Impeller pitch fundamentals : What are the ABC's ?

[door54]

After reading a great thread (What's wrong with my RTX????) and the Motherload of info that was presented in the interaction, I'm gung ho to modify my ride. Air intake and exhaust improvements along with an intake grate would sure be a direction I'd like to go. Air and exhaust would be the start , but there seem to be some fine lines when it comes to impellers and the potential variables of their performance. From what I picked up in the thread, weaving an intake grate into the equation requires some thought too. Can you guys put some light on this?
I'm also entertaining the notion of the Riva sponsons to top it off.
I'm very happy with how my RTX runs and I think if these changes were introduced it would be all for the better. without going the route of a Stage 1 or 2 kit.
I tend to push the envelope, and I dont think I'd want to go much further. I think putting my butt on a RXT-X 260 would just be bad medicine.

 

[red2blue]

What exactly do you want to know?

 

[KK40384]

I'm assuming you're referring to my old thread. If you plan on just a few bolt ons a 14/17 will serve you well.

 

[door54]

I'm interested in learning about prop pitch variations.

For example KK recommends a 14/17. Another sharp on this forum who is also running a RXT, loves his 13/18. What are you running on your RXT red2blue?

What are the performance characteristics of the 14/17 and its 3 degree spread vs. the 13/18 with its 5 degree spread?

 

[red2blue]

I'm interested in learning about prop pitch variations.

For example KK recommends a 14/17. Another sharp on this forum who is also running a RXT, loves his 13/18. What are you running on your RXT red2blue?

What are the performance characteristics of the 14/17 and its 3 degree spread vs. the 13/18 with its 5 degree spread?

I'm running a 14/19+2 on my modded '05 RXT ...flushed Riva grate, 2*wedge, skegs, rear air, S3SC, free-flo exhaust and assorted minor freebies. I'm seeing 72.7 @8050 rpm.

The first number 14 is the leading edge...the 19 is the trailing edge...the +2 is the added pitch I've tweeked the trailing edge in order to bring my rpm down while at the same time adding top end speed.

The 13 leading edge won't grab as much water as the 14...but the 18 trailing edge will move it out faster than the 17. This last was in regards to the 13/18 vs 14/17 comparison. The 14/17 grabbing more water should have a better hole shot..while the 13/18 should have a better top end if the r's are high enough.

Your entire propulsion system is an equation. Get a part out of balance with the rest and the whole suffers for it. The by far best bang for the buck first part for a modded ski would be a DIY 4" front air intake. Once your ski is breathing easier...you will then be able to up the prop...either tweeking the oem(my suggestion)...or going with a taller than oem. Those two mods by themselves will give you some relativly inexpensive speed when compared to a stock ski.

 

[door54]

Now we're talkin'- Thanks for the no 'dummy down' response

First paragraph- I'm gonna break this down to digest it- Flushed intake grate...top loader?...Riva flushed or red2blue flushed?
Wedge...? Pump?
skegs -are for handling... after market skegs? how do you attach?
S3SC ?
Rear air? breathing/intake? increased breathing's a no brainer if thats what it is.....
Free Flow exhuast- Breathing...well, exhaust...= 72.7 @ what? 200 rpms below limiter? You have my attention.

Second Para If you have an aggressive front edge, dont you need a equivelent trailing edge? how can it be more or less?



To be continued

 

[KK40384]

I'm running a 14/19+2 on my modded '05 RXT ...flushed Riva grate, 2*wedge, skegs, rear air, S3SC, free-flo exhaust and assorted minor freebies. I'm seeing 72.7 @8050 rpm.

The first number 14 is the leading edge...the 19 is the trailing edge...the +2 is the added pitch I've tweeked the trailing edge in order to bring my rpm down while at the same time adding top end speed.

The 13 leading edge won't grab as much water as the 14...but the 18 trailing edge will move it out faster than the 17. This last was in regards to the 13/18 vs 14/17 comparison. The 14/17 grabbing more water should have a better hole shot..while the 13/18 should have a better top end if the r's are high enough.

