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Thread: speed

  1. #11
    ChetCapoli
    [QUOTE]Originally posted by Blown509Liberator:
    P.S. Pass the Donuts.
    MikeW
    Aw shucks,
    Any left for me to pass guys?? Looks like my three favorite coffee comrades are at it again! Just like ducks all in a row....quack, quack, quack. Hb your a little late though arent ya?? Almost three hours till you posted and no banners either...what's up with that? You werent going to post you say??? HEEHEE! Sure! I say skip the donuts and talk with GS since he was nice enough to post on the subject.
    Chet
    P.S. hey 509, a little donut diet just might get you the 100 your looking for ya know. http://free.***boat.net/ubb/smile.gif

  2. #12
    SPECTRABRENT
    The numbers sound like 454 with an A impeller, not a 468.
    Brent

  3. #13
    DickDanger
    I had great luck with GS Marine in Corona, so if you are close to that area, give Greg a call. He was a good guy to deal with when I was in there last year. -DD out

  4. #14
    HBjet
    Greg at GS is also another great choice for pump work. If you have access to shipping UPS, you can also send your pump to Don's Pump shop, or Hi Tech Performance. You can also send your pump to R&D Marine or even Walts Marine. Oh, I almost forgot, Big A Performance is another good choice. Tell you what, you could even send it to Aggressor and they will cut an impeller just right for your setup. Also, if your the do-it-yourself kind of guy, you can have anyone of these shops send you parts to do the pump rebuild yourself. If you also have spare time, maybe you can de-rig your whole boat and flip it over to remove the hook out yourself. Just an idea. I want you to have every option posted so you can decide what will suit you best. Good Luck
    HBjet
    BTW, Chet, did your post even help the guy?

  5. #15
    LVjetboy
    Hi Jet21,
    If you're still reading this post, I have a few comments. Yes, JPC estimates 328 hp for a Berkeley A at 4700...this based on pump manufacturer's curves. However, when you change the pump or impeller size, the data point (or drag reference point in stand alone version) no longer applies to speed versus hp calculations. Makes sense as the data point only works for the pump/impeller tested on your hull. But the JPC doesn't know this...minor glitch as I should clear the data point and mph edit boxes when the pump/impeller combo is changed to avoid confusion. If you haven't used JPC, then never mind.
    Back to your original question. Here's the steps: Plug 4700 on a Berkeley A into JPC (or manuf. charts) and get 328 hp. Then plug your data point (61.7@4700) into JPC for your hull drag reference. This accounts for hull shape and size, loading, etc. mentioned by Greg, "the dog" and others. Next, enter your goal of 65 mph to beat the props. JPC calculates 361 hp needed or a 33 hp increase. Next change the impeller to a B (ignore speed boxes) and increase rpms until you have a match for 361 hp. Note that the 33 hp increase will turn the B near 5100. This is a 400 rpm change in engine speed.
    Finally, use actual dyno test data or a simulator program to estimate hp improvement on your 468 from 4700 to 5100. Since you probably don't have dyno data, I ran Desktop Dyno to estimate the hp peak and slope:
    454 bored 60 over (468)
    9.5:1
    Wedge heads, stock ports/valves
    2.19 exh, 1.88 int
    750 cfm single plane
    headers w/mufflers
    Hi-po street cam
    Hyd. lifters
    Results: 395 hp at 4700, 400 at 5000 rpm.
    Since the engine is near it's peak (according to the simulator) very little change is seen at this level. That's a change in 5 hp for 300 rpm...not enough to reach your goal. Other combo's I ran showed about 10 hp...still not enough. So my guess is you might see 1 mph gain at the identical test conditions as you had before with a B cut, but will fall short of 65 mph...and smoking the prop dudes.
    Finally, I'd like to say that while impeller charts may not be best at estimating absolute power levels, they are good at estimating delta's...which means you get a good answer for what-if changes and delta's not dependent on absolute levels.
    Bottom line: My bet is at best you'd see 63 mph with B impeller.
    jer

