My Megasquirt F.I. system

Discussion in 'High Tech for Old Iron' started by 86regalwith455, May 16, 2004.

  1. 69RivieraGS

    69RivieraGS Well-Known Member


    Where did you get this drill bit? I know of a company that will rent one but I wasn't away that MSD made one! Thanks!
     
  2. D-Con

    D-Con Kills Rats and Mice

    Jegs PN 121-2160 Summit # MSD-2160 $155.00

    I might sell mine once I am done with it. I needed to buy as my schedule makes renting a logistical problem.
     
  3. 86regalwith455

    86regalwith455 Well-Known Member

    I only paid $8 for the 17/64th drill bit at a local tool supply house.
    After drilling the 3/8 pilot hole, the 17/64 will cut the fuel rail like butter, but don't go all the way through, the 3/8 pilot hole is plenty big enuff to feed the injector. You MUST use a brill press, and clamp the rail down or the holes will not be straight.

    Dean
     
  4. D-Con

    D-Con Kills Rats and Mice

    This drills the manifold side injector pocket. I'd be bummed for me (happy for you) if you replaced that with and $8 bit....

    Let me know as it's currently on b/o and I can cancel it...
     
  5. 86regalwith455

    86regalwith455 Well-Known Member

    Your drilling the manifold? I see. You should be able to do that the same way I did my fuel rails. Start with a pilot hole (3/8"), then follow with the 17/32" drill bit, go all the way through. What type of injectors are you using?
    Do you have a drill press, or are you doing it free hand?

    I don't see why you have to buy such an expensive tool.

    In my last post 17/64 should be 17/32.

    Dean
     
  6. 69RivieraGS

    69RivieraGS Well-Known Member

    I agree that drill is way too expensive. But on the plus side you should be able to do both the manifold and fuel rail with the same bit if you should chose to keep it on order.
     
  7. D-Con

    D-Con Kills Rats and Mice

    Hey, I'm all for that! I'll cancel the order tomorrow.

    I'm a bit confused though, as if I go all the way though with the 17/32, how does the o-ring seat? I thought the hole was shouldered with a tapered seat for the o-ring?

    I will use at least a drill press if not a mill.

    I have no idea on injector type at this point. You tell me! I want something conventional in dimensions. Should be ~50 #/hr to support 600 HP (I might get there someday).
     

    Attached Files:

    Last edited: Jan 22, 2006
  8. 86regalwith455

    86regalwith455 Well-Known Member

    D-con,

    The 17/32 drill bit makes the hole the correct size for the injector o-ring, about .531. Use the Quad 4 style injector, which is the same style as say an 88' TPI injector, and a 90' Bronco w/351w injector. The Accell injectors (acc-150830)are for an 88' Camaro w/TPI, they fit exact in replacement of the Quad 4 injectors I built my fuel rails around.

    Dean
     
  9. D-Con

    D-Con Kills Rats and Mice

  10. 86regalwith455

    86regalwith455 Well-Known Member

    That's the style!

    Dean
     
  11. D-Con

    D-Con Kills Rats and Mice

    How is your tuning going? Everything dialed in nicely?
     
  12. 86regalwith455

    86regalwith455 Well-Known Member

    It's running excellent now that I have the correct size injectors. I plan on going to the race track in Feb.

    Dean
     
  13. nrh trans

    nrh trans Member

    beware

    JB Weld becomes soft at 250 degees F.. It will at 200 degees become dissosiated by the fuel and fail. Carry a fire extinguisher or be sad so so very sad. PS. tig welding is not at all difficult , Jessy James has mastered it and he's a blithering idiot.
     
  14. 86regalwith455

    86regalwith455 Well-Known Member

  15. tlivingd

    tlivingd BIG BLOCK, THE ANTI PRIUS

    gettin really intrested in a megaquirt system. what are you guys squirtin using for ignition control? I'd really like to play with ignition timing when I do mine. I'm debating on using MSII or MSI with the E software support extention. oh btw. first gen turbo eclipses and talons have perfect factory injectors for us hitting 520 hp with a 455 and the eclipse guys are dumping them on ebay for about 45 to 60 bucks for 4. :Smarty:

    I'd love to see some fuel ignition maps if you have em.

