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Discussion Starter #1
The other night I was sitting around a campfire with my uncle and a friend of mine. Me and my buddy are both into Supras, naturally, and my uncle grew up with muscle cars and has been a mechanic at a shop for almost 12 years, so he knows what he's talking about. We got talking about cars and I said Supras will rule the world, so he asked why. I said there are a bunch of 700, 800+ rear-wheel horse supras. He proceded to go on about how that is crap, the engine only puts out like 350hp, but since it is measured at the rear wheels, and it goes through the drivetrain, horsepower is multiplied by the trans. and diff, so it seems like it has tons of power whenreally it doesnt. I argued, saying it doesnt matter when it goes through, it can never make more power AFTER going through hears then before. You cant "make" power, if anything it would be weaker.
Then he explained it this way:
Horsepower is a function of torque and RPM. Your engine puts out so much torque, and at a certain RPM (say 5500), you have so much horsepower. At 3000 rpm, you have less horse than at 5000. I was with him so far. So one horsepower is is the work required to move so much weight a certain distance. If you hooked a pully up to the crankshaft of an engine (so, not going through any gears), to move, say 1000lbs 10 feet, would take so long at 2000rpm, and less time at 5000rpm, since you have more horsepower. If you put a tranny on that, and put it in first, it would pull very slowly (low HP), but put it in 5th and it would move it quickly (high HP). His point was that, at the wheels you will have MORE horsepower than at the crank, so in his opinion, a 1200 RWHP supra only has maybe half that at the crank. My opinion was you cant gain horsepower by gearing, and a 1200RWHP supra has MORE HP at the crank and loses some through the drivetrain. His final argument was this; if he were to try and lift an engine block (or some other heavy thing), with a rope slung over ONE pully, it would be relatively impossible. A persons arms (representing the engine), has so much strength available to lift with (torque) with no assistance. If you used a triple pully (transmission gears), you could easily lift the block. Hence, it seems that you have more strength than you have. If you were to measure the force applied at the end of the rope (rear-wheel horse), on one pully you can only apply a minimal ammount of force, but through multiple-pullies you can apply much more force. That is how they claim to have 1200 horsepower. Now he had me. So what I dont know is, on a dyno, what gear do you run in? Do they take gearing into account? Can you measure crank-hp?
 

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I'd say he's comparing apples and oranges. Gearing doesn't represent a mechanical advantage gained by a device such as a lever or pulley. Gearing simply transfers existing force into another direction. This transfer in fact costs power. I'm suprised he didn't argue that since oil is involved in the gear box that hydrolic pressure wasn't also a factor.
 

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Sorry, I didn't answer the whole question - on a dyno they would probably use the gear that has the closest to a one to one ratio - on a M58 that would be 3rd as 4th and 5th have some overdrive, (I don't know the exact ratio perhaps someone else can post).

Crank horse power would be measured on a bench - the factor numbers are generally bench numbers.
 

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Ken,

1. On a chassis dyno (where your car is strapped in), you are SUPPOSED to use whatever tranny gear is your 1:1 ratio. For our W58 5-speeds, this would be 4th gear. For those w/ Automatics, it would be 3rd (you lockout the 4th gear OD). For the MKIV guys, they are SUPPOSED to be using 5th gear on their Getrag 6-speeds. For some reason, the majority of them don't, they use 4th gear, which I know for a fact is not their 1:1 ratio.

2. Gearing is already factored in. Does not matter what you have for a rear diff ratio.

3. You can't measure actual crank hp on a chassis dyno, you will have to pull your motor & put it on a bench dyno that will properly measure the crank hp. On our Supra's for a chassis dyno (we will use a Dynojet as a example), they say take your rwhp & add 15 - 18% (numbers may vary, depending on who you talk to) & that will get your crank hp. For those w/ 4wd (like DSM's or possibly Nissan Skyline's) the numbers can really be different...

Don't forget, the rollers on a chassis dyno are under a load, it's supposed to simulate actual driving conditions. The rollers don't spin that freely. Everytime I dyno a manual tranny, I have to remember to give it more gas/slip the clutch more, when I first get the wheels moving. Yep I've easily stalled the motor before.

