First non GM block Merc.

[QC]

Rick, I think you and I know this is a losing battle! :frusty:

Drives me nuts. You'd think I'd get over it. I guess that makes me a Troll

The problem is when you write "WOT" it is assumed you mean WOT RPM as in prop selection. I have run into this a lot here.

Maybe this will clear that up... Peak Torque is achieved by opening the throttle to the widest open position and then measuring the maximum torque along the entire operating range. The highest measured torque is "Peak Torque". The RPM at which this is achieved is called Peak Torque RPM.

When you take the torque at each RPM measured and then use the formula (torque x RPM/5252) you "convert" the measured torque to horsepower for the entire curve. This is only achieved, again, by lugging the engine at wide open throttle along the entire operating range. This is called, as noted before, a lug curve. Can be called a torque curve as well, but what it ultimately determines is a horsepower curve. To continue to try and separate them ignores what the whole exercise is about: determining work over time. And again, unless you have no clock in your life, you ultimately care about horsepower along the entire range. And also again, if you do not operate your boat with the throttle 100% mashed, at peak torque RPM (lower than peak horsepower usually), then you NEVER experience Peak Torque in a marine application. Never.

In a car, you can be cruising along at peak torque RPM, let's say 3500 and 55 MPH in 4th gear. If you do not shift gears, and start climbing a grade that gradually increases it will require, to maintain speed, that you gradually increase the throttle setting. Eventually, you will reach wide open throttle (WOT). Again, in this example, we are still at 3500 RPM and 55 MPH, no downshift. Once you reach WOT, and the car is neither decelerating or accelerating you have achieved peak torque. Great, write it all down, and celebrate. Now try and repeat this in a boat. We'll be waiting....

 

[bruceb58]

Drives me nuts. You'd think I'd get over it. I guess that makes me a Troll

No...according to Doyall, we are curmudgeons!

 

[HT32BSX115]

In a car, you can be cruising along at peak torque RPM, let's say 3500 and 55 MPH in 4th gear. If you do not shift gears, and start climbing a grade that gradually increases it will require, to maintain speed, that you gradually increase the throttle setting. Eventually, you will reach wide open throttle (WOT). Again, in this example, we are still at 3500 RPM and 55 MPH, no downshift. Once you reach WOT, and the car is neither decelerating or accelerating you have achieved peak torque. Great, write it all down, and celebrate. Now try and repeat this in a boat. We'll be waiting....

Yeah.....that would be great if you could get a HP readout on the "dashboard" while you're doing all this (and the Cops aren't around!!)

 

[QC]

No...according to Doyall, we are curmudgeons!

Saw that. While posting I was thinking of ending my last one with: "posted in honor of the Great Curmudgeon in the Sky. JB." He would've been proud of that title... Sniff...

Edit: when I bold anything it underlines it. Can't fix it

 

[bruceb58]

when I bold anything it underlines it. Can't fix it

Weird!

 

[JustJason]

Well, you'll have to tell me what is not correct I guess............



The torque at 5600 RPM....... for that engine is approx 360 Lb-Ft.

Provide the measured HP from 1800-5600 RPM (measured every 50 RPM or so, ) and I'll be glad to do the arithmetic for you.

That's the only way you'll determine the "Peak" torque.

If you have information for that engine providing HP and torque and it did NOT come from an actual DYNOMOMETER test, then it's it's an estimation from a similarly built engine that WAS DYNO tested.

It was how you worded it, which is why I called you on it, because it's part of the point I have been trying to make this entire time. You wrote "It is only a simple arithmetic relationship between the two. If you have RPM and HP (or RPM & WATTS) you can calculate the torque........ at any measured RPM." I wanted you to give me the peak torque of the engine based on the HP and RPMS I gave you. I didn't want to know the torque at max rpms, I wanted to know peak torque. And that can not be answered without having an HP curve chart for the engine, which is what I had said manufactures should have, but they don't. Without one, I can not compare the 4.5 liter to anything else I may have a chart for. To say 250 horsepower at 5k rpms is meaningless by itself. Because what really matters is what you compare it to.

In a car, you can be cruising along at peak torque RPM, let's say 3500 and 55 MPH in 4th gear. If you do not shift gears, and start climbing a grade that gradually increases it will require, to maintain speed, that you gradually increase the throttle setting. Eventually, you will reach wide open throttle (WOT). Again, in this example, we are still at 3500 RPM and 55 MPH, no downshift. Once you reach WOT, and the car is neither decelerating or accelerating you have achieved peak torque. Great, write it all down, and celebrate. Now try and repeat this in a boat. We'll be waiting....

