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Thread: Largest injectors for a stock ECU?

  1. #1
    Largest injectors for a stock ECU?

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    Largest injectors for a stock ECU?

    I think I always heard that the largest injector that could be run on a stock Honda ECU is 310cc. I may even have heard that from RC engineering at one time.

    Anyone have any experience running this size or larger?

    I am thinking more of the idle department more than anything.
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  2. #2
    Largest injectors for a stock ECU?
    cygnus x-1's Avatar
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    Re: Largest injectors for a stock ECU?

    Quote Originally Posted by Oldblueaccord View Post
    I think I always heard that the largest injector that could be run on a stock Honda ECU is 310cc. I may even have heard that from RC engineering at one time.

    Anyone have any experience running this size or larger?

    I am thinking more of the idle department more than anything.

    The ECU isn't going to know what the flow rate of the injectors is; it will just turn them on and off. In closed loop operation it will look at the O2 sensor and try to adjust the fueling based on that, so in theory you could run larger injectors to run a larger engine with the same tune. I think the stock ECU uses closed loop at idle and during cruise, with WOT being open loop.

    Is this for your E85 experiments? Using a roughly 25% larger injector might actually work running a stock engine with a stock ECU. It will be down on power but would be better than with the stock injectors.

    C|

  3. #3
    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    Quote Originally Posted by cygnus x-1 View Post
    The ECU isn't going to know what the flow rate of the injectors is; it will just turn them on and off. In closed loop operation it will look at the O2 sensor and try to adjust the fueling based on that, so in theory you could run larger injectors to run a larger engine with the same tune. I think the stock ECU uses closed loop at idle and during cruise, with WOT being open loop.

    Is this for your E85 experiments? Using a roughly 25% larger injector might actually work running a stock engine with a stock ECU. It will be down on power but would be better than with the stock injectors.

    C|
    Yes, im thinking about going full e85. I am currently pretty lean at WOT with 250cc injectors.1.2 1.3 lambada. I got some wideband logs if your interested. closed lop everything is good. Its just open loop and cold idle im lean.

    All the online calcs say the 250cc should be fine with 110 hp and e85.

    I am thinking my choice is bigger injectors, about 30%.

    EDIT: calc here and looking at there fuel pumps.

    Fuel Injector Calculator | Fuel Calculators | Resources | DeatschWerks
    Last edited by Oldblueaccord; 11-04-2014 at 09:48 AM.
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    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    Just wanted to confirm Im running 320cc with the stock ECU driver with no problems. These are RC injectors so I would consider them "stock" style. I understand there are newer more efficient injectors being made now days. I think the 310cc limit was just and old wives tale from back in the day.
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  5. #5
    Largest injectors for a stock ECU?
    ShiRen's Avatar
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    Re: Largest injectors for a stock ECU?

    Are you tuned for e85 or are you just running an injector that's yay percent larger?

  6. #6
    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    No tune just 30% larger injectors.

    EDIT: and 40 psi static fuel pressure.
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    Largest injectors for a stock ECU?
    ShiRen's Avatar
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    Re: Largest injectors for a stock ECU?

    You ever had a wideband on her? Honestly, idk how the fuel injected cars run tbh, I reckon it keeps it pretty lean and thats why you can't run much timing bone stock. Do you have your timing set any more aggressive?
    I don't think my carb would like e85, but I need a flex fuel tune on the ctr. I still want to boost the compression of the A, but idk if I ever will.

  8. #8
    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    Oh yeah ran a wide band a year before I did anything to it running E10 and then ran E30 for years. I wanted to understand what the fuel injection was doing all the time hot cold and any throttle position. My operational theory was closed loop the o2 sensors run Lambda and the fuel trims will run 30% plus or minus. So far I have proved this out as true with or EFI setup.

    I ran what is labeled E85 here but its always over 70% for a full year box stock and then I went with the 30% larger injectors and fuel pressure set at 40 psi static. I use the fuel pressure to tune the cold idle and the WOT. I do run the timing up since it will never ping.

