opening up the exhaust and replacing the wastegate.

if i had that goal I'd choose a different turbo.

the sr20det t25 turbo comes to mind.
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Old 10-16-2007, 01:34 PM   #9
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ill take a look at that. i got a good deal from a friend on the greddy.
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Old 10-16-2007, 01:35 PM   #10
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ups- read ya wrong
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