Torque vs Horsepower

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Originally Posted by RayCJ
Originally Posted by 4x4le
#2 is where I am getting confused. This is precisely how I tuned engines but I used eddy currents instead of a generator and load boxes. If the load increased at a rate that bogged the engine before the throttle was opened up then something in that test isnt right. Perhaps the engine isnt rated for those load levels at those rpms?


4x4le... Sorry for the slow reply. During the day, I do not have Internet access...

In many cases, the purpose of the tests I outlined was to establish the rating for the engine -not to test it against known values... The values were often not known. These devices were $pecial-purpo$e, to be used in places like the railroads, public utilities, mining industry etc. As such, the results had to be verified by at least 2 independent (and accredited) labs. In some cases, the reports were ultimately submitted to government agencies like the Dept of Transportation, Dept of Energy etc. That said, the goal was not to find-out if the engine was a perfect representation of the Otto cycle... the purpose was to test it under real conditions, not a 5 second zip through the RPM range.

Also, the steps I outlined were slightly simplified for the purpose of this discussion. In reality, a protocol, written and reviewed by the senior engineers (I was fresh out of college), was followed. This involved specified amounts of warm-up time, specified amounts of time under load at each RPM step etc... Significant effort went into fuel measurement. If any test could not be done according to protocol and schedule, all data was scrapped and re-done from scratch.

As for the WOT situation... There were many kinds of engines, most 4 stroke diesel, some 2 stroke diesel. Some turbocharged, some supercharged, some NA, some intercooled -and some engines were turboshafts (i.e. jet engine). All bets are off making assumptions about WOT and what the engine is supposed to be doing.


Originally Posted by Shannow
RayCJ...yes, when we were doing dyno testing at university, it was steady state, plot a curve.

The fact that modern chassis and engine dynos sweep through the RPM range either means that the true power isn't measured (some is used to accelerate for that couple of seconds), or there's fudges in there.


It's been a long time since I did this kind of work but, I'm pretty suspicious of these dyno-sweeps. I've also done a little investigation about the "inertia" dynos and they have me scratching my head.. You say there is a little fudging going on... I tend to think there's a whole chocolate factory's worth of fudge going on. I'm not seeing the light or feeling the love. Would love to tell you about a childhood story about "scratching heads" -but I think it might be over the top given the "complexity" of this thread.


Ray



Check out my first post, either page 1 or 2 I think, about where I used to do tuning for peoples scca and nasa race cars and driftcars as well as streetcars. I always used dynodynamics or dynatech which are not inertia dynos and I went into my distane for them.

Anyways I understand that there are a lot of engines that are not air throttle controlled but I can actually think of a few instances where even on a gas 4 cycle that i could bog before "max effort". It was turbo charged engines and i could actually push the turbo past its surge line at lower rpms and have on throttle surge so i had to back off the boost (still full throttle) in order to reduce the requested effort. Boost could be raised higher at higher rpms still.
I can for sure see where turbine engines could fall into this, i can see where 4 cycle turbo diesels could. I can see where naturally asperated diesels end up just making heat instead of power or hit a tip over point, and I can see where supercharged 2 stroke diesels would hit a similar wall as a 4 stroke naturally asperated diesel.


Dyno sweeps were never my thing. I always tuned steady state. I was never even looking at hp or tq when tuning but rather the effort the dyno was resisting my efforts with. After all the load cells at all the given rpms were tuned we would do a few "sweeps" at different loads to see what power it made. Tuning steady state usually had the car in perfect driving order and just made the pedal feel strong everywhere.

I think where some of the confusion came from is everyone has 4 cycle gas or diesel engines in mind with this conversation. Thinking about stationary engines that holds a given rpm does not translate well to the dynamics of a automobile engine.
 
Originally Posted by ZeeOSix
When I see a dyno chart that shows an engine makes more power with less then WOT then I'll believe it. Maybe I should be driving my car at only 75% throttle when going down the drag strip.
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The more i have been thinking about it the more it makes sense. Look at my last post for some explanation.
If you have ever been to a tractor pull you have seen it firsthand too. The tractors with big diesel engines or the diesel cycle engines converted to running on methonal have to be "brought up" on load slowly and if the throttle outruns the turbo they bog because they get overfuled. I can imagine huge stationary engines fitting into similar categories however its not much of a needed point in a thread about auto engines.
 
