502 power VS torque

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Deano
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Re: 502 power VS torque

Post by Deano » Tue Feb 27, 2018 12:06 pm

IMO, the fact remains that 2.12 gear isn't enough to attain the end he is after. He needs at least a 2.3x and maybe more.
Given the power required, he will be FAR better off with that 502 being a 540; again given his intent in the original post.

A 502 - 2.12 combo can rock a 16 maybe 17 ft. boat; a 21' boat, not so much. Dry ?
A 540 - 2.3x combo has a FAR better chance of doing what he is wanting to do.
ladyblackwater wrote:It's all going to depend on how you set it up and what you want to do with the boat. You will definitely need to run a 2.37 ratio or smaller and a good Superwide prop. If you are looking to do a lot of dry ground running and with a load you are looking at needing 700+ hp and close to 800 torque.
What will live a happier, longer life making that kind of power? A 502 or a 540?

I don't know that your graphing the 540-2.3x combo would show how large the difference would really be, but if your methodology is correct it should. Such a graph would be far more relevant and usable as what you have so far hasn't much addressed running dry.
In either case, the difference will be very readily noticeable if he stops 30 yards from the water.
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Re: 502 power VS torque

Post by Slidin Gator » Tue Feb 27, 2018 1:03 pm

Deano wrote:IMO, the fact remains that 2.12 gear isn't enough to attain the end he is after. He needs at least a 2.3x and maybe more.
Given the power required, he will be FAR better off with that 502 being a 540; again given his intent in the original post.

A 502 - 2.12 combo can rock a 16 maybe 17 ft. boat; a 21' boat, not so much. Dry ?
A 540 - 2.3x combo has a FAR better chance of doing what he is wanting to do.
10-4 Deano, I agree with everything that you say. I had a bit of tunnel vision and focused strictly on the 502 because that is the original posted question. I have plenty of doubt that the 502 is going to be enough for the intended use too. I am trying to keep the number of variables investigated at once to a minimum, otherwise it gets way too confusing to follow. The interesting thing is that the LS platform makes close to the same torque over the same RPM band as the 502 3A as posted above.

Reading between the lines of NOLA's original post, he asked if he should build the motor for low end torque or high end Hp. A 540 bore and stroke certainly adds cost to the build, but perhaps that is in the budget, and the 540 would definitely be a better example of a "Torque" motor for this application. NOLA should weigh in.

When I get more time I will search for some 540 numbers. If anyone has a torque curve to send me it would save some time for sure.

Just a quick search gave me this:
http://www.shafiroff.com/chevy-crate-en ... street.php

Horsepower 715 @ 6200 RPM
Torque 665 @ 4500 RPM
Bore & Stroke 4.500 x 4.250
Compression Ratio 10.5 to 1
Fuel Requirement 92 Octane
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: 502 power VS torque

Post by Slidin Gator » Tue Feb 27, 2018 2:13 pm

Changing the gear ratios on my spreadsheet is easy. Adding a different motor takes the time.

Here is the same 502 comparison, but with the 3 gear ratios being discussed now.

Image
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: 502 power VS torque

Post by CarMotorBarge » Tue Feb 27, 2018 7:46 pm

Slidin Gator wrote:Changing the gear ratios on my spreadsheet is easy. Adding a different motor takes the time.

Here is the same 502 comparison, but with the 3 gear ratios being discussed now.

Image
Based on this graph of the 2.12, 2.37, and 2.55 gears, which engine and gear ratio will make the most thrust and at what RPM (engine or prop)?
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Re: 502 power VS torque

Post by OneBFC » Tue Feb 27, 2018 9:01 pm

Well, I will just leave this here and you guys can finish figuring out what's going on from there. This is the Version 3 pt II 502 from the above examples. I mean, you can see that you make more thrust with 545 lbs of torque than you do with 594 lbs of torque. I think it's pretty darn clear what matters?