    -nate
     
  16. DualQuad55

    DualQuad55 Well-Known Member

    Hi,
    I am looking for some info to do the same type of set up. I have much available from the Northstar 4.6L engines at work.
    Do you know where I can find the flowrate (lb/hr) of these injectors? My brother works in the parts dept and can not get any info through GM.
    I have checked a few sites listed on this thread and others but can not come up with any info. They supply 300hp from the factory, but I don't know if they will handle 400+hp. Does Cubic inch displacement factor in at all, or just est. hp?
    How do you adjust the fuel curve? do you just keep adding/subtracting fuel pulse width until you reach the correct O2 readings? is there a chart you can go off?
    I wish to run bare minimum sensors such as TPS, MAP, O2, coolant. This should suffice to fire off the injectors, no?
    How much change is needed when changing throttle body flow rate/size? I am looking for a set up that would allow easy changing of throttle valve/bodies to creat different looks.
    Any info would be greatly appreciated, Thanks.
     
  17. tlivingd

    tlivingd BIG BLOCK, THE ANTI PRIUS

    I'd have to look on the flowrate. CI does factor somewhat in hp, but x amount of fuel will give Y amount of energy. If i subtract the losses of an engine from that amount of energy it should come up with a close amount of hp.

    you can run it backwards. for example. I want about 450-500 hp. now the Injectors i've chosen support about 500-550 hp. they are 450cc/minute injectors when I use 8. There is a table in the Megasquirt manual that you can use for injector sizing and will get you close. but this also depends on how much air you can get into and out of the engine.

    The fuel curve is decided by the O2 sensor. your actually looking for what they call stoichmetric ratio. gasoline has a specific ratio it likes to run at and make power at and slow down at. I believe with perfect automotive combustion and to hold speed you want about 14:1. acceleration you add more fuel. thus changing the ratio i think closer to 18:1. deceleration is closer to 11:1 (running lean) http://www.megasquirt.info/v22manual/mtune.htm

    I'm actually going to run mine w/o a TPS sensor with a rochester carb used as a TB. i'm going to base mine on my MAP sensor to know when i'm accelerating or decelerating. I will then need an O2 and temp sensors.
    I'm not using a TPS because of the huge diffrence in size of the air flow valves from the primary to secondary valves and since they don't move together I cant just use it as a percentage.

    All I can recommend is to read everything on the site www.megasquirt.info. Above are plans i'm doing and have not done so yet.

    the injectors work like a wall switch. they're either on or off. but they turn on and off very quickly. pulse width is how long they turn on for until the next cycle. if they're on they will just spray fuel. if their off they're off. now lets say the lights on to your house turn on and off 1 second apart. (you'll see that they're on and off.) now lets turn them on and off in a half second. but their cycle is still one second long. so they come on and off twice.

    now lets say you want to accelerate that your injector is on for that full second. it will get 100cc of fuel. (for example) now lets say you want to cruze and it takes half the fuel. the injector will stay open for half second and dump 50cc of fuel wait half a second till the next command. now lets say you want to idle. (the injector only stays open for .25 of a second) and will wait 3/4 of a second waiting for the next command. you should now have 25cc of fuel.

    now imagine instead of a second it does this in hundredths of a second.

    hope this makes sense
     
  18. 69RivieraGS

    69RivieraGS Well-Known Member

    There's a great tool here for judging injector sizes:
    http://www.megasquirt.info/v22manual/minj.htm#size

    I usually use this as a general tool and then once I get the system running I'll check what air/fuel ratio I'm running at different RPMs and make sure the injector duty cycles are not getting close to 90% at high RPMs. If they are, then I'd need to go to a larger injector.

