Choosing injectors for batch fire MPI.

[JeepsAndGuns]

Now that I have the 7427 pcm in and running, and getting the hang of tuning it, I am ready for the next step, mod a intake and convert over to batch fire MPFI with this 16197427 pcm.

So, what are we limited to, as far as injectors that would be compatable? I would think the injectors ohms would have something to do with it?
If at all possiable I want to run EV6 style injectors with the nice 4 hole spray pattern.
I have quite a few (12 actually) of the dodge neon 0280155703 injectors laying around. (running these in the 4.0 in my 93 wrangler and love them) They are the EV6 4 hole pattern injectors.
I measured them and they are 12.5 ohms (plus or minus .1) They flow 238cc/min at 3 bar, witch according to the calculators online I have found, would flow about the right ammount for my engine at around 39-41 psi.

So what says the experts out there? If not, what other options do I have, that are roughly the same flow rate?

[Six_Shooter]

Biggest thing is impedance matching, meaning High-Z injectors.

Then proper amount of flow capacity, or close to it.

Physical fitment is also a concern.

If you're modifying the intake anyway, then you can make it and the fuel rail fit what ever injector you can physically fit. If you start with an existing port injection manifold, you will be limited to the size and style that was meant to be used in that intake.

[JeepsAndGuns]

Well, this will be on my AMC 401 engine. They stopped making those in 1978, so no factory MPFI intakes, and there is no other brands/type of intakes that can be modded to fit. This will be custom.

"Biggest thing is impedance matching, meaning High-Z injectors"

Ok, you just said something in japaniese...lol...I have no idea what that means. Can you enlighten me?

[EagleMark]

yeah, learn us? :innocent2:

I know of Peak and Hold injectors, Saturated Injectors...

So what is High Z?

Are they just for 280Zs? :laugh:

Opps, or is yours a 260Z?

[1project2many]

Learn ya??? Well, you asked.

So you're familiar with resistance. In A/C circuits and pulsing DC circuits using coils there's impedance. Impedance is roughly similar to resistance but it also includes things like the canceling effects of currents out of phase and currents dampened by capacitance. Resistance is resistance to electrical flow and is measured in Ohms. It is represented by R in many formulas. Since impedance is also the total resistance to electrical flow it is also measured in Ohms. However, it's represented by Z in many equations to indicate that it's not purely resistance. So what does this mean when selecting an injector??

Nothing!!

Resistance is the dominant property of the injector. Resistance also determines the driver type used in the ecm. A high Z injector is a high impedance injector is a high resistance injector is a high Ohms injector. It is more technically correct to say an injector has impedance so you will often see this term and "high Z" or "low Z" used in injector discussions. Saturated injectors have high resistance and peak and hold injectors are low resistance. Saturated injectors and drivers get their name because the circuit is at "full current" the entire time the injector is opened... it's saturated with current. Peak and hold injector drivers get their name because the circuit allows higher current while the injector is opening then lowers current once the injector is open to prevent overheating. An old fashioned GM starter solenoid is the same way, with a "pull in" coil and a "hold" coil. That's a "peak and hold" solenoid.

Look for injectors with 12 - 16 Ohms and you should be ok.

[JeepsAndGuns]

So basicly, we are saying these should work just fine?

[1project2many]

Yep, that's what Six was saying. Match the Ohms rating and you should be ok.

[JeepsAndGuns]

Now the hard part, buying a intake and finding a machine shop that can do the required work, do it good, and at a reasonable price.

For a intake, so far this one is looking like its gonna be the best bet.
http://www.summitracing.com/parts/EDL-7531/

Right now I am running the regular edl. preformer intake, and looking at it, it doesnt look like it would lend itself to be easy to mod for injectors because of the way the runners are cast. The air gap looks like a modded preformer and it looks like it wouldnt be too hard to set up for injectors, as the runners are shaped a little diffrently and are more even where the injectors would be.
They also make a open plenimum intake, but its a high rpm intake, and I dont want that. This is a lower rpm engine, I rarely take it past 3k, sometimes as high as 4k if I am really standing on it, but thats rarely.