Red = hp
Blue = Torque
Yellow = Propeller Thrust

Image

Here's a link to an actual spread sheet too so you can input any numbers you want.

https://docs.google.com/spreadsheets/d/ ... sp=sharing
-Russ
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The only thing stopping you is FEAR
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Re: 502 power VS torque

Post by CarMotorBarge » Tue Feb 27, 2018 9:17 pm

OneBFC wrote:Well, I will just leave this here and you guys can finish figuring out what's going on from there. This is the Version 3 pt II 502 from the above examples. I mean, you can see that you make more thrust with 545 lbs of torque than you do with 594 lbs of torque. I think it's pretty darn clear what matters?

Red = hp
Blue = Torque
Yellow = Propeller Thrust

Image

Here's a link to an actual spread sheet too so you can input any numbers you want.

https://docs.google.com/spreadsheets/d/ ... sp=sharing
I can't believe it. The max thrust doesn't occur where the max torque is. Maybe that is why I asked for the HSP curves earlier. :stirpot: :stirpot: :stirpot: :stirpot:
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Re: 502 power VS torque

Post by SWAMPHUNTER45 » Tue Feb 27, 2018 9:23 pm

What does that form say?

THEORETICAL

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OneBFC
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Re: 502 power VS torque

Post by OneBFC » Tue Feb 27, 2018 10:11 pm

Wait, are you saying that the above graph is wrong somehow? Please explain?

I made this graph and I also provided access to see exactly how I made it. Feel free to find the flaw in it somewhere so I can correct it. The only thing I will give a nod to is the fact that the thrust numbers represent absolute best case and are not attainable due to cage wire, engine placement, etc.

That doesn't change one bit the fact that max thrust will occur at max hp and not max torque. Period.

This isn't designed to say "build a zero torque engine and you'll be fine." I'm not saying that at all. I'm just saying that HP > Torque when it comes to making useful thrust and when building or sourcing an engine, you need to make HP a priority because you can always size a gear reduction to make it work (within reason).

Realize that a Turbine engine like the kind used on some airplanes that spins 30,000 RPM and makes almost 2300 hp is only making 400lbft of torque. Can those engineers be so wrong?

Which curve is the thrust cruve following? HP or TQ?

Help me understand why you think my advice is wrong.
-Russ
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The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
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Re: 502 power VS torque

Post by Prototype » Tue Feb 27, 2018 11:14 pm

One,

I didn't have time to read everything but it sounds like your trying to graph a premo rig from the numbers? How can a 0540 put a whoop ass on a built stroker? How can that also be reversed?
Ultimately I'd say your searching for a number or formula that hasn't been found yet.
Tune your boat and prop to max motor torque and find it's a dog. Not the average dog, but a fat princess dog that loves being feed a lot.
Considering your footer doing 85 on dry land, I wonder what your asking?

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Re: 502 power VS torque

Post by OneBFC » Wed Feb 28, 2018 12:17 am

ladyblackwater wrote:OneBFC where are you getting your data for this graph. Also what Gear ratio and what prop are you using? It takes way more information than what you are giving to believe your graph.
I took the 502 engine data from a post in this thread just a few posts ago.....

I have measured the thrust my boat makes on a thrust tester. I also know how much power it makes at a given RPM while thrust testing at the same time due to the information the GM ECU provides. This allows you to determine a formula for HP to Thrust (For my boat of course) and I have applied a simplified version of that to the above graph. The actual exact thrust output is not all that important however to this discussion. What's important is the relationship of HP to Thrust. It follows HP, not TQ. Propellers need power to make thrust.

You can clearly see that the 502 engine in that graph makes 545 lbft torque at 4500 and it also makes that same torque at 6500. The difference is that the POWER of the engine at 6500 is considerably higher than when it's at 4500 and therefore it makes more thrust. Torque doesn't dictate what your thrust will be...

you could bolt a really inefficient warp drive propeller onto that engine and it would make less total thrust per hp compared to a good modern blade setup, but it will STILL mirror the HP curve and NOT the Torque curve.

I don't know what else to give you guys for proof. What exactly do you not believe here?

