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Thread: 730 Hp

  1. #21
    victorfb
    Cheech. the right combo of torque and HP is very important. but you have to factor in all the other aspects. wieght and load is a big factor. cyclone got that 730HP by a good combo of parts. as a matter of fact, i have the cam he used last season, but i also have a smaller cam. i have the same 502 bottom end as his, but i am not running the AFR heads like he is. mine are the GM aluminium oval ports with 2.25int and 1.88ex. that big cam is not a match to my heads and im not rich enough to go out and buy AFRs. so i will run my smaller hyd. roller cam. the other is a solid roller. if your interested in trying to build a similiar mill, let me know. ill be willing to part with the cam.

  2. #22
    victorfb
    PC rat . i cant agree with you more. thanks for the post.

  3. #23
    PC Rat
    victorfb,
    Is that cam an off the shelf or custom ground?
    If you have the time, could you pm the specs to me, - more curious than anything.
    Brian

  4. #24
    victorfb
    its a custom grind mike (cyclone) had done. i dont have the card, but i did right down the specs. ill send em to ya

  5. #25
    LVjetboy
    Myth #2. "An engine produces the same hp no matter what rpm it turns" Wrong. Most engines have a power peak. Some more defined than others. Operate off that power peak and you don't get the same performance. Now think about the fact that I didn't say off-torque peak. Why? Because torque peak is not important for impeller matching or performance. Think about that a bit then tell me why torque is the same as power. Torque and power peak at different rpm's...where you gonna match your impeller? Oh wait, let's not look at charts, let's just do trial and error and stumble on the answer maybe. It's only money.
    Myth #3. "Hp is calculated and Q is measured on the dyno, therefore Q is more important since Hp is a derived term" Wrong. Q is not measured on the dyno. It is also derived. Oh pray tell...how could that be? I quess from Myth #3 since Q is also a derived term, it isn't important? Faulty reasoning.
    Myth #4. "An engine makes both Q and Hp, you need both therefore neither one is more important than the other for performance" Wrong. A typical Ghandi response. Just match your impeller to your Q peak rpm and see what you get for performance.
    Myth #5. "AT the SAME RPM, you will run the same speed with either an A impeller or a B impeller." Wrong. You will run a different speed with the same rpm on an A versus the same rpm on a B. Why? Because at 5000 rpm, the A will absorb more power and flow more water than a B at 5000 rpm. The A will go faster. Assuming your engine can turn it 5000 rpm. But that assumption is inherent in the Myth #5 statement.
    Can a small block putting 500 hp to an impeller match a big block putting 500 hp to an impeller? You bet. In fact the small block would win because it weighs less yet puts the same 500 hp to the impeller (neglecting efficiency losses) Why? Because it's all about power not torque. If you don't understand why this is then you won't understand why power is more important than torque.
    Can you build a 500 hp small block as cheap as a 500 hp big block? Who cares? That's not the question here...copy?
    PCrat. I never said I didn't want torque. Obviously, a running engine will have both...takes no brain surgeon to figure that out. Also takes no brain surgeon to quote the equation for Q and Hp.
    I said focusing on torque is misleading...you should focus on power to the impeller. I said knowing an engine's power output is more important than knowing an engine's torque output. You don't think this topic is important? Then talk to the racer who didn't understand why power was more important than torque and matched his impeller to his engine's torque peak. See what he thinks now about the difference between torque and power.
    I'm think I'm wasting my time.
    jer

  6. #26
    miketsouth
    Originally posted by LVjetboy
    I'm think I'm wasting my time.
    jer
    Some people just cannot give up torque
    for me you preachin to the choir
    http://mywebpages.comcast.net/mikejet/forgettorque.JPG
    mikeT

  7. #27
    cyclone
    Here's what i've noticed from looking at my dyno sheets and the on-water testing i've completed with my boat. keep in mind that these are dyno corrected numbers not measured.
    My engine made peak torque at 5,100 rpm (678 lbs/ft) after that the torque begins to fall off.
    671 lbs/ft at 5,400 rpm
    661.8 lbs/ft at 5,600 rpm
    654.5 lbs/ft at 5,800 rpm
    and so on...
    from 4,000 rpm to 6,000 rpm the motor never made less than 645 lbs/ft of torque on the dyno and has a pretty flat torque curve.
    On most occasions the motor only spins 5,600-5,800 rpms (at the river in 100 degree heat) with a few hundred rpm jump when the weather is near 80 degrees.
    The fastest i ever ran the boat was 94.4 mph
    Now according to the dyno sheet, peak HP (741 hp) was made at 6,400 rpm.
    at:
    5,000 rpm-646 hp
    5,500 rpm-698 hp
    6,000 rpm-730 hp
    6,200 rpm-734 hp
    6,400 rpm-741 hp
    6,500 rpm-735 hp
    what i've learned from my own boat is that as the torque falls off the boat stops gaining speed, even though the motor is still capable of generating more hp. why is this? i haven't a clue as i'm no rocket scientist.

  8. #28
    victorfb
    its because your worried more about torque and not HP mike. dont you listen to whats being said here? torque means nothing in a jetboat.

  9. #29
    cyclone
    i'm worried about anything that can make my boat run faster. I'm still confused on the whole subject, this was just an observation i made while staring at the dyno sheet.

  10. #30
    Infomaniac
    I'm so confused
    I am surprised this subject has not come up before.
    Actually LVjetboy I agree but am very curious about what unit you use for "Power" if it is not HP or Torque.

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