how much hp to turn impeller? [Archive]

LVjetboy

10-18-2003, 01:11 AM

Well, assuming Berkeley published data correct, JPC's accurate for Berkeley.
But mfg's are flakey when it comes to test data. You know, not enough time or money to test. Some just copy Berkeley curves and calibrate (extrapolate?) from a few test points. Then again, how accurate is your typical lake jetter squinting at top speed and reading the tach at 5200? Or he quotes his engine as 618 hp? Is that 618 per dyno measured...or corrected, or just estimated from printed sources? And would that be the same 618 during actual test conditions when he alegedly read his tach (however accurate) at 5200?
Then there's always pump flow work or blueprinting and what does that do to the stock pump curves?
Lots of unknowns. But it's the best we got and certainly better than nothing. Even with all these unknowns, if you account for different test conditions, equipment accuracy and pump mods, I think you can get close.
jer

slotracer

10-18-2003, 06:21 AM

my boat turns 5200 tops its a mild 454 with tunnel ram, 049 oval heads, 2 600 holleys gps with another boat that gps at 69 and i was still pulling away. we figure that i am doing right around 70-71. jim brock did the pump its a berk jc with a little bit of work done to it. boat is a 18ft. tahti tiger. not bad for a family cruiser.
pat(slotracer) :D

Infomaniac

10-18-2003, 07:04 AM

Wait a minute. :rolleyes:
A few months back I mentioned those charts were pretty accurate.
Would be a good backup when questioning dyno numbers.
I was attacked from both flanks and the rear. :D
Never saw any final results from that deal.
Decided to just be quiet about it rather than gang fight.

572Daytona

10-18-2003, 09:56 AM

I think the impeller charts are pretty much in the ballpark. I'm turning an American Turbine AA at 5300-5400 rpm with just over 600HP which is right in line with what the chart says.

victorfb

10-18-2003, 10:33 AM

please dont hurt me over this one. ok, if an "A" is turning 5500rpm, and a "B" is also turning 5500rpm, wouldnt the "A" be flowing more water? ie faster speed? im not understanding why someone builds more HP, but cuts the impeller to a "B". wouldnt you want to flow more but keep the rpms down were the torque curve is?

Dog

10-18-2003, 11:16 AM

From what I have seen with an "AA" to "B" your not
looseing enough to worry about. You want to match the engines HP.
Last boat we worked on started with an "AA" turning 5800RPM. Went to an "A" turning 6300RPM
and it was a night and day difference in accelaration and top speed. The motor was cammed to work with more RPM.

LVjetboy

10-18-2003, 12:41 PM

Victor, dogs right, for maximum thrust you want maximum power to the impeller, not torque. So for top speed you match impeller to your engine's power curve, (tempered with reliability concerns and so on) whether that means picking an AA, A or B. Some engine mods shift the power peak rpm, others leave the peak alone but give you more power. So "building more hp" doesn't always mean going to a bigger or smaller impeller.
In my case, going from a 454 to a 540 shifted peak rpm and increased it by nearly 300 hp. The combination of those two shifts nearly followed the B impeller curve, so no change in size needed to match peak power. But as Daytona mentioned, a slight upsize for me may pay-off in less engine wear with no big loss in hp...that because the dyno run shows my engine's power curve fairly level from 5800 to 6200. So in my case I could go 1/2 to one size up without loosing too much top end.
Info,
Come on in...the water's fine :D
Ok, here's the best I can do for a Berkeley B check. This from my dyno run and lake test:
Dyno Test
6200 = 634 hp
Air Temp: 95 F
Elevation (est): 900 ft
Station Barametric Pressure: 28.84 inHg
Relative Humidity: 41%
Lake Test
6200 = 643 hp (JPC estimated for Berk B)
Air Temp: 80 F
Elevation: 1142 ft
Station Barametric Pressure(est): 28.64 inHg
Relative Humidity(est): 15%
If I adjust dyno run power to lake test conditions I get 654 hp...which compares to 643 hp estimated by curves. There are other small differences, but we're talking within 20 hp or so of curves as close as I can tell...on the high side of course. This difference I'd say is likely because my impeller is flowed. But I'd say pretty close.
jer
[ October 18, 2003, 01:59 PM: Message edited by: LVjetboy ]

