Electronic fuel injection Help please

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hagent
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Electronic fuel injection Help please

Post by hagent » Sat Mar 25, 2006 5:05 am

Hello everyone.

For my next project I would like to build a Lockwood style PJ with electronic fuel injection.

I got off ebay a few used car fuel injectors, and now the fun begins.

I was wondering if anyone knows the best way to attach these fuel injectors to a PJ. I'm not very familiar with all the fittings and attachments. I'm concerned with heat build up on the O rings, and holding them in correctly.

Also is it OK to have the fuel pump pressurize the fuel lines and injectors with no type of circulation? If there is none will this burn the pump out?

Also I was thinking about using an air hose to pressurize a container full of fuel instead of using an electric fuel pump, but I'm a little concerned that it might just turn into a big grenade, and I want to be safe.
Oh... the thougt occured to me to use some sort of plastic bag to seperate the air from the fuel it'self....

Thanks guys.

Hagen
Hagen Tannberg

Hank
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re: Electronic fuel injection Help please

Post by Hank » Sat Mar 25, 2006 12:53 pm

Hagent- You don't mention if the injectors are rail type or throttle body.
Either type would require a return line to the fuel supply, whether you use a system pressurized by gas or a pump.
I've used GM throttle body injectors (search the old forum, I believe the posts are still there regarding this). The Injectors were cut out of the original fixtures and new ones machined of Aluminum.
My use of these injectors was with a valved engine.

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Re: Electronic fuel injection Help please

Post by Stuart » Sat Mar 25, 2006 3:28 pm

hagent wrote:Hello everyone.

Also I was thinking about using an air hose to pressurize a container full of fuel instead of using an electric fuel pump, but I'm a little concerned that it might just turn into a big grenade, and I want to be safe.
Oh... the thougt occured to me to use some sort of plastic bag to seperate the air from the fuel it'self....

Thanks guys.

Hagen
I use a weed sprayer and that seems to work okay. Regarding pressurized air, you could use another gas, CO2 or even propane!
I'm writing an automated airplane designer in java, useful later when you guys get ready to bolt a p-jet onto some wings

hagent
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re: Electronic fuel injection Help please

Post by hagent » Sat Mar 25, 2006 7:51 pm

Sorry about that.

The injector I'm sure came off a rail type system.

It appears they are the Bosch 0280155811 type.

Thanks for the propane idea, I totally blanked on that one.


Does someone make a weldable steel connection for this? So far I have only found aluminum.

Thank you,
Hagen Tannberg

hagent
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re: Electronic fuel injection Help please

Post by hagent » Sat Mar 25, 2006 8:34 pm

http://cgi.ebay.com/ebaymotors/Fuel-Inj ... 7317QQrdZ1

OK I found these mounts out of aluminum. I'm guessing these are for the fuel exit end. Now I just need to find the fittings for the fuel intake to the injector. I don't see any type of locking mechanisims. So these injectors are they just held down in place?

I guess I could make the intake out of an aluminum tube on the PJ and have a steel coller that would hold the intake.

Would I need two of these? One of the intake and exit ends? They would then be held in place with force only.

Wish I knew more about this stuff.

Hagen
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re: Electronic fuel injection Help please

Post by Rossco » Mon Mar 27, 2006 12:38 am

Hi Hagen,

Automotive fuel injectors are indeed held in with only a small downward force.
Most have a collar or attachment plate that holds them down to the intake manifold with individual bolts, or a common rail. Often this is the fuel rail, and the injector is just stuck inbetween loosely with an oring on the fuel line (top) and manifold (bottom). These obviously dont have any bracket, or mounting on them at all, just an o ring at either end, and the electrical plug sitcking out the side at a 45 deg angle. You can infact turn them as far as the lead will permit while running, without any difference in operation.

The 'O' ring is the integral part of the injector, because this is the only seal to the manifold. It just sits in there squashed into the hole.
There is very little pressure acting on this 'o' ring, just atm on the outside to the vacuum of the intake manifold. The fuel in connection has to be much better as it takes full fuel pressure. If the manifold o ring leaks (a problem that does indeed occur) it "sucks" air, throwing the idle and/or mixture off.

Most fuel pumps do have an internal bypass type system that limits their own peak pressure (off the top of my head, commonly around 60psi). Operating without a return flow wouldnt be immediatly fatal to the pump, although remember that you are running it full load all the time, asking for limited life in my oppinion.
The other thing to think of along these lines is your flow control.
With constant pressure, you would have to "throttle" your injector with the duty cycle of the electrical pulse fully.

