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  1. #1

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    Help a [turbo] RXP brother out with nozzle/prop rpm questions.

    Guys, I built a turbo '04 RXP that's gone 81 mph at 13 psi boost at 8450 rpm. I'm fairly certain that I can get 85 mph at 17 psi boost and 8900 rpm, but I didn't push the boost/rpm that high.

    Most RXP guys start rev'ing the pee out of these engines once you get over 80 mph. The characteristic of the centrifugal supercharger is that when you rev it higher, it makes more boost and power. The turbo isn't like that, though.

    I believe the turbo motor makes more power at 8000 than 9000 rpm since it will mimic the NA 155 hp motor's power range. However, all the R&D that's been done to date over 80 mph involves spinning the motor way up. So, no one really knows what pitch and nozzle it will take to get 85+ mph at 8000 rpm.

    So, my question is this: What prop pitch and nozzle size do you GPR guys use to get the high speeds at relatively low rpm? Say, the typical 85-90 mph GPR, what rpm is it turning, what pitch prop and nozzle size?

    Thanks!
    Mike


  2. #2
    Well us single pipers are only spinning 71-7200 or so. The triple pipe boats are up around 8000 though. I'm just guessing they are using a 14/20-14/24 with 85 or 87 mm nozzle. The pumps on the RXP and GPR are much different though I'm sure so I don't know how this all relates? The GPR pump is a 155mm, not sure about the RXP?
    Last edited by VOODOO; 02-23-2008 at 03:04 PM.

  3. #3
    rpms will also equal power with a turbo. i have built and tuned several high hp hondas and you will make more power at a higher rpm if the engine allows. I think these 4-tech motors are very similar. My last drag car had a 10.5k redline.

  4. #4

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    Quote Originally Posted by codymouse54321 View Post
    rpms will also equal power with a turbo. i have built and tuned several high hp hondas and you will make more power at a higher rpm if the engine allows. I think these 4-tech motors are very similar. My last drag car had a 10.5k redline.
    Right, but my turbo 388 redlines at 6300 and makes 950 hp at 5700 rpm. I have plenty of dyno results under my belt that show that the turbo hp and torque curves are very similar to the NA curves, just elevated. If that's the case, then the turbo 4-tec should make power at the same or close to the same rpm as the NA 155 hp 4-tec's, which is around 7300. The centrifugal supercharger always raises the peak hp rpm, sometimes 1000 rpm or more. Replace your Honda turbo with a vortech and you better go to 12k rpm.

    Mike

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