- Location
- Great Pacific Northwest
85mm.
Freestyle engine questions. Opinions welcome
- Thread starter East623
- Start date
85mm.
Blue
Judging your cheapness
- Location
- St Cloud Florida
85mm is typical for 144 and 148
89mm is common for 155.
Sent from my SAMSUNG-SM-N920A using Tapatalk
89mm is common for 155.
Sent from my SAMSUNG-SM-N920A using Tapatalk
- Location
- Social Circle, GA
You guys that said 85mm, did it have a taper angle at all or 85mm straight bore?
- Location
- Great Pacific Northwest
I was talking to a builder here yesterday about that exact thing...He said, taper bore to 85, since stock nozzles have taper on them from stock.
- Location
- Social Circle, GA
He was saying retain the same taper angle as stock to 85mm? I can do that. I work at a machine shop. Shouldn't be too hard haha
cookn
Kamikaze
- Location
- where you live
Yea I just bore mine out on the manual lathe. I have never noticed a performance difference between the taper bore and straight bore
- Location
- outer banks
depends on engine size but around 86mm should be ok
- Location
- South Florida
I dont think the taper matters at all. It's all about the radius at the smallest point.
- Location
- Charlotte NC
Well if it's tapered, the smallest radius is the outside edge. If it's not tapered then the smallest radius is the outside edge all the way in till it opens up bigger. The taper allows you to make the over all nozzle volume larger. If I need to loosen up a pump more, I can add more taper, knock the vanes out of it, etc.
But what it really comes down to is what works best with your setup. Each motor, hull, pump combo are different. It takes time on the water, bending props, playing with nozzle sizes and pump cones. Pump tuning makes a huge difference, but it's also time consuming and the learning curve can hurt your wallet.
- Location
- South Florida
I completely agree with your last paragraph.
But look at the effects of doubling the length: very, very small compared to radius. And its not like you can really add that much volume with a small amount of taper.
If you cut the vanes out then the flow will become more turbulent than laminar and the whole equation goes out the window and flow drops.
But look at the effects of doubling the length: very, very small compared to radius. And its not like you can really add that much volume with a small amount of taper.
If you cut the vanes out then the flow will become more turbulent than laminar and the whole equation goes out the window and flow drops.
- Location
- Charlotte NC
We are talking about opening up a nozzle 2.5mm, that's very very small. Take no taper at 85mm and then toss in a 5 degree taper at 85mm. If you did the boring yourself on a lathe, you would see the difference in the amount of material removed. While it may not be much, opening up a nozzle 2.5mm doesn't sound like much either. The vanes in the nozzle really don't do as much as you think. While each builder and tuner is different, if you are already running a mag pump do you think those nozzle vans really help straighten the water out? But experience is the best tool. Check out what some of these pro boats, see what their nozzles look like.
Rc617
I blow clouds, premix clouds
- Location
- Stockton ca
I second what @tntsuperjet says about the 1021 TPE. He's an awesome engine/pipe builder and got my TPE 964 with oem 46 carbs flatwater flipping my surf layup BOB Gen2 (126lbs hull) so i could only imagine the 1021's Potential.
The bores have a taper (called a "draft") because of being a cast part, not because of any fluid dynamics black magic. It has a draft so the part releases from the mold. If the bores were machined from the factory then they'd be straight since this would be the most economical way to machine. Otherwise they'd have to be done via CNC or lathe to get a taper.
You'd have to run a proper CFD model to calculate the delta between a straight bore versus a tapered bore. The bore diameters, lengths, draft angle, pressure, volume and overall rate would all play factors in the end result. The difference will likely be minimal due to the draft angle being small but won't be zero. Velocity is gained between the beginning of the draft of the bore to the end so you'll likely find that the same results can be found between a straight bore of one size versus a tapered bore of another. Both types can net the same results.