[EagleMark]

Looks like it has a spot for injectors. I know Marlo might take on the job, he's the one that does the GM/IH Hybrid distributors.

[1project2many]

Dual plane carby intakes are often tough to convert to efi. Large, open plenums are usually better for high rpm use in carburetors but in EFI an open plenum doesn't hurt low end like it does with the carb. If you can get a Torker for decent $$ it could be tuned to work.

What would be really nice to get is a long runner intake to compliment a low rpm cam. I'm not sure how much you want to pay to buy a carbie intake thane have it adapted, but maybe building a manifold from scratch is cheaper or at least more rewarding for the price? Plenty of guys selling "sheet metal intakes" could build something.

Indy cylinder heads sells a manifold that might be a nice choice, if it fits the stock heads. Price book showed the manifold at less than $400. Maybe injector holes could be added before shipping?
http://image.moparmusclemagazine.com/f/31924293/mopp_0501_19_z+amc_v8_block_engine+intake_manifold .jpg

More info: http://www.moparmusclemagazine.com/tech ... to_19.html (http://www.moparmusclemagazine.com/techarticles/engine/mopp_0501_amc_v8_block_engine/photo_19.html)" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;"

MSD sells a "special" stepped mill / drill bit which has proper dimensions for many injectors. This can be used to put injector openings into a manifold flange provided there's enough aluminum there. And you can by injector "sleeves" designed to be welded into a manifold. I might be able to dig up the box of sleeves I have here to get MFG and part number if needed.

[JeepsAndGuns]

Dual plane carby intakes are often tough to convert to efi. Large, open plenums are usually better for high rpm use in carburetors but in EFI an open plenum doesn't hurt low end like it does with the carb. If you can get a Torker for decent $$ it could be tuned to work.



Interesting. I had looked at the torker intakes and the runner design looked like it would be about right, and easy to mod for injectors, but I have been writing it off because I thought it would kill my low end. So from what your saying, the longer runner open plenum intakes like that are actually better for mpfi and wont kill my low end? This engine rarely sees over 3K rpm, and about the highest I ever rev it is 4K when I am really hammering on it. But thats not very often.
The indy intake seems nice, but I dont see provisions for a PCV and other normal vaccume ports. Even though its got the bosses in it for injectors, I think its geared more twards race engines. I'm gonna do a little more looking around and see what I can dig up.

[EagleMark]

Long runners and open plenums don't effect engine preformance on port injected motors. It does on carbed motors because the fuel and air is mixed in the intake. Hence a wet intake manifold. Port injected is dry intake manifold. It just supplies air.

[gregs78cam]

Long runners and open plenums don't effect engine preformance on port injected motors.


I would agree for the most part, to a point. The exception to that is the TPI setup. i.e. long small cross section runners that did make a difference below(for the better) and above(actually hurt) 4500 rpm.


I have been thinking about building my own intake for MPFI on the Camaro. I just haven't quite settled on a runner design I like. I want the injectors pinted directly at the back of the valve not the bottom of the port where the intake meets the head. Still in the planning stages though.

[EagleMark]

That is a better pointing position. But to build and intake for a Chevy when so many are available?

I think the pointing at valve is not done originally because of injector clearance to intake and fuel rail issues. Batch fire would make no difference, seqencail... maybe...

[gregs78cam]

That is a better pointing position. But to build and intake for a Chevy when so many are available?

I think the pointing at valve is not done originally because of injector clearance to intake and fuel rail issues. Batch fire would make no difference, seqencail... maybe...

I was thinking that batch fire would be more important to have it pointed at the valve because if the injector fires at a closed valve the hot valve would help to keep the fuel vaporized until it opens, maybe better than the side of the runner can. If the injector fires at or ahead of an open valve it wouldn't make much difference....no?

[EagleMark]

It was just a theory, I have no information or engineering knowledge on it.

It would keep valve cooler, but that is not an issue on intakes... it's so close to intake valve or on intake valve, I don't think it would be worth the effort? It's all getting sucked in so fast it hardly has a chance to settle. DIS would probably be a better improvement!