Have you ever dyno'd the MKII or any car for that matter before?? Just curious... :)

(Redpra has been dyno'd at least a dozen times over the last 4 years, the Silver Slug got dyno'd this past Spring).

artm: all of our 1:1 ratios are exactly that!!! The gear ratio's are 1.000
 

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Chris, in that case would using 3rd to get your dyno number show lower hp that using 4th. The dyno operator had me do my last pull in 3rd - I was disappointed with the number I got as I've done numerous mods and I was going back to the drawing board to retune to find out why power was so low.

Art
 

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hmm, that's funny how the mechanic thought you could have more hp at crank, etc.

Anyway, as everyone should be aware, hp and torque are related like you and a mechanic agree. Just that hp is a function of work done over time and torque is involved. HP and torque cannot be independent. Notice how hp and torque is always the same at around 5250rpm? True that tq #'s are always higher than hp less than 5250rpm but they are related. Not sure how gearing (1st vs 5th) on a dyno could affect this. Interesting...
 

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Well actually dynojet's and the like have VERY minimal load and really do not simulate driving very well. most dynos have huge rollers that do not take well to the sensitivity in the motor and the little things that could normally be picked up with what I am about to describe.

Now I know that most of these dynos none can really afford or even find for that matter. And the only realy downfall to the free load dynojet's is that you sorta have to guess and tune and see what the results are, and you cannot see the results until the run is done as opposed to the dynomometer below. Its not a huge deal, but I have had lots of time with both and for straight tuning even under low throttle its awesome. You can hold a certain rpm with the amount of load you can put onthe dyno and just start tunign low throttle just as you were driving on the road, but instaed its to a wideband o2! With a dynomometer, you have really cool options on them such as: having a low rolelr inirtia enabling the rollers to be much more sensitve and feel a lot more than a HUGE roller could: You also have a true tunign state, where you calculate the time it takes for your car to accelerate in a certain gear (dynoing gear) to a certain MPH with no load on the car. You Dial it in along with the wheel diameter and such and you after a few calculation get exactly (or very very close) the right load you should put on the rollers to duplicate what it would take for your car to run taht same time on the dyno. Theres a lot more to these kinds of dynos, there are I think only like 6 or 7 in the US (as they are like 100,000 machines)... they typically read a little lower than a dynojet as they have more load in an efort to tune better, which is what its really about 8)

Anyhow your uncle is wrong. take yoru arm (engine) thing for example... It is much easier to pull the weight when you are not hooked up to the so called pullet system (tranny) as the tranny means that you also have the aded weight of the wheels, which ultimately means you have to pull/push the car. hence directly from the flywheel/crank you will read much higher numbers regardless of dyno type, wheel type, tranny type or drivetrain type. THough it is actually what your engine is putting out, when you add the vehicle into perpective along with all teh drag of going through the driveshaft/tranny and all that the loss is usually about 12-15% for RWD, about 10-12% for FWD and about 18-23% for AWD (like my DSM)....
 

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to add to the "your uncles wrong club" gears arent pulleys, but if your using a 1:1 ratio for a dyno pull, its like tying a rope to something, and pulling it without aid of a pulley or any other mechanical assistance.

so tell your uncle to try that one, lol, then tell me whether he has more power if he uses his other arm, because thats what a dyno is meant to do.
it takes a specific load, for fairness in testing, then makes all the cars spin that load.
the car that spins it the fastest and easiest has the most power, traction factors excluded.
 

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And yet another "your uncle is wrong" only for different reasons. He was close when he said the tranny will amplify hp, the gearing will actually amplify torque, the ability to lift something heavy with your pulleys. Think about a little four cylinder truck pulling a boat, it can do it just fine in the low gears where torque is amplified but loses out when you have to shift up. Where your uncle got it wrong is with the hp part, since hp takes time into account it doesn't matter how easy it is to "lift" your heavy weight. Using his example: if you tie a rope through a set of pulleys and lift up your engine block it will look like you are very strong but to determine your hp you have to factor in that it took you much longer to lift the engine than you could have if you didn't have all the pulleys. So if your equation for one pulley looked like HP=X/Y where X= the weight lifted and Y= the time it took, then when you put in the set of pulleys the equation might look something like this HP=10*X/10*Y. You see you are lifting much more weight but since it took longer the end result is the same.

