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Messages - ChetsJug

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Projects / Re: Does a jet drive need all that hp??
« on: October 29, 2017, 05:08:51 PM »
... The torque curve on a jet pump is completely and 100% linear. This basically means the faster the engine spins, the more torque is needed for acceleration. This means that smaller displacement engines will need to spin a bazillion RPM against a gear box to get the torque back....

GT
[p]
Thank you GT for being the only one that read my entire post without skipping to the soapbox biblethumping. I am well read in torque charts and I can see your points. I am a diesel mechanic and 35 year truck driver. I have always thirsted for knowledge of how to operate my beast. I'm not stupid nor am I here to be cute.

If others had read my post thru, I said a Pinto motor for an example and clearly stated I would never do that (you'd think the Ford Lover would have had a little sympathy; HA!  ;) ). Someone said I would see "How wrong I was" Well I never made a point to be wrong about, I stated first thing I was lost and asked a question. I also said I am considering (I hate having to repeat myself  :banghead:) a Wankel 3 rotor which has proven themselves in jet boats, or an electric motor set up. That being said...

I have found some more information and enlightened my self on the high performance impellers that need more torque. Thus you chart did tell me what I need for the speed I want to cruise at. I'm also a half-assed pilot and suddenly related Aviation to this area of thought. I remember that a boat is like an airplane in that you don't stomp on it to get up to speed and then throttle back and coast. You have to stay on it a cursing speed to maintain altitude, or in this case, trim & velocity.

I totally get needing to go up to higher RPM's and the power it takes. Thank you for your guidence  8)

For the rest of you, rest assured I will never ask a question around here again. I'll walk my dog through a Sharia Law neighborhood next time I want to listen to a bunch of insults.

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Projects / Does a jet drive need all that hp??
« on: October 27, 2017, 02:46:06 PM »
my baby brother started with the boat in the family. 18' & Berkeley behind a  454. He had a guy build the motor to 400+ HP and wanted more when he had the money.

I'm a little lost. I could see more HP as you put on bigger and bigger props. I cant see that much difference in impellers. Once you reach 3,000 rpm's the pump is going to pump the same CFM isn't it? Why couldn't a 4 cyl Pinto motor do the same thing and save gobbs of gas?

Im thinking a Rotary Wankel or electric motor... No, I'm not using a Pinto :p

Seriously, what HP can you drop down to before you loose top end. I'm not looking to go 70. Skiing speed would be fine maybe in the 40-45 range.

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