Author Topic: Fuel injection retrofit  (Read 15671 times)

Offline connie_rider

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Re: Fuel injection retrofit
« Reply #15 on: February 28, 2018, 12:59:19 pm »
Best of luck on this.
I haven't a clue on how to do such a build, but I think it would be a lot easier to do the first on a inline 4 {because the carb arrangement}.
If I remember my son's Magna correctly, the front and rear carbs had different jetting to keep the rear cylinder cool?
  If so, you would have to handle that need in your plans, and not with an inline 4.

Ride safe, Ted

Offline gpineau

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Re: Fuel injection retrofit
« Reply #16 on: February 28, 2018, 04:31:21 pm »
I have heard that before but I think it is bull. I dont know where the story started but I have cleaned a lot of  magna V4 carbs and never see a jet that was different between front to back.   I may be wrong because I am not the first person to work on them but they all have the same number stamped on them.

Back to the efi experiment.
Getting the V4 working with EFI will be a challenge for me. Actually getting a lawn mower working is a challenge.  I am a decent garage monkey and can fabricate and wire most anything. So I think the hardware side will be just a bunch of assembly. I am also a decent programmer so I think the programming will not be a problem either.

The biggest hurdle for me will be understanding the algorithms for adjusting the timing and pulse widths of the injectors.  Once I understand it I can code it.  Most designs I see have a look up table based on rpm, load, throttle position, air and water temperature. I just need to understand those relationships very well before I can start writing software.

Correct me if I am wrong but I believe that both the V4 and the inline 4 Connie use a wasted spark coil setup. Where when one cylinder is the compression stroke ready to fire  its companion sharing the same coil is on the exhaust stroke.  And while that cylinder is on the power stroke it's companion is on the intake stroke.  In fact there is always only one cylinder ever on the intake at any time and its injector should be triggered just a few degrees after his companion was ignited for the power stroke.  Do you follow me?

knowing that the two front cylinders are companions and the  two back cylinders are companions should make building a prototype manifold and injector set-up easier.
 
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Offline connie_rider

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Re: Fuel injection retrofit
« Reply #17 on: March 01, 2018, 07:52:24 am »
I'll stand corrected on the Magna. Worked on them, only a little, so not much knowledge on how the cylinder's are paired.
Connie is wasted spark. Firing order is 1,2,4,3.
Hope this works out for you. Interesting project.

On the programming etc, BDF could help you far more than I...

Ride safe, Ted
« Last Edit: March 01, 2018, 06:35:18 pm by connie_rider »

Offline gpineau

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Re: Fuel injection retrofit
« Reply #18 on: March 01, 2018, 05:29:56 pm »
Here is the skinny on the V4 Magna.
I'm thinking I can cheat on the the injectors and have two cylinders share an injector. And again maybe not. I need to get the carbs off and do some measuring.
 Study, study, study....
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Offline connie_rider

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Re: Fuel injection retrofit
« Reply #19 on: March 01, 2018, 06:39:56 pm »
You sed; its injector should be triggered just a few degrees after his companion was ignited for the power stroke.

Question; as the timing changes as RPM's increase. Do you want to control injectors by the signal to the plug (that changes) , or the signal at the pick up Coil (which doesn't change)?
ie; Do injectors also change their firing point, based on RPM?

Ride safe, Ted

Offline gpineau

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Re: Fuel injection retrofit
« Reply #20 on: March 01, 2018, 08:12:31 pm »
From what I have read you want to open the injector just after the intake valve opens and the piston is on the down stroke. That would not change ever unless there was a variable cam.

But you are right the spark timing advances with rpm so the injectors should be timed to the crankshaft sensor and not the spark. I dont think it is critical timing. The next thing that happens after the spark fires is that an intake valve is going to open and a cylinder will begin to suck in air and fuel.  Of course you would like there to be a stream of air to inject the fuel into but I don't think it is that big a deal to fire the injector a little early. What is most important it the amount of fuel you inject . If it is a bit early it will maybe wet the intake valve a little but in milliseconds it will be sucked into the cylinder anyway.
« Last Edit: March 02, 2018, 09:16:23 am by gpineau »
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Offline B.D.F.

