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HP vs Cu. In.

T

Texasmark1

Well-known Member
Got this new 2014 fangled dangle calendar from the localish hardware store. It's a "Yesterday's Tractor" edition. Has tractors from a steamer, year forget, to internal combustion from 1936.

The question is taking a Case Model 200 for example, recalling cu. in. 258, drawbar hp, 27, belt 30 apparently on at least gas.

Since hp is torque x rpm and a constant of proportionality, and today you can get 1 hp per cu in in some engines, what was lacking in yesteryear?

Then assuming a 12% fuel-air mix and that many cubes to have to fill with this naturally aspired fuel mix and only getting 27 hp out of it were they not highly inefficient back when gas was a nickel a gallon.....oh and you toiled all day for $2?

Just curious,
Mark
 
Two factors of which I am aware are speed and compression ratio. There are others too, but I can't recall much about them.
Zach
 
One of the biggest gain in HP has been in airflow in the last 15 years. The new Hemis from Chrysler are putting out race horse power of the sixty's. Computer design has been great for engine builders. That and the old tractors were low compression kero engines.
 
Remember, horsepower ratings have changed. A Farmall M was 39 new. When I was in high school it was 50. Now it's something like 57. When I was at Rolag in 2006, they hooked in 1912 65 horse case steam engine to the dynamometer. In 1912 horses he was rated at 65. And after all these years of wear, he was putting out 270 hp by today's standards.
 
Geez. Everyone must be at the computer because like me, it't too cold outside.......brrrrrr. Really fast responses.

Wow on the steamer and the IH. Interesting comment on compression. Seems nobody publishes that for the old engines. Course maybe you needed that to run multi-fuels. Course on the rpm comment, the new ones run up at 2500 or so and my '60's Fords make PTO at 1600 but both are not that fast.

Mark
 

Also, keep in mind the horsepower of the older tractors was measured at either the drawbar, or the pto, or at the belt pulley. In other words, the horsepower was measured at the point where the work was being done.

Not so today. The engines of today have the horsepower measured at the flywheel, and NO adjustments are made in regard to horsepower losses through the drive train.

As an example, way back when in auto mechanics classes at the community college, we had a floor dynamometer. You drove the whole car onto that machine, strapped it down, and then put the car through its paces. The horsepower was measured where the rear tires "met the road"

The small block V8 in my Chevy was rated at 195 horsepower and it ran extremely well, but could muster up only 60 horsepower on that dynamometer.
 
Didn't they use the term "brake hp" for engine hp at the
crankshaft with no accessories connected, like alternator, ps
pump, ac compressor, water pump? I have some old "Motors"
engine manuals from back in the late '50's.

On outboard engines, back in around 1984 they quit rating
engines as "brake hp" and started rating as you said where the
power is applied.....the prop. Made about a 15% decrease in
previously advertised numbers for the same engine at the same
rpm.

Mark
 
Your formula does not always work on internal combustion engines. It has been years but I used to show my class 2 engines that ran the same RPM, were rated at the same horsepower but the torque outputs were different. Study some Nebraska tractor tests and how they run the test. Also remember as RPM goes up Torque goes down. That is why say the drive shaft on a 350 horse power semi truck engine is a lot larger than say on a 350 horse power engine in a guys Saturday night circle track race car.
 
Not 100% sure, but F1 engines may come closer to 1 hp/cc. Racing motorcycles crank out the hp too.

Do you know why motorcycle riders dray a knee in a turn? THEY ARE PRAYING!
 
We had tank engines that were 1790 CI, but only had 1000 hp using fuel injection. The first M88's Recovery vehicles had this and would pull almost 100000 pounds of drawbar pull using this heavy field dynamometer. Hal
a140965.jpg

a140966.jpg
 
They were designed to make lots of torque, not horsepower.

Low compression, heavy flywheel, low RPM, long stroke, long connecting rods, low duration/lift/overlap cams.

All about putting slow, controllable, predictable, enduring power to the ground.
 
Well I know that cubes make the difference. I also know that tractors hit their torque peak at low rpms and it is usually flat from there out. Also know that big flywheels and long strokes with good compression lug. I guess the "constant of proportionality" is what keeps it all within proportion and makes all the variables fit the situation.

