Extended Impeller RPM Chart

[Sleeper CP]

so, based on your assumptions, this chart was one size off? according to this chart, if you're turning an A 5700, you're making about 575hp. even if you get it to 6000, chart says 690hp.. are you ready to call bullshiat yet?, or are we just gonna continue with this chart being "right on"...
of course, you'd be all the way up to 690hp but, you'll have to show me a jet boat as heavy as yours run 90+ with 690hp; cuz i aint gonna believe it...t
BP,
Math is math, it is not subjective. I have no problem with the fact that our engine is down 125HP from the corrected numbers on a 114-116 degree day.
If you took our boat out in the winter on a 60 degree day at sea level with a 700 hp engine it could push it to 90 mph. The math doesn't lie.
But that 700 hp engine wont do it on a 90 degree day or a typical 105-110 degree river day.
Sleeper CP
565" Ford Lover

[Sleeper CP]

Food for thought: i swapped out impellers, which came from the same manufacturer, with the same cut size, and saw a difference of almost 400 peak rpm between the two. the difference was one was a mag bronze and one was stainless. both impeller were prepped by the same guy.
the point is that there are few absolutes and the most we can do is generalize about why jet pumps do what they do and when they do it.
Which performed better? Did the additional 400 rpm give you a better ET or mph.?
Sleeper CP

[IMPATIENT 1]

i turned the dom b-cut to 6900-7k last weekend with 10lbs boost, pump was loaded well when i done it. felt goooood till the block gave out

[hotbo]

i was at lost lake saturday, so i know it was kind of warm.
so, based on your assumptions, this chart was one size off? according to this chart, if you're turning an A 5700, you're making about 575hp. even if you get it to 6000, chart says 690hp.. are you ready to call bullshiat yet?, or are we just gonna continue with this chart being "right on"...
this last weekend, air was bad. when air is bad, at some point for your engine, it needs to be jetted down just a bit. you mentioned your exhaust was black, probably because you were running a 1500-2500 d/a jetting.
in my deal, i've found a "magic" d/a where i need to jet down, if i'm not already. it depends on temp, b/p, humidity and dew point. i'll toss ya a curve; at marble falls, all three mornings, temp was below 80, d/a around 3400-3500. i saw 5780 off the bottle. in the afternoon runs, d/a went up to 4600-4800, and i saw 5880 off the bottle. i never made any changes to the engine all weekend. any thoughts?:idea:
one other thing; you have a big engine, and big engines don't change as much as smaller engines do, with respect to weather changes. your richness caused more problems than the d/a; had you changed jets, you would have picked up a little. but from the rpm point you should have been at, you most likely won't pick up a shiat load of rpm just because the air gets better. i'll toss out a guess, that if you get it jetted correctly for the conditions, you could see a max of 5950 at 1000' of d/a. maybe 6k, but i'd guess slightly less. bakersfield usually has pretty good air in october:sqeyes:
of course, you'd be all the way up to 690hp but, you'll have to show me a jet boat as heavy as yours run 90+ with 690hp; cuz i aint gonna believe it...
once again someone has no respect for a chart that cuases so much conflict if you would read what sleeper stated maybe you would understand.?not tryin to sound like a asshole hear but if you think you can make a better chart please do so,so that we can all be inlightened on a better chart that you must have.:idea: this chart is pretty damn close to alot of stuff out there sure it will vary some but not so much it is useless.later trav.

[Sleeper CP]

Re-vised chart
http://i201.photobucket.com/albums/a...g?t=1189020353
Sleeper CP
Take a look at the above chart: A 700 hp @ 6,000 rpm BB (corrected numbers) will loose approx 16% of it's power at 112-115 degree day. That is a 112-115 hp loss. So instead of being able to turn a typical "A" impeller 6,000 rpm's or a fully detailed race "B" 6200-6400 that engine will only be making approx 585 HP, so the "A" will only spin to 5,600- 5,700 rpm's.
Sleeper CP

[bp]

