Thread: Project ZXi

Yeah, y dat? If I'm to beat any of Slasher's collection of XP's I'm gonna need it. I can't find any other exhaust......

I decided to try muckin around with nozzle extentions. Did one 2day, internal sleeve. If it seems to limit flow, might need 2 try external sleeve.

Pump dia. is 84mm, nozzle was 90mm, but is now 83mm. Nozzle was extended by 55mm.



Testing will start tomorrow, or w-end at latest

Ok.........didn't work.......well. It worked TOO well as a steering boost but limited flow too much. I think an oversize (diameter) nozzle with a 10-20mm extention would be ideal for this craft.

Try a ring on the outside ?

You would have noticed bottom end power loss and gained top end speed with that mod.

If your looking for a lil more grunt machine out your reduction nozzle section of pump.

This was a compulsory thing on SXI race skis so they could punch there lazy butts off the line back in the day.

Look at a Superjet and compare to a SXI and you will see why the Sjet jumps down low.

It was a loss both bottom & top end but theory does dictate more top end, less bottom doesn't it???

I am chasing any improvement but the holeshot would b a dream come true (with the skis I'm up against ) .

What u r sayin makes sense Mooka. I had considered machining out the reduction nozzle. Do u have a bore size in mind....ie take off 1mm (being 0.5mm all round), or 2mm or 3mm? How thin can that nozzle b without becoming too weak? (It's alloy) & currently about 8mm thick. Also how much top end will I lose, d'ya reckon?

Should the steering nozzle then be bored too or is an external extention satisfactory?

I could do the trial & error thing but other than timely, once gone too far it's irreversable. Any help appreciated. Thanks Mooka.

To be honest I cant remember the amount bored out of my old SXI / SXI PRO and SXR.

If you have 8mm of meat try going 2mm then test ride.
You wont need to adjust the turn nozzle.
You will not so much notice a top speed loss but will definatley get some boost from the take off power increase.

On my current SXR I run bigger bore reduction and nozzle sizing to any other Limited ski set ups in Oz.
My Skat Trak trim system was sized to give more oomph for my weight in relation to other racers.

Is there a formula for working out the best reduction nozzle size vs steering nozzle size? I figure it's got to do with capable flow thru the intake & capable flow under pressure vs probable engine strain. I hope there's a simpler way than workin all that out.

I guess if u could work out the water flow rate at full throttle without the reduction nozzle on then u would have a basis to work from. But easier said than done eh...

I'm not about to do it but in a pool with marks on it to indicate depth & therefore volume units between each mark, with the ski nose down enuf to get the grate submerged & the pump above, shooting outside the pool, u could count the time it takes to pump that amount.

Sheesh, altering the thrust??? I think I'm in over my head. But...one can learn a lot this way...... or.............one could ask someone in the know.

Don't worry....I will. Was just tired & my over worked mind was workin overtime . As soon as I get a spare hr or so, reduction nozzle will b relieved of 2mm.

Nozzle bore & pwr pipe........could b an XP killer yet.....