Infomaniac

10-18-2003, 01:45 PM

About 1.2 HP per cubic inch. :cool:
Who would have thunk it? :D

DEL51

10-18-2003, 10:08 PM

I am running a stainless AA with inducer at 58-6100 rpm.I had my pump built at Don's pump service. 5800 was the last run of the season. My dyno curve is from 4200 rpm up to 6500 rpm.I achieved 1000 Hp at 5600 rpm.I have not tested since the low rpm near the end of the season and have since removed the valve springs for the winter.If I am Pushing 1000 hp at at 5600 how can the chart be accurate? It is a dominator pump.

LVjetboy

10-18-2003, 11:46 PM

Info, I was hoping for a bit more but 1.2 hp per cuin not bad considering mild compression and hydraulic rollers.
Del51, can you post or email me hp data from your dyno run between 5000 to 6500? I'm curious what you got.
A couple points. What was the measured dyno hp at 6100? JPC says "stock" Dominator AA impeller needs 922 hp. Don's flowed impeller may need a bit more. I've had pump work by Don too btw. If your 1000 hp was a corrected number, the curves may be closer than it seems?
How does dyno data conditions compare to your lake conditions? This brings up another good point. You can only compare dyno hp data to your full throttle rpm...6100...or later 5800. Not part throttle. 5600 is not a valid match point to dyno data unless 5600 is all you could get with full throttle.
And the loss in rpms from 6100 to 5800 is also a question. Was that from a change in lake test conditions? Or an engine problem that invalidates dyno comparisons?
Oh ya, and what hull are you running and how fast?
jer
[ October 19, 2003, 12:48 AM: Message edited by: LVjetboy ]

Infomaniac

10-19-2003, 06:17 AM

jer
1.2 per cube is good. :)
That is all I will guarantee to a customer for a N/A pump gas engine. They can buy from a fudge master if that is not acceptable. Their boat will not go any faster.
My comment was directed to the folks that claim 1.48 from their N/A single carb pump gas deals.
I have always stated 1.2 is about it. I am getting ready to build and test a new EFI deal over the winter. 8 stack injection might exceed that carbed CID/HP ratio just a bit?

Moomawnster

10-19-2003, 06:45 AM

You guys are awesome ! Can HP be loosely calculated by using the RPM ? I am getting 63 mph @ 4000 rpm , Aggressor "B" impeller, 350 sbc I keep claiming 240 hp But that was 17 years ago ! eek! I want to build 400 hp or close to see what that does for my little Tahiti ! but .... from reading this post I think I may be over my depth ! Moo
[ October 19, 2003, 07:53 AM: Message edited by: Moomawnster ]

LVjetboy

10-19-2003, 11:27 AM

Aggressor B @ 4000 = 200 hp
That's actual power not rated. Now if you did build that 355 to put out a true 400 hp at the lake...then 80's are possible with your jet.
jer

Blown 472

10-20-2003, 08:36 AM

Hey Jer, what does it say for a b cut in an e pump at 5200 rpm?

LVjetboy

10-20-2003, 10:27 PM

I forgot, do you have an Aggressor impeller or is it Berkeley?
jer

Jet City

10-21-2003, 05:05 AM

Originally posted by Blown 472
Hey Jer, what does it say for a b cut in an e pump at 5200 rpm?
I show 380hp for that.