Your entire propulsion system is an equation. Get a part out of balance with the rest and the whole suffers for it. The by far best bang for the buck first part for a modded ski would be a DIY 4" front air intake. Once your ski is breathing easier...you will then be able to up the prop...either tweeking the oem(my suggestion)...or going with a taller than oem. Those two mods by themselves will give you some relativly inexpensive speed when compared to a stock ski.

Not to hijack the thread but could you post a pic of your 4" intake? I'm in the process of building one myself and could use some ideas.

 

[door54]

Continued...

Hmmm... overly excited response on my part. Pesky beer.

OK, fit the pitch to your riding style, (or whats important to you), then, you can mod adjust to recapture some of the loss at the other end of the equation...Starting with AIR.

Which brings us to KK's request. Could you post a pic or two of that 4" ? And maybe a thought or two on how the fab process evolved?

Thanks

p.s. off subject- caught the "supercharge rebuild" thread that took place after I shut down last night. Sure got me thinking about my 60 hr and 70hr units. One thing was clear though... I'll steer clear of the path that 'ground chuck' took.

 

[red2blue]

Now we're talkin'- Thanks for the no 'dummy down' response

First paragraph- I'm gonna break this down to digest it- Flushed intake grate...top loader?yes...Riva flushed or red2blue flushed?I flushed it to the plate
Wedge...? Pump?2 degree wedge between the pump and nozzle...gets the nose of this couch outa the water, a bit more speed
skegs -are for handling... after market skegs?yes how do you attach?2 part epoxy and on good allignment trick
S3SC ?old Riva stage 3 wheel
Rear air? breathing/intake? increased breathing's a no brainer if thats what it is.....yes..a DIY rear air intake
Free Flow exhuast- Breathing...well, exhaust...= 72.7 @ what? 200 rpms below limiter? You have my attention.limiter on my ski is 8100...hard limiter at 8150.
Second Para If you have an aggressive front edge, dont you need a equivelent trailing edge? how can it be more or less?I'm not a prop guru....most of those gaurd their secrets well...when you find out the answer...do share...heh



To be continued

(10 character requirement)

 

[red2blue]

Continued...

Hmmm... overly excited response on my part. Pesky beer.

OK, fit the pitch to your riding style, (or whats important to you), then, you can mod adjust to recapture some of the loss at the other end of the equation...Starting with AIR.

Which brings us to KK's request. Could you post a pic or two of that 4" ? And maybe a thought or two on how the fab process evolved?

Thanks

p.s. off subject- caught the "supercharge rebuild" thread that took place after I shut down last night. Sure got me thinking about my 60 hr and 70hr units. One thing was clear though... I'll steer clear of the path that 'ground chuck' took.

This is my 5" to a 3" rear air intake...

 

[red2blue]

The 4" front is best seen here...

http://pwcmuscle.com/index.php?main_page=product_info&products_id=239

Fizzle is a good guy, known him on the boards for years. You can make your own or just buy the kit he's already put together. If you do make your own...use kana-flex wd620 (i believe) hose....smooth bore and strong. The use of the "filter"...isn't neccessary....a simple screen zip tied across the front is fine. The routing follows the oem intake so...it's tough in a few spots...not impossible.

 

[door54]

Whew, I obviously came to the right place. Ok..one step at a time

1. We were talkin about a 4'' inch front intake upgrade ...right? and the Fizzle kit looks like a consistent 4" run....AND your running a 5 to 3 rear??? Curious how you junction that.

 

[red2blue]

Whew, I obviously came to the right place. Ok..one step at a time

1. We were talkin about a 4'' inch front intake upgrade ...right? and the Fizzle kit looks like a consistent 4" run....AND your running a 5 to 3 rear??? Curious how you junction that.

Fizzle uses an adapter to connect the 4" hose to the 3" inlet on the sc. A lot of diy'ers buy a 4"x3" reducing 90* bend from...specter silicone intakes....or some such. You'd also have to have a 4" coupling to join the hose to the 90* bend.

On my intake...I have a stainless screen...from a veggie strainer...clamped around a length of 5" aluminum tubing....that is coupled to a 5"x4" reducing 90* which is then coupled to a 4"x3" reducing 45* bend.