Mark
 
Combustion chamber shape and design. Port shape and design. Variable duration cams. Double overhead cams. Compression-Expansion ratio. Air/fuel and ignition via computer control. Improved metallurgy, casting and machining.
Until the 1990's a gasoline engine grossing 1HP per cu" was a snarly finicky race engine that was short lived, wasted fuel and was expensive. Now the wife's run about econobox suv nets 182HP from 145cu". The 350cu" four barrel in the 1986 pickup nets 165HP while pinging on regular gas.
 
Speaking of RPM's....I remember when I was a kid there was a guy that owned a gas station that fancied himself a mechanic. What a joke. His idea of a tune-up was grabbing the throttle linkage and cranking the rpm's. While the engine was roaring he would slowly pour a quart of water in the carb. Said it cleaned out the engine. We laughingly called it Harry's 8 grand tune up.
 
(quoted from post at 15:04:46 01/06/14)

.....Since hp is torque x rpm and a constant of proportionality, and today you can get 1 hp per cu in in some engines, what was lacking in yesteryear?......

Just curious,
Mark
Click to expand...

In answer to your question: The early engines lacked cylinder pressure.

I like to look at it this way;

HP = (BMEP x Cu In x RPM) / 792,000

BMEP is called, Brake Mean Effective Pressure. This is defined as, the average pressure which if it existed in the cylinder would produce the HP as measured on a Dynamometer.

From the equation we can see to increase the HP we need to increase: the BMEP (cylinder pressure) and/or, Cu In and/or RPM. The Ford Eco-boost is one example of a modern engine by makes use of cylinder pressure to produce power and torque.

See BuickandDeere's post for many of the changes in modern engines to increase BMEP while allowing the engines to be driveable in every day use.
 
I prefer to use the phrase "duty cycle" even tho it is probably more applicable to electric motors the principal is the same. A Case 1070 has 451 cubes to make 110 hp. Came out in early '70,s and still farming strong today. OK so take the same 110 hp only produced from a 110 cid engine ( 1 hp per cu in ) which would more than likely take a turbo and turn 3500-5000 rpm to do it and tell how many would even make it ten years let alone 40 or 50 yrs. Farming / farmers neither one lend theirselves very well to the "throw away" theory in machinery. There were approx. 100,000 late styled JD "B",s built from '47-'52. If you take out for abuse or neglect I would bet there are still 25000 left today that are still capabable of farming with. 190 cid making 27 hp at 1000-1200 rpm. See how many of todays 27 hp "yard rancher" tractors are alive even 15 yrs from now. And they aren't used all day long in the field either. So if you want a 40 yr "duty cycle" so to speak then you surely don't want 1 hp per cu in or any where near it or the compression/rpm and /or turbocharging it takes to get it. Remember . he's talking tractors here or at least that's how I read it.
 
258 cubic inch AMC Jeep engine gets 150hp at 4400 rpm in 1970s- but 120hp in Germany using DIN instead of SAE standards. 258 tractor engine at likely 1600 rpm in 1960s, maybe 2000 rpm for IHC industrial and a JD would be turning maybe 1200 rpm for a 50 or 60 series about that size twin- B"s had a 170 some inch engine pre-WW2 and 25 hp at 900 rpm or so. early compression ratios for a distillate were about 4.5 to 6:1 depending again on manufacturer. High compression, high altitude pistons were 6.5 to 7.5:1 and that was about all a N Ford could handle without detonation with 1950s leaded fuels. Harley engine 1960s were about 1/2 hp cubic inch at 4000 for W, G 45 inchers, 55 hp for FL panheads 74 inchers with 7:1 compression ratio- The FLH had about 8:1 compression more duration on cam and rated 65 hp at 5000 rpm. VW beetle engine same displacement was about 6.5:1 or 7.3:1 and rated 30 or 36hp DIN 4000/4400 rpm- SAE rating was 40hp and they were advertised as such in US. Air flow by port size, valve size and valve opening and duration open is a critical factor, compression ratio and operating speed another. A sort stroke, big bore engine can have bigger valves than a small bore, long stroke- so a 4 inch stroke, 3 inch bore IHC H compare to a 3 inch stroke 4 inch bore Chevy 150 inch engine about same displacement as the H running 4400 rpm instead of 1650 rpm would be expected to have more hp. Piston skirt design and speed factors before breakage is a slight limitation to rpm, so is valve spring pressure, mass of valve train as a limitation before valve "float" rpm. 5500 rpm in 1960s with hydraulic zero lash lifter common- solid lifter for racing gave another 1000 rpm with 170 pound valve springs instead of 125/150 pound springs- that was known for the small block chevies, buicks with the roller bearing rockers. Varying features of engines determine hp ratings at flywheel and the rest of drive train adjusts for the hp at ground. RN
 
(quoted from post at 20:36:06 01/06/14) Speaking of RPM's....I remember when I was a kid there was a guy that owned a gas station that fancied himself a mechanic. What a joke. His idea of a tune-up was grabbing the throttle linkage and cranking the rpm's. While the engine was roaring he would slowly pour a quart of water in the carb. Said it cleaned out the engine. We laughingly called it Harry's 8 grand tune up.
Click to expand...