Blown 472

10-21-2003, 05:11 AM

Originally posted by LVjetboy
I forgot, do you have an Aggressor impeller or is it Berkeley?
jer
It is a legend

LVjetboy

10-21-2003, 08:48 AM

Legend B @ 5200 = 415 hp
There was talk about Legends new impeller absorbing more hp...if so I don't have charts for that yet.
jer

Blown 472

10-21-2003, 08:58 AM

Hot damn, Thanks Jer, not bad for a blowd up, crappy iron headed ****ed Over Rebuilt Dodge, that pushes the damn dipstick out when you lean on it hard.:rolleyes: :rolleyes:

21rayson

10-21-2003, 11:34 AM

how about a smallblock zz4 crate engine with a berkley b impeller and a loader grate gps @ 71.4 and 5000 rpmhttp://www.***boat.com/image_center/data/500/155jet_boat_pic-med.JPG

Jet City

10-21-2003, 12:38 PM

Originally posted by 21rayson
how about a smallblock zz4 crate engine with a berkley b impeller and a loader grate gps @ 71.4 and 5000 rpm
Looks like 338hp to me. It would take 430hp @ 5417rpm for that same boat to see 80mph (I was curious).
Blown 472, sorry about the bunk numbers, I based off berk imp.

21rayson

10-21-2003, 07:51 PM

Originally posted by 21rayson
how about a smallblock zz4 crate engine with a berkley b impeller and a loader grate gps @ 71.4 and 5000 rpmhttp://www.***boat.com/image_center/data/500/155jet_boat_pic-med.JPG so i guess gm lied about the horsepower ratings of a zz4 crate motor. i added a msd dist and 6al box plus a rpm air gap manifold and changed to 1.6 roller rockers. oh i forgot the pump is just rebuilt.

Infomaniac

10-22-2003, 03:33 AM

They claim more HP @ 5000?
A few hundred RPM's can make a big difference in HP.
Not that this is the case but: Easy for an engine builder to claim X amount of HP from their engines. X might be true but it also might make that power at an RPM that the engine will never see once installed in a boat. Great for selling engines though.

Jungle Boy

10-22-2003, 03:53 AM

Originally posted by 21rayson
so i guess gm lied about the horsepower ratings of a zz4 crate motor. i added a msd dist and 6al box plus a rpm air gap manifold and changed to 1.6 roller rockers. oh i forgot the pump is just rebuilt.
I have been present when brand new ZZ4s have been on the dyno at AMS in Edmonton, as Eagle sells these motors as one of their options. They are close to the advertised HP in most cases. AMS does some port matching, light head porting and added the 1:6 roller rockers with a 750 cfm carb and has seen 403 HP/430?? torque. I have owned one of these engines for a pleasure boat for 3 years and I know of many more out there. It's been a great engine and spins my B impeller at 4800 / 5000 depending on the weather and altitude. They are a great little motor. I'm wondering on which air gap manifold did you install and did you see any RPM increase after adding it.

Blown 472

10-22-2003, 05:03 AM

Originally posted by Infomaniac
They claim more HP @ 5000?
A few hundred RPM's can make a big difference in HP.
Not that this is the case but: Easy for an engine builder to claim X amount of HP from their engines. X might be true but it also might make that power at an RPM that the engine will never see once installed in a boat. Great for selling engines though.
True dat, I learned the hard way after trying to copy engines from magazines and finding out it would not turn the dyno rpm in my boat.:rolleyes:

OMEGA_BUBBLE_JET

10-22-2003, 08:32 AM

Originally posted by Blown 472
True dat, I learned the hard way after trying to copy engines from magazines and finding out it would not turn the dyno rpm in my boat.:rolleyes: you mean everything you read in a magazine or on the internet is not true???:confused: who'd of thought:rolleyes: :eek: :p :D
Omega

Jet City

10-22-2003, 06:22 PM

Originally posted by 21rayson
so i guess gm lied about the horsepower ratings of a zz4 crate motor. i added a msd dist and 6al box plus a rpm air gap manifold and changed to 1.6 roller rockers. oh i forgot the pump is just rebuilt.
I just looked through my GM catalog, are we talking about 350/ZZ4 part # 24502609? I show it as being rated at 355 hp @ 5250 rpm, my catalog is several years old though. I have a question for you, GM states not for marine use for this and other such crate engines, do you have any idea why? I assume you didn't do anything special before intalling yours, or did you?