    Duty cycle is the percentage that an injector is open per intake rotation time. Say you're spinning at 5000 rpm. One rev would last 0.012sec, or 12ms (5000rev/min * 1 min/60sec = 83.3rev/sec, then take the inverse to get sec/rev = 0.012s/rev). But you're only taking in fuel every 2 revs(4-cycle engine), so you multiply that number by 2. So one intake cycle is 24ms(12ms*2 = 24ms). Now, if your injectors have to stay open for 21ms to give your engine enough fuel for that engine condition then you'd have a duty cycle of 87.5% (21ms/24ms = 0.875)

    I'm currently running a megasquirt on my 94 V6 camaro that I added a turbocharger to. I monitor my actual air/fuel ratio realtime with a wideband O2 sensor. You can use a narrow band sensor(the kind used on pretty much all domestic and most imports since the '80s) but the only info you can get out of a narrow band is if you're running a stoicheometric mixture(14.7:1 -> 14.7 lbs of air for every 1 lb of fuel). They will tell you if you are lean(higher A/F ratio) or rich(lower A/F ratio) but not by how much. A wide band sensor tells you exactly what A/F ratio you're running at any time. It's really the only way to tune an EFI system, otherwise you're flying blind. And Wide bands aren't nearly as expensive as they used to be. I run this one:
    http://www.innovatemotorsports.com/xcart/customer/product.php?productid=16169&cat=253&page=1

    It doesn't have a gage to mount in your dash but it connects directly to the megasquirt and gives it your mixture information and if you have a laptop in the car you can view the A/F ratio along with all of the other info for your engine on the screen. Innovate also sells one with a gage but it's $400. But once you get your fuel table all set up you shouldn't have to monitor the A/F ratio.

    On my turbocharged V6 I run a rich mixture when under boost(~12:1 or 11.5:1). But for just a naturally aspirated car you'd probably see max power under WOT somewhere around 13:1 or so. The factory sets up most cars to cruise at 14.7 because it represents complete combustion and has the least amount of emmissions. It's a good balance btwn emmissions and economy. I have been playing around with lean cruise on my car. I think some car manufactures had played around with it but essintially what it is is leaning out your mixture when you're just cruising down the highway and part throttle and not needing much power at all. I leaned mine out to ~16:1 - 16.5:1 when just cruising down the highway and it improved my gas mileage by 2-3 MPG.

    With megasquirt you basically just change the values in the fuel table to change the mixture at any given engine condition(based on RPM and manifold pressure). You just increase the values if you need more fuel and decrese them if you need less. Taking datalogs of runs and then looking at them to see where the table needs to be changed is usually the way I do it.

    As far as sensors, megasquirt needs MAP, coolant, intake air temp, O2, and TPS. But tlivingd brought up a good point. If you're throttle body isn'y very linear in flow with respect to throttle shaft position, you can ignore the TPS and just set up megasquirt to look for fast changes in MAP signal to see if you need to add an acceleration enrichment(just like the accelerator pump on a quadrajet).

    Hope this helps to answer some of your questions.
     
  19. 69RivieraGS

    69RivieraGS Well-Known Member


    I'm working on building up a 430 to run off a megasquirt right now. I'm working on converting my stock points distrubutor to a magnetic pick-up. I can then use a 7 or 8 pin HEI GM module and megasquirt to control the timing. You could also just use the 455 HEI distributor and feed the magnatic pick-up signal to a 7 or 8 pin HEI module and do the same thing. I just wanted to convert my points distributor because I like the smaller profile, instead of the huge cap and body that the HEI distributors have.
    Here's the info on running the 7-pin HEI with megasquirt:
    http://megasquirt.sourceforge.net/extra/setup-hei7.html
     
  20. 69RivieraGS

    69RivieraGS Well-Known Member

    If I had to guess on the injector sizes of the 4.6L 300hp Northstar I'd say around 24-26 lbs/hr. But that is just a guess. A 5.7L 270hp camaro LT1 engine uses 24lb/hr injectors, just for comparison.
     

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