His argument using different rpm is also completely bogus because all engine will make different amounts of power at different rpm, you would have to use the same rpm in each gear. If you did that you would find that first gear would lift a lot of weight slowly and 5th would lift a little weight very quickly. This is due to torque multiplication through the gearing. I'm sorry to hear that your uncle is so misinformed, it's people like him that give mechanics a bad rap because they just know how to fix a given problem and not actually understand what they are doing.
 

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Sorry but your uncle is wrong (add one more to that club). The reason is in his pulley scenario (actually a block and tackle). Physics says it takes the same amount of energy to lift 1,000 lbs whether you do it directly (no pulleys) or with 4 pulleys. The reason being is because when you go through all those pullys Your arm may pull 24" of rope and you will only lift the engine 6"! Now if you are going to still lift the engine 24" you have to pull the rope 24" 4 times!! The total amount of energy expended is the same, just spread out over a greater distance (24 X 4 = 96"). And the more pulleys used the greater the frictional losses.
I have worked with 2 kinds of dynos. The first was a generator type that was hooked directly to the engine and load was applied by adding electrical load to the generator using an electrical resistance heat grid. The power was measured in kilowatts on that one, which is actuallly more accurate than HP, and we had to run the numbers through a conversion formula to arrive at HP figures.
The second dyno I worked with was a water dyno. This was a machine much like a jet pump on a boat that had a variable discharge orfice. The smaller you made the discharge hole and the faster you pumped the water the more pressure generated and the greater force needed to push the water. HP figures have to be extrapolated from the amount of pressure generated.
The moral of that part of the story is ALL dynos with ANY kind of engine strapped into them have to invent HP #s based on the amount of force (torque) measured.
Either way they are both fairly accurate devices for measuring torque/HP because they measure FORCE!
HP is an arbitrary measurement of force measured over time (speed/velocity is a factor here). Torque is raw force. Gears multiply torque yes, but HP suffers much like the pulley arragement I mentioned earlier. When time is factored in with a 4:1 ratio it cuts the HP rating by roughly 75%! (4 pulls to 1) That is why the HP #s mentioned earlier in this thread suffered in lower gears. THe same amount of force took 4 times the time and distance.
Tell your uncle to look at it this way. The Supra is 3.0L. Add 2 ATMs of boost and you have and engine that is digesting 9L (1 atm NA and 2 more of boost) of displacement (549 cu in) and has an effective compression ratio of around 18-22:1.
Now Mr Muscle car,... (insert uncle's name here) Take an 18:1 compression IHRA pro stock engine displacing 550-600 cubic inches and you have the equivalent of the average 2JZGTE running 28+ lbs of boost on the dyno,....
The only difference is the Supra engine is fuel injected!!
Do those Pro Stock boys wish they could run FI? You bet your A$$ they do, it would be worth another 20-50 HP if they could!!
Now,... I don't believe the Supra will ever "take over the world" But the import drag series and people like Craig Paisley have made the rest of the drag racing world sit upand take notice. And the 2JZ has proven to be unbeatable in the turbo-supercharged classes, relatively cheap to build and VERY reliable..
A 2,300 lb car running in the 6's speaks for itself,... Tell him to run the numbers through a HP calculator.
Sorry for the length,....
Just my $20.00 worth!!
Jamie
PS. I am an old V8 person and I love the torque of a big block. I have made more 1/4 mile passes than I care to think about in a big block muscle car that ran in the 10s. But there is no denying the 2JZ is one awesome piece of engineering.
 

