CRXtoRX7

Alright, just got rebuild done about 400 miles ago, and every thing has been running pretty good. I have a to4b hybrid and streetport, so I upgraded the secondaries to 720cc(i am doing the primaries soon). I have a pretty much untuned SAFCII. So my problem is, if i accelerate at about 0-1psi boost, when i hit 3800 my car completely bogs down and doesnt stop bogging until I let off. Now you are thinking, well tune the secondaries down! Already tried tuning them down 15%-20% with no change. My friend went with secondary 750ccs and he said his car didnt feel like this before he tuned them down. My car completely bogs. Now, what I think could be the problem. The injectors I got were supposedly Greddy 720cc's low impedence. They said denso on them and had a different color than my stock j-specs and my friends stock a-specs, so I think they are legitimately 720's/ My car takes high imp, so I wired a resistor (1 per injector) in. I can't remember what type of resistor, i just did it according to a thread on this forum. Anyways, I am thinking maybe the injectors were already high imp or something? Anybody have an idea? im really stumped.

Ben

GXLBidwell

did you try ajusting the tps?

CRXtoRX7

the tps is set at 2.3 volts right now, its the only way my car will idle since its a fresh rebuild.

West TX RX-7

Ignition trigger? Or did this all start soon as you installed the new injectors?

CRXtoRX7

which is/does what?

Mobius

My car takes high imp, so I wired a resistor (1 per injector) in. I can't remember what type of resistor, i just did it according to a thread on this forum. Anyways, I am thinking maybe the injectors were already high imp or something? Anybody have an idea? im really stumped.


Yeah. I'd say that's a good place to start. You can tell if you injectors are high or low impedence by using a multimeter.

Secondly, just sticking a resistor from radioshack in there isn't going to make them high impedence all of the sudden.

Resistence and Impedence are not necassarily one and the same for all electrical cases, especially those pertaining to signaling.


http://www.gamry.com/App_Notes/Refer..._Impedance.htm


Definition of Impedance

Almost everyone has heard of Ohm’s Law, which relates voltage to electrical current flow in an electrical circuit.

E = I · R

R is the resistance of an electrical circuit. It has units of ohms. A resistance has the important property that its value is independent of the frequency of an alternating current (AC) signal applied to it.

Often current flow depends on AC frequency. In this case a more general form of Ohm’s Law is used.

E = I · Z

Z is called the impedance of the circuit. It is a complex number with a magnitude expressed in ohms. Unlike a resistance, an impedance can change value with frequency.

The complex impedance of a reference electrode is often dominated by resistive effects. For this reason, the terms resistance and impedance are often used interchangeably when discussing reference electrode impedance.




Gamry Instruments Ó 1997-2003

Gregs

3800 is when the 5/6th port actuators kick in, yours are prolly dead or clogged up bad
my car on occasion has a slight delay at that rpm, generally when the engine isint FULLY warmed up

-greg

Gregs

3800 is when the 5/6th port actuators kick in, yours are prolly dead or clogged up bad
my car on occasion has a slight delay at that rpm, generally when the engine isint FULLY warmed up

-greg

CRXtoRX7

I have a turbo, so no on the 5/6 ports. Its most definately fuel related. I bought the car with a blown engine, but I drove it on one rotor for a few miles to get it home. It ran fine about 3800 then, but that was on stock 550 injectors. The 720's went in with the rebuild, so it has been from the get-go. Anyone have a proper way to wire 720's for high impedence? I can't find the link I used to wire them previously. I know i bought two white block looking resistors, i think they were 10amp or something like that. 10 something. I wired them into one of the two wires going into each injector. Soldered connections with elec. tape. Some one help me! I have to dyno tune it in a couple weeks, and that won't be possible if i cant take it above 3800rpms. any input appreciated.

CRXtoRX7

and mobius, I see that maybe my radioshack wire-job isnt doing the trick, but you leave no way to correct it, so I still have the same dilemma. Any ideas?

Ben

SonicRaT

iTrader: (6)

what color are the tops of the injectors you put in? Should be a 10 watt 10 ohm resistor (where did you install them at, under the hood is a bad idea, it's best to wire them in at the ECU). Also, do you have a check engine light on? Have you checked for codes? Your TPS is also WAAAAY off, that thing should be around 1volt at idle, regardless if it's a fresh rebuild.

Oh, and by the way, the radioshack resistors will work just fine.

CRXtoRX7

it was a 10watt 10ohm resistor from radioshack as i recall. Maybe I will rewire at the ecu, I was just following the direstions I found. Check engine light is off, but I will check for codes soon. I'll set that tps back, and see how it goes no that there are some more miles on it. Is there any way to check if i am getting the right impedance on the injectors with the resistors? I think the tops of the injectors were lime green, but they may have been tanish. I cant quite remember, I think green. thanks,
Ben

SonicRaT

iTrader: (6)

Green are the 680's from a GSL-SE (generally opened up to 720's) If you have them wired in place, I wouldn't worry about it, but it's possible you overheated the resistor (common when they're mounted in the engine bay) Good luck.

