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  1. #1
    hill160881's Avatar
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    Poor programming and bad gas kills the msx 150!

    So I have been trying to piece together the basic map profile used by polaris when they programmed the msx150.

    So the main reason I am putting this up is I plan to go with a different ecu and want to outline why. I am Not using motec or aem. If you like these units then keep your walmart setup many love them but after using haltec and fast I won't be using AEM ever again. I have removed them and replaced with megasquirt because no one could get it to work and read the sensors correctly. Motec is ok but I am not familiar with it and have been told by many they avoid them.

    I digress...

    The reason to go standalone on a stock ski is simple. Polaris BOTCHED the program from start to finish.

    Problem #1. They have it mapped for 96 octane fuel. So where can I get this in America?
    Problem #2. They allow full boost at 4400 rpm. WTF? This may lead to a better hole shot but with 91 octane will detonate bad with full boost at such a low rpm. Should be 5400rpm at least.
    Problem #3 They mapped it wayyyyy to rich, To the point of loosing horse power.
    Problem #4 redline is set to low. 7400RPMs on a 8800rpm engine? Should be 8000-8200rpm in my opinion.
    Problem #5 The ecu does not read engine coolant temp. WTF? So if the engines coolant pump fails, like they do, you won't get any warning something is wrong. It only tells you if there is inadequate flow through the system provided by the jet pump. Basically it warns you of an over heat after it's to late.
    Problem #6 oil pressure switch is set at 11psi. WTF. By the time you get an low oil pressure light it's to late......
    Problem #7 system IFB. Not needed and removable. Randy at weber power used to sell a wiring harness that would delete the system IFB and go mechanical throttle if desired. It is not available any longer. A new SIFB is $200 and if it fails you are stranded. And they fail.

    Now there are other issues but these are the programming ones that lead to the engine failing so quickly in my opinion. Not including the mechanical ones.

    Any thoughts.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Where are you getting the stock ECU program info from?

    The 96 octane number, is that RON?

    My guess is that Weber did the ECU programming for Polaris since Polaris had little experience with the Weber turbo engine at that time. Weber may have rushed the process of fitting their land vehicle engine to watercraft and possibly not fully understood all the differences.

    Martin noted the stock watercraft overly rich fuel mixture when he developed his versions of the stock Bosch ECU reflash, building on his experience with the Weber snowmobile engines.

    RPM limits may have been influenced by worries about over revving when the jet pump unhooks at full throttle.

    Full boost at 4400RPM the engine won't spend much time at that RPM if it spins the jet pump up rapidly to much higher RPM.

    What does the system actually do when it senses low oil pressure?

    If Weber/Polaris knew the water pump drive and SIFB module were going to be failure prone I imagine they would have revised the parts before releasing to manufacture. When the original ECU programming was happening I presume they were operating with assumptions regarding reliability of the parts and the overall package.

    There may have been time pressures and limited resources to fully vet all the decisions that went into the ECU programming.

  3. #3
    hill160881's Avatar
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    Quote Originally Posted by K447 View Post
    Where are you getting the stock ECU program info from?

    The 96 octane number, is that RON?

    My guess is that Weber did the ECU programming for Polaris since Polaris had little experience with the Weber turbo engine at that time. Weber may have rushed the process of fitting their land vehicle engine to watercraft and possibly not fully understood all the differences.

    Martin noted the stock watercraft overly rich fuel mixture when he developed his versions of the stock Bosch ECU reflash, building on his experience with the Weber snowmobile engines.

    RPM limits may have been influenced by worries about over revving when the jet pump unhooks at full throttle.

    Full boost at 4400RPM the engine won't spend much time at that RPM if it spins the jet pump up rapidly to much higher RPM.

    What does the system actually do when it senses low oil pressure?

    If Weber/Polaris knew the water pump drive and SIFB module were going to be failure prone I imagine they would have revised the parts before releasing to manufacture. When the original ECU programming was happening I presume they were operating with assumptions regarding reliability of the parts and the overall package.

    There may have been time pressures and limited resources to fully vet all the decisions that went into the ECU programming.
    I can't tell you where I get all my info but they come from the horses mouth on the octane numbers. I say mapped for 96 octane to describe how aggressive they were with trimming advance. You may be correct with the RON octane vs MON octane though. They are not calculated the same. But close.

    Martin has not been forthcoming with much info. I like the fact he offers this reflash but given the limited number of people willing to attempt standalone engine management it seems silly to hide this info. Also the equipment to reprogram a stock Bosch ecu is stupidly expensive. No one will take business from him.

    You are correct that they kept the red line where they did to avoid floating valves when it looses traction at wot. But a simple valve spring shim will prevent this.

    To much boost on an over aggressively programmed engine with poor fuel will only take one good detonation to do serious damage. It does not matter how long or short a time it spends at a given rpm. To much boost at low RPMs with to much timing advance is how you shatter pistons and suck valves.

    When you get a low oil pressure light it has dropped below 11psi. This means the engine has already done serious damage and that flashing light is just telling you you need a new engine. It needs to alert you at 20+ psi. It should never run lower than 30. Currently the computer does nothing in the event of low oil pressure aside from a flashing light.

    I have no doubt there were time constraints on the developers. But the fact remains this engine is way out of its class and was over programmed to keep up with the engines twice it's size. It is a top end engine for water craft not a hole shot engine and they tried to get both.

    There was a 4 cylinder developed by weber based on this engine and was never put into anything. I believe this was the next generation but was shelved by weber when polaris quit making pwc. Can you emagine a 1500cc 4 cylinder version of this engine? Nothing even today would keep up with it.
    Last edited by hill160881; 09-03-2014 at 05:25 PM.

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