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  1. #1
    hill160881's Avatar
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    Potential of the weber MPE750 power plant?

    I am wondering what the potential of the weber 750 twin is? I have herd of 230 hp but is that all?

    I have a theory that if the compression were lowered to 8:1 and the rods were upgraded to the H beam rods that the engine could handle 30+ psi of boost. I also believe that the engine could produce 300 hp if the hard limit were moved to 8200 with the extra boost.

    The he point is I have seen 1.6 letter engines produce 600+ hp reliably. Why not close to 300 for one half that size?

    What are the limiting factors? The head and air flow? Heat? Oil bearing failure?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    A watercraft engine needs to be able to produce maximum power sustained for many minutes at a time. Road engines rarely need to produce maximum power for more than a few seconds at a time.

    A watercraft engine needs to be reliable. You cannot walk home if it breaks down.

    You are sitting on top of the engine. It had better hold together.

  3. #3
    Kosh's Avatar
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    I'm pretty sure the limiting factor is money.
    it would be nice to know how much they get of the 800cc versions.

  4. #4
    hill160881's Avatar
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    When taking something to its maximum potential longevity is not what we are looking for. Has there been an instance where the engine in a pwc came apart and injured the rider?

    I think the upper end of a reliable engine would be about 230 hp and the best anyone would get is about 300hp. I may try on the second msx 150 I have. I think all I would need to upgrade would be the drive shaft. At worst I would need to fit a different bigger jet pump.

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    Here are some comments I've gleaned from Desperado's past threads I regarding the Weber potential. He's the ECU guru and really seems to know this stuff about the Webers.

    No matter how you slice or dice it..... please smile and have a beer whenever someone tells you a weber engine can produce 200+bhp -- this is just not possible.... unless you run 24psi+ boost with 116+ Octane.... then again, engine longevity would be limited. Keep in mind that 175bhp for a 3/4 liter engine means we are extracting 233bhp per liter. If you were to extrapolate this kind of power output to a 3.5 liter automotive engine, this kind of efficiency would yield 815bhp . No doubt the Weber MPE750 engine is a world class powerplant.
    ... agree the 150 engine is on the edge. (edge of HP)

    This has nothing to do with the engine itself. It mostly has to do with the fact the engine is overpropped from the factory and is required to generate too much hp at too low rpm. EGT goes up and pistons/turbos are fried. The sled version is 140bhp at a rated 8,000rpm at 14.5psi turbo boost --- never seen a piston/turbo issue on these engines even though the EGT runs 1,600F degrees post turbo. After installing a Garrett GT25R on my Weber, the peak hp rpm increased to 8,400..... 280 hours on the engine so far and 100% reliable.... that's at 19.5psi boost.

    The turbine side of the turbo on the MSX is larger than the snowmobile counterpart... the compressor side is the same. This means the MSX has a greater rpm potential...... that being said, allowing the engine to turn higher rpm to reach peak hp is required to ensure greater engine longevity. The MPE750 is a world class engine... there is no reason other than overloading that can explain why so many of these engines have failed in the marine applications.... Let the engine spin to 7,600rpm, minimum, and enjoy. Trying to pump nearly 15psi boost at anything lower than 7,400 will kill this engine as a result of high EGT and detonation.
    That said... I'm very interested to see how far you can take your Webers!

    Cheers!

  6. #6
    hill160881's Avatar
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    There are production 1.6l inline 4 cylinders making 500+ Wheel hp, "production". That's well over 250 hp/l.

    Also I understand the difference between working hp and dyno hp. I am talking about dyno hp. A properly built weber should be able to produce 250hp at least. I also don't think he took into account newer technology's, different metals, coatings, twin charged setups better electronics and computer controls........ A lot has happened in the last few years.

    We will see. I am putting together a setup I think will make the power wanted. Lower compression to 8:1. Twin turbo, looking for 30 psi. Set it up with a hard redline of 8400 RPMs. Stand alone computer control, motec or similar. H beam rods. Ceramic coated combustion chamber and exhaust ports, ceramic coating on exhaust wheel on turbo, frictionless coating on all bearing surfaces. TI valve springs and keeps...... As soon as I get the one I am building now finished I will consider building it. The fab work for the turbos is what will be the biggest issue for me because I don't have the welding equipment. As well as the programming. I am not great at the programming side of it and better at the installing stuff. I am not bad at fabricating when I have the tools.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by hill160881 View Post
    ... Has there been an instance where the engine in a pwc came apart and injured the rider?
    ...
    I don't know whether such a thing has happened.

    There was this from a couple of years ago.


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  9. #9
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    Quote Originally Posted by 785 lugs View Post


  10. #10
    hill160881's Avatar
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    Well that solves that



    Now ow I know who to contact.

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