Stock ECU - can it handle higher flow injectors?
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Thread: Stock ECU - can it handle higher flow injectors?

  1. #1
    Fellow Frogger! blahblah's Avatar
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    Default Stock ECU - can it handle higher flow injectors?

    Hello,

    I have a 306 XSI with a XU10J4R in it. The stock Bosch injectors (0280155803) flow 150g/min at 3 Bar (according to Bosch)

    The nearest higher flow rate that I've found would be Citroen Xsara VTS injectors (0280156139) flow 187g/min at 3 Bar.

    Both have the same resistance of 14.5 ohms and appear to be 'plug 'n play' from a mechanical/connector perspective.

    Given this is nearly 20% more, would the stock ECU adapt to the increased flow, or would I be best looking at an aftermarket ECU?

    I would be looking at a cam regrind later on (Peter Ts offerings come to mind) and fitting a XU10J4RS inlet/exhaust manifold.

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    A XU10J4RS upgrade isn't practical from a cost perspective - but lower cost experimentation is. I'm after modest power gains and the tinkering is part of the fun!


    Cheers,

    Chris

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    Maybe, but I wouldn't bet on it without a fairly expensive ($1000+) re-map.

    At the risk of asking the obvious, why do you need more fuel? More fuel is only useful if you can get more air in.
    PeterT is really the man to be asking.
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    1000+ Posts PeterT's Avatar
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    Adding 24% more fuel across the entire range would be a disaster. The XU10J4R injector is quite small and the ECU is multipoint only, so there's little head room to support more power. The XU10J4RS ECU is sequential, so it can support a relatively small injector as there is less injector dead time.

    So you'll either need a remap or an aftermarket ECU in addition to larger injectors. A remap will cost less but it's a once only solution and won't allow you to fiddle. BigRR has a std XU10J4R with a Haltech and larger injectors and it's surprising how much more power the Dyno guy extracted. I would highly recommend changing the ECU & injectors before changing cams.

    There are plenty of new injectors on eBay. You just need to get the top & bottom o-ring sizes correct, in addition to the length.

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    Fellow Frogger! stew's Avatar
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    Some of these are fine. Idle to 600rpm on a 4 cyl. I have no idea what happens during a remap on the ECU however.
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    Default Hmm ??

    Quote Originally Posted by blahblah View Post
    Hello,

    I have a 306 XSI with a XU10J4R in it. The stock Bosch injectors (0280155803) flow 150g/min at 3 Bar (according to Bosch) The nearest higher flow rate that I've found would be Citroen Xsara VTS injectors (0280156139) flow 187g/min at 3 Bar.
    -------------------------- but lower cost experimentation is. I'm after modest power gains and the tinkering is part of the fun!
    Cheers, Chris
    Hi Chris
    I think you are asking the wrong question. What you should be asking is "what should I do to have a bit of fun tinkering with my 306 and learning a bit on the way ". Now that is understood here as we all started that way back in the good old days
    But I think before you start changing injectors or whatever, you need to read a lot more about modifing motors and the way that is achieved. Go to the web or better still the library and find some books and see what is the step by step process to achieve some more power. Then plan a couple of things to do that are in your budget and see how you can go about doing them. Perhaps the injectors will not be in the first changes.
    Ask for some more ideas if you like
    Jaahn

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    Fellow Frogger! blahblah's Avatar
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    Hi all, thanks for the replies...
    Thanks Peter for the info on motor and the ECU/injectors path - I'll pursue this path in the longer term. I can get new higher flow Bosch injectors fairly cheap so will tuck these away for later. With the ECU I'll do some research as to what suits the 306 and can be integrated fairly easily. Also needs to be something that local Perth guy's (or myself) can tune...

    Jaahn, I was, err, 'fixated' on the injectors as I was thinking the cam change path would require it - Peter T mentions the injectors being an limitation on his web site. It's definitely a lesson in knowledge of each engine and it's quirks. I had a BX 16v and that motor responds well to a cam with no other changes - whereas this motor's looks like its limited by the fuelling and good gains can be made by changing the injectors/ecu.
    You have a point and if you have tweaks to try then I'm all ears! I have seen references to changing the intake/exhaust manifolds for minor improvements.

    I'm not forgetting suspension etc with this - the car needs new front struts and the gearshift has quite a bit of play too. So will tinker with this also...

    Cheers,

    Chris

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    Such a responsive chassis, ideal to support a power increase. I drove ours again the other day, marvellous handling!

    I'll be interested to hear the outcome at some later stage. Happy playing.
    JohnW

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    Hi blahblah

    There are other people on AF who know a lot more than myself and I am not really familiar with this particular motor. But why would I let that stop me telling you what to do !! This is a forum after all.

    As I do not know your circumstances these are just general ideas. If you want to have a bit of fun and learn a bit then having a sporty feel to the motor is usually more fun. A standard motor has plenty of torque mid range but can get a bit flat as the revs rise even if safe to rev higher. So making more torque at a higher RPM is good to drive, even staying with the standard red line. Any loss at low RPM will not be a worry to you, as you just change down a gear.

    So what is the way to more sporty power. The standard way is to get more air in and out. More air= burn more fuel= more GO. Both intake and exhaust modifications will be necessary to enable the engine to rev more if you fit a cam also. Otherwise the cam is half wasted

    So the intake system needs work. Air filter/ducting/manifold, etc can be improved. Free power here really. Shorter manifold runners off another model will help at the top end too. Gumtree is your friend !

    Exhaust system improved for higher flow and less restriction. Better manifold/extractors, bigger cat, better/bigger exhaust, muffler(nice note !). Some fancy exhaust manifolds available from other models here too. Free power here too. So far you have not really done much and the results may surprise you.

    The ECU should handle the difference in fuel needed if the O2 sensor is working OK. If not a cheap piggy back ECU kit may do the trick. For a play you could advance the inlet cam timing a tooth and see what happens. Not much real cost so far.

    Perhaps the next step is a replacement ECU and a big step up in learning. There is always a build yourself ECU too if that is to your liking and budget. Buy a laptop and a broadband o2 sensor and go for it.

    As a general statement again, that engine is used in many forms, in lots of cars. A study of the mods made to different HP versions will give you an idea of what the manufacture did to get more out of the motor for the sporty models and even the rally versions. Google is your friend here

    Have fun Jaahn
    PS when I wanted to brush up on my old knowledge on modding cars again, I went to the Tech library with an Automotive section. Found some great books there that were more current. And workshop manuals too for lots of cars !
    Last edited by jaahn; 6th April 2017 at 11:33 AM.

  9. #9
    1000+ Posts PeterT's Avatar
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    The stock ECU definitely can't cope with a cam change. Also, you need to be careful with maximum lift. Whilst your head can physically fit RS cams, it only has single valve springs, which limits max lift to approx. 0.380". Fitting a std RS cam to an R head results in unacceptable spring bind allowance.

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