Thread:

Impellor chart

I'm not sure why anyone would make an impeller chart with a worn out pump

The chart was made with an in-spec pump.

S CP

You're welcome..


S CP

Originally Posted by BAJA JA

Would a bowl stuffer change the curve much? I know since every thing was done it runs WAY WAY more efficiently. Just seems like I'm way down on H.P. now according to the chart. Tottally rebuilt 454 and berk pump with SS "AA" imp and a bowl stuffer. Stage 1 rebuild. Turns about 4300 @ 58 MPH. Does this seem like its in the ballpark.I like the way it runs. Just curious.

Not likley you would see much change from a stuffer or see a "seat of pants" change. Although there are suble differences between mfgs below is the chart we reference for AT/Dom , 4300=350 hp honestly is about right depending on the actual build (compression , cam, heads, intake, exaust etc )

H.P. 9.5 9.25 AA A B C
150 2900 3050 3200 3600 3800 4050
200 3200 3350 3500 4000 4200 4450
250 3450 3600 3700 4300 4500 4800
300 3800 3950 4050 4550 4800 5100
350 4050 4200 4300 4750 5100 5350
400 4250 4400 4500 5050 5300 5600
450 4450 4600 4700 5250 5500 5850
500 4650 4800 4950 5400 5700 6050
550 4800 4950 5100 5550 5850 N/

To me the impeller charts are as useful as believing "magazine Horsepower" numbers. Only the guys with loosely setup or worn out pumps like to believe them. In no particular order, some of the things that affect pump rpm: what brand of impeller, what "cut" is the impeller, has someone that has no understanding of flow dynamics altered the impeller or bowl, what rpm the engines peak HP is made at, wearring side clearance, early narrow or late wider wearring, shouldered wearring? and its front clearance, rideplate angle, shoe type, stock or HP handhole cover, bowl type, suction housing type, bowl to impeller clearance, nozzle size, loader grate, blocker grate, dominator type impeller/bowl, stuffer, droop and type, attack angle of the pump to the hull, "spoon" in front of the inlet, mods to the side rudders next to the inlet, "E" pump, amount of dissolved solids in the water, stock or detailed impeller/bowl, adequate fuel pressure, adequate ignition system, and I'm sure others will chime in with whatever I forgot. The most important issue here is: does your engine peak HP/RPM coincide with the RPM that the pump allows it to turn? If not, change something in the motor or the pump to make them match and a higher top speed will result. Remember; always add however much horsepower you can afford first, then match the pump to it, the end results will be cheaper and the top speed higher. Unless of course you have unlimited funds and like to buy/try a lot of stuff, or are just plane lucky. Just my opinions....... TIMINATOR

Question...
my 468 spins my Aggressor full A which ='s a Berk 2-A @ 5,300 RPM which ='s X HP on an imp chart.
So, if my engine never was to be put on a dyno, how would I know what my engines total HP/TQ and fall-off curve would be to pick the best impeller?
The smaller and smaller imp I go will produce more rpm > until the engine over revs and self destructs.

I would ask GN7 the above...but he would just get pissed

I find that The "B" impeller launches my boat better than an "A" impeller. This is with the use of an inducer, being a tunnel hull, it gulps air otherwise.

Originally Posted by HammerDown

Question...
my 468 spins my Aggressor full A which ='s a Berk 2-A @ 5,300 RPM which ='s X HP on an imp chart.
So, if my engine never was to be put on a dyno, how would I know what my engines total HP/TQ and fall-off curve would be to pick the best impeller?

EWAG = educated wild ass guess

They make dyno's so we don't have to guess. They are a great tool to use.


S CP

Originally Posted by TIMINATOR

To me the impeller charts are as useful as believing "magazine Horsepower" numbers. Only the guys with loosely setup or worn out pumps like to believe them.

really......................


I don't think my pump is worn out and I'm pretty damn sure Jack at MPD told me the detailed "B" he built for me would take an honest 820-825 hp to spin 6,200 and 1,100 to spin 6,800:





and before I met Jack and I ran an A/T years ago I just had to call and ask what the hp requiremt was to spin their impeller...... I was able to apply the info to a chart down to 50-100 rpm.



S CP

Pretty widely accepted that impeller charts are not the "Holy grail" but rather usefull tool and a reasonable guide and reference We like them
Tom

Heres Duanes for the sake of the thread