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  1. #1
    bttek1's Avatar
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    B-kit with a Rotax Racing ECU without extra fuel STOP NOW!

    Hey guys.. Okay, now that my testing is ALMOST finished this is what I can tell you. I want to first thank Nills Castillo for his ongoing tech support and expertise!! My primary occupation regarding engine tuning is in the Corvette/LS1, LS6, LS2 and LS7 based tuning. I work for Kelley Performance in Hallandale Beach and use a Dynojet 248c chassis dyno with wideband 02 and perform ecu tuning on these platforms. Now that this is out of the way I can tell you what I have found:


    If you are running a "B" kit with a Rotax Racing ECU without any additional fuel STOP NOW!!!

    I have been running 42 lb fuel injectors using Nills Castillo's fuel controller and maxing out these injectors running 13 lbs of boost has an A/F ratio of over 15:4 A/F!!! The problem is that with the newest Rotax re-flashed ecu has little to no knock control so even though the boat seems happy and continues to accelerate there is a VERY high probablilty of detonation occurring. I have NOT tested the stock injectors but at 38 lbs/hr they can only be running leaner than the test 42 lb/hr that I was using.

    I have spent the last 3 weeks changing injectors and fine tuning the fuel map and I am almost there. I had to go with bosch 50 lb/hr injectors and will soon test some Siemens 55 lb/hr to get the A/F exactly where I want it.

    Currently I am spinning a loaned (Thanks Nills) Solas 15-20 impeller at 8500 RPM's with an A/F ratio @ 12.4:1 with another loaned "B" kit S/C (Thanks Frank Boyle) @12 psi boost. When I replace the stock waterbox I gain 1 psi of boost and improved acceleration but it is LOUD!! My A/F ratio increases at this point and I get back into the 13:1 A/F range so this is the reason for the 55 lb/hr injectors.

    I have already went as high as 60 lb/hr but these injectors are very difficult to tune properly at low RPM's as the fuel is not atomizing as well compared to the smaller injectors and I do not have the ability to adjust the IFR (Injector Flow Rate) in the Rotax ECU. This is where a fully programmable ECU would come in handy. The new EMS system should work very well in this type of application where one needs complete control to manipulate these settings.

    On a side note I must say that I am VERY impressed with the Rotax Racing intercooler. I have measured discharge temps from the S/C @ 12-13 psi as hight as 127 degrees C (260 F) and on the other side of the I/C at 34 degrees C (93.2 F) and this is in 76 degree water!! This is a decrease of over 150 degrees F!! VERY impressive!!

    As soon as my testing has completed with the larger injectors I will post the results.



    Thanks!!

    Brian
    BT Tech


  2. #2
    EZ Dock of Long Island Shibby1485's Avatar
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    let's say for arguments sake someone did what u said NOT to do.... what damage could have occured, and what should one do to verify any internal damage? compression test each cylinder?

    not gonna lie.... i'm a LITTLE nervous... and i rather not post all the details, lol

    thanks for all your research and facts!

  3. #3
    Jarrett's Avatar
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    Thanks for that info.

    Quote Originally Posted by bttek1
    I have NOT tested the stock injectors but at 38 lbs/hr they can only be running leaner than the test 42 lb/hr that I was using.
    So the stock injectors are 38 lbs/hr? Hypothetically, would there be concern in running the stock 38 lbs/hr injectors @ 9 psi boost with the reflashed Rotax Racing ECU? How about stock injectors at 11 psi with the reflashed RR ECU? Thanks.

  4. #4
    bttek1's Avatar
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    It would really depend on how many WOT runs one did at such a lean fuel mixture. I can tell you that these engines are built very well and the fact that the RXP has forged internal components really helps things stay together.

    You can do a compression test on each cylinder to verify that all 3 numbers are close to each other. My best guess is that you are probably okay but I would NOT go WOT anymore without adding additional fuel.

    I have heard that many people are melting exhaust components due to extreme heat. This is usually caused by an abnormaly lean fuel mixture causing the EGT temps to go sky high. I have a waterbox from a client where the aluminum parts inside are melted because of this!!


    Thanks!!

