waterbox on ultra 150

[ultradean]

i am thinking of puting a tdr waterbox on my stock ultra....yes i would like a little more noise....but are they very, very loud? and i know it will not make it leap out of the water....but will i get some low end and a little top end?....i have heard every thing from 2 mph more to loss of mph because of loss of back pressure...i will be getting it cheap....i am also adding a prop and head later....thanks for the help

[Bill O'Neal]

I wouldn't expect performance gains, but you can count on more noise.

[ultradean]

thank you, BUT.....always a big but.....why won't an aftermarket waterbox give you gains? i know your answer i think....because of loss of back pressure.....well putting an aftermarket exhaust/pipe on a ski does wonders...this is because the engine breaths better....well why can't a waterbox help...heck you would think it would be mandatory with a pipe to increase the new flow....please explain what i am missing here o great one!

[Bryan Glynn]

The biggest reason you don't see gains, is that the stock waterboxes are already as well designed as it gets.

[tomsl750]

Yeah, not to open up an old wound, but ask Bill how much he put into the r/d of some of his waterboxs...

[ March 05, 2002, 09:53 PM: Message edited by: tomsl750 ]

[Bill O'Neal]

Ultradean,

A waterbox is an important part of the exhaust system of a two stroke jetski. It provides us with just the right amount of back pressure to tune the expansion chambers, and at the same time keeps the noise down. Noise is one of the tools used by politicians, park rangers, and busybodies to shut down our pwc riding on public waterways and lakes.

Your belief that an expansion chamber works better because "it breathes better" is not exactly true in the sense that it would work like an open set of headers on an automobile.

Usually, a high performance aftermarket exhaust system has more chamber volume and a fairly small stinger proportionately. If they wanted the pipe to breath better, they would put a larger diameter stinger on the pipes and run a straight tube to the transom. But they don't.

Our two strokes don't have cams and valves to open and shut the intake and exhaust passages. We have ports, open ports. The timing of the signal wave bouncing back into the clyinder from the exhaust port is crucial to the engine to retain the fresh charge of intakes gasses in the chamber and clyinder above the exhaust port.

Just installing a freer breathing exhaust system will hurt your performance, not help it. In conjunction with certain other modifications, it is sometimes necessary to increase the capacity of the muffler to handle the extra flow of gasses, but you have an otherwise stock Ultra, which probably wouldn't benefit from a waterbox swap, because it doesn't produce any "extra" flow.

After spending many many hours and dollars testing waterboxes on our 951-1050 project this past winter, we came to the conclusion that all of the different modifications that we made to the waterboxes that we tested, hurt our performance and cost us horsepower. We did learn some things, but we also learned that not always are their gains where you would expect them to be.

So when someone arbitrarily asks me if addding an aftermarket waterbox will add power, I have to say no, not normally, but you will make your ski louder, which is a very bad thing to do to the rest of us pwc'ers.

[ultradean]

so should i get the waterbox or not? lol....thanks....no waterbox for me then