Infomaniac

10-22-2003, 07:39 PM

The extra 250 RPM might be the 17 HP or so difference. Sounds pretty close to me.

wenkel

10-22-2003, 09:29 PM

how accurate is desktop dyno, I have put together a combo on a 496 stroker that will make about 675 hp and 709 tq at 5000, 724 hp and 691 tq at 5500, and 763hp and 668 tq at 6000, dont know if it would make it to 6000 with that much hp or torque. But this is more than 1.2 per cubic inch. So is it possible or is desktop dyno off a little bit?

Dog

10-22-2003, 09:49 PM

Everything you use is a tool for you. Desktop Dyno is only as good as the information you put in it. Garbage in = garbage out. What head flow numbers did you use? What camshaft specs did you use?
I hope there are some other people that have used DTD and Dynoed the motor and can give some accuracy numbers.

572Daytona

10-22-2003, 09:53 PM

Also what compression ratio did you use. You can get way more than 1.2hp/ci in a high compression motor...you just can't use pump gas to do it.

wenkel

10-22-2003, 10:37 PM

compression was 10.5 and flow rating was right out of a mag Chevy High Performance where they put together a 496 that put out 700 on a dyno at 10.5 compression, only thing different i did on desktopdyno was I added a different cam and it also is general about what intake and crb setup, also pretty general about the exhaust. what do you think? possible or not likely?

LVjetboy

10-22-2003, 10:58 PM

21Rayson, 71.4 mph...nice jet. ZZ4 crate "rated" power not the same as impeller "required" power at the lake. Rated power most likely at different conditions than your lake test...so you see less power absorbed by the impeller at lower rpm's.
So also follows the 1.2 hp/cuin. This power-to-cubic-inches based on corrected or measured? Based on race fuel or dock gas compression? As info posted, rated at what rpm? These things not unknowable or mysterious, just need accounting for to compare oranges to oranges.
jer

Duke

10-22-2003, 11:46 PM

Originally posted by Jet City Rebel
Looks like 338hp to me. It would take 430hp @ 5417rpm for that same boat to see 80mph (I was curious).
Blown 472, sorry about the bunk numbers, I based off berk imp.
that mean 100 shot of n2 will take you to 80...

Infomaniac

10-23-2003, 08:28 AM

10.5 compression is a bit beyond pump gas. It can be done but the engine has to be very cool and the timing backed WAY off.
1.2 HP/CID is my standard for pump gas carb n/a engines. 9.6:1 at the most running at normal Mercruiser type RPM's. Typical boat engine.
You can get more from one of these engines with a big solid cam and a lot more RPM's, but would not be able to use those RPM's in the boat. Could claim the HP numbers though.

HOSS

10-23-2003, 08:33 AM

I have 10.25 comp in my 350. Iron heads. Combustion chamber shape plays a big role. Run pump with 36 total.

Infomaniac

10-23-2003, 09:18 AM

Originally posted by HOSS
I have 10.25 comp in my 350. Iron heads. Combustion chamber shape plays a big role. Run pump with 36 total.
Are you positive about the exact compression ratio?

HOSS

10-23-2003, 09:41 AM

Yes. I have Dart 2 Sportsmans. 72cc, .060, want to say 15 off the deck but could be 25, .028 compressed composite gasket

HOSS

10-23-2003, 10:07 AM

Sorry, flat tops. 2 valve reliefs. TRW`s forged.

Infomaniac

10-23-2003, 11:23 AM

pretty close
10.11 pistons .005 in the hole less if more in the hole
10.236 zero deck.
only allowing 2cc for valve reliefs. less if 4cc reliefs.

Jet City

10-23-2003, 03:50 PM

Originally posted by LVjetboy
21Rayson, 71.4 mph...nice jet. ZZ4 crate "rated" power not the same as impeller "required" power at the lake. Rated power most likely at different conditions than your lake test...so you see less power absorbed by the impeller at lower rpm's.
So also follows the 1.2 hp/cuin. This power-to-cubic-inches based on corrected or measured? Based on race fuel or dock gas compression? As info posted, rated at what rpm? These things not unknowable or mysterious, just need accounting for to compare oranges to oranges.
jer
I had a similar thought, lots of variables between the GM dyno run that determined that HP rating and a lake speed run. The biggest one in my mind is engine temp, many of these boats run far cooler than what is best for peak power output. On a side note, I think 71.4 mph out of a glass lake hull/ZZ4 crate engine kick's ass!