Soot and carbon is removed by steam.
 
(quoted from post at 21:06:45 01/06/14) I prefer to use the phrase "duty cycle" even tho it is probably more applicable to electric motors the principal is the same. A Case 1070 has 451 cubes to make 110 hp. Came out in early '70,s and still farming strong today. OK so take the same 110 hp only produced from a 110 cid engine ( 1 hp per cu in ) which would more than likely take a turbo and turn 3500-5000 rpm to do it and tell how many would even make it ten years let alone 40 or 50 yrs. Farming / farmers neither one lend theirselves very well to the "throw away" theory in machinery. There were approx. 100,000 late styled JD "B",s built from '47-'52. If you take out for abuse or neglect I would bet there are still 25000 left today that are still capabable of farming with. 190 cid making 27 hp at 1000-1200 rpm. See how many of todays 27 hp "yard rancher" tractors are alive even 15 yrs from now. And they aren't used all day long in the field either. So if you want a 40 yr "duty cycle" so to speak then you surely don't want 1 hp per cu in or any where near it or the compression/rpm and /or turbocharging it takes to get it. Remember . he's talking tractors here or at least that's how I read it.
Click to expand...

Load up the B and work it day after day and that engine will be apart for major work by 3000-5000hrs.
The 6.0L in my truck has approx 158,000 miles and 4600hrs. Needs a 1-2 quart of oil between 10,000 mile oil changes. Probably good for double the distance and hours before an OH will be required.
 
In short, there wasn't a demand for high horsepower per displacement, for a number of reasons:

Low octane fuels (really fuels of unpredictable octane) made high compression ratios impractical. What was the compression ratio of that tractor? Probably 7 or 8 to 1. Both horsepower and efficiency are directly related to compression ratio; without high-octane fuel you simply can't have either one.

It was simpler to engineer a heavy, slow-turning engine than a lightweight high-speed engine. There was no real premium on horsepower-to-weight, so make it heavy. The budget to create a new engine today is astronomical. Millions of dollars are spent on engineering before the first block is cast. Then millions more are spent on prototypes; thousands of hours are accumulated in test cells. This kind of effort is necessary if you want a high-horsepower engine that will last. Back then, everything was overbuilt, with the assumption being it wouldn't break if you built it heavy enough.

In some cases, the technology just didn't exist. Variable valve timing, electronic ignition, CNC machining, and closed-loop engine management systems are just a few examples of technology used today to improve efficiency and/or performance.

One thing we should not think is that engineers of the forties and fifties didn't know how to get a lot of horsepower out of an engine. Any engineering solution is a compromise between conflicting requirements: cost, reliability and weight, for example. Those engines made perfect sense at the time, and their longevity is a testament to their durability and utility.
 
Years ago I read that in a hard working engine there was a certain maximum piston speed threshold. If the piston moved faster than this certain speed the heat couldn't be transferred away from the cylinder wall fast enough by the coolant. A longer stroke engine ran slower because the piston speed was faster at a given RPM. This article also mentioned 1/2HP/cube was the maximum horsepower that could be attained without melting or scoring pistons.

Today the horsepower threshold has been bumped to more than 1/2 hp/cube in working engines by the use of oil coolers, oil spray on the underneath of the pistons and I'm sure other methods I'm not aware of. Piston speed doesn't seem to be much faster. Jim
 
I have a hard time with that. I was at a steam show this summer. Watched 3 old tractors and one steamer on dyno, using a belt adapter to the pto. All of them had a hard time pulling their rated hp. The steamer couldn't because the state has limited their pressure. They then put a 560 Diesel on the dyno and it had its 6o something hp. The M won't have 56 hp with out a compression increase. A stock M was about the same as a Super H.
 
