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Thread: better injectors for better economy

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    better injectors for better economy

    In the thread below, one forum member noted better fuel economy after changing injectors.
    I was curious and bought three matched injectors, tuned to a max flow of 220ccm. This is a bit less than the supposedly correct 230ccm of the OEM injectors.

    https://mirageforum.com/forum/showth...-amp-flow-rate

    Changing them was easy, and took about 20 minutes. The FSM has detailed instructions.

    The differences of the injectors:
    The circle of the ten holes that output the fuel has a 50% or so greater diameter, the ten actual holes being the same diameter as the old ones. The spray mist of the new ones is finer than the OEM. You can tell by cranking the engine with removed fuel rail, and visibly comparing old and new injectors.

    The differences driving:
    The new injectors are rated 220ccm as opposed to 230ccm of the OEM variety. As expected, there is now a little bit less power. I could have ordered them with 230ccm and retain power, but I preferred better economy to more power. Better economy was the motive for changing.
    During warm-up, or about the first ten minutes, the fuel consumption is definitely lower. Once the engine is fully warm, there is almost no difference. In total, with my style of driving I save about 5 to 10% fuel, depending on the driven distance.

    This is where I bought them, and what was bought. The total cost including freight was €46 being roughly US$ 50.

    https://chaopei.en.alibaba.com/produ...1987f9d6dk1Uvp


    NB: After changing injectors, the ECU has to learn the new settings for idle!
    The FSM says to fully warm up the engine, then turn it off and start it again 10 seconds later, and let it idle for ten minutes before turning it off again.
    The ECU will then have learned how to idle properly with the new injectors.


    Last edited by foama; 04-30-2019 at 01:20 PM.

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    Nice find foama. I'm curious to see how these injectors hold up over time, and how your engine works with them, especially if the fuel savings is sustained or if the ECU simply adapts to the new flow rate.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Senior Member DonkeyPal's Avatar
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    I wonder if the new injectors will work better than the originals in every season of the year?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 automatic: 43.0 mpg (US) ... 18.3 km/L ... 5.5 L/100 km ... 51.7 mpg (Imp)


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    Just A Mirage!
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    I'm really curious too if you get to keep the fuel savings after it's relearned them. I'd like to know if there's a major gain in MPG by doing this as well.

    Likewise, I wonder if it works in the other direction -- if the engine will take advantage of a bigger injector automatically.

        __________________________________________

        click to view fuel log View my fuel log 2017 Mirage GT 1.2 automatic: 37.5 mpg (US) ... 15.9 km/L ... 6.3 L/100 km ... 45.0 mpg (Imp)


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    Still Plays With Cars Loren's Avatar
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    It's a closed loop system. The ECU will adjust fuel until the O2 sensor reads stoich. It will do this until/unless you either run out of adjustment range (you'd have to fit injectors that are 20-25% too small, or lower fuel pressure to reduce their flow), or you LIE to the ECU electronically and make it THINK that a condition other than stoich is 14.7. If you get the injectors so small, or fuel pressure so low that the ECU can't adjust to a stoich condition, you'll get an error code and very likely go into limp mode because running lean is dangerous for the engine.

    When you're out of closed loop (like during warm-up, or when you're at WOT), then your smaller fuel injector might result in less fuel being delivered... and less power. But, at that point, if what you wanted was less power and more economy... simply don't go to WOT!

    To answer Phaux's question, the obverse is also true. Larger injectors... the ECU will adjust as long as you're in closed loop operation. Put injectors in there that are up to 20% larger, the ECU will figure it out. BEYOND that, then you'd run rich. The ECU would detect it as some sort of error (O2 sensor output out of range or something), and you'd get a code.

    If you want to lie to the ECU (always a noble pursuit), you could fit a configurable Wideband O2 sensor. I've played with the Innovate LC-1 before. You can program it's analog output to whatever you want. So, you could program it with an altered output range that would put out the correct voltage for 14.7:1 AFR at, say... 15.2:1 AFR.

    But, simply fitting slightly smaller injectors... I really don't think it going to have any effect long term. The ECU has "long term fuel trims" that will adjust for that in short order.

    The ECU is very good at supplying the CORRECT amount of fuel for the amount of AIR going into the engine with the current conditions, and the commands of the driver. You want to get better economy, simply put less air through the engine. Either don't open the throttle as much, or RESTRICT the intake in some manner so that even if you open the throttle... less air is going in. Less air = less fuel.

    This is why the electronic throttle recalibrators CAN help with fuel economy. They can effectively make 25% pedal = 10% throttle. Less air into the engine. Less fuel used.

    Modern fuel injection is actually very simple if you take the time to understand it. There ARE ways to cheat it. But, smaller fuel injectors is not one of them.
    Simplify and add lightness.

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    Senior Member AtomicPunk's Avatar
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    Fantastic explanation! Nicely done.

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    I agree, but am still curious to see what results foama will have down the road.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Senior Member Mitz's Avatar
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    Quote Originally Posted by Loren View Post

    ...

    If you want to lie to the ECU (always a noble pursuit), you could fit a configurable Wideband O2 sensor. I've played with the Innovate LC-1 before. You can program it's analog output to whatever you want. So, you could program it with an altered output range that would put out the correct voltage for 14.7:1 AFR at, say... 15.2:1 AFR.

    ...
    Perhaps Magnum Tuning's O2 sensor option is simpler?

    https://www.magnumtuning.com/en/deta...subishi/mirage

    https://www.magnumtuning.com/en/deta...subishi/mirage

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    My motive for changing the injectors was better economy, better economy, and better economy!


    The slightly reduced max flow rate does not make much difference to performance, and if it did, I probably might not even notice it in daily driving. Maybe I should have ordered them with 230ccm flow rate instead. The way I drive results roughly in a "B"-average of around 4.4L/100km in winter, and 0.2L better in summer. Our cars use very much more fuel during warm-up, the colder the more.

    The better the injectors spray or "atomize" the fuel, the better it is evaporated, and thus a lesser amount of injected fuel is needed to create what the ECU sees as the correct fuel to air ratio.
    The spray mist of the new ones is finer than the OEM. You can easily tell by cranking the engine with the removed fuel rail, and visibly comparing the spray of old and new injectors.

    With injectors built for a high flow rate, and these being used at lower flow rates, spraying is less than perfect. The finest spray or best atomization is achieved near max flow rate. That said, the higher the fuel pressure, the better it is atomized. Running at 3.5 bar fuel pressure, our cars have about the max pressure the injectors and the fuel pump can take in the long run. Raising that pressure would create other problems, so I won't modify that.
    Last edited by foama; 05-01-2019 at 08:32 AM.

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    I will post a report of the observed mpg differences when I am sure about the results, not earlier.
    This could be in several weeks, or in whatever time is necessary. Thanks for your patience.

    Preliminary UPDATE:

    After the first ride, the figures displayed were very much better.
    I don't know how much consumption really changed, but this picture was taken about 20 minutes after driving began. The display was not reset on start.
    The trip was on well-built country roads going through villages and built-up areas, much of it out of town at 80 - 90 km/h.

    Name:  1st may 2019.JPG
Views: 1047
Size:  72.4 KB


    Last edited by foama; 05-01-2019 at 02:16 PM.

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