  6. #16
    flat broke
    Originally posted by mach1 454:
    i have a 20 foot mach1 with a jet drive. my jet is different from all the other jets iv seen. its a berkely that mounts on to the transom unlike the others that iv seen that mount on to the buttom of the boat, and go thrue the transome. mine bolts straight on to the transom. what is the differnce in this set up. people who see my jet drive always tell me that they have never seen this kind of jet. also i bought the boat without a grate on it and till this day i still dont have one. the jet sticks out pretty far from the transom. any info on my jet set up would be apreciated. thanx
    mach1 454
    Mach 1,
    It sounds like you have an "JE" pump in your boat. The differences between this pump and a JA,JB,JC, or JG is that the JE uses a mold insert in the boat hull to fabricate a fiberglass housing around the intake of the pump which does not cut into the bottom of the hull(except the fiberglass insert) The benefits of this pump are easy access to the impeller because the bowl and hand hole are outside the transom, and more space in the boat because the pump is set back more than the others mentioned.
    The downside is that the intake area is smaller than the other pumps and the water has to make a sharper bend up to the impeller than the other pumps. They're not bad pumps, you just probably wont see many/any of them in drag boats. Obviously its working well for you (reference to your speeding ticket), so enjoy your extra interior space and ease of maintenence.
    Chris, www.liquidaddiction.net (http://www.liquidaddiction.net)

  7. #17
    RiverDave
    Originally posted by LVjetboy:
    Hi Jet21,
    If you're still reading this post, I have a few comments. Yes, JPC estimates 328 hp for a Berkeley A at 4700...this based on pump manufacturer's curves. However, when you change the pump or impeller size, the data point (or drag reference point in stand alone version) no longer applies to speed versus hp calculations. Makes sense as the data point only works for the pump/impeller tested on your hull. But the JPC doesn't know this...minor glitch as I should clear the data point and mph edit boxes when the pump/impeller combo is changed to avoid confusion. If you haven't used JPC, then never mind.
    Back to your original question. Here's the steps: Plug 4700 on a Berkeley A into JPC (or manuf. charts) and get 328 hp. Then plug your data point (61.7@4700) into JPC for your hull drag reference. This accounts for hull shape and size, loading, etc. mentioned by Greg, "the dog" and others. Next, enter your goal of 65 mph to beat the props. JPC calculates 361 hp needed or a 33 hp increase. Next change the impeller to a B (ignore speed boxes) and increase rpms until you have a match for 361 hp. Note that the 33 hp increase will turn the B near 5100. This is a 400 rpm change in engine speed.
    Finally, use actual dyno test data or a simulator program to estimate hp improvement on your 468 from 4700 to 5100. Since you probably don't have dyno data, I ran Desktop Dyno to estimate the hp peak and slope:
    454 bored 60 over (468)
    9.5:1
    Wedge heads, stock ports/valves
    2.19 exh, 1.88 int
    750 cfm single plane
    headers w/mufflers
    Hi-po street cam
    Hyd. lifters
    Results: 395 hp at 4700, 400 at 5000 rpm.
    Since the engine is near it's peak (according to the simulator) very little change is seen at this level. That's a change in 5 hp for 300 rpm...not enough to reach your goal. Other combo's I ran showed about 10 hp...still not enough. So my guess is you might see 1 mph gain at the identical test conditions as you had before with a B cut, but will fall short of 65 mph...and smoking the prop dudes.
    Finally, I'd like to say that while impeller charts may not be best at estimating absolute power levels, they are good at estimating delta's...which means you get a good answer for what-if changes and delta's not dependent on absolute levels.
    Bottom line: My bet is at best you'd see 63 mph with B impeller.
    jer
    LVJetboy, while I'm not sure of it's accuracy becuase I'm unfamiliar witht the program and jet boats in general, that's gotta be the most helpfull post I think I've ever seen on the boards.
    RD

  8. #18
    quig
    Hey RD now you are talking!!! I have not even got my jet close to the water yet and this being my first ever boat I can't tell you what I have learned from the likes of LV & the rest of the good folk in here .I may not post alot but I read everything good & bad and having said that I hope everyone continues to be so helpful to those of us who are less knowledgeable http://free.***boat.net/ubb/smile.gif
    quig.

  9. #19
    AGGRESSOR JETS
    Cut the Impeller you have to a "B" @ 8.750 on the large Dia. and follow the Berkeley chart for angle Degree, or Use 32.5 Degree on the Vane angle. And then see what you have - This should put you in your number. Impeller cut $25 - $50 bucks should get you done- Or you can take it to any good shop and have it done. Good Luck-Dave
    P.S I seen the post on bottom hook -check it out- you dont need a suction holding you wet down below.
    [This message has been edited by AGGRESSOR JETS (edited February 02, 2002).]

  10. #20
    AGGRESSOR JETS
    Greg if your on you going to make Supercross tonight. Dave

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