How does a Dyno Really Work?
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That guy don't know nuthin. Dynos work with magic fairy dust.
Phreakish
Well-Known Member
Ideally you'd want to replace an engine mount with a load cell. You need the cell to take the entire load through it to get a decent result.
You'd also want to make the opposite mount allow at least a full degree of freedom on an axis parallel to the crankshaft (like a spool mount).
Then you could use the distance between the mounts to turn the load cell force into a torque. Record rpm at the same time and you could graph torque and hp too.
67Dart273
Well-Known Member
I REALLY started a controversy here when I claimed that there is "no such thing" as horsepower, and there isn't. HP is a myth, it is in fact a mathematical product, it s a "thing" that can NOT be measured. Dynos do not measure HP. They measure torque, and to calculate HP you need the torque figure as well as RPM or time and distance. Then you take those figures and plug them onto the HP formula, either with a computer or pencil and paper
I don't know how you could ever be accurate with an engine mount deal, because you would be fighting the chassis / engine interaction on bumps,etc, on the road/ track. And, you'd have to have some kind of radius figured out to actually measure torque, but it is an interesting idea.
Anybody ever heard of truck electromagnetic hill retarders? Someone actually made a dyno out of one. They look like very large disc rotors on the driveshaft, only they do not use brake shoes. They use huge strong electromagnets, to provide the braking action.
And of course actual brakes HAVE been used for dyno's but they would have to be fairly short term, to combat overheating and brake fade. All that torque has to be converted to SOMETHING!!! Either actual work, or heat!!!
Horsepower = Torque x RPM / 5,252
I don't know how you could ever be accurate with an engine mount deal, because you would be fighting the chassis / engine interaction on bumps,etc, on the road/ track. And, you'd have to have some kind of radius figured out to actually measure torque, but it is an interesting idea.
Anybody ever heard of truck electromagnetic hill retarders? Someone actually made a dyno out of one. They look like very large disc rotors on the driveshaft, only they do not use brake shoes. They use huge strong electromagnets, to provide the braking action.
And of course actual brakes HAVE been used for dyno's but they would have to be fairly short term, to combat overheating and brake fade. All that torque has to be converted to SOMETHING!!! Either actual work, or heat!!!
Horsepower = Torque x RPM / 5,252
I started to think you'd have to replace a mount, even if not totally accurate still should give useful data, surprised no one sells mounts like that.
This guy got an interesting way of getting a tq curve, with a tach, lev o gage and a camera to record the curve and with a peak tq guesstimate should be able to figure out a close dyno graph.
Horsepower ain't a myth, that's like saying watt's is a myth, even if it can't be directly measured, doesn't make it not real. And we can measure it's effect we do with 0-60 mph quarter mile times, even the dyno, got to give the engine a job 1st (waterbrake) before you can measure tq and rpm.
JDMopar
Well-Known Member
@67Dart273 I had a Telma brake on my bucket truck back when I was in the line crew. That thing worked slicker'n cat poop on linoleum! Basically a Jake brake without all the racket.
I like the magic fairy explanation better and if yall don't then you got somethin wrong with you.
Phreakish
Well-Known Member
Technically speaking, a torque strap could do it, but the setup would have to be careful. When a mount takes up any force, it can distort the load measured by the cell and give an error.
Plenty of ways torque could be backed out of acceleration, and so long as there's no tire slip it will be fairly accurate.
Funny,
I thought 1 horse power was lifting (against gravity) 550lbs 1 foot in 1 second.
Not to get into an argument but...
Foot-lb vs lb-foot
Foot-lb vs lb-foot
There shouldn't be some have a weird understanding of torque and hp, I think most don't get what rpm brings to the table, it's like talking about amps and watts without acknowledging volts.
Post #9 is how it works. Any other talk is just gay.
Newbomb Turk
Well-Known Member
That’s an incredible statement since torque has never moved a vehicle. Not even an inch.
Torque maybe a rotation force but without rotation (rpm) it does noting by itself.
I don't think some see fully how rpm contributes, torque is the average force coming out of the crank that somewhat varies with rpm mainly cause Volumetric Efficiency (VE) varies with rpm compared to an electric engine where torque is mainly flat cause of steady supply of electricity at all operating rpms.
Rpm isn't a by-product it's an equal factor to torque in moving your car (performance), HP basically the sum of all the power strokes (rpm), the easiest way to look at rpm contribution is by hp % of torque at each rpm.
We all know at 5252 rpm hp is always 100% of torque, but it's the same at other rpms as well, the hp/tq % amount is static at each rpm, under 5252 rpm, hp is always less than torque Eg. 1313 rpm = 25%, 2626 rpm = 50%, 3939 rpm = 75%, etc..
Why people love so called torque engines (displacement) on the street cause the HP is generally gonna be less than torque at street rpm/speeds why diesel are perfered at super low rpm operation cause they make so much