Reply With QuoteI always wondered about hull and hardware differences vs. estimated power ratings. How much faster/quuicker is the new boat??
LVJetboy- have read your posts about this and was curious if you take into account hull design and hardware setup. Reason i ask is that in my old Rogers v-bottom (stock berk intake, berk jg pump, AMT AA impeller) my blown Chevy engine would turn the impeller anywhwere between 6,600 -6,800 rpm full loaded.
I purposely put the same engine and impeller into my 19-foot tunnel hull with an aggressor 5-degree intake, bowl and suction housing just to see what would happen to the amount of power absorbed by the impeller. The engine turns approximately 200 rpm less depending on weather conditions. Seems to me that the bottom design and hardware is loading the impeller much better. What do you think? It was an interesting if not at all scientific experiment.
I always wondered about hull and hardware differences vs. estimated power ratings. How much faster/quuicker is the new boat??
At the river its been up to 10 mph faster. At the track it ran 5 mph faster and .030 quicker than the old boat. my third time driving the boat was at the track and i had a heck of a time learning to holeshot it effectively without a launch controller. I've since learned to drive the boat much better so i'm going to assume the next time i take it to the track it will pick up several tenths out of the hole.
Whats the data look like compared to the Rogers? Is there really that much more inlet press.?
Ill buy the fact that your loading the new pump harder than the Roger's,but the Rogers had a pretty healthy supply of water too.Could Mike really be loading the new one so much harder that he lost 200 RPM? Im havin' a hard time buyin it.Could the RPM's have gone somewhere else?
Ive been to both sides...WAY too much water, and not enough, no RPM changes either way.. I'm thinking if you loaded the pump to the point where it was dropping 200 RPM it would overcharge the inlet.Actually im questioning the whole idea of loading the engine down 200 RPM due to a heavy water supply.
I could be wrong, and probably am.
CS
the data i gathered at the last race is pretty much useless as far as comparing it to the data on the Rogers. The sensors weren't calibrated correctly. it was useful looking at it from point of view of spotting overall trends between the runs of that particular race, but not to compare to previous races with the old boat. For example, the intake pressure at half track in the Rogers was usually right about 25 psi.
At the last race i was seeing 80 psi with the new sensors in the new boat.
I honestly have no idea on this one but it is interesting. I know you said your Aggressor pump is box stock, but was your jg pump box stock or had it been massaged? If the jg bowl had been worked over is it possible that it just simply flowed better(less restricted) than the stock bowl you are running now thus letting the motor spin higher? Are you going to leave your current bowl stock or have it worked? What about your impeller? Cyclone, are you going to switch over to an Aggressor impeller or do you like the AT imp. better? It is my understanding that the Aggressor bowls work best with an Aggressor impeller. Your boat would be a great test bed to find out. Also, I read in one of your threads that at the track you were running around 116mph in the new boat but at the river you have had it to 124mph. To what do you attribute the big jump in speed? I have always thought most jets were pretty much doing all they could do speed wise by the time they had gone 1/4 mile, do you think the big jump in speed was simply from just holding it WFO longer at the river or had you made set up changes since running at the track? Beautiful boat by the way!!!
ps. Sorry for all the questions, I'm just curious.
When i raced the Rogers i was running an AMT bowl that had been massaged. The Aggressor stuff i'm running now is currently stock. i put the old impeller in the new boat for comparison sake. The motor is exactly the same. I was curious what different the hull and pump would make with the same motor and impeller.
Its taken practice to get my boat to come out of the hole quickly without cavitating the pump. too much throttle and it goes nowhere fast. At the track my boat was still accelerating at the 1/4 mile mark. At the river I'll sometimes stand on the pedal for longer than that when the water is good. That's how i ended up with more speed at the river. I'm sure the current played a part in that as well.
At some point when i have time the pump will recieve some attention which should help the holeshot.
The pump inlet pressure is only part of the story, the quality of water makes as much difference as the pressure. If the pressure is high, but the turbulence and aeration(partial) are also high, the rpm can be artificially higher too. This is why a lesser HP motor can turn the same cut impeller higher RPM, in a different boat or setup! Its also why a pump rpm/hp chart is only a guideline. When the water flow is more laminar, and balanced from top to bottom, and side to side, the inlet pressure can be lower, and the rpm will drop due to Quality of water loading being better. Aerated water has less mass than "solid" water, and what we use for thrust is mass of water. On some motors with either less HP or less bottom end torque, the boat will run faster with "looser" water to the pump, this allows the motor to rpm higher, perhaps into a higher HP range. The similar effect is generated by changing nozzles. Remember: higher inlet pressure is achieved by a deeper shoe,deeper grate, or spoon in the bottom to increase the BACKPRESSURE into the inlet! The increase in intake pressure usually causes increased hull drag also. I prefer to work on increasing the quality of intake water and reduce the pressure to reduce the drag. On my 21 Daytona, I kept reducing the pressure as the quality of flow got better, and ended up running 113-115 mph with around 14-16 lbs. intake pressure. On shutdown, the boat would coast like it was on ice. I had an ignition failure at top speed, thats how I found THAT out! When I first got the boat, at 78 mph a sudden shutdown would about throw you over the windshield. There are many ways to skin a cat, this is only one way, but its what I like, and am comfortable with. P.S. a cat is like a tiny female in a cheap fur coat...... TIMINATORLET THE B.S. BEGIN!
Cyclone, I'd not be afraid to say at this point that the 5 degree Aggressor intake has a lot to do with the better quality of water to the pump. I have used many of these intakes and I have the feeling that is exactly what they do. I know some may think I'm cheerleading here, but I'm not. You see, I handle all brands of pumps and parts. I sell what works and it's not the same for every boat. I took a Berkeley intake out of Rick's 19 ft Daytona tunnel, (Flashback), and installed a 5 degree Aggressor intake. It did exactly the same thing. It ran just a little faster at 200 rpm less, and also improved E.T. some.
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