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Re: Fuel injection retrofit
« Reply #21 on: March 02, 2018, 10:11:10 am »
What you are talking about is timed fuel injection Ted, and it is not usually done that way for the simple reason that fuel injectors are sized to be open around 85% of the time when the engine is using the maximum amount of fuel that it can. And no valve on any engine is ever open 85% of the time, so a great deal of an injector's open cycle occurs with the intake valve closed anyway, no matter when the injection cycle is started. On top of that, the benefits of timed fuel injection are not that great when applied to normal road vehicles, and there is always the risk of stratifying the fuel / air charge inside the combustion chamber if injection cycles are too short at very high engine speeds. In other words, if a much larger injector is used so that only, say, 20% of the injector's capacity is used so that it can deliver a full fuel volume when the intake valve is open.

These concepts get really complicated really quickly. I find the best way to deal with them in general is to basically just do what everyone else already does and use the method in common use for the vehicle in question.

Brian

You sed; its injector should be triggered just a few degrees after his companion was ignited for the power stroke.

Question; as the timing changes as RPM's increase. Do you want to control injectors by the signal to the plug (that changes) , or the signal at the pick up Coil (which doesn't change)?
ie; Do injectors also change their firing point, based on RPM?

Ride safe, Ted
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Offline connie_rider

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Re: Fuel injection retrofit
« Reply #22 on: March 03, 2018, 08:59:05 am »
Thanks Brian.
It's taking me some time to absorb what you said.
Still not sure I have it all, but I'll keep pondering it.  :banghead:
NOTE: This is not my build it is gpineau's.
            I'm just enjoying the discussion/learning..

Our previous discussion was just about the trigger point for the injectors.
  gpineau had stated he planed to base his trigger point, of the fire signal (that signal would change with the timing),
  I made the point that the signal from the pick up coil might be better because that signal would not change with
         the ignition timing.
    We agreed that the pick up signal would be the best trigger source.

Still trying to wrap your 85% point, into the plan to use 1 injector to fuel 2 cylinders.. ie; Pondering continues.  :nuts:
      I know 1 injector per pair of cylinders will work, but when to spray the fuel, and for how long is confusing...
         My assumptions are; the (1)  injector will fire each time one of those (2) cylinders is on a intake stroke.
         At 10,000 RPM's, this will happen 10,000 times per minute. {each cylinder would have 5,000 intake strokes)
          An injector sprays at a constant rate, so pulse width determines how much fuel is delivered.
          As RPM's increase, the time that the valve is open becomes shorter.
          If the delivery is a constant rate, but the amount of time is less at higher RPM's, you would have to spray fuel into the
            intake before the valve opens.. (to ensure enough fuel is available when the valve is open)
          Opening the throttle allows more air, so fuel quantity must also increase. (ie; longer pulse width)
          In my mind that suggests your 85% figure indicates; a properly sized injector fires 85% of each rotate {at WOT}.
            That 85% of one rotation needs to be before (and during) the time that the valve is open.
         At 10,000 RPM's, this has to happen 10,000 times per minute, with pulse width, and injector timing varying. {as RPM's change}.
                    Am I on the right track??

NOTE: I am not speaking for gpineau. Just trying to understand a bit more...
          Both of you know more about this than I.
          I particularly want to hear what gpineau thinks about my pondering..
               Good discussion!!

Ride safe, Ted
« Last Edit: March 03, 2018, 10:56:52 am by connie_rider »

Offline gpineau

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Re: Fuel injection retrofit
« Reply #23 on: March 03, 2018, 09:24:41 am »
Connie_rider.

Those are some good thoughts and are along the same thought I had when I first started thinking about this.  Maybe I am reading too much or thinking too much or both.
But I have come to the conclusion (in my feeble mind) that timing is not that important. What IS important is to get the air/fuel ratio correct. Its not just air and its not just fuel that make things work. Its maintaining the proper air/fuel ratio. If the air flow increases then so must the fuel being injected. If it takes keeping the injector open 100% of the time then that is what needs to be done or get a larger injector.

If you think about it that is what a carburetor does. It does not time anything. I is tuned to mix the proper amount of fuel with the incoming air regardless of the amount of air flowing through. Just keeping the mix right.

I went back and looked at some of the earliest injector designs and they did not time anything. The injector was just a means of spraying fuel into the air. They just sent the proper amount of fuel into the manifold to keep the mix right and it seemed to work pretty well.