DogHouse

10-23-2003, 08:11 PM

Originally posted by Infomaniac
10.5 compression is a bit beyond pump gas. It can be done but the engine has to be very cool and the timing backed WAY off.
1.2 HP/CID is my standard for pump gas carb n/a engines. 9.6:1 at the most running at normal Mercruiser type RPM's. Typical boat engine.
You can get more from one of these engines with a big solid cam and a lot more RPM's, but would not be able to use those RPM's in the boat. Could claim the HP numbers though.
Well I hate to be argumentative, ok not really, but here are the hp/ci numbers we made, also posted in another thread:
With n/a EFI, 91 oct, we made 1.22 @5000, 1.32 @5500, 1.34 at 6000, 1.36 @6500, corrected of course because that's the only way to provide meaningful comparisons of engines tested on different days under different conditions. Yes, in the boat on a normal blazing hot day they will be lower. My boat regularly sees over 6k rpm. This motor also idles between 800-900 rpm and carries over 700 ft-lbs torque from 3100-6000 rpm. No exotic parts here, just a solid roller, coatings, 10.8:1, 36 deg timing, coolant temp while on the dyno in the 150-160 range, no detonation, EFI with knock sensor just in case. Tested on Larry Peto's "fudge factory" dyno. :rolleyes: Anyone who doubts the validity of Larry's work or his dyno, just go to Havasu for a poker run and see who everyone is chasing at 165 mph. Ok, this last poker run not withstanding (blown freeze plug, oops, everyone has a bad day now and then). I think that the 1.2 number is a good target for a mellow low maintenance motor (i.e. hydraulic roller valve trane) that can also be tolerant of lessor grade fuels, but it is not the cutting edge of pump gas any more.
:D

LVjetboy

10-23-2003, 11:54 PM

Well if comparing corrected hp/cuin...
Dyno tested: 1.33@6200
9.8:1
N/A carbureted
89 Octane
Hyd. roller
Mufflers
The 1.33 maybe a tad low because I'm running better flowing mufflers than the dyno test above.
jer

Infomaniac

10-24-2003, 06:04 AM

Originally posted by DogHouse
Well I hate to be argumentative, ok not really, but here are the hp/ci numbers we made, also posted in another thread:
With n/a EFI, 91 oct, we made 1.22 @5000, 1.32 @5500, 1.34 at 6000, 1.36 @6500, corrected of course because that's the only way to provide meaningful comparisons of engines tested on different days under different conditions. Yes, in the boat on a normal blazing hot day they will be lower. My boat regularly sees over 6k rpm. This motor also idles between 800-900 rpm and carries over 700 ft-lbs torque from 3100-6000 rpm. No exotic parts here, just a solid roller, coatings, 10.8:1, 36 deg timing, coolant temp while on the dyno in the 150-160 range, no detonation, EFI with knock sensor just in case. Tested on Larry Peto's "fudge factory" dyno. :rolleyes: Anyone who doubts the validity of Larry's work or his dyno, just go to Havasu for a poker run and see who everyone is chasing at 165 mph. Ok, this last poker run not withstanding (blown freeze plug, oops, everyone has a bad day now and then). I think that the 1.2 number is a good target for a mellow low maintenance motor (i.e. hydraulic roller valve trane) that can also be tolerant of lessor grade fuels, but it is not the cutting edge of pump gas any more.
:D
Let me make one thing perfectly clear: I HAVE NEVER SAID ANYTHING NEGATIVE ABOUT Larry Peto OR HIS DYNO. Any other engine builder either.
And I believe your engine falls out of the criteria that I related to. Some people focus on the 1.2 thing quoted and fail to see anything else stated.
One more time for the record. N/A ,CARB, STOCK MERCRUISER RANGE RPM's
Maybe not the best forum to use this example in. Jets typically turn more RPM's. I generally keep this info in the gear heads forum. And it is directed primarily for sterndrive engines.
Also no EFI computer adjusting the fuel and ignition curves to allow more compression. Compression and RPM's will make a lot more power.