Maybe I should just quit trying to point out the obvious. It just really pains me to see people getting pointed in a suboptimal direction so I'm trying to either convince the Torque hold outs that maybe they should rethink things, OR, have someone show me the error of my own ways with some kind of proof beyond, "My 540BBC wooped that 8000000hp LSTT boat's but, 540BBC rules!" Because, frankly, that doesn't mean a darn thing to anyone due to all of the differences between the boat bulids. I need to see some kind of math, theory, thrust test results backed by matching dyno numbers, etc.

It would be helpful if you doubt that HP is what matters if you could post some actual information to support that instead of "I don't believe you" type responses. Tell me where I am wrong. PROVE it.

Here's an AC engine dyno I could dig up.....where do you think max Thrust occurs on this engine? (EDIT: THIS GRAPH HAS SEPARATE AXIS FOR TORQUE SO THE HP AND TQ VALUES DON'T CROSS AT A STANDAED 5250 AND CAN CAUSE CONFUSION

Image
Prototype wrote:One,

I didn't have time to read everything but it sounds like your trying to graph a premo rig from the numbers? How can a 0540 put a whoop ass on a built stroker? How can that also be reversed?
Ultimately I'd say your searching for a number or formula that hasn't been found yet.
Tune your boat and prop to max motor torque and find it's a dog. Not the average dog, but a fat princess dog that loves being feed a lot.
Considering your footer doing 85 on dry land, I wonder what your asking?
Mouse: I am not asking anything, I'm making the case that Torque is not the primary engine attribute you want to chase if you are looking to make the best thrust possible.
Last edited by OneBFC on Thu Mar 01, 2018 8:02 am, edited 2 times in total.
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
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Re: 502 power VS torque

Post by SWAMPHUNTER45 » Wed Feb 28, 2018 6:52 am

Any prop thrust experts on here?

Is there any data on the size of the thrust column ?

Do some blade designs produce a narrow column of air at a higher velocity ?

Do other blade designs produce a wide column at a lower velocity but with greater volume or CFM mass ?

Think of a .223 vs 45-70 that old 45-70 don't have pretty energy numbers but in real world killing will blow you off your feet.

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Re: 502 power VS torque

Post by CarMotorBarge » Wed Feb 28, 2018 7:04 am

Slidin Gator wrote: Here is the ZZ502 "Torque" motor curve right off Chevy's website:
Image
Here is a curve for the high RPM “Horsepower” motor.
Image
So I am going to tell everybody to throw away any torque curves you see from a dyno sheet. :shock: To be honest, they are causing more trouble and confusion in the airboat world and it is better to just throw them in the trash.

However, you definitely want to keep the HSP curves from the dyno sheets. You can actually get some useful info about how to setup an airboat for a particular engine. 8) Here is what the HSP curve from a dyno sheet can tell you:

1. The HSP curve tells you what RPM to turn the engine at WOT to achieve the maximum amount of thrust. Maximum thrust is achieved where maximum HSP is located. Look at the 502 Deluxe HSP curve above. This engine should be turned at 5200 RPMs to get the maximum thrust. The 502 3A motor should be turned at 6200 RPMs to make the maximum thrust.

2. The HSP curve can be used to determine what ratio you should use for a particular engine and prop. Lets assume that we want to turn a prop 2000 RPMs at WOT. The 502 Deluxe engine above will use a 2.55 ratio (2000 x 2.55 = 5100). 5100 engine RPMs is close to the max HSP generated at 5200. The 502 3A engine will require a 2.88 gear (2000 x 2.88 = 5760). For this engine and max prop RPM it would be nice to have a ratio between 2.88 and 3.26, but there isn't.

3. The HSP curve also be used to compare the low end torque between 2 different engines. All you have to do is overlay the HSP curve of engine 1 on top of the HSP of engine 2. If an engine is making more HSP at a given RPM, it is also making more torque.

Out of the 3 items above, a torque curve will only tell you item 3 (comparing torque between 2 engines). You can not derive items 1 and 2 from a torque sheet. That is why you throw the torque curves in the trash and keep the HSP curves. :stirpot: :stirpot: :stirpot: :stirpot: :stirpot: :stirpot:
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Re: 502 power VS torque

Post by SWAMPHUNTER45 » Wed Feb 28, 2018 7:14 am

Run a crate 502 at 6,000 on an airboat for an extended period and you will be buying a box of diapers to mop up the oil in your bilge !

