Wicked69

If you are using the factory PCM and wiring harness...what size injector is too big. Or does it have to do with the low or high impedence? Reason I ask is I am running E85 and have low impedence 160's but in an attempt to not use an injector driver I am thinking about trading these out for a set of low impedence 96's. Would I still need the injector driver because of the low impedence?

I do not plan to run over 19lbs of boost and hopefully can reach my goal at 15lbs of boost. Just trying to understand if it is injector size, low or high impedence or a combination of both?

SATAN

iTrader: (2)

It is the low impedance that is screwing you, not the actual flow rating. The injector drivers in the PCM are not designed to run low impedance. They will be pushing too much current and will burn out. That is WHY you need the injector driver box.

They make 160# high impedance injectors now though, but they are more expensive than traditional injectors.

black98ws6ta

iTrader: (77)

They also make 220's in high impedance but they get more expensive above 80 lb/hr. I've got a set of the 220's in my mustang on e85 and they work well. Got them from FIC here on the board.

ninetres

iTrader: (35)

Good question. I'm also interested in an answer. I have an injector driver, and am nervous the stock PCM might struggle to idle lean enough with 120lb injectors. If I remember correctly, my tuner had my 96s turned all the way down and it was still rich at idle. 370ci.

HydroStream6

iTrader: (16)

I'm on high impedance 160s with the Versafueler box and at 3 bar base on E85 I've got my tune pretty decent. 370ci and I'm idling around 13.5:1 (gas AFR). It's doable but takes some work.

Sarg

iTrader: (6)

I have idles 220's on a factory (tuned) ecu on a 2.5 liter motor at 14.7 air fuel. It can be done, but it takes a good bit of work on the tune. I can't imagine the ls ecu being so restrictive that you could not make 96 lb or even 160 lb injectors work just fine. Boost referenced regulator will definitely help though.

bmech211

Wicked,
You don't want to pair low imp. injectors to an ECU designed to run high imp., as the series current and amperage will eventually smoke your computer.

If you're apprehensive about dropping coin on an injector driver, and you're pretty handy with a soldering iron, make your own resistor box similar to the one below, which if I remember correctly cost less than a hundred bucks.

Most saturated injectors operate at about 14 ohms +/-, and peak/holds at about 2 ohms +/-. You'll need (8) 12 ohm resistors and when coupled to your peak/hold injectors will give you a series resistance of 14ohms (just like stock).

I'll take the "safe assumption" route and guess you'd mount these in the engine compartment somewhere so you'd want to try and stick to a higher wattage resistor (high heat has a dramatic affect on wattage). I suggest 25w to 50w.

It's really simple and you do have a little flexible margin for error.

JAX04

iTrader: (17)

^^^^^^^^^^^^^^^^^^^^^^

Now thats an interesting approach, never thought about that, Kudos for thinking outside the box

ZL1Killa

iTrader: (17)

injector - solenoid, on/off device. your limits will be the low (minimum) values in the PCM with regards to tuning at the minimum.

and then there is injector data...
http://www.injectordynamics.com/injectors.html

http://www.injectordynamics.com/ID725.html

I'm no expert and I'm no where near understanding all of this, but if you simulate or test an injector and do the math behind it to realize its operating range, all can be revealed. then it is a matter of tuning it properly with the particular PCM/ECM whatever controller/computer.

My brain was fried after having many conversations with Paul Yaw.

http://www.injectordynamics.com/ID2000.html
ID2000 , 2000 cc injectors or 190 LB/hr @ 43.5psi = ~220 LB/hr @ 58psi.

then there is always going with dual injectors per cylinder...NRE people.

The questions that have been asked, I think are answered. My question is what is your duty cycle at your 160LB/hr if you are thinking about switching to a 96 LB/hr? I know it is all about cost, but you didn't necessarily need the low impedance injectors to meet your fueling requirements, however it may have been cheaper than buying ID2000 ... I don't know, I have never bought low impedance injectors, nor driver box(es).

bmech211

ZL1Killa,

All valid points and definitely injector duty cycle should be taken into account.

Also keep in mind that the flow rates for running E85 are going to be greater because of its rich stoichiometric ratio (something like 9.75:1). And not to mention you make more power on E85 the richer you go!! Unfortunately in this "give take relationship" fuel economy will suffer.

I would suggest running the largest injector you can that doesn't sacrifice idle, or at least not take it beyond the point where rough idle is intolerable to the owner. I'm sure one could sit down and run the numbers to come to a solid compromise in duty cycle vs. idle.

As far as high vs. low impedance, peak/hold injectors have faster response times compared to saturated types. Technology changes have probably improved upon some of these nuances, but capable tuners are good enough to pre-program a bit of their "fuzzy logic" in the tune to compensate.

71 chevy

iTrader: (18)

Injector Resistors

However, instead of the flyback board, you may choose to use resistors in series with your injectors.

Several people reported that resistors do NOT result in significantly longer opening times, or any other troublesome effects, so this is a good solution for many installs. To eliminate PWM altogether, use a 5 to 8 ohm resistor (with a 20 to 25 watt rating) in series with each injector.