DogHouse

10-24-2003, 07:10 AM

Originally posted by Infomaniac
Let me make one thing perfectly clear: I HAVE NEVER SAID ANYTHING NEGATIVE ABOUT Larry Peto OR HIS DYNO. Any other engine builder either.
Agreed, you have never come right out and stated that any particular builder is full of sh!t and has a jacked up dyno, but repeated comments about "fudge factories" and "fudge masters" can easily lead one to believe that you would discredit anyone that makes more than the golden 1.2 ratio, including several people who have posted on these boards. Then when you say that a person can get a motor claiming a higher ratio and not make the boat go any faster, that pretty much shows me that you don't believe their power claims. That is fine, certainly your right to believe or not believe whatever you want, but it is also our right to argue the point! And by the way, you are not always clear about the stipulations surrounding that number. That's one of the problems with arguing numbers on the boards, not easy to make sure we're comparing apples to apples.
As far as my motor is concerned, I don't think that it's all that great, but it does exceed what some people have said to be the limit for pump gas, hence the argument! It's definitely not the most optimized example here; others have done better. After looking at my dyno sheets I see that I have too much cam for the rpm that I like to run and could probably make a little more torque and better power at my target rpm with less duration. We also did not have enough dyno time to finish fine tuning the efi at the very top end and it's slightly fat. Probably never notice the difference in the boat though.

Infomaniac

10-24-2003, 09:12 AM

Your right man. Everyone is intitled to their opinion and also to debate someone's opinion.
I like to make sure the debate is friendly professional and actually appropriate if I am involved.
Most of the time if I question someone's numbers, I do not have a clue who built it. And I never questioned yours.
The only time I really feel that dyno correction factors have been fudged is when an astronomical number is produced that exceeds very reputable engine builder's numbers by far.
I ran dyno's for many years and have first hand knowledge of the process.
********OH YEA *********
Sometimes the debate leads me to acknowledge that I was full of shit and sadly mistaken. :D

DogHouse

10-24-2003, 10:44 AM

Originally posted by Infomaniac
********OH YEA *********
Sometimes the debate leads me to acknowledge that I was full of shit and sadly mistaken. :D
Welcome to the club, LMAO! :D

Moomawnster

10-25-2003, 01:56 AM

Originally posted by LVjetboy
Aggressor B @ 4000 = 200 hp
That's actual power not rated. Now if you did build that 355 to put out a true 400 hp at the lake...then 80's are possible with your jet.
jer
Thanks JB 240 hp was the factory rating in 1986, I figured 17 yrs has taken some Hp out of it , Is 400 hp a reasonable # for a 355 ? I want to start this thing soon , spring is coming ! :D

LVjetboy

10-26-2003, 12:13 AM

Moo...a corrected 400 possible with good flowing heads and cam. Even 450 with trick heads and right combo check this:
383 Cubic inches
Hot Rod/Summit 383, from Hot Rod March 1992
350 block, .030 over
3.75" stock 400 crank
5.7" production rods
Keith Black Hypereutectic Pistons, Compression 9.5:1
Crane Cams hydraulic cam; 236/246 @ .050, .510/.512" lift, 112deg lobe sep
AFR 190cc aluminum heads, 80cc chambers, 2.02/1.60" valves
Crane Cams aluminum roller rocker arms; 1.6 intake, 1.5 exhaust
Edelbrock Victor Jr. intake mainfold, Holley 750 double pumper carb
1-3/4" headers
450@5750
This engine is the same exact engine that Summit sells as its 450hp 383 engine. It is streetable and even with stock parts, it should last since it is only meant to rev to 6000 rpm. This one is available from Summit, I believe the engine minus accessories is about $3800.
That'd get you 375-400 actual at the lake, depending on where you boat of course. That with a small block weight savings and you're cookin!
But guys like Info are more qualified to answer your engine questions than me.
jer