My real world observation is they must side load pistons because they tend to use oil a lot as they wear.

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Re: 502 power VS torque

Post by CarMotorBarge » Wed Feb 28, 2018 7:20 am

Slidin Gator wrote: Image

Image
These engine torque curves and prop shaft torque to prop RPM curves need to be thrown in the trash also. :shock: The engine torque curves need to be replaced with HSP curves so you can determine engine RPM WOT and gear ratio.

The prop shaft torque to prop RPM curves also don't provide anything useful. What RPM will the prop make the most thrust at? I don't think it is where the maximum prop shaft torque is generated. :shock: Is a 2.88 ratio always better than a 2.68 and 2.12 ratio because it makes more prop shaft torque? I doubt that is true. The fundamental problem is that this chart contains no prop data. It is just engine torque multiplied by gear ratio with torque loss taken out for the gearbox. This chart would be useful if it was overlayed onto the thrust and required torque curves for an actual prop (for example the thrust and required torque curves for the 4 blade R thrust tested on Water Thunder's thrust tester earlier in this thread).
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Re: 502 power VS torque

Post by CarMotorBarge » Wed Feb 28, 2018 7:28 am

SWAMPHUNTER45 wrote:Run a crate 502 at 6,000 on an airboat for an extended period and you will be buying a box of diapers to mop up the oil in your bilge !

My real world observation is they must side load pistons because they tend to use oil a lot as they wear.
No one is saying to run the 502 3A at 6000 RPMs for an extended time. Depending on the boat setup (hull design, weight, passengers, etc.), the 502 3A would cruise in the 2500 to 4000 range. 6000 would only be required occasionally to get out of a sticky spot on the hill. Also the 502 Deluxe is only ran at 5200 RPMs because of the HSP curve.

I would worry about the valve train reliability before the side loading on the pistons. You see substantially more valve train issues than bottom end issues on an airboat.
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Re: 502 power VS torque

Post by loudmouse » Wed Feb 28, 2018 7:30 am

If you want a torque monster of an engine, build it for 5800/6000 rpm. For pump gas, 10.5 to 1, a big head, preferably no smaller than 345cc, depends on CID, a big valve, a low overlap cam with high lift to match head, a dual plane intake with long runners and a 1050 4150 carb. The longer the stroke the more torque it will make. Put a 2.37 box with 4 blade JX for when you get that beast on a plane ur cruz rpms will be lower and fuel consumption will also be lower. After all that money spent, ur stock 502 with 10 or 11 lbs of boost will be a lot stronger everywhere in the rpm band and probably for less money with efi.
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Re: 502 power VS torque

Post by OneBFC » Wed Feb 28, 2018 8:12 am

ladyblackwater wrote:Ding Ding Ding that shows your graph is only a major guess. You can NOT use your motor, gearbox and prop combination for your data because he is not wanting and can not use your combination. You are comparing Apple's to Oranges again. You do know that your thrust data you got from your prop at said Rpm's is NOT the same with every prop company and gearbox ratio?
There is no guessing with the data I provided. I physically tested and recorded data which was then put into a spreadsheet to obtain a formula. It is as far from an apples to oranges comparison as you can get.

All we have from YOU is a constant repeating opinion with no data at all to back up your claims.

So, until you can prove with supporting information that Power is not the factor that determines thrust, then you should seriously reconsider your point of view.

You do realise that all text books on this subject will say the same thing I am? I have provided, several times, links to that material for reference as well.

You should read it and here is just one, non text book, reference that is a pita to read, but, provides actual real information.

http://web.mit.edu/16.unified/www/SPRIN ... rpower.pdf

Here is an easier resource:
https://en.m.wikipedia.org/wiki/Thrust

If you still don't believe it after that, well, I guess we didn't go to the moon in the 60's either?
-Russ
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Re: 502 power VS torque

Post by OneBFC » Wed Feb 28, 2018 8:30 am

ladyblackwater wrote:This will be nothing but a back and forth thing because some people just don't get it. :banghead:
Yep, you better look in the mirror there.
ladyblackwater wrote:a 1000Hp around 6500+ Rpm motor with very little torque would have been a better choice than my 750+Hp with 750+ torque at 5400 rpm :angry5: :banghead:
Why don't you show us a dyno for these two motors you are talking about? I'd like to see a 1000hp 500+ inch displacement engine that produces "very little torque" as compared to the same displacement engine at 750hp at around the RPMs you mentioned.

