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  1. #1
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    Injector selection for mega boost

    I've been trying to work on tuning my ski but have a few questions on injector selection when using RRFPR..
    I have a 2006 Riva stage III, ET140 and Race tech RRFPR..

    My question is- Is it better to go with bigger injectors(60's) and turn your base pressure down or go with what I have(50's) and turn the pressure way up? is there a pro/con for each?

    Will 50's even cut it?

    I'm planning on going to a buddies house on Sunday to hook it up to a LM1 but it's a 2 hour ride over to the west coast and want to make sure I take the correct injectors.

    Thanks..

    Alex


  2. #2
    Site Admin Green Hulk's Avatar
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    Alex, i have tried the 55's but didn't like the low end. If i lowered the base pressure to the point it wasn't rich on the bottom end it was too lean on the top end.

    If i raised the based pressure up to where it was perfect at WOT then i was rich on the bottom.

    I would like to try it again with some 60's though and see what happens. I think it was the brand of 55's that i was using that was throwing things off.

    Good luck and let us know what happens.

  3. #3
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    I think the 55's or the 60's should work. We went from 48's to 55's on a stage 3 boat and was leaner on the bottom and mid with the 55's with 11.9 @ wot. We could not get the a/f below 13 with the 48's and it was pig rich at idle. 10.2 In our findings it seemed that the bigger injectors with a lower base pressure will idle leaner than smaller ones at a higher base pressure and the larger injectors were better @wot. I have heard though that you dont want to go below a 40 lb base pressure so to large of injectors are not good either. I think a good set of 55's will work ok. No matter what we do without a fuel controller it wont be perfect.
    As Jerry mentioned it may have been the brand of injectors he tried. We have a set of 55's over here we can borrow to try but if we dial it in with these it will be very important you purchase the same brand as what we dial it in with.

  4. #4
    Site Admin Green Hulk's Avatar
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    speedski what brand are they?

  5. #5
    speedskixp's Avatar
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    Quote Originally Posted by Green Hulk View Post
    speedski what brand are they?
    Thats a good question. I will find out. I do know that the have a cone spray pattern but not sure of the brand. I will let you guys know.

  6. #6
    West Texas RXP skoepp's Avatar
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    Hey guys, sorry to hijack, but what would be considered too rich at idle?
    How rich can you be at idle before you start fouling plugs.

    thanks

  7. #7
    speedskixp's Avatar
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    Quote Originally Posted by skoepp View Post
    Hey guys, sorry to hijack, but what would be considered too rich at idle?
    How rich can you be at idle before you start fouling plugs.

    thanks
    Anything below 11 is really rich @ idle. I would say mid 10s may start fouling plugs but not sure. A rich idle is inevidable with just a single rrfpr and these big chargers.

  8. #8
    There is a RRFPR that is adj from 1-1 to 1-10 rise Mark at Racetech is working with one.When I'm done my open boat I may be going this route.He set his base pressure at 30psi and it rises to 70psi at full throttle.It also can be set were it starts the rise.

  9. #9

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    Problem you will run into is that injectors dont spray well at real low pressures.
    Most injectors are flow rated at 43.5#s of fuel pressure.Which is what your base SHOULD be.With a rising rate reg plumbed into a vacuum port it will lower itself off throttle also down to the mid 30s depending on the vacuum your engine makes,which will help.
    The idle quality MIGHT be off with pressures that low.

    50# injectors should allow around 300HP give or take.

    The largest drop in injector (high impedance) is a 60#er that should be good for 350-375 hp

  10. #10
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    Ok the down side of going with a big injector at a lower pressure is the injector not spraying correctly, what about a smaller injector at both max on both injector output and fuel pump pressure? I gonna try my 50's first if it gets within a few #'s of what the max pressure the pump will put out I'll jump up to 55's..Maybe i'll get a chance to do the same with 60's.. I'll let you guys know..

    Alex
    Quote Originally Posted by Otto J View Post
    Problem you will run into is that injectors dont spray well at real low pressures.
    Most injectors are flow rated at 43.5#s of fuel pressure.
    The idle quality MIGHT be off with pressures that low.

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