    Carbs best I have done is I run a Quadrajet 50/50,E85 and 87 octane on my 440 which has worked out really well. It was alot of work to get it that far. it was an engine that someone else built with to much compression/cam unless I ran turbo blue race fuel. I always had to run the timing way way down to make it run on the street. E85 mix its back to stock or better timing no ping.They now make carbs that run E85 so I would look that way with an aftermarket two barrels. You need more than just bigger jets in a carb ALL the passages have to be enlarged to flow enough fuel.

    Occasional I run 30% on my LT4 motor,but its still under warranty so I need to be careful, and I run it in my 6.4 Hemi quit a bit. Ill probably convert that one to full E85 or well make it flex fuel compatible since I drive the Jeep out of town occasionally.

    Most box stock OBD2 vehicles run very very well at 30%.
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  9. #9
    Largest injectors for a stock ECU?
    ShiRen's Avatar
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    Re: Largest injectors for a stock ECU?

    Cool, I know youve been on e85 for quote some time. What afr does the stock ecu target, 15-16 on pump gas?
    If I was going weber I'd have no issue with a bit of ethanol, but I am dead set on my bike carbs, I don't exactly trust them either but theyll be better than my ol keihin. I don't actually have ethanol available locally, but I could chase 400hp with flex fuel in the ctr, doesn't have to have it in every tank.

  10. #10
    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    1 Lambda or 14.7 on gas scale closed loop. 12.5 cold idle and WOT. Usually lower at WOT I have seen 11.1-11.3. Gear and RPM do make a difference and Hondas little tricky linkage underdash makes you think your not at WOT when really you are. Stick your head under there and check it out.

    My Innovate gauge wont read Lambda no matter what I try and they wont help me so I gave up on them. I can see it on my laptop hooked to it. I got some videos and meaning to add it to my E85 thread I just never get around to it.

    If you start fooling with it just stick to using Lambda since almost all fuel is mixed anyway.
    1988 Lxi owner since August 1995
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  11. #11
    Largest injectors for a stock ECU?
    ShiRen's Avatar
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    Re: Largest injectors for a stock ECU?

    Im surprised it doesn't target slightly lean, Ive had my afr gauge on my car before I did very much at all to the car and it used to run a lot leaner, now it only leans out part throttle, but wot will hit 10 shortly. Idk if I know about the linkage, I just have a stress relief thing that keeps me stretching the cable passed wot, because I can push the pedal way passed wot. I have learned what the pedal feels like in relation to the throttle blades, when I had my manual secondaries actuated by a zip tie I could really feel it lol.
    My innovative MTX-L is a piece of crap, terribly unreliable, but I have thought I killed the Bosch LSUv1 numerous times and it just came back, it seems pretty accurate too, though I am running the sensor on a single header tube and I need to move it to the collector.

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    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?




    1988 Lxi owner since August 1995
    336k miles running strong!
    Now running E85.

    My Acura Type R front brake thread

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  13. #13
    Largest injectors for a stock ECU?
    ShiRen's Avatar
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    Re: Largest injectors for a stock ECU?

    Lol it runs like a sewing machine, polar opposite of mine. Your second vid is private btw.

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    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    I need to hire a videographer im terrible.
    1988 Lxi owner since August 1995
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    Largest injectors for a stock ECU?
    ShiRen's Avatar
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    Re: Largest injectors for a stock ECU?

    Start vlogging daily I will sub, your accent is great

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    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    well your gonna really lol I was raised in New York....
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  17. #17
    Largest injectors for a stock ECU?
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    Re: Largest injectors for a stock ECU?

    Quote Originally Posted by Oldblueaccord View Post
    well your gonna really lol I was raised in New York....
    Carpetbagger.


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  18. #18
    Largest injectors for a stock ECU?

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    Re: Largest injectors for a stock ECU?

    Amen to that no income tax, no emissions, no safety inspections on cars. They just made it a 100$ fine able to NOT have car insurance.
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