While we are talking about old tractors lasting. I
have a 1983 Allis 6060 it runs 2650 wide open and
has a turbo and intercooler. This tractor has almost
8000 hrs and has never had anything wrong except
some leaking injectors and the plastic went bad in
the injection pump. Oh it has been set on a little
over 100 hp its entire life. That is .5 hp per cu
in. It is 200 cu in. We have a newer Kubota with 126
hp. It is even smoother and quieter. I am betting in
30 yrs it is still going strong also.
 
Re read my last sentence. Also by "loading up the B" as they were in the field it was run mostly wide open or at least 90% which is where it made it's 27 hp. Now "load up" your 6.0 and run it up to the rpm where it's max hp is rated and you will NOT even see close to 158,000. My 5.7 Suburbans never see over 3000 rpm and cruise on freeway at 15-1800 rpm. They will last forever that way. Such is NOT the life of a farm tractor and that IS what he was asking about.
 
Which is exactly what farmers expected and answers his original question perfectly. Back when a 300 hp articulated tractor was considered tops, how many do you think they would have sold had they put a 3.8 Turbo Buick V-6 (300 hp @ 4-5000 rpm) as apposed to the one that had a 300 hp JD 6 cyl a triple the cubes running at 2000-2200 rpm ?? Nothing against the 3.8 turbo but it won't last long pulling a 25-30' field digger all day. It is true that for the sake of measurement only, 300 hp = 300hp. The engines are for completely different applications and do NOT interchange just because they have the same Hp.
 
We finally agree on something , B&D!! We used to do that on a car that was randomly missing or a little low on comp. as it would,either through thermal shock or steam as you said, knock loose all the carbon around valves/ports etc and they would usually run better afterwords as long as it wasn't a mechanical problem.
 
Any engine, in theory, is capable of producing 1 hp/ci. Whether it lasts at the output is questionable. An engine is technically a large air pump that has explosions go off in it, the more air you can move, the more power you make. Max RPM, cylinder head flow, port shape, manifold configuration (intake and exhaust), valve size, cam timing and duration, valve overlap, ignition timing, carb/injector size, piston weight, valve spring pressure, balancing of the rotating assembly, even lifter diameter, can all affect how much power an engine can make -and survive- at.

The reason those old ones didn't do it is that the engineers didn't have the knowledge/experience, materials, and tolerances that they have today, that allow them to make an engine that can do it.
 
(quoted from post at 18:47:07 01/06/14) in 1957 Desoto / crysler boasted 345 hp from 345 cubic inch v-8 ... stock
Click to expand...


Go back and read prior post. That was the engine alone. Wasn't even turning it's own water pump. When the changed the standards to measure HP all engine accessories had to be mounted and functional to determine HP. HP ratings took a nose dive in just a single year. Chevy claimed I think it was 350HP from a HO 350 and 425 HP from a 427. Just cause they claimed it doesn't make it true.

Rick
 
After reading all this I have 70 year old brain overload. Maybe the true HP testing was like 52 years ago. Get beside your buddy on main street on Saturday night and someone holler go. Our town had no stoplight.

PS Did weight of automobile have anything to do with winning?
 
I know you are rite ,chrysler claimed to be 1st to achieve that in theory ,,. POPS' 57 Desoto was VERY FAST,,he busted the speedometer.lol . that said .. I often wonder how it would do on the drag line against my 96 crwon vic ,,or my brothers 79/ 400 trans am .against the Desoto . the crown vic would top out early screamin ,, and the trans am would be ..GONE!,, LOL
 
(quoted from post at 15:12:29 01/06/14) Remember, horsepower ratings have changed. A Farmall M was 39 new. When I was in high school it was 50. Now it's something like 57. When I was at Rolag in 2006, they hooked in 1912 65 horse case steam engine to the dynamometer. In 1912 horses he was rated at 65. And after all these years of wear, he was putting out 270 hp by today's standards.
Click to expand...

Sorry, but that's a bunch of baloney.

The definition of a horsepower has not changed. It's been 550 ft-lbs per second since God was a boy.

The reason a Farmall M had more horsepower when you were in high school was due to the overbore "firecrater" style pistons that were put in them when the engines were rebuilt. Cubes were increased. Compression ratio was increased. Hence, more power. 50 was normal for a rebuilt engine then, and 57 is normal now because of even bigger overbore kits, better parts fit, better materials, and planing the head and block umpteen times over the last 70 years.