Mobius

Oh, and by the way, the radioshack resistors will work just fine.


Sorry, from the way he seemed to put it, he just bought some resistors and blamo high impedence all the sudden. What I'm saying is that just sticking any old resistor in won't work. Since nobody mentioned any specifics.

I wasn't trying to be insulting or sarcastic by saying "radioshack" but if you're going to tamper with
your injectors like this, you have to be very precise.

For all I know, you do have the right resistors but your connections aren't solid. You can have a 3800 crossover hesitation that comes simply from the contacts to your injectors plugs being bad/not solid/poor solder.

CRXtoRX7

hmm. well, since my wires are now messed, should i take out the resistors, solder in a wire in place, and wire some new resistors in by the ecu? Will the injector wire color codes be in the haynes manual or fsm?

SonicRaT

iTrader: (6)

Sorry if it looked like I was slamming you or something. I was just letting him know that they'd work fine as long as he went with the 10ohm/10watt. Though you did provide good info


Anywho, back to subject. Generally I've found the engine bay gets too hot and burns them up, I'd solder/heat shrink the wires back to original, then solder them in at the ECU. The FSM should say which wires they are, I'd have to look to find them on a S5.

Mobius

Yeah, CRX...

I know that people have done this, and say it works....I'm Not sold on it. I think that some people get lucky and it works.

My suggestion would be to not solder at the ECU or do anything else until you get some more input from other more knowledgeable forum members.


Sonic, its cool....I'd just hate to see this problem go from bad to worse.

CRXtoRX7

well sonicrat, i have an s4 tii ecu. if you know the colors, it would help me, since reading wiring diagrams isn't exactly pleasant. Now i want to know what the correct impedance would need to be for it to actually be correct. I will do the resoldering soon, never shrinkwrapped anything, but I assume electrical tape will do the job. thank you both for your help, if anyone else wants to chime in with some more advice, I am open to more...

Thanks,
Ben

SonicRaT

iTrader: (6)

They're the green wires in the smallest connector, should be light green, and then light green with 3 other colors (black, red and orange maybe? Not exactly sure) They should be two next to each other, offset by 1 pin ontop the other set, I believe the first one was 3 pins in on the top row, and the lower set was two pins in, or this could be reversed. You'll see once you look at it.

Mobius

Well if I run across any other helpful info I'll certainly pass it along. What bugs me is that both online service manuals for 86-88 & 89-92 list the injector resistence at 12-16 ohms.

But I remember measureing them for n/a 86 at 1.2-3 ohms....(maybe I'm confusing that with the BAC?)

Anyway, I guess that the idea is that if you add the right durable resistor to the 1.2-3 then you get into the range of 12-16.

Well, like I said, not saying I think its a good idea, but what if your injectors are at an intitial resistence that puts you either above or below the desired range for your proceedure for some reason? So instead of getting into the 12-16 you're either at >=11.99999 or <= 17.111111?

Since the resistence of an injector is a range, do you think you might need to go with a little beefier or lighter resistor?

I see how my comment "more knowledgeable" could be taken wrong. My Bad....That's not what I meant at all.

If anyone's gonna help you get this to work it'll be
Sonic Rat.

SonicRaT

iTrader: (6)

You've actually got it backwards. You're taking it down from 12-13, to 2-3. If your injectors are off from 2-3 or 12-13, then the injectors are bad. The reason why the FSM's don't list it, is because the scanned ones aren't from the early model FC's. Low imp injectors are 2-3ohms, high are 12-13, you're just dropping the ECU's signaling down by 10 ohms to be in the 2-3ohm range (the older FC's did this by using a resistor pack bolted to the fender) So it's basically the same thing as stock, just wired elsewhere.

RXciting

just wondering where is this resistor pack..?? next/near to what??

RRTEC

iTrader: (13)

up front under the air box, it is silver and rectangular....^^^^^^^^^^

RXciting

oh ok.. i know what your talking bout.. thanks

CRXtoRX7

sonic, i just found this today:
its the color and other information on the mazda injectors--

84-85 13B NT low square center 680cc orange 195500-0900
86-87 13B NT low square center 460cc red 195500-1350
86-87 13B T low square center 550cc tan 195500-1370
88 13B NT high square offset 460cc purple 195500-1350
88 13b T high square offset 550cc purple 195500-1370
89-91 13B NT high oval center 460cc red 195500-2010
89-91 13B T high oval center 550cc purple 195500-2020

no green in sight
but anyways thats allright. Rotaryressurection.com/injector.html

it also says to splice at the injector lead. This is weird, I don't think the location of the resistor is the problem, but I don't know what else could be. I will try the relocation this week, but any other ideas of what else to check?

oh and since you all know a good amount about wiring...maybe someone can help on another thread i had...https://www.rx7club.com/showthread.p...hreadid=292798

thanks