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For a really dumbed down argument I'll add mine since I don't know the technicality of it all. :p

In your uncles argument if he's saying the only reason it seems that supra's produce so much hp is cause of the gearing ask him why they don't apply those gearing technologies to the old big block V8's (since he's obviously arguing it's just the new cars, or supras, and comparing them to old cars and hp numbers). Wouldn't you think all those muscle car guys would give thier arm and leg for a transmission that would DOUBLE hp!? Ask your uncle if he'd pay for a transmission that could do that to an old V8.
If that doubles thier perceived hp at the wheels (which is what makes the real difference on road & track) everyone would immediatly be installing these on all cars. If that were true, installing a 350hp boss 351 engine in a new supra it would be producing over 700hp at the wheels right off the bat! Believe me, if this were true we'd all be cramming old big blocks in our supras. Hell installing a 220hp 302 in a supra would be producing 440rwhp stock!

Or switch that around. If there were a supra-style transmission technology available to turn a 350hp boss 351 mustang into a 700rwhp+ car there would be a huge influx of companies making new transmissions for these old cars. We'd have 850rwhp hemi cuda's showing up at tracks pulling 9's like nothing. 850+rwhp vettes tearing it up out there. 800hp trans ams... all STOCK with just a new supra-style transmission. ;)

no need for cartechnobabble :p
 

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Discussion Starter #12
<quote>The Supra is 3.0L. Add 2 ATMs of boost and you have and engine that is digesting 9L (1 atm NA and 2 more of boost) of displacement (549 cu in) and has an effective compression ratio of around 18-22:1.
Now Mr Muscle car,... (insert uncle's name here) Take an 18:1 compression IHRA pro stock engine displacing 550-600 cubic inches and you have the equivalent of the average 2JZGTE running 28+ lbs of boost on the dyno,.... </quote>

That is what wins the HP argument right there.
Now, at 28psi, say pushing 1000rwhp, how long could you run that engine? You'll never get 200k miles, but theoretically how many miles could you go before blowing something; his other argument was reliability. Sure, he says, put a mass turbo on a small engine and it will make amazing horse, but like a stock-car engine, you get a few runs and it will be toast and need a rebuild. He's a tough one to argue with :)
 

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"The term horsepower was coined at the start of the industrial revolution to describe the amount of work a machine could do compared to the standard power source----a real live horse".
Earl Davis
 

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Dave A. said:
Geee, after it's all said and done, some still seem to be arguing over the term "Horsepower". Hmmm, I wonder how many modern day mechanics actually realize that the term "Horsepower" was actually invented many eons ago by a man who used his horse to lift heavy chunks of coal from a coal mine to the surface with a rope and a bucket??

Well, actually the inventor was a guy named James Watt who defined one (1) horsepower as being a unit of power equal to 745.7 watts or 33,000 lbs-ft of torque per minute.


Horsepower = RPM X Torque divided by 5,252

Torque= 5,252 X Horsepower divided by RPM

HP per cubic inch = flywheel horsepower divided by displacement
 

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Dave A. said:
Quote: "That is what wins the HP argument right there".



Sure does!


8)
Uh Dave...The last 3 posts are all from you. Are you talking to yourself now?

Heh heh...

Have a great 4th of July - I'm off to blow stuff up.
 

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That is what wins the HP argument right there.
Now, at 28psi, say pushing 1000rwhp, how long could you run that engine? You'll never get 200k miles, but theoretically how many miles could you go before blowing something; his other argument was reliability. Sure, he says, put a mass turbo on a small engine and it will make amazing horse, but like a stock-car engine, you get a few runs and it will be toast and need a rebuild. He's a tough one to argue with :)[/
I'll bet a a well tuned 2JZ with a decent bottom end running 2 ATMs of boost will live longer on the street than a 600 cu in Chev big block with 20:1 compression!! Especially if you can get the Chev to put down the HP numbers the 2JZGTE will!!
Jamie
 

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Your uncle's other argument is reliability? How long does he think souped-up big blocks last? One of my firends used to drag mopar muscle cars - he destroyed an engine like every weekend he raced. I'm not sure how long a 1000hp supra would last , but surely as long as that. Depends on what sort of reinforced parts are used I suppose. Turbocharged engines in WW2 airplanes used to push massive hp and last for hundreds of hours of hard use. surely technology is better today. My cousin ran his poor little 240sx turbo at 18psi and it still lasted a couple of years.
 
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