Since we are talking about boats and not cars i'm going to go the other way around. Here is my example, and this is real world. Take 2 identical boats. Both boats are the same hulls, same sterndrives, same gear ratios, same overall weights, and same propellers. Boat 1 has a 5.0 MPI rated at 270 horsepower. Boat 2 has a 5.7 Carb rated at 260 horsepower. I won't nitpick the 10 horsepower difference. But keep in mind the larger displacement engine has less horse power.

Run both boats up to full throttle. Once you get there. Are top speeds going to be reasonably the same. Yes they will be reasonably the same.

Slowly inch back the throttles, 100 rpms at a time on both boats. Here is the question. Which boat falls of plane first, and why?

And also again, if you do not operate your boat with the throttle 100% mashed, at peak torque RPM (lower than peak horsepower usually), then you NEVER experience Peak Torque in a marine application. Never.

This can be a wording issue. But it's not the way I learned. And I learned on hydraulic dynos. The way I learned things is peak torque is generated at whatever rpm the load starts to overcome the power available. For example, lets say I think my peak torque occurs at 3500. So I spin an engine up to 3500 rpms under a modest load and keep it there, and then add load until the rpms start to drop, whatever number I get according to the dyno I write down. Since the rpms dropped, the load has overcome the power available, and the engine has "Peaked". Now I go to both 3400 rpms and 3600 rpms and do the same thing. I slowly apply that same load. If the rpms drop before I can fully apply that same load, it can now be said that the engine develops peak torque at 3500 rpms. Again just to make this clear. If I can apply a simulated load of 100lbs/ft at 3500 rpms all day long, but if I increase the load to 101, and the rpms drop, the engine has hit its peak torque.

This is the answer to why the 5.0 will always fall of plane first. It's the same horsepower as the 5.7, and according to most of ya'll horsepower is all that matters. But when you apply the same load to both engines the 5.0 will always falter first because the torque simply isn't there.

 

[bruceb58]

The way I learned things is peak torque is generated at whatever rpm the load starts to overcome the power available.

That's an interesting circular expression!

according to most of ya'll horsepower is all that matters.

Were just saying HP is a function of torque using a simple mathematical formula.

 

[QC]

Run both boats up to full throttle. Once you get there. Are top speeds going to be reasonably the same. Yes they will be reasonably the same.

Slowly inch back the throttles, 100 rpms at a time on both boats. Here is the question. Which boat falls of plane first, and why?

Actually the answer is the 5.0 would be slightly faster, and they would fall off plane at EXACTLTY the same RPM. That is if all else is equal, and the horsepower ratings are correct. (also assumes same rated RPM as you said same props, same ratios). BTW, I suggested the same exercise with your boat, in reverse, inch it up 100 RPM at a time. If she planes without the handle mashed, then you NEVER saw peak torque, So how would the lower torque number affect prop speed? Propellers curves are linear, and fixed, they do not "know" what is twisting them... Torque curves are, errr, curved.

This can be a wording issue. But it's not the way I learned. And I learned on hydraulic dynos. The way I learned things is peak torque is generated at whatever rpm the load starts to overcome the power available. For example, lets say I think my peak torque occurs at 3500. So I spin an engine up to 3500 rpms under a modest load and keep it there, and then add load until the rpms start to drop, whatever number I get according to the dyno I write down. Since the rpms dropped, the load has overcome the power available, and the engine has "Peaked". Now I go to both 3400 rpms and 3600 rpms and do the same thing. I slowly apply that same load. If the rpms drop before I can fully apply that same load, it can now be said that the engine develops peak torque at 3500 rpms. Again just to make this clear. If I can apply a simulated load of 100lbs/ft at 3500 rpms all day long, but if I increase the load to 101, and the rpms drop, the engine has hit its peak torque.

This is exactly how it is done. How does that suggest that a prop must have peak torque on it? That's why I used a car, the ever increasing grade. There is no grade on the water except swells. Maybe that big arse wave in Perfect Storm could get you to a 100% lug (point where power available and load are equal actually) Again,. throttle has to be 100% mashed to achieve peak torque. If your throttle ain't mashed, you ain't there.

This is the answer to why the 5.0 will always fall of plane first. It's the same horsepower as the 5.7, and according to most of ya'll horsepower is all that matters. But when you apply the same load to both engines the 5.0 will always falter first because the torque simply isn't there.

No, when you apply more load than either has the power to overcome they will both falter. In your example above, dropping 100 RPM at a time, that never happens. Think it through, you're backing off the throttle, ever reducing torque, not increasing it. Please read this objectively. Cannot be refuted actually

 

[Scott Danforth]

Here is my take on peak torque RPM. for the average diesel, it is generally between 1500 and 1800 RPM. for a naturally aspirated motor this value is generally between 3 and 4000 RPM. Without knowing the specific BMEP, aspiration, and a whole bunch of other factors the best I can offer is a generality.