The two other options i see imediatly;
Have locked pulse timing to the injector, obvious on a "single" frequecy engine, although variable for initial "tuning". AND, locked duty cycle for a constant timed injection. Then throttle compleatly with fuel pressure via a return valve setup. This i would see as having good integrity, although not the fine control.

OR, throttle with the duty cycle from a constant pressure. This way it would be compleat electronic throttle (good for remote aplication).
I would still use a return pressure valve for initial throttle range settings.

One more problem i see... dont go sticking your fuel injector into a overly extended, small diameter pipe from the intake (to limit heat). The spray pattern does need to have some area to expand out, or it will just hit the walls and run down as liquid fuel anyway.
One way around this, would be to get an injector with a very tight spray pattern and a deflector plate. These are designed much like a regular spray nozzle, that fires a high speed streem into an obstruction to "smash" it up. You could then aim it at a seperated spray plate, so to have it detached from any real heat.
Remember where they live normaly, try to design for similar conditions, and itll be fine!

Just some thoughts from an Auto Sparky. Hope it helps.
Great to see you doing this, ive meen meaning to for ever.

Rossco
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re: Electronic fuel injection Help please

Post by hagent » Mon Mar 27, 2006 4:35 am

Hey thanks Rossco for the info.

For some reason I thought that the injectors that I had would inject fuel directly into the CC of the car and not into the manifold. With 9 ATM on average I thought there would be some sort of locking mechanizim.

I was looking at those parts on ebay and I think I just might make them my self out of steel. It shouldn't be that hard and then I can just weld them to the CC or intake tube. Guess I have to make a trip to Industrial Metal supply soon.

I will have to buy a cheap oscillascope so I can make my timing circuit for the fuel injectors. It will be fun!
Hagen Tannberg

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re: Electronic fuel injection Help please

Post by Fricke » Mon Mar 27, 2006 4:26 pm

Place the fuel injector before a nozzle, and use the fuel injector to control the flow of the fuel.

This way you can have a small nozzle in the intake and the bulkier fuelinjector in a more suitable place.

Oilburner nozzles or even water misting nozzles work fine. All depends on how fine mist you need.

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re: Electronic fuel injection Help please

Post by tufty » Mon Mar 27, 2006 5:23 pm

I'd suggest using a pump+return system rather than a pressurised tank. the mere thought of having a pressurised fuel tank near red hot metal makes me go all wobbly.

Simon

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re: Electronic fuel injection Help please

Post by Rossco » Tue Mar 28, 2006 5:06 am

But Fricke, why then use the fuel injector???
A carfuly built return/pressure set up, with a nozzle would, and has worked like that for many projects.

The whole idea of using an electronicly operated fuel injector is precision timing, and spray attomisation all in one! Using it behind anything will severly dampen both.

I say go for it Hagen! And oscilascope? Nice indeed, although i would say unnessasary.
Build yourself a simple 555/mofset pulse generator, and have both frequency and duty cycle variable with a fine and corse adjustment each.
Measure frequency with a meter, or calculate from your variable cap, and duty cycle as a percentage straight from your linear potentiometers (resistor). Both compleat with a 1 to 10 scale on the knob.

Your just tempting me to do this. Ive just got so much else going on tho.
Also, I dont have a suitable engine to do this with at the moment. (the new one sucks, attomises and times its own)

Rossco
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Re: re: Electronic fuel injection Help please

Post by Fricke » Tue Mar 28, 2006 10:10 am

Rossco wrote:But Fricke, why then use the fuel injector???
A carfuly built return/pressure set up, with a nozzle would, and has worked like that for many projects.

The whole idea of using an electronicly operated fuel injector is precision timing, and spray attomisation all in one! Using it behind anything will severly dampen both.
Well Rossco - I wrote this: "This way you can have a small nozzle in the intake and the bulkier fuelinjector in a more suitable place."

As most of Your PJ´s are quite small. And the intakes are quite small.

And I gave ONE option not THE option!

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re: Electronic fuel injection Help please

Post by Rossco » Tue Mar 28, 2006 10:26 am

mmm, dont take me wrong Fricke.
I too have many of my own opinions that i like to lay out, as you can see! Ha.
I get too exited at times. Ive been wanting for a long time to see a comercial injector, supposedly perfected to date for injecting a timed, precice amount of atomised fuel into an intake, not that unlike ours.
Youd think that with my resources, id pull my finger out myself hey!

