More rpm more power?

L

last

I just read through the post of 212hp on that x2 650 and found it quite amusing.

I came up with a few questions though.

What is the average rpm of say a 701 or 650 superjet wot? I'm thinking like 6 or 7 thousand rpm? With that in mind, my bike (cbr1000rr) turns like 12,000 and the r6 is turning like 15. It would make sense to spin the jet ski motor faster and get some more hp out of it? although that may only help at for top speed and would probably require a smaller pump or lower pitched prop?

I'm just asking if anyone has experience with smaller sized motors spinning faster and what kind of performance increases or decreases they've had?
 
K

kid4now

X-H
Location
Miami Fl
Im sure someone will jump in with more technical info but I think it has to do with jet pumps are only efficient up to a certain rpm.
 
bit

bit

Rider Mod Needed
Location
Catfish, NC
Take you bike out and put it in 5th gear, then start from a stop until you hit the rev limiter. That should answer a big part of your question. Skis don't have transmissions.
 
L

last

If that were the case why do you think they don't do something like the snowmobile Continuously Variable Transmission set up? i would think especially in the larger sit downs there would be room for some type of transmission like this although belts don't work well in water.

About starting out in the highest gear.. did you see the Top Gear where they tested the z06 corvette where they did start out in the highest gear till top speed? YouTube - Broadcast Yourself.
 
L

last

i would compare a ride on a superjet more like going from idle to 50 mph on the bike.. in first gear.... but then theres a lot more rpm towards the top...
 
Zeon

Zeon

WNY Crew
Location
Buffalo, NY/ Crystal beach, Ontario
putting a bike in 5th gear an taking off is not even relivent to the question.

right now a normal ski revs to what 6500? idk... but if they added another 4k of rpms to the end it wouldent effect how it runs innitially. so it would NOT be like taking off iin 5th gear.


i do wonder why the rev limiter isent higher
 
douglee25

douglee25

m3booooy
Location
South Jersey
Reving higher isn't going to dictate that you will make more power. Depending on engine combination and how it was setup, horsepower and torque will fall off at a certain point. With that said, your power may actually go down as the revs increase. Engines have a point of diminishing return.

Doug
 
W

waxhead

wannabe backflipper
Location
gold coast
hp is a equation worked out by using rpm and torque
as the engine goes past its point of max torque it reduces
rpm rises but as torque goes down it overtakes the rate of rpm increase and hp drops

to get a high rpm high hp engine you have port it accordinly this will mean you lose low end
 
bit

bit

Rider Mod Needed
Location
Catfish, NC
xeon said:
putting a bike in 5th gear an taking off is not even relivent to the question.

right now a normal ski revs to what 6500? idk... but if they added another 4k of rpms to the end it wouldent effect how it runs innitially. so it would NOT be like taking off iin 5th gear.


i do wonder why the rev limiter isent higher
Click to expand...
What you fail to consider/realize are the engine dynamics that must happen to allow the engine to rev higher. It is way to much info to get in to here, but long story short. Most engines have a relatively small RPM range where the intake and exhaust ports can allow for effective cylinder filling. 2 strokes are great engines because they can be made to have a very broad power band, but the same dynamics apply.

waxhead said:
to get a high rpm high hp engine you have port it accordinly this will mean you lose low end
Click to expand...
Exactly
 
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