Perfect Pass Star Gazer with Z Box vs Zero Off - Apples to Oranges comparison?

[Scott Russell]

1 hour ago, Horton said:

Whatever comes of this project I am for sure going to try to ski behind the 91 MC with ZO next time I go to Bell Acqua.

I look forward to hearing your feedback when you do. That project excites me. I almost bought a new 454 Pro Star in 1988 (it may have actually be a 89 model, but I'm not sure). I loved that hull. The teal and green colors on that boat were my favorites. 

[Fastguy888]

I ended up with a 1994 Tige SLM 2000 with the 454 MPI (Fuel Injected) 7.4L with a claimed 415hp and TRQ. With the latest PP with Z-Box it feels much more like a ZO boat than less powerful motors; however, you will never get the instant response like others have noted with ZO. 

[Mastercrafter]

1 hour ago, Horton said:

Whatever comes of this project I am for sure going to try to ski behind the 91 MC with ZO next time I go to Bell Acqua.

Is there another ZO 91 out there? Mine went to Florida and I kind of miss it. What engine does the Bell Aqua boat have? 

[Scott Russell]

3 minutes ago, Fastguy888 said:

I ended up with a 1994 Tige SLM 2000 with the 454 MPI (Fuel Injected) 7.4L with a claimed 415hp and TRQ. With the latest PP with Z-Box it feels much more like a ZO boat than less powerful motors; however, you will never get the instant response like others have noted with ZO. 

Well, it's at least encouraging that I wasn't completely off base thinking the difference in torque at the rpm the engine would be in while in the course was making a difference.

I'd love to hear from some people who have pre-direct injection engine boat with ZO and see if they experience the same response without direct injection engines as the newer engines that do have it. 

[Mastercrafter]

1 hour ago, Scott Russell said:

I look forward to hearing your feedback when you do. That project excites me. I almost bought a new 454 Pro Star in 1988 (it may have actually be a 99 model, but I'm not sure). I loved that hull. The teal and green colors on that boat were my favorites. 

I have a complete 1988 Prostar 454 HO powertrain if you know anyone looking 😎

[Horton]

@Mastercrafter I do not know the specs on that boat. It belongs to an old friend who had it repowered a few years ago. If I get to ski behind it I will get some photos and details. 

[Scott Russell]

3 minutes ago, Mastercrafter said:

I have a complete 1988 Prostar 454 HO powertrain if you know anyone looking 😎

Am safe in assuming this the boat that you put a 6.0 with ZO into? If so, how did they compare? I know you didn't (couldn't) have ZO on the 454, but as far as pulling power, how did the 6.0 compare to the big block?

[Mastercrafter]

16 minutes ago, Scott Russell said:

Am safe in assuming this the boat that you put a 6.0 with ZO into? If so, how did they compare? I know you didn't (couldn't) have ZO on the 454, but as far as pulling power, how did the 6.0 compare to the big block?

Actually never ran the 454. It needed rebuilt and I parted out the boat. The repower was a 1991 with a 5.7L Ilmor. 
 

The 5.7 in the 1991 felt a bit stronger than my 2015 Prostar with the same engine. There’s 800lbs difference in the boats. 
 

As @jpwhit said, I got a 3 blade jump prop for my 2015 and that really made the boat come alive and feel more like a 6.0 or 6.2, but I’m turning 4150 down the lake at 36. 

[Scott Russell]

When talking about the response time difference between a direct injected engine and a port injected engine, it got me thinking so I did some quick math. 

At 4K rpm, a GM LS engine would have an intake port air velocity of roughly 150 feet per second. In the average V8 port injected engine, the injector nozzle is roughly 6" from the intake valve. So the fuel has to travel 6" before it can be combusted. 

At 4K rpm the injector will fire 33 times per second. The math suggests 66 times per second, but keep in mind that in a 4 stroke engine, combustion only takes place every two revolutions of the crankshaft. 

At 150 feet per second air velocity, the fuel from the port injector takes 1/300 of a second (or .00333 if you prefer) to get from the injector to the combustion chamber. 

A direct port engine fires the fuel directly into the chamber. 

Doesn't sound like much difference, does it?
 