Originally Posted by 4x4le
Originally Posted by ZeeOSix
When I see a dyno chart that shows an engine makes more power with less then WOT then I'll believe it. Maybe I should be driving my car at only 75% throttle when going down the drag strip.
wink.gif


The more i have been thinking about it the more it makes sense. Look at my last post for some explanation.
If you have ever been to a tractor pull you have seen it firsthand too. The tractors with big diesel engines or the diesel cycle engines converted to running on methonal have to be "brought up" on load slowly and if the throttle outruns the turbo they bog because they get overfuled. I can imagine huge stationary engines fitting into similar categories however its not much of a needed point in a thread about auto engines.


Also think about the applications. A big diesel used in a tractor pull is most likely kept near the RPM where max torque is produced because they want as much torque as possible going to the wheels. I'd bet the throttle is still at 100% open at that RPM to achieve max torque. There's no way any engine that uses air to make combustion is going to make more power with less air and fuel when it's tuned right. Same may be true with big industrial diesel engines that sit at one RPM all day at their max torque output RPM so their maximum torque is used to drive some kind of machinery, etc.
 
Originally Posted by ZeeOSix
When I see a dyno chart that shows an engine makes more power with less then WOT then I'll believe it. Maybe I should be driving my car at only 75% throttle when going down the drag strip.
wink.gif
Throttle position = amount of air ingested. More air = more power if the A/F ratio is optimum at all times for power production.


You're free to do whatever you want on a drag strip. When I'm on a 15 turn road course, a little more is going on than just mashing the pedal and the reaction of the engine (up and down) is heavily relied on.
wink.gif
 
Originally Posted by 4x4le
Originally Posted by ZeeOSix
When I see a dyno chart that shows an engine makes more power with less then WOT then I'll believe it. Maybe I should be driving my car at only 75% throttle when going down the drag strip.
wink.gif



The more i have been thinking about it the more it makes sense. Look at my last post for some explanation.
If you have ever been to a tractor pull you have seen it firsthand too. The tractors with big diesel engines or the diesel cycle engines converted to running on methonal have to be "brought up" on load slowly and if the throttle outruns the turbo they bog because they get overfuled. I can imagine huge stationary engines fitting into similar categories however its not much of a needed point in a thread about auto engines.



I've read all your posts and they all make sense. We were doing our best to explain about Torque and HP. I personally was trying to simplify the explanation and get away from "hitting walls quickly vs, splattering the bricks far and wide" -and I should have left well-enough, alone.

Anyhow, I'm probably going to sign-out of this thread as it's not my intention to "get the last word" and rack-up my post count.

Ray

PS 4x4: Look for private message and we'll go offline.
 
I don't see any place on these graphs where this engine made more HP at a lower throttle position. This is always going to hold true because throttle position equates to ingested air volume which equates to an associated level of HP and T for that throttle opening %.

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There are allot of engines that are fuel controlled and have no throttle was the point he was making earlier. You can easily push turbos past surge points or flood an engine by fueling too hard at too low of an rpm.
 
A single torque number is not important, but the shape of the torque curve is. A gas engine with the same shape torque curve as diesel engine will have the same towing performance if the gas engine is geared down so its redline output after gear reduction is the same as the diesels. The reason you don't see gas engine powered semi trucks is because they will not last 1,000,000 miles because they will be screaming along at high RPMs and the components are weaker in a gas engine. Then you must consider fuel efficiency where some of the largest diesel engines are at least 50% efficient like the ones in shipping container ships. No gas engine will come close to this value.
 
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Originally Posted by 02SE
This reminds me why when a spectator inevitably asks me how much horsepower a Top Fuel engine makes, I just say "a lot". I do get a kick out of overhearing some of their theories as to what 'torque' and 'horsepower' represent, though.
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Mostly, I end up doing the face-palm thing.
 
Originally Posted by RayCJ
Look folks, my first job was with Electro Dynamics (Division of General Motors). They made locomotives, generators and electric motors -Really big ones. All work was done at IITRI (Illinois Institute of Technology Railroad Institute).




GM's division that built locomotives was the Electromotive Division. Was that the one you worked at?
 
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Originally Posted by A_Harman
Originally Posted by RayCJ
Look folks, my first job was with Electro Dynamics (Division of General Motors). They made locomotives, generators and electric motors -Really big ones. All work was done at IITRI (Illinois Institute of Technology Railroad Institute).




GM's division that built locomotives was the Electromotive Division. Was that the one you worked at?



My bad... mis-spelled the name. It's been 39 years. I was doing graduate work at IIT which had a DoD funded IITRRI (Illinois Institute of Technology Railroad Research Institute) but also did contract work for private industry. Believe it or not, I was actually working on CPU-based anti-knock sensors based on feedback signals from strain gauges. Pretty radical stuff for it's day...
 
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