That wasn't real hard to understand. If he's spinning an MPD A 5700, it looks like right at 700hp on this chart..
so the chart is right on unless it's an mpd impeller? plus, the socalled 700hp is AN ASSUMPTION, based on a generality, not factual data. this chart shows 575 to turn an A 5700; that's what the thing shows, i'm not making it up. 700 is a long long way from 575. so, where would the chart land for an mpd aa? and, 700 isn't where the line crosses at 5700; but even if it were that close, you could say reasonable accurate.
Magic?? :notam: Your jetting was obviously pretty far off in the AM, and more favorable to the afternoon weather if you picked up rpm with only 1200'-1300' da change. I wouldn't change jets with 1200' DA change unless jetting was already on the edge before the DA change. DA changes really have to be huge to get much out of a jet change AFA noticable power/performance, especially in a jet. If you're jetted for 1500' and rnning at 4500', then yes, that's a bit extreme, but going from 3500-4800 and gaining rpm, IMO, wasn't about jetting, and not at the rpm level we're talking.
JMOFWIW.
jetting was perfect for a normal 3500 d/a in the am (i was NOT jetted for 1500'). which was one of the reasons i had a 100rpm gain in the afternoon when d/a went up.
d/a changes don't have to be huge to get something out of a jet change, but in my engine, which is much larger than your old engine, d/a has to cross a certain point. if i -don't- change around that point, i'll see a significant fall off in performance as d/a continues to climb, and the engine is running too rich. below that, it won't necessarily be too lean with one size difference, but the little increase will allow the engine to produce a few more rpm.
jetting DID have an impact on the morning performance in 3500' d/a, and also why rpm increased in the afternoon with 1200-1300' higher d/a. this happened on 3 consecutive days. i now know why it happened, and am debating with myself over what to do about it next time, if anything. if you can figure out why it happened, i'll say that's correct; otherwise it's my info.
hotbo, there IS a better calculator out there that lvjetboy started years ago, collecting actual data from everyone he could. it may not be "absolute", but it's much closer for every type of impeller out there. as i said before, this chart -may- have been close in 1992, but with changes developed in the industry over the past 15 years, it's not that close in many applications. the bottom line for me is that i can give you example after example in which this chart is off 100-200hp. it really doesn't matter to me, and you can believe whatever you feel good about.

[Sleeper CP]

so the chart is right on unless it's an mpd impeller? plus, the socalled 700hp is AN ASSUMPTION, based on a generality, not factual data. this chart shows 575 to turn an A 5700; that's what the thing shows, i'm not making it up. 700 is a long long way from 575. so, where would the chart land for an mpd aa? and, 700 isn't where the line crosses at 5700; but even if it were that close, you could say reasonable accurate.
.
As far as the MPD impeller goes(and a G&S Marine) the reason the impeller bites one size larger is that they re-shape the face of the impeller for a bigger bite. Kind of like changing the pitch of a propeller by putting more "cup" into it. It reduces slip and has a more aggressive bite.
What 700 hp is an Assumption? If it was from my engine on Saturday it's not much of an assumption. If I know the temp , and have an observed number with a known temp I can apply another correction factor to the number and get rather close.
"this chart shows 575 to turn an A to 5700" That is true, but this chart is only a base line for stock or detailed impellers. Not full race impellers. And I already know from two sources(actually from the horses mouth) both Jack and Greg told me straight out that one of their fully blue-printed impellers are more efficient than and have a bigger bite than the impellers used on the chart and therefore require more power to turn than the chart shows. Typically their impellers are one size different. I can accept that, they told me so, I don't think either one of them would have a reason to lie to me about that. And it would make since that one of their fully detailed impellers would perform differently than a stock one. I for one hope so for what it costs, either wise I would just stick a stock impeller in the bowl and go.
I'm sure they have seen the chart before and are fully aware of it.
Lastly, on the question of a MPD "AA" my guess would be: Approx 650 hp at 5250, 750hp at 5550, 850 hp at 5850 and 900 hp at 6000 and 1100hp at 6600. These are actual at the shaft HP numbers. So as this discussion got started yesterday; adjusted for temp, the 900 hp at 6000 would be an engine that could produce approx. 1,075 corrected hp. That would be approx. 900 hp on a 112-116 degree day. Just a guess:idea:
Sleeper CP
565" Ford Lover

[pw_Tony]

Bump

[junkyardhunter]

its dead in here :skull: