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Thread: 851 SP3 replica project.

  1. #101
    Join Date
    Aug 2009
    Location
    Spain
    Posts
    345

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    I really didnít do anything special to the engine. And yes, I use 107/107 timing so, no difference there. Squish to 1,00 mm and slightly ported heads. I also made a conical bush to replace the original in Sil motor exhaust headers so that the exhaust gas flow finds a gradual smooth transition instead of the sharp step existing in the originals which abruptly start at 50 mm. Iíd say that maybe the combination of the 50 mm exhaust and the higher capacity emgine may be a good match: enough not to hurt peak power but not so big as to affect lower revs scavenging.

  2. #102
    Join Date
    Aug 2007
    Location
    Cornwall S.W. England
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    5,125

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    Another question chap..
    Do you know if the S4R injectors flow more fuel than the Webber "Greens" used on the single injectors fitted to the '92 851 and later 888's?
    The Webber "Greens" are good for 65 rwbhp, so 130 is the maximum that can be had from them.
    But better single injectors can be found that flow more fuel at a lower pressure, which would allow more power to be made.

    Steve R

  3. #103
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    Aug 2009
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    Spain
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    I think all green injectors are the same thing. They might be replaced by 12 hole which have the same flow as itís likely they have some advantage at the top end as the only advantage of shower-type injectors is that the longer distance allows for better atomization. This is just a theory though as this bike is not a rolling lab but my personal fun bike (and I love her just how sehe is!)

    But regarding your question, an idea came to my mind a couple of weeks ago... I was working on a customerís track 1098R. This is the only 5A ECU equipped bike with two injectors per cylinder. In theory this ECU doesnít have the ability to handle more than one but it does in this casee. They have independent output from the ECU, they are both side-by-side shower-type injectors, being the atomization pattern the only difference (I tested them to have the same flow): the main injector (works throughout the hole rev range) has 12 holes and a wider spray pattern and the hi-rev injector has 4 holes and a narrower spray pattern, which seems logical as itís aim is to give extra fuel at WOT.
    According to Ducati documentation ďthe secondary injector starts to flow fuel when the main one reaches its limit capacityĒ. I wondered if this was true and so I downloaded and edited the bikeís map: It is true as thereís just ONE fuel map in it, so thereís something in the ECU software that tells the ECU the treshold value from which the secondary injector is fired... The problem is that this is very difficult to take to our 851ís as the ECU in 1098R also controls the CAN line, etc. Difficult to make a practical arrangement on an 851 and try to make it work... I donít have the time, nor do I find the need...

    And finally it was the fuel pump which was faulty on this bike, so I got another happy customer but an end to my research...

  4. #104
    Join Date
    Jan 2015
    Location
    Chicago
    Posts
    342

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    I just had my (green) injectors bored by RC Engineering to flow more.
    '01 996R, '94 888 SPO Ltd, '88 851 Adamo racebike, '91 ZX-7R K1 homologation, '89 NSR250 MC18r5k, '01 Derbi GPR50/75, '71 CB450/500 cafť.

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