This last post of yours is, again, all opinion and zero data.
-Russ
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Re: 502 power VS torque

Post by OneBFC » Wed Feb 28, 2018 9:17 am

ladyblackwater wrote:OneBFC I'm just going off what you are saying. You are the one saying that it's all about HP and don't worry about Torque. I'll post my numbers up later when I get a minute to post them.
Sounds good, I look forward to seeing it.

while we wait for that, here's some interesting dyno sheets from two 632 engines. Which engine will make more useful thrust when attached to a propeller?

Engine A
Image

Engine B
Image

Engine B web page (LOTS of good info): https://www.skipwhiteperformance.com/ca ... ine_86022/
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
Life begins at 2 BAR, Just a good ole boy

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Re: 502 power VS torque

Post by loudmouse » Wed Feb 28, 2018 9:45 am

This from a person who has a very good knowledge of building engines and what is takes parts wise to achieve the goal we're after whether it be a airboat, a 4800lb drag truck, or a 2000lb dragster, if ur torque on a sbc/bbc is close to the hp u are choking the engine for air!!!! That my friend is what 99% of all engine builders do......... Would you rather have an engine that produces 750lb torque and 750 hp or would you rather have 750lb torque and 850hp? :dontknow: :violent1: Same amount of money spent and both at very similar rpm. :stirpot: :stirpot:
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Re: 502 power VS torque

Post by Deano » Wed Feb 28, 2018 9:50 am

Brother Russ, I am surprised you would post this graph.
I see you got it off their website, so the bullshit is theirs, not yours, but . . . really?

Image

Do you not see a very fundamental flaw here in this graph for this
engine that not only defies the laws of physics, but mathematics as well?
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but it is not the path to knowledge; it has no place in the endeavor of science."
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Re: 502 power VS torque

Post by OneBFC » Wed Feb 28, 2018 9:54 am

ladyblackwater wrote: I can say I don't know what motor would have more thrust and neither can anyone that hasn't thrust tested that exact motor with the same prop and gear. The Rpm's that these motors need to turn are way to high and that's the reason I stayed away from the 632 motor on my boat.
The bolded part of your quote is what I'm trying to help you learn.

Let's pick this back up once you provide data on your setup so we can use a baseline that you are familiar with.
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
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Re: 502 power VS torque

Post by OneBFC » Wed Feb 28, 2018 9:58 am

Deano wrote:Brother Russ, I am surprised you would post this graph.
I see you got it off their website, so the bull**** is theirs, not yours, but . . . really?

Image

Do you not see a very fundamental flaw here in this graph for this
engine that not only defies the laws of physics, but mathematics as well?
Yes Deano your right, this is a bad example. It was late and I'm human. The torque and hP can't cross at that low RPM.

So, indeed, this is a poor example.

I was just looking for an engine with HP output higher than the torque and didn't think to check it.

I'm ashamed to have posted that now and I do appreicate you pointing it out. Let the record stand corrected. I edit the post to clarify the mistake.
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
Life begins at 2 BAR, Just a good ole boy

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Re: 502 power VS torque

Post by loudmouse » Wed Feb 28, 2018 10:06 am

There is no denying what I jus wrote. 850hp engine will have more snap(you's words not mine) and turn more prop than the 750hp engine. It will also make more torque and hp through the entire rpm band rpm for rpm. All for the same money spent. Thats what I do!!!
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Gas required Water optional :dontknow:
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14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

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Re: 502 power VS torque

Post by kwanjangnihm » Wed Feb 28, 2018 10:11 am

CMB - why don't we use your waterthunder dyno sheet (HP & TQ) & thrust numbers for this thread as an example?

Can you supply slidin gator this data so he can plot & chart so we can all see the relationship. :salute:
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