If it takes 16.95 seconds to get through the slalom course on a pass, a single injector fires 559 times during the pass. That equates to a 1.86 second total time delay vs direct injection over the course of a pass through the course. 

That sounds like a huge number when you are only talking about 16.95 seconds to complete the run, doesn't it? 

Well that would depend upon how much of the 16.95 seconds it's making fuel delivery corrections. It's making them all the way through the pass, then I can definitely see why response would be better with direct injection. I've never ridden in a boat with ZO, so I've never been able to hear what the engine is doing first hand, but I'd bet it is correcting quite a bit of the time. 

Before I did the math, I was questioning if Direct Injection was really making that much difference in response. After doing the math, assuming it corrects a LOT, I would think it makes a pretty noticeable difference to a short line skier over port injection. 

This is when it would really be great to hear from some port injected engine ZO boat owners, vs the newer DI engine ZO boat owners. No amount of data will override real world user experience. 

[Scott Russell]

8 minutes ago, Mastercrafter said:

Actually never ran the 454. It needed rebuilt and I parted out the boat. The repower was a 1991 with a 5.7L Ilmor. 
 

The 5.7 in the 1991 felt a bit stronger than my 2015 Prostar with the same engine. There’s 800lbs difference in the boats. 
 

As @jpwhit said, I got a 3 blade jump prop for my 2015 and that really made the boat come alive and feel more like a 6.0 or 6.2, but I’m turning 4150 down the lake at 36. 

Did you feel like that prop and the higher RPM helped to keep speed more stable without ZO intervention? or no noticeable difference?

[Kevin89MC]

I don't really have any substance to add as I'm just a mediocre course skier (getting into -32 on a good day) and a mediocre mechanic (try to keep all my vehicles and boat out of any shop for all maintenance and repairs if possible), but I just wanted to say I find this thread absolutely fascinating! Thanks to this forum (and my main ski partner) I'm skiing as good now at 53 as I ever have, and I try tackle more projects as the years go by (learning how to weld, re-upholstering my boat seats, about to dive into fiberglass and gelcoat repair) all because of my quest to learn more and get better. I love the knowledge sharing! Wouldn't be where I'm at without the internet, the key is figuring out the good info from the bad! 🙂 Scott I really appreciate & respect your desire to make a better (or at least unique) boat, and I love reading about other's knowledge about tournament skiing, engines and ZO/PP. Thanks John for hosting such a great platform for discussions like this to take place, and good luck Scott with your project however it develops. Looking forward to seeing however it shapes up!

Kevin

[Scott Russell]

Thank you for the kind words Kevin. I love tinkering with mechanical things and enjoy a good challenge. As long as John lets me hang around, I'll share progress once things get started. As I've said before, this is just the planning stage. I still haven't 100% settled on a boat I want to do this with yet. but I think I have it narrowed down to either a 91-94 MC, or a 97-01 SN. I'm looking around at boats now, but the reality is, I won't be buying till after the first of the year. Hopefully there are some nice older boats to choose from then. I'm definitely not going to buy a rough boat that needs a lot of hull, interior or peripheral equipment work. The perfect scenario would be to find a garage queen with a blown engine, where the boat is mint, but it needs a power plant. It'll never happen, but a guy can dream. 

[jhughes]

No comparison between the 91-94 MC and the 97-01 SN. Use the SN. The SN drives, tracks, and keeps spray down like a modern-ish boat, the MC does not.

[Dano]

I know this idea won't get a lot of love.  If he's looking for different.  I'd love to see a repower  of mid 90's Tige, Brendella, Centurion, or other.... really any boat that skied well.  I know how one of those boats skied, I know the motor wasn't super powered,  the tracking wasn't great, the spray seems fine at least to -38, and I know the wakes are just fine.  A few years back MC seemingly just added some additional tracking fins to help their tracking, maybe doing the same could help some of these older boats?  I know thats overly simplified explanation of what MC did..... it's just an idea.

We all know how much love the SN196 has. It was a good boat new, it's a good boat repowered,  it's been done before multiple times. 

[Scott Russell]

49 minutes ago, Dano said:

I know this idea won't get a lot of love.  If he's looking for different.  I'd love to see a repower  of mid 90's Tige, Brendella, Centurion, or other.... really any boat that skied well.  I know how one of those boats skied, I know the motor wasn't super powered,  the tracking wasn't great, the spray seems fine at least to -38, and I know the wakes are just fine.  A few years back MC seemingly just added some additional tracking fins to help their tracking, maybe doing the same could help some of these older boats?  I know thats overly simplified explanation of what MC did..... it's just an idea.

We all know how much love the SN196 has. It was a good boat new, it's a good boat repowered,  it's been done before multiple times. 

The goal in the end would be to have a very nice, comfortable boat that is good enough that tournament skiers would want to ski/practice behind it. I just want to be sure I start with very nice, fairly pristine example. So far, a lot of the boats you mentioned that I find for sale are basically worn out. Regardless of the boat, I think in the end you'll find that I'm doing something that hasn't been done. It's a repower, but not the typical "go buy an engine with more power to replace the old one" kinda deal. 

[Drago]

3 hours ago, Mastercrafter said:

The 5.7 in the 1991 felt a bit stronger than my 2015 Prostar with the same engine. There’s 800lbs difference in the boats. 

And the prostar is pushing more water.

@DanoAmerican Skier, MB Boss (?)

[Dano]

@Drago ya both of those are intriguing too along with sanger, Supra, American skier . My point was some of the 90's boats were super cool but it was the 90's and they were built on the cheap and they really didn't differentiate much as far as power plants go.  Maybe with some current technology and some upgrades to props and tracking fins etc...those hulls could be really cool. 

 

[Mastercrafter]

4 hours ago, Scott Russell said:

Did you feel like that prop and the higher RPM helped to keep speed more stable without ZO intervention? or no noticeable difference?

The pull felt a little firmer and more responsive with the new prop. Put a smile on my face but likely won’t score any more buoys. The stock 5.7 setup was great but now it’s “obsolete” and all the boats at tournaments have 60-100 more HP than mine. This was a cheap fun alternative to a boat upgrade 🙃
 

 

[Scott Russell]

9 minutes ago, Mastercrafter said:

The pull felt a little firmer and more responsive with the new prop. Put a smile on my face but likely won’t score any more buoys. The stock 5.7 setup was great but now it’s “obsolete” and all the boats at tournaments have 60-100 more HP than mine. This was a cheap fun alternative to a boat upgrade 🙃
 

 

I'm trying to learn how much of the new tournament boat's performance is Zero Off and how much of it is the additional power. I see the word response used a lot to describe the performance of the new boats with Zero Off. Is it Zero Off, or the responsiveness of Direct Injection? I don't know, but I'd like to figure that out.

[Horton]

@Scott Russell All I can tell you is that a 900 hour 2008 Nautique 196 with a PCM Excalibur 5.7 330 hp  and ZO is a decent tournament training boat. I put 100 hours on one over the winter a few years ago.

196 is smaller & lighter boat compared to the current boats. I have skied one of these boats with a 6L and it was an freight train. My guess is I could adjust but I would not call the boat friendly

[Scott Russell]

2 minutes ago, Horton said:

@Scott Russell All I can tell you is that a 900 hour 2008 Nautique 196 with a PCM Excalibur 5.7 330 hp  and ZO is a decent tournament training boat. I put 100 hours on one over the winter a few years ago.

196 is smaller & lighter boat compared to the current boats. I have skied one of these boats with a 6L and it was an freight train. My guess is I could adjust but I would not call the boat friendly

So the 6L was too responsive with ZO in the lighter boat? Did it time ok? Or was it too quick through the course? 

That sounds like situation where you need access to those back end settings you mentioned earlier. Do you think that would have helped? Or was it just too much power for the weight of the boat?

[Horton]

In this case it is not about responsiveness. It is just about give. 

Yes ZO ALLWAYS gets a perfect time. I does not care about the skier. It gets its time and if you give it too much power it will abuse the skier - unless you detune something. 