In short, a straight bore is easier to machine and a tapered is easier to cast. If cutting a stock nozzle, match the taper simply to retain the most amount of material. If cutting an aftermarket nozzle, match whichever it uses whether it be straight or tapered.
Edited to keep from confusing Tim. I'm talking about the bore, not the entire nozzle.
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tntsuperjet
Tntperformance-engineering.com
- Location
- Georgetown ca
37, I read you draw draft comment.
But you couldn't be more wrong.
Take 61x nozzle small taper long constant.
Then take the 62t nozzle short constant. Longer taper.
In a race boat 62t nozzle with the exact same size bore is good for .6-.8 tenths of a mph.
In a boat that goes 56 plus mph. That is the best bang for the buck out there.
So it's more then draft for tool release.
The taper angle changes many things with how the fluid dynamics reacts.
Why you think different tail comes make a dofference in pump load!
If you take a perfectly tuned motor and pump combo and slap a nozzle that's 2.5mm larger on it you will then be spinning the prop.
You guys are so used to big engines you don't see the true changes nozzle size makes. But for us old guys who had to make single carb 440cc piston port motors run hard. We had nozzles that where .020 different and would change nozzles pretty much every weekend depending on air and water temp to keep these boats on song.
Nozzle vanes greatly affect the boat in handling as well as different power feel.
Boat with vane nozzle feels as if it has less hit. Very slight but if your good rider tuner you notice it instantly.
Soon as people stop thinking they need low end to flip a boat off idle the sooner people will gain better results.
The problem is to many people see one guy do it and then they have to have that.
Let me just say this by the time you get the throttle lever to the grip your bottom and mid are way past over and your into top end.
How about the fact that Dasa sends out there free ride motors with more port timing then there old race motors, so in all theory that equals more revs and top end. But yet 95% of free ride guys all scream want more low end.
But yet there isn't one engine builder that has a low end ported motor on the market.
Bottom line. Bottom end Motors don't make enough power to flip a mouse all jacked up on meth.
But you couldn't be more wrong.
Take 61x nozzle small taper long constant.
Then take the 62t nozzle short constant. Longer taper.
In a race boat 62t nozzle with the exact same size bore is good for .6-.8 tenths of a mph.
In a boat that goes 56 plus mph. That is the best bang for the buck out there.
So it's more then draft for tool release.
The taper angle changes many things with how the fluid dynamics reacts.
Why you think different tail comes make a dofference in pump load!
If you take a perfectly tuned motor and pump combo and slap a nozzle that's 2.5mm larger on it you will then be spinning the prop.
You guys are so used to big engines you don't see the true changes nozzle size makes. But for us old guys who had to make single carb 440cc piston port motors run hard. We had nozzles that where .020 different and would change nozzles pretty much every weekend depending on air and water temp to keep these boats on song.
Nozzle vanes greatly affect the boat in handling as well as different power feel.
Boat with vane nozzle feels as if it has less hit. Very slight but if your good rider tuner you notice it instantly.
Soon as people stop thinking they need low end to flip a boat off idle the sooner people will gain better results.
The problem is to many people see one guy do it and then they have to have that.
Let me just say this by the time you get the throttle lever to the grip your bottom and mid are way past over and your into top end.
How about the fact that Dasa sends out there free ride motors with more port timing then there old race motors, so in all theory that equals more revs and top end. But yet 95% of free ride guys all scream want more low end.
But yet there isn't one engine builder that has a low end ported motor on the market.
Bottom line. Bottom end Motors don't make enough power to flip a mouse all jacked up on meth.
Edit: Where we're having a disconnect is in the overall reduction nozzle geometry. You're talking about swapping nozzles. I'm only talking about the final bore size and draft, not the overall angle of reduction. Comparing a 25.5° 61X nozzle to a 21.0° 62T nozzle is a major geometry change and absolutely will net different results. I'd never argue against that. Above I'm only talking about the last inch of bore. The original comment I was addressing was about boring a nozzle, not changing it entirely. Big difference, bud.
