Thread: why "only" 69.22 MPH?
05-29-2005, 05:59 PM #1
- Join Date
- May 2005
why "only" 69.22 MPH?
These numbers are for stock skis as taken from "Personal Watercraft Illustrated"
Anyways, and I am not complaining...it is plenty fast enough for me...but, I was wondering why, if the RXP has 215 HP, why does it "only" go 69.22 MPH? You would think that kind of power would be capable of a heck of a lot more speed. The next fastest is the GP1300R and it is "only" just shy of 4 MPH slower than the RXP but using only 170 HP.
I am not looking for mod suggestions, so please don't tell me to Mod this and mod that. I was just wondering.
05-29-2005, 06:05 PM #2
An RXP stock power isn't 215 but more like 190/200.
And besides 69 is GOOD, better than most RXPs I have seen.
05-29-2005, 06:31 PM #3
- Join Date
- May 2005
Thanks, but that is not the point I was looking for.
215...190/200...whatever it is.
Why does it only go as fast as it does? Whether 69.22, or 80, or 58. My question is why does it "only" go that fast.
I guess the question should not only pertain to RXPs. But all PWCs. With the kind of horsepower they have, you would think they would be capable of higher speeds.
05-29-2005, 06:37 PM #4
Speed depends on thrust, drag and weight, thrust fights drag and weight.
Example, the Ultra 150 and the STXR, SAME motor, about the same weight but the Ultra is a good 4 mph faster but handles like shit because the hull is so much out of the water.
05-29-2005, 11:00 PM #5
These are they the best reasons...
Two strokes always put out more power than four strokes. That is why they add turbo, SC and IC to four strokes to give them more boost. Compared to the kawi ultra 150 1176cc motor at 145 hp (avg speed 64 mph)and the kawi 12f with a 1198cc motor with only 125 hp (avg speed at 54 mph).
The four stroke engines are more heavier and weight will slow you down also.
The ski pumps are one of the least inefficient pumps around. No matter how tight the blade and housing is you still will let water pass by the blades.
Plus the biggest thing, your ski is not spinning on wheels like cars so you have a lot more friction with water and hull contact. That is why you try to get most of your hull out of the water on plane.
So if you gain 1 or 2 mph with mods on a ski that is good. That can make a difference of pulling ahead of someone your racing. That is why you see people spending hundreds of $ just to make their ski go a couple mph faster.
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