So going forward I don't want to overthink this and just stick the the basic idea of delivering fuel to the manifold based on the measured/calculated air flow.

So now I m going to begin. I have been collecting ideas and parts for the past year and now it is time to do something. I am going to start on the manifold. I pulled the carbs yesterday and took some measurements and determined that I can use 1.5 inch pipe to get from the manifold to the intake ports and I am thinking I will use a 4 inch pipe for the manifold/air-box. It will all fit with some room to spare.  I will post some drawing when i get closer to the final design. 
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Offline connie_rider

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Re: Fuel injection retrofit
« Reply #24 on: March 03, 2018, 11:15:05 am »
I agree about the manifold first.
Also I agree about AFR.
But you can't spray continuously as the mixture would be rich at Idle, and lean at WOT.
  (Carbs, draw fuel at the correct AFR with each intake).
I think; Injector Pulse widths have to adjust with throttle opening, rpm's, (plus others) to maintain AFR.
            If they vary, injection timing has to vary as well. (longer pulses initiate sooner/before the intake stroke)

Just realized your planning 2 throttle bodies.
So, each will have an injector built into it. Good plan..
Have you determined which throttle bodies you'll use?

Ride safe, Ted
« Last Edit: March 05, 2018, 08:07:02 am by connie_rider »

Offline gpineau

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Re: Fuel injection retrofit
« Reply #25 on: March 03, 2018, 06:51:57 pm »
I think I will use one throttle body.  I have a number of carburetors laying around that I could cannibalize to make a throttle body. I have a Volkswagen carb that is just begging to be cut in half. 

The prototype is going to be ugly.
A 4 inch sewer pipe .
Four  1.5 inch pipes to the intake ports.
Dont know if I will mount the throttle body to the side or the top.  Just depends on how it all fits.  Still thinking.
You know if I mount the injectors very close to the intake ports then the throttle body can be anywhere in the vicinity.
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Offline connie_rider

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Re: Fuel injection retrofit
« Reply #26 on: March 03, 2018, 07:50:35 pm »
Now, I'm really baffled...

Ride safe, Ted

Offline gpineau

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Re: Fuel injection retrofit
« Reply #27 on: March 03, 2018, 08:46:50 pm »
Baffled about?

Something like this manifold.  Its for an inline 4 cyl (like a Connie). But imagine it with holes on both sides of the big pipe to mate up with a V4.
The throttle body can be mounted on top or it could be mounted at  one end .

Gerry
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Offline connie_rider

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Re: Fuel injection retrofit
« Reply #28 on: March 04, 2018, 05:52:15 am »
Sounds like your talking about using a single downdraft or maybe side draft carb body?
An actual throttle body, with TPS sensor would seem to be easier.
Plus I think you'll need MAP or MAS sensors?

(Downdraft) I just can't figure how it will fit under the gas tank.
2 Injectors? Located where? Probably need to be near the valves.

I'm not saying don't do it. Just don't understand how you can make it work.
NOTE: Not familiar with intake port layout on a Magna.

Ride safe, Ted

Offline gpineau

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Re: Fuel injection retrofit
« Reply #29 on: March 04, 2018, 09:10:57 am »
I have several ideas in my head. but have a look at this picture. Imagine all the room you have when you remove the carbs and air box. I mean its not a huge but there is plenty of room for a throttle-body and a manifold. The space above the carbs is not all tank. There is a wide opening toward the front of the tank where the air box and filter is now.  Down draft, side draft or obtuse angle ...it doesn't matter.  Just where ever it will fit. There are no carbs or floats or fuel levels to worry about. Just air. 

I plan to use a map sensor mounted somewhere on the manifold.

I have a throttle body off a 95 Hyundai. I will use it because it has the throttle sensor attached . 

The way I see it here are the important pieces of the plumbing. 
1. injectors close to the  intake ports. (although  I have see some designs where the injectors are in the manifold below the throttle body)
2. Throttle body and manifold
3. plumbing to connect 1 and 2.

I'm off today so I have time to move the bikes around and get the victim into the garage to start making real measurements.

This is a multi phase project. There is the mechanical design and fabrication, the electronics piece and then the software programming. I don't expect to finish this for at least a year.  Maybe by the time I finish I will be educated enough to claim I know what i am doing.  :D
 
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