Easy way to tell is look at newer and newer cars and see if detroit and others started pointing injectors at intake valve more?

Now read up on direct injection! Not that we could convert an old engine to it. But that is a huge leap in internal combustion engines. No fuel in intake or on valves. Cools combustion chambers which allows leaner mixtures, dual injector shots! Way high pressures! Cool stuff!

Off Topic: Hey you interested in doing a thread on 4l60E tranny improvements VIA PCM?

[EagleMark]

Batch fire would make no difference, seqencail... maybe...

You were right, I typed that backasswards...

I still don't think the effort to build an intake would be worth any if any improvement. Just thinking about it I don't know how you could lay down the injector without it being IN the intake runner? Hence my first thought of why it's not done because of clearence.... but if you put the fuel rail on the outside toward valve cover instead of towards inside towards throttle body? That would give you more room to lay down the injector angle!

[gregs78cam]

:doh:

[EagleMark]

:laugh:

Hope that was a good :doh:

:laugh:

[JeepsAndGuns]

Well I dropped the hammer on a intake. I think its out of stock because it had a expected ship date of 11-2. Pictures once its in my hands :rockon:

[1project2many]

The TPI Chevy fires the injectors 8 times for every cam revolution. One injector pulse per distributor pulse. It takes a bunch of heat to vaporize that fuel. The intake valve isn't a large piece of metal. It cools quickly and can't draw a substantial amount of heat from the head. Injectors directed at the port floor will spray fuel at the head itself where there's plenty of thermal mass to contribute to vaporization. What's interesting to think about is that as the fuel droplets vaporize and expand, the gas will push O2 back up the runners. So the initial intake charge after the valve opens is extremely rich, followed by an extremely lean shot of intake "air." There has to be a lot of swirl going on during the compression stroke to get this mixture blended a little better.

Intake runner length plays a huge part in determining the rpm where the manifold makes best power. But the TPI's power was limited by runner diameter, not length. The same runner on a 302 CI engine would go to 5k, but on a 383 it was starving around 4k. Now the AirSensors / F.I.R.S.T. TPI manifold, OTOH, did not suffer from the same limitations. http://www.firstfuelinjection.com/images/PDRM0377L.jpg Somewhere on the 'web is a page describing a 406 powered Vette making over 400hp using one of these manifolds. Definitely not your stock GM TPI.

As far as converting an engine to direct injection, the latest round of 60 degree GM V6 engines are just that, pfi engines converted to DI. GM designed this system to be installed with as few changes as possible. And from what I've read, it's relatively trouble free. Found a nice post by a GM tech the other day which detailed some changes, but I can't seem to find it now.

JeepsAndGuns, can't wait to see what you've found.

[JeepsAndGuns]

JeepsAndGuns, can't wait to see what you've found.

And here it is! Just got deliveried yesterday.

http://img.photobucket.com/albums/v606/JeepsAndGuns/2011-11-11172841.jpg

http://img.photobucket.com/albums/v606/JeepsAndGuns/2011-11-11172904.jpg

[EagleMark]

Nice! :rockon:

[1project2many]

That intake should be a nice improvement over stock. Did you get fual rails, or are you planning to machine them from rail stock? If you look at the pics in the TB thread, that intake was designed for the short Weber Marelli injectors that Edelbrock uses with the pro-flow kits. I had to use spacers and make a few changes to switch to standard height GM Delphi injectors.

I'm not an AMC guy. What's with the dual bolt patterns?

[JeepsAndGuns]

Yes I got the fuel rails too. Thats them in front of it on the bench in the first pic.
I noticed from looking at pictures of the complete kit online and looking at replacement injectors on edelbrocks website that it used those short pico injectors. I figured the o-rings were most likely the same size and I should be able to use standard bosch style injectors with just a little spacer that shouldnt be too hard to make.
I test fit my injectors and they fit just fine. Just gotta cut out some spacers.

The dual bolt pattern on the center holes is so the intake can fit the older heads as well as the newer ones. (old square port, and newer dogleg port heads)