[Dano]

I think I have a good understanding of perfect pass and how it works/responds. I am not at all familiar with ZO aside from the fact that i have to ski it at tournaments.  PP seams to assume that there will be some speed variation and takes inputs from a  GPS,  accelerometer, RPM, and individual ball timing, to respond to skier inputs.  In doing so it seems like it produces a pull that is more forgiving as it's response may not be as immediate.   first skier acts, PP responds, and may look to correct further if the timing segment was slow or fast essentially spreading out the response time. This system may be easier for a skier to work with than how ZO responds.  I'm not sure if PP is more intuitive as to where the skier is in the course and when it can throttle without punishing the skier or if that is just a function of it's ability to respond quickly.  

  Am I right in that ZO simply reacts very quickly to any speed variation. So if a skier slows the boat at all ZO will respond aggressively to not only get back to set speed but also to make up for the lost time ASAP, maybe at all costs regardless of where skier may be in the course?  I know from experience that once one falls out of rythm with ZO It's like being in the ring with Mike Tyson.  Does ZO give individual ball times like PP. or does it just show overall?

For the record I ski PP on an old boat.  When I ski tournaments i generally run the same ball count.  The difference is that with PP I can get out of shape and fight and pull and lean and get out the gates.  With ZO if it gets scrappy it gets real ugly.  I fully regret arguing with ZO every time it happens.

 

[jpwhit]

9 hours ago, Scott Russell said:

I'm trying to learn how much of the new tournament boat's performance is Zero Off and how much of it is the additional power. I see the word response used a lot to describe the performance of the new boats with Zero Off. Is it Zero Off, or the responsiveness of Direct Injection? I don't know, but I'd like to figure that out.

Most of the newer boats have hulls that create a lot more drag in order to have very little spray and nice wake characteristics even with a larger and heavier hull. I think that's where the additional power is needed. I think proof of that is what @Horton mentioned. Even in a 200 for example, which is a high drag hull, Zero Off will always get near perfect times at sea level. The 5.7 in a high drag hull will struggle for folks that ski at higher altitude lakes. More power is also needed for pulling jump. So, these newer boats do need significantly higher power engine options to cover all the disciplines and situations they encounter. 

I tend to think the difference in the feel of the pull of modern boats has little to do with engine power. I think it's almost all about how ZO relies heavily on accelerometer data to be able to respond very quickly to skier loading the line. 

If I were designing my own modern speed control system, the main thing I would try to change is to accommodate the feel of the pull for the skier, while still keeping the ease of use and consistency of staying within the time tolerances. But I do also recognize that this could be a very expensive and time consuming thing to accomplish. Because "feel of the pull" is a pretty subjective thing. And designing a control system to a very subjective parameter guarantees that you'll have to spend an order of magnitude more testing and tuning time and user input collection time developing the system. For a business, that can be a very hard thing to justify, because someone has to convince the accountants that the additional investment will result an even higher return on that investment. That's where having competing companies working in this space, and giving the end users the ability to pick between the two, would tend to lead to continuous and steady improvement.

[jpwhit]

In the post above, I meant to say "even a 5.7L 200 for example, which is a high drag hull, Zero Off will always get near perfect times at sea level. Even when pulling large strong skiers."

[Horton]

@jpwhit I have never seen a zero off though get slow times because of power issues. I'm sure it's happened in some crazy extreme example but a 5.7 200 will get good times up and down the lake.

[Drago]

37 minutes ago, Horton said:

@jpwhit I have never seen a zero off though get slow times because of power issues. I'm sure it's happened in some crazy extreme example but a 5.7 200 will get good times up and down the lake.

The 5.7 doesn't  cut it with a 36mph  shortline skier in most of Colorado (at lowest around 5,000') in a 200 or '14+ ProStar. An extreme example. It will "work" on a few of the longer/lower-elevation lakes.

[Horton]

@Drago at elevation the 5.7 feels like poop to the skier or it actually doesn't get a good time?

[Drago]

4 hours ago, Horton said:

@Drago at elevation the 5.7 feels like poop to the skier or it actually doesn't get a good time?

Slow times. Felt just fine @ 34

[03RLXi]

On 10/7/2023 at 4:45 AM, Drago said:

Not sure pp can play with dbw ...

Can buy PerfectPass in mechanical servo version or DBW version