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
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?
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.