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  1. #1

    mr-1 survive raising compression

    thoughts on if a mr-1 engine would survive a bump in compression from the stock 11.4:1 to 13:1 ?

    that and would cooling be an issue with the added compression? asking because i have a damaged fx140 block that im going to bore and either sleeve or have nickasil plated. and aftermarket piston choices are from 02-03 r1 sportbike. and compression ratio is 13:1 for shelf stock pistons from wiseco.

    ill be running a stand alone ecu so tuning won't be an issue.


  2. #2
    Lightning Struck's Avatar
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    Almost any engine will *survive* as long as timing and fuel quality requirements are met.. I think you'd probably be into race gas terretory

  3. #3
    im just wondering about the continuous duty thing. yeah sure sportbikes have sky high compression but they are throttled and don't stay at 10k rpm all the time. seems these engines are detuned so that they survive. just starting to wonder what the weak link on the mr-1 engine is. especially when aftermarket rods, pistons, and valvetrain is added. Hope the reduction box doesn't fail on me.
    i run 93 octane non ethanol right now so hoping to stay in that territory. just looking to gain tq and compression always helps.

  4. #4
    Lightning Struck's Avatar
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    The R1's cams and RPM also stave off detonation. I think you'd be pressing your luck on this one with 93 octane

  5. #5
    hopefully when i get my pistons there is enough meat in the dome to machine some of it off and lower it down in the 12.5:1 compression ratio. just sucks there is no support for this engine when it was a really good engine in the r1 sportbikes. which had huge aftermarket support. sure ive seen stock motors come apart but mostly always neglect, or misuse. really wanting to find out the weakness of the mr-1 before it goes boom. im staying n/a but don't see why with sleeves or at least a deck plate, stronger rods, and forged pistons this engine wouldn't be capable of handling boost. I mean you don't see the 98-03 r1 motors just coming apart. like i said im gonna try. just because i have one. if it fails then lesson learned and just get another or do the sho swap.

  6. #6
    cigarlust's Avatar
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    The MR-1 motor is a fantastic motor stock, I agree it has been detuned, but what other stock 4 stroke ski spins 10.1K rpms?

    I think you are playing with fire, I'd shelf your fx core and look for a 1.8L or go for a Doo conversion... I know riva played with the MR-1 motor and couldn't get a good combo that wouldn't go boom.

    Plus the strain put on the engine from the pump hooking and unhooking compared to "linear power delivery" on a bike... I think is where you'll have problems.

  7. #7
    i work on ski's every day. mostly seadoo's. i haven't been too impressed with the 4-tec. too much bs with mpem's, finiky wiring, and an ecu that can't do much. yes there are plenty of people out there getting power out of the 4-tec and doing it verry well. same as the 1.8l. but either way you have to do mods to the engine and engine managment. and yes ive spoken to bruce at riva about the mr-1. just wonder how far they went in their testing about the motor going boom. stock rods? stock pistons? ect.

    again almost same engine used in the yami sleds, the nitro and the apex. and tons of aftermarket support. im not looking for 300 hp out of this thing. just maybe 180. hopefully with tuning, bored throttle bodies, and raise in compression will yeild an aditional 20 hp over stock fxho 160hp.

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