As QC indicated with his bolded and underlined text. it is usually measured on a dyno by loading the motor and drawing it to its knees and then recording to provide the torque curve across the RPM band.

the torque curve also determines the motors ability to take a load at a given RPM. Peaky torque curves kind of suck, what one really wants is a really nicely shaped torque curve that rises quickly, is fairly flat across the mid-range RPM's and drops slowly. This will give you a really nice HP curve or prop curve.

WOT is simply Wide Open Throttle. The resulting RPM that the motor can hit at WOT will depend on the load applied to the motor, and the torque curve of the motor.

other than that, can someone pass the popcorn?

 

[JustJason]

Actually the answer is the 5.0 would be slightly faster, and they would fall off plane at EXACTLTY the same RPM.

And this I disagree with you on. The 5.0 falls of plane significantly quicker. (it's also a lot slower to get on plane, even though technically it has 10 more horsepower over the 5.7 carb, and I do mean a lot slower)

 

[HT32BSX115]

Saw that. While posting I was thinking of ending my last one with: "posted in honor of the Great Curmudgeon in the Sky. JB." He would've been proud of that title... Sniff...

Edit: when I bold anything it underlines it. Can't fix it

Bold works on mine. Try a different browser and see if it still does it. Firefox seems to be handling javascript differently these days.....AND every time they update it something else "breaks"!!

 

[HT32BSX115]

Bold works on mine. Try a different browser and see if it still does it. Firefox seems to be handling javascript differently these days.....AND every time they update it something else "breaks"!!

Ok, Here's another post using a different browser........

Konqueror Version 4.11.5 Using KDE Development Platform 4.14.2

I used Bold, Italics, and underline and quotes .....but now I can't seem to turn the "bold" off!

strange......


Looks like I have to copy NON-bold text to change "back".........


my wierd $-hit-o-meter is pegging out!!

Looks like it saved the underline but didn't do the bold or italics above!!

 

[QC]

Oddly enough, this is IE11 which I just started using last week.

 

[QC]

And this I disagree with you on. The 5.0 falls of plane significantly quicker. (it's also a lot slower to get on plane, even though technically it has 10 more horsepower over the 5.7 carb, and I do mean a lot slower)

This portion of this exchange is just odd to me. Same weight, same prop, same ratio, same hull, then they obviously fall off plane at the same RPM (going down). You literally cannot be at peak torque when you are backing off of the throttle...

Do you mind sharing the boat dimensions? To make sure I am not being misunderstood. A heavy cruiser, with marginal power, will indeed benefit from a higher peak torque combination if all else is the same. B3s help solve this as well. In the examples you gave I assumed 20 footers. This may be where we are off. If they are on the ragged edge of acceptable, then yes, the larger displacement engine would be more suited to the task of planing.

The question, from the beginning was "why don't they publish torque curves?" and my response is "because you can't do anything with it."

 

[JustJason]

You literally cannot be at peak torque when you are backing off of the throttle...

Yes you can.

The boat is a fictional boat and it really doesn't matter. But in real life single 5.0's MPI's are going into boats as big as 30 feet. With 1 or 2 people the motor and boat performs okay. When the boat is fully loaded with the family, or if you have a mid 20's boat with a single 5.0 MPI and tow with it. They are absolute dogs, and in some cases will not plane with stock props when fully loaded to whatever is stamped on the USCG placard on the boat. This is real life, and I run into this weekly because many a people are either cheap, and buy a boat with the smallest base engine. Or they are mislead by salesmen, promising the 5.0 will deliver good performance on a heavier or highly loaded boat, when it will not. This is a problem I deal with a few times a month.

That "fictional" engine I was hitting rick with earlier was the engine in my truck. It makes 381 HP at 5400 rpms but it makes peak torque of 401 lbs/ft at 3600 rpms. So yes you can be at peak torque at a lower rpm. Some engines make a lot more horsepower than they do torque, like sportbike motorcycle engine, or high reving jetski engines. Other engines make more torque than they do horsepower, like my truck engine or most diesels. Some engines are in the middle of those two extremes, but either favoring horsepower or favoring torque.

Earlier you wrote

This is all about the words, and to some of us that matters. A higher peak torque engine develops more horsepower at mid range revs. You can't separate them as most try to do.