Maybe im not understanding what you mean? i would be very interested in your ipinion on some further detail and advantages of such a setup.
I have to admit, i assume all too much when it comes to constant flow injector nozzles, and know very little!
Maybe in a separate thread for Hagen's (hopefully) next projects sake?

Rossco

PS. Ive been reading up on the modern deisel injectors too... Veeeeery intersting!
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Re: re: Electronic fuel injection Help please

Post by tufty » Tue Mar 28, 2006 10:40 am

Fricke wrote:
Rossco wrote:But Fricke, why then use the fuel injector???
A carfuly built return/pressure set up, with a nozzle would, and has worked like that for many projects.

The whole idea of using an electronicly operated fuel injector is precision timing, and spray attomisation all in one! Using it behind anything will severly dampen both.
Well Rossco - I wrote this: "This way you can have a small nozzle in the intake and the bulkier fuelinjector in a more suitable place."

As most of Your PJ´s are quite small. And the intakes are quite small.

And I gave ONE option not THE option!
Rossco's right, though, I think. The bigger the volume of fuel feed system after the injector and before the nozzle, the more precision you lose. Even in a rigid feed system, there will be a pressure 'ramp up' and 'ramp down', meaning that the start of injection will be delayed, as will the end (not really a problem, as the combustion cycle will adjust to fit), and that the start and end of the injection cycle will be at lower pressure, resulting in less efficient fuel atomisation during those points in the cycle. At pulsejet cycle speeds, I'd actually expect the buffering to provide a near-constant feed of fuel at lower pressures than intended, thus making the use of an injector and timing circuit completely superfluous.

I could be wrong, of course.

Simon

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re: Electronic fuel injection Help please

Post by Rossco » Tue Mar 28, 2006 12:55 pm

Yes, Tufty. This is why, among other reasons (like using deisel), im looking into the elecric/hydraulic/deisel injectors. The injector builds its pressure before opening its firing port at all. Then, it fires a primer charge before the main injection. Injector pressures are incredible! and damn near instantanious. All from a low pressure, common rail supply.

Hagen, just be sure to keep us posted.
One thing really interesting would be to look at the duration and frequency of automotive injectors at their intended use. Comparing to a cylinder of lesser volme, although much higher frequency would be one of the first steps foward in this project i say.
I have done quite some work on injection diagnostics and mapping, as well as injector servicing and testing, so i will get some usefull info together for you.

Rossco
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Re: re: Electronic fuel injection Help please

Post by tufty » Tue Mar 28, 2006 1:39 pm

Rossco wrote:Yes, Tufty. This is why, among other reasons (like using deisel), im looking into the elecric/hydraulic/deisel injectors. The injector builds its pressure before opening its firing port at all. Then, it fires a primer charge before the main injection. Injector pressures are incredible! and damn near instantanious. All from a low pressure, common rail supply.
Oooh. Interesting. Links?
Rossco wrote:One thing really interesting would be to look at the duration and frequency of automotive injectors at their intended use. Comparing to a cylinder of lesser volme, although much higher frequency would be one of the first steps foward in this project i say.
Might be worth looking at motorcycle parts, revs are generally higher...

As a rough guess (fag packet calcs), and assuming a standard 4x4-stroke motor: Your standard automotive injector is designed to work once every 16 strokes, or every 8 crank revolutions in other words, and for one half a crank revolution max.

For a pulsejet we want it to operate once per half cycle, and to be actively injecting for about half that time (I think, maybe someone knows better?).

As a guess, we're looking for something like 200 - 300hz (erring on the fast side), which would mean in automotive terms 2 to 300 x 8 = 1600 - 2400 rpm, which is well within the capabilities of most auto injectors. However, in a normal auto duty cycle, the injector would have 7.5 times longer to 'recharge', to keep this within limits we'd have to be looking at an injector designed to run motors at 7.5 times more revs than that, i.e. somewhere between 12,000 and 18,000 rpm. And that's a _lot_ more than most automotive injectors are designed for. Small (250cc and thereabouts) race bikes do that sort of revs, maybe there are injected models out there that could be salvaged?

Of course, I could well be wrong here, the recharge time may be irrelevant, in which case standard automotive parts would do the trick very well.

Simon

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