The horsepowers used to measure 39 then were/are the same horsepowers used to measure 57 now.
 
Wurtsila-Sulzer RTA 96, largest engine ever built. 14 cyl inline 2 cycle turbo diesel that runs on modified crude oil. It runs at 100 rpm, has 18' stroke and bore of over 3'.It has 1.56 million cubic inches. At that speed it makes 90,000 hp and will do it for decades without overhaul , which it must to be cost effective. It is used in the worlds largest container ship. Now I'm sure it has the latest in hi-tech machining and engineering but you could just take 90 1000hp prostock drag car engines at 500 cid ea equalling 45000 cubic inches and hook them all together and get the same hp at a fraction of the cost. And then they could overhaul each one of them after each trip,assuming they lasted that long since that 1000 hp is made at 7000 rpm. But hey, they ARE making 2 hp per cubic inch so they must be a superior engine , right? It's a BOAT!!! And what he was asking about was TRACTORS !! It's about application , duty cycle and yes, efficiency. Google this engine and see what it says about it's fuel efficiency. Horsepower figures are nothing but marketing tools and don't really have much bearing on what will do the job and what won't. Just seems to be a hard point to make.
 
B and D,

Did we go to nuke school together? Seems your responses are "east" coasterly trimmed and abrupt.

D.
Not meant as antagonistic.
 
(quoted from post at 22:40:46 01/07/14) B and D,

Did we go to nuke school together? Seems your responses are "east" coasterly trimmed and abrupt.

D.
Not meant as antagonistic.
Click to expand...

Closest I ever came to being in the service was 10years as a fireman and Captain for 4yrs .
Civilian nuclear on PHW reactors.
I suppose " just the facts" does on occasion cause some miscommunications .
 
(quoted from post at 21:47:07 01/06/14) in 1957 Desoto / crysler boasted 345 hp from 345 cubic inch v-8 ... stock
Click to expand...

And don't forget in the same year, 1957, Chevy put out the 283 ci fuel injected engine rated at 283 HP also.
 

Right. I believe, if memory doesn't fail me, that Chevy's 450 HP rated 454 in 1970 ended up all the way down to like 245 when they changed to SAE as installed standards, by like 1973 or so. Of course, this was also the beginning of the Federal mandated emissions, which led to big changes in tuning specs to meet those standards.

Something that always strikes me as funny is, I used to hear guys talking about changing out the heads, cam, adding headers, different carb, and so forth, just looking for 50 or so HP. With some of those old all motor cars, you could get that much just by changing the mufflers!

Another really big thing that has contributed to the higher HP 'installed' ratings is the much closer tolerances they can put today's engines together to. In the late 60's, a Z-28 Camaro was factory rated at 290 HP, which was obviously intentionally low, but if you balanced and blueprinted the engine, they made more like 500 HP. Back in the day, the NHRA re-rated them several times to account for this fact, trying to keep other cars that 'on paper' should have been equal, competitive with them. I don't think you could realize that same kind of gain with today's engines from doing that, simply because they are put together so much closer to 'blueprint' from the factory.
 
The 302 Z28 engine was 290 flywheel HP. It was the optional dual four barrel cross ram intake, high performance cam, valve springs and open tubular headers that made the 302 into an 8000 rpm engine.
 
(quoted from post at 08:53:45 01/12/14) The 302 Z28 engine was 290 flywheel HP. It was the optional dual four barrel cross ram intake, high performance cam, valve springs and open tubular headers that made the 302 into an 8000 rpm engine.
Click to expand...

1969 Z28, NHRA F/Stock, 302, all factory except headers as per the rules, SINGLE four barrel, 5.56 rear end gear, 9000 RPM launches and shifts, eight inch Racemasters, 11.80 in the quarter mile. This was in 1972. The dual four cross ram turned it into a 11000 RPM engine. The other changes you mentioned along with some head porting turned it into a Super Stocker, running in the 10's. Today, the same car turns the quarter in the low 9's, launches at 14000 RPM, but has a lot more changes, like tube chassis for starters, big tires, cage, and so on. Wish I still had it, but it would take near $200K to get it back now.
 

I like these numbers in a plain boring 376cu" pickup engine that runs on reg gasoline. Lasts 300,000 miles and gets 15+ mpg.


Torque (lb-ft @ rpm): 460 @ 4100
Horsepower (hp @ rpm): 420 @ 5600
 
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