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tntsuperjet
Tntperformance-engineering.com
- Location
- Georgetown ca
37, ok now we on same page.
Sorry for that.
But if I bore 62t at a 6.5 deg taper I can get a 89.5 mm final size at end.
But it will act as if it's 92mm in a straight bore.
So if your tight in the pump it will help to taper bore the nozzle.
But if your not heavily propped it won't help the slightest bit. Good chance it will hurt
Sorry for that.
But if I bore 62t at a 6.5 deg taper I can get a 89.5 mm final size at end.
But it will act as if it's 92mm in a straight bore.
So if your tight in the pump it will help to taper bore the nozzle.
But if your not heavily propped it won't help the slightest bit. Good chance it will hurt
- Location
- South Florida
I guess that proves that the flow isn't laminar.
- Location
- Social Circle, GA
I need to do some serious reading on pump size, prop pitch, and reduction nozzles. I will agree with the gentleman who stated that bottom end isn't all you need. I don't think top end power is necessary either though. Bottom-mid range is where most of the action is going on for freestyle/free ride from what I've learned thus far. That's why I was glad to hear my ski has V-Force 3 reed blocks instead of Boyeson Rad Valve reed blocks. Coming from motocross V Force traditionally gives more mid range and a harder hit while Boyeson is more of a top end/smoothening out result. Granted jetskis and dirt bikes are much different but I feel like a lot of the technology is shared except the pump area which I would equate to gearing, tire selection and suspension mixed together.
The last thing I want to do is get a combination that is a nightmare because of my limited experience. For that reason I wish to take everything in steps.
I'm thinking pump first, whether it be a 144 or 148 mag but that's happening soon. After than MSD total loss. I'd like to play with that and see what kind of results I can get. Then after that carbs most likely. If I decide to retain the 38s then I'll do the blackjack mods. If I go bigger I'm still undecided on what size, I don't want to go too big to hurt my throttle response. I don't want to flip off idle, I'd rather do it more in the mid range which is where I try to ride anyways, a twitch of the finger away from being on the pipe.
The last thing I want to do is get a combination that is a nightmare because of my limited experience. For that reason I wish to take everything in steps.
I'm thinking pump first, whether it be a 144 or 148 mag but that's happening soon. After than MSD total loss. I'd like to play with that and see what kind of results I can get. Then after that carbs most likely. If I decide to retain the 38s then I'll do the blackjack mods. If I go bigger I'm still undecided on what size, I don't want to go too big to hurt my throttle response. I don't want to flip off idle, I'd rather do it more in the mid range which is where I try to ride anyways, a twitch of the finger away from being on the pipe.
- Location
- Washington DC
You correct with pump tuning being the key. However all the reading in the world won't help much. Theory is great but as I've learned every ski is different. Even when built exactly the same. With out testing multiple nozzles and props it's hard to know whether or not it's actually correct.
% 90 percent of the people on this board have skis that are "close enough. " They run pretty good with parts and tuning ideas they get off here and talking to other people. I used to be one of them.
Then I took my ski to Phillip Clemmons and he dialed it in and it was night and day. It went from pretty good to "I didn't think this motor had that much in it" . It wasn't a 1hr quick fix it took a few weekends messing with props nozzles, carb and pipe settings.
Also iv learned there isn't a such thing as "over carbing" on a jet ski. I'm running 48s on my 760 +4mil motor. Much more crisp and responsive than the 38s ever were. Again it goes back to tuning though
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2HIGH4U
Princess POWER
- Location
- BrisbaneAUS
Not trying to insult anyone on this site at all ,but I really can't see the difference in a freestyle situation between taper and straight boring ,some people talk about it being .6 to .8 mph quicker,yeah racing around and around and around bouys but hitting a wave in the surf or your own wake ,I really can't see the difference,being a freestyle oriented site? Again not trying to cause trouble