    Brian
    BT Tech



    Quote Originally Posted by Shibby1485
    let's say for arguments sake someone did what u said NOT to do.... what damage could have occured, and what should one do to verify any internal damage? compression test each cylinder?

    not gonna lie.... i'm a LITTLE nervous... and i rather not post all the details, lol

    thanks for all your research and facts!

  5. #5
    bttek1's Avatar
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    I have not personally tested the A/F ratio running 11 psi with the stock injectors but my best guess is that it would be lean.

    With a Vortec S/C impeller running 42 lbs/hr and using the fuel controller I had no problems setting the fuel map at 12.4:1 at WOT. With stock injectors, I had to modifly the fuel map considerably to run at that A/F ratio.

    Thanks!!

    Brian
    BT Tech


    Quote Originally Posted by Jarrett
    Thanks for that info.

    Quote Originally Posted by bttek1
    I have NOT tested the stock injectors but at 38 lbs/hr they can only be running leaner than the test 42 lb/hr that I was using.
    So the stock injectors are 38 lbs/hr? Hypothetically, would there be concern in running the stock 38 lbs/hr injectors @ 9 psi boost with the reflashed Rotax Racing ECU? How about stock injectors at 11 psi with the reflashed RR ECU? Thanks.

  6. #6
    xenonx's Avatar
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    Overheating with reflash ECU

    bttek1 wrote:
    With a Vortec S/C impeller running 42 lbs/hr and using the fuel controller I had no problems setting the fuel map at 12.4:1 at WOT. With stock injectors, I had to modifly the fuel map considerably to run at that A/F ratio.
    I am coming in a little late here...are you saying that with reflash or Race ECU and current Vortec S/C (riva stgII) that one running stock injectors would run lean?

    I currently have a Riva Stage II setup on my RXT and was considering buying the RR ECU. I have also been waiting on the sidelines for people like yourself to do the testing to find out what is safe as far as bolt on mods are concerned.

    I am not crazy about dropping $1150 on the Race ECU and then dropping $800 more on a fuel controller. The injector cost is not bad though.

    Can you clarify?
    Thanks for any info.

    xenonx

  7. #7
    bttek1's Avatar
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    Re: Overheating with reflash ECU

    With just running a vortec S/C impeller and air intake running stock injectors with the racing ecu would probably be fine.

    The issue that I was addressing is with the larger S/C with 13psi of boost. Don't forget its not just the additional boost but the larger volume of air that is creating the lean condition.

    Thanks!!

    Brian
    BT Tech


    Quote Originally Posted by xenonx
    bttek1 wrote:
    With a Vortec S/C impeller running 42 lbs/hr and using the fuel controller I had no problems setting the fuel map at 12.4:1 at WOT. With stock injectors, I had to modifly the fuel map considerably to run at that A/F ratio.
    I am coming in a little late here...are you saying that with reflash or Race ECU and current Vortec S/C (riva stgII) that one running stock injectors would run lean?

    I currently have a Riva Stage II setup on my RXT and was considering buying the RR ECU. I have also been waiting on the sidelines for people like yourself to do the testing to find out what is safe as far as bolt on mods are concerned.

    I am not crazy about dropping $1150 on the Race ECU and then dropping $800 more on a fuel controller. The injector cost is not bad though.

    Can you clarify?
    Thanks for any info.

    xenonx

  8. #8

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    Brian, any testing with the stock oem 38 lbs/hr injectors with the stock class (4502) R/R ECU?

  9. #9
    Moderator two2curupt's Avatar
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    Wow excellent R&D work Brian!!! I think you might have saved a few ppl's summer fun with those results...As you said about the bigger injectors...Are they going to pose a problem @ idle?? I would imagine fuel economy is out of the question as well??
    And sorry for the questions....Did you run the metal washers? And if so any issues with them?
    Once again Brian...Probably one of the more informative posts we have seen on these supercharger upgrades...Keep up the awsome work!!..

  10. #10
    JD 1's Avatar
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    Best thread Ive ever read on this forum, everyone should thank Brian for his findings.
    Shibbs you should be fine, low time and low rpm's are in your favor... Mr. Im running rich :P

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