If you want to avoid using PWM with your low-impedance injectors, you can use ballast resistors in series with the injectors. You should use one resistor (20-25 Watts) in series with each injector, otherwise the injectors may not all draw the same current, and the failure modes become complicated and difficult to diagnose. As well, you would need a very large resistor to handle more injectors. For example, if you allowed 2 Amps through four 1.2 Ohm injectors wired in parallel (0.3 Ohms total) to one 7 Ohm resistor, the power dissipated would be:

P = V * I = 12.5 Volts * 2 amps x 4 injectors = 100 Watts!

If you use resistors that limit injector current to less than 2 amps, you can disable the PWM mode (by setting PWM% to 100%, and time threshold to 25.4msec) and treat the system as high-impedance. To limit the current to under 2 amps, you need:

resistor ohms = (alternator voltage / 2.0 amps) - injector resistance

For example:

resistor ohms = (14.0 volts / 2.0 amps) - 1.2 ohms

=> resistor ohms = 7.0 - 1.2 = 5.8 ohms

You can also use the calculator below. Enter your injector resistance in ohms, your hold current in amps, as well as your injector impedance in ohms, in the form below and press the "Compute resistor" button.

http://www.megamanual.com/v22manual/minj.htm

71 chevy

iTrader: (18)

http://www.toymods.org.au/forums/tec...tml#post908614

71 chevy

iTrader: (18)

something like this should work good in an automotive environment because it already has the automotive wire soldered on so it gives you something to solder on to , and a lot of room for mistakes

http://canadiancruisercustomizing.co...products_id=12

Wicked69

So you are just soldering 1 of these resistors in line with the wires that are plugging into the fuel injector? They come 2 in a pack so less than $50. I just want to clarify.

bmech211

My "dumb down" understanding is that the injector current rises exponentially at a rate that is dependent on the solenoid status (open or closed), and the impedance of the injector (LOW/HIGH). This in turn sends a sensing current to a resistor in the ECU that subsequently controls the driver logic, and determines the current needed to initially open the injector and hold it there for the duration of its duty cycle.
Its this sensing resistor that has the propensity to blow up if one were to connect low impedance injectors directly to the computer without a resistor pack; Due to higher sensing currents.

I am by no means an electronics professional, but this is how it was explained and demonstrated to me back in the day. Stinky circuit board smoke and all.

71 chevy

iTrader: (18)

i believe you just solder one in line with the power wire and leave the ground as is but i could be wrong.

you would want to verify that.

bmech211

Wicked,

You splice the resistors in on the positive side. You should grab a wiring diagram to find out exactly which wires those would be. Don't mess with the negative side, as this is what triggers the opening and closing of the injector (switch-to-ground).

All you're essentially doing here is dropping the resistance of the WHOLE circuit once it's completed by the firing injector.

EDIT: Not to step on 71Chevy's toes, but I'd be reluctant (because of my lack of experience) to suggest messing around with the driver logic. You won't go wrong by keeping the system within the operating parameters it was designed. Thus I'd shoot for maintaing a circuit resistance that closely matches stock (14ohms +/-).

71 chevy

iTrader: (18)

which is exactly what the resistors do. there is no messing with the driver logic that I see. maybe you can expound.



but, using the ubiquitous OHMS LAW, if you have a circuit designed for high impedance injectors, say 14ohm, in a 14v circuit,

i= v/r, i=14/14 = 1 amp going to the injector

put a low imp injector in its place(mine checked at 2.5 ohms)

i= v/r , i=14/2.5 = 5.6 amps going to the injector. it would not last minutes

so, from the links above, all the resistor is doing is limiting the current to the low impedance injectors down to what they can handle so you can run it in a system designed for him imp injectors.

bmech211

So taking the ECU out of the equation, running peak/hold injector circuitry @ 14ohms limits the current to 1 amp. This is ideal for the "hold" current, however, you'll lack the higher "peak" current required to snap the injector open.

If we reverse the scenario and throw in a resistor that brings the current up to, let's say 4 amps, you now have the "peak" current to open the injector but you've also induced a higher "hold" current as well, and the ECU may eventually burn out.

As mentioned earlier current is controlled via a sensing resistor and transistor, and pretty much operates within the parameters of the injector circuitry (in our case 1amp). In order to run peak/hold injectors we actually need current that is controlled via switching to get that initial 4amps required to open the injector. I'm most certain that these ECU's don't have that capability, but this is essentially what an external peak/hold injector driver does.

So basically, what it all boils down to when running peak/hold injectors on a saturated system is that you introduce some latency in the initial stages of injector opening. Meaning the benefit of a shorter injector-opening response time is nil.

Wicked69

Wow!!!!! You friggin guys are giving me a headache.....lol. This is damn good information though. I have a friend BOB who is doing my harness for me. He has done several but has never heard of using injectors or a driver box. However, I am going to send him this link and I am sure he will know where you guys are coming from. If it is too much for him I may just have to make the injector trade after all 71 Chevy and let you set my harness up in exchange.