Good to see you Jason. Didn't know you were hanging out again

My engine is a peak torque engine, it develops 401 lbs/foot at 3600 rpms and that is the most amount of torque it makes. According to the calculator, at this same 3600 rpms its only about 275 horsepower at this very moment. But if you keep on reving it you can get 381 horsepower at the top of it's rpm range at 5600.

In general, and especially with the GM engines. Most blocks produce more peak horsepower than they do peak torque. But big blocks (and strokers) give you more peak torque than they do peak horsepower.

You have your analogies about hp vs tq. Mine is simply tq is a measurement of how much work an engine can do starting from a dead stop. Hp is how much work an engine can do starting from a rolling start. TQ is how much pulling power you have from a dead stop. For example from a dead stop. If you attach a 1 foot bar at the center of my crankshaft and attach a weight to that bar, and run the engine. It can lift 399 pounds, it can lift 400lbs, and it can lift 401 pounds. But it can not lift 402 pounds. That is the point where the engine would essentially stall. However, once it goes rolling. The engine can still get past its peak torque spot and still develop "overall power" overall if you can spin it faster. Between the flywheel, the crankshaft, and a few other bits you have essentially 100+ pounds of dead weight all spinning to the left. Spinning weight has inertia. Inertia is stored energy. You can add energy to that existing stored energy by spinning that weight faster and faster. And this is horsepower. Horsepower is adding energy to existing energy, torque is creating energy from nothing. The limitation as to which you can add it is 2 fold. 1 mechanical, how fast can you spin it before the mechanical stress becomes to much and it falls apart. And 2, how much energy can you extract from the fuel being consumed. Straight gas has more power in it than E10, or E85. Nitromethane has more power in it than straight gas.

There are 3 types of boaters

1. Lake boaters that consistently run engines to full throttle, all of the time.

2. Ocean boaters that can not run engines to full throttle all of the time because conditions do not allow it

3. Boaters oriented towards towsports, or heavy loading. And they never approach full throttle because most of the time they run the boat in what would be considered for all intents and purposes an overloaded condition. IE - Filling up a ballast bag and towing a wakeboarder.

Maximum HP only really matters if your #1. If your 2 or 3 it doesn't really apply to you.

 

[Tail_Gunner]

Watching this discussion is amazing. How the formula for HP was arrived and the bench mark is old hat but in my opinion well founded. Now with that said..guy's really is it linear for a given displacement ...hell no how could it be. I am not sure what is being debated here actually who does??? But this I can tell you it's all about timing event's and substainabilty....is a 4.3 ever going to be a 5.7 taken to the extreme's hell no....period end of story.

Smile's and have a read http://news.pickuptrucks.com/2011/0...ter-ecoboost-v6-and-5-0-liter-v8-engines.html

 

[HT32BSX115]

Oddly enough, this is IE11 which I just started using last week.

Um.....I am not sure I would use IE11. Even though they have likely finally "fixed" it:

The Department of Homeland Security's US-CERT team has issued an official advisory, warning Windows customers that they should not use any modern version of Internet Explorer, from IE6 to IE11. It's important to note that Microsoft's Security Advisory 2963983 lists the exploit as a problem even with IE11 running on Windows 8.1 and Windows RT 8.1. It isn't clear from Microsoft's list if the problem also affects Windows 8, Windows RT, and/or Windows 8.1 Update, although Server 2003, Server 2008, 2008 R2, 2012, and Server 2012 R2 running with their default settings aren't vulnerable.

Microshaft usually Spends a fair amount of time either ignoring, denying, or delaying response fixing problems with IE.

I of course, do not have this problem.......Micro$hat didn't bother to provide an "IE for Linux" !!! AND I don't think I would use it anyway!!

 

[QC]

Guys... I am talking about the actual meaning of the words torque and horsepower. You can never be at "peak" torque unless the throttle is wide open. Or in a diesel if the fuel rate is at it's max at peak torque RPM (no throttle). Yes, you can be at peak torque RPM at part throttle, but that's the point, you can't lug a marine engine without ballast or a net, or towing something or if you are underpowered. I know of what I speak, use the words the way you want. Over and out.

 

[bruceb58]

I am just going to watch from now on...this is getting hilarious!

LOL...fictional boats...fictional theory...

 

[HT32BSX115]

Guys... I am talking about the actual meaning of the words torque and horsepower. You can never be at "peak" torque unless the throttle is wide open. Or in a diesel if the fuel rate is at it's max at peak torque RPM (no throttle). Yes, you can be at peak torque RPM at part throttle, but that's the point, you can't lug a marine engine without ballast or a net, or towing something or if you are underpowered. I know of what I speak, use the words the way you want. Over and out.

We're still talking about torque and HP?

We need to start a GOOD oil thread now!!