After removing my injectors today I discovered this, and was wondering.


Having two different sets of low/high impedance injectors on an 87 t2 would there be any bad effects? Purple top on one set and orange on other (maybe faded red?)

Car appears to have the resistor box under where the stock airbox would be but none of the wiring looks modified.

My question is why would someone do this and would it be bad for the car.

I do have other injectors so I should be able to run a full matching set

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Nah, the actual injector impedance wouldn't matter as long as the ECU sees sufficient load, whether from the injector itself, or an injector/resistor combo.

Why? Some injectors are more common than others, and with a greater supply comes a drop in price!

 

Check for cuts in the wiring at the ECU connectors. The Injector wires are LG, LG/W, LG/B, LG/R and on the small plug if I recall correctly. If it has the resistor pack wire up, then the two injector circuits with the high impedance injectors will have ~18-20 ohms resistance. This translates to injectors that are really slow to respond. I'd also suggest checking the resistance on the injectors and noting the tab (offset or centered) to be sure they're different impedance. Color isn't the best way to tell, since there is some overlap.

 

Well I've hooked up the ecu before because mine was missing the ecu when I bought it and nothing appeared modified near the clips.

Could having the slow responding injectors cause a lean condition and overheating?

Turbo on the car has side/end play as well as hoses looking white around it, car has upgraded exhaust...I'm thinking car was overboosted. (I've got an s5 turbo setup to replace it)

Reason I ask is the engine looks to have coolant issues due to a possible blown coolant seal more than likely.

I'll check the injectors tommorow.

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Colors are deceiving as Time fades the plastic and then the color appears to be something different.
The thing that remains the same is the Part Number in the plastic in the injector.Also the injector Impedance when measured with a meter.
You can run HI's as Primary and LO's as Secondary(for instance) If you have resistors on the harness or wire the resistor pack so that it only uses the resistors for the LO Impedance set on the engine.
I Had LO primary,and HI (1000) secondary,and I bypassed 2 resistors in the pack to let the ECU see it's usual HI impedance.

 

I don't think anything has been bypassed , everything looks stock.

The injectors are obvious different colors , I want to say the purple were used as secondaries but not 100% sure. (Took them out after they were hanging on the harness on top of the engine today long after removing both fuel rails)

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Slow-responding injectors might cause some stumbling at the injector transition point (3800 RPM) or some rich/lean hesitations on throttle input. It might also not be noticed. I've never tried.

I'd double check that the ones you're calling red/orange are not 460cc NA injectors. The only S4 TII injectors I've seen were tan or light purple.

[quote=FAQ]
What size injectors does my RX-7 use? What colour are they?
Year Engine Plug Size Colour Part #
84-85 13B NA, low square center, 680cc, orange, 195500-0900
86-87 13B NA, low square center, 460cc, red, 195500-1350
86-87 13B Turbo, low square center, 550cc, tan, 195500-1370
88 13B NA, high square offset, 460cc, purple, 195500-1350
88 13B Turbo, high square offset, 550cc, purple, 195500-1370
89-91 13B NA, high oval center, 460cc, red, 195500-2010
89-91 13B Turbo, high oval center, 550cc, purple, 195500-2020

 

If this guy was running na injectors he'd half to be half retarded. I'll see tommorow when I check

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84-85 680cc is what they are.

Others are either 87 or 88 550s I don't know the difference to look for

Hmmm...I wonder how many ppl use these

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look up the part numbers!

 

Lots of people use the GSL-SE injectors as secondaries. I've always gone to 720cc injectors as a first mod for the fuel system after a larger pump, but whatever, it's up to your preference / needs.

 

The 87 and 88 have identical part numbers.

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What good would having 680cc secondaries be if you dont have an upgraded fuel pump, or upgraded ecu?

I mean I'd rather use 720cc secondaries, but these I got free, I wasn't, be one who put them in.

Though I see no point running them if I still can't run above 9psi on stock ecu with a fcd.

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Notice the raised tab that slides into the injector clips on the purple 550s? Because that is centered, those are low impedance. High impedance had an offset tab. You can also put a multimeter across the terminals.

GSL-SE injectors should be low impedance too, so the resistor pack setup is correct.

 

OK cool.

So having these 680cc injectors is really only to insure I dont run lean on 9 psi?

I don't see any reason to run more boost on an otherwise stock setup.

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Are you sure there 680cc?

I have two tan 550's and two purple 550's in my car and they are all low impedance, multimeter verified. Car runs great!

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/injector-question-1019341/

 

680 and 720's are so close i doubt you'd be able to tell the difference. maybe you do have a bigger fuel pump and ecu?

 

I got the ecu myself because it was missing when I bought the car so I know its stock. The fuel pump I haven't checked so it could be upgraded , but might not be

Also to the other guy saying I'm wrong and they could be 550's , I know they're 680's because the part number on them matches the part number listed above for 680cc 84-85 gsl se injectors.

Why'd gsl-se have such big injectors anyways??

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GSL-SEs only had 2 injectors total.

If your ECU is stock, using 680cc secondaries will make it run extra rich under load. It's a crude way to keep the engine from blowing with higher-than-stock boost.

 

Well I was going to run more boost anyways.

I was gonna go for 9psi Max on my setup until I completely upgrade the ecu and fuel system, maybe even less (7-8 psi) boost if I use the spare engine and it has low compression so it'll last until I can afford a rebuild.

S5 turbo , full exhaust, fcd.

I'm thinking I'll probably have to port the turbo waste gate, or will it be okay stock, I'll need to get tools to port it if so.

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Rtek 1.7+ FD fuel pump + manual boost controller and a ported wastgate is a cheap, effective way to run up to ~12psi safely. FCDs and oversize injectors without control are really hack modifications. And a stock S5 wastgate is decent size, but once you open up the intake/exhaust it'll creep.

On stock fuel, I always advise no more than 9 psi. I have seen firsthand that 10 psi with an FCD and 9.0 CR rotors = blown engine. The fuel pump is the weakest link, followed by the injector size and injector transition point being too high.

 

Well I'm on 8.5:1 being a s4, wasn't planning on more than 9 psi on my near stock setup.

I have a full exhaust , fcd , and I'm going to run stock airbox, blitz bov.

I figured I'd run the bigger 680cc injectors for secondaries as a safety measure to insure I dont run lean.

How hard would it be for a first timer to port the s5 waste gate? I'd leave it stock , but it seems ideal to port it. Especially since its already off the car

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Take a look at a BNR turbo.( www.bnrturbos.com)
I had a Stage 3 and the car went like a scalded dog!

 

I've seen them many times drooling over em and the power they make, im just keeping my turbo stock.

Maybe a while down the road I'd look into the upgrade, for now just want to port out the wastegate.

Later on I'd probably want a stage 2 or 3 , the fast spool with good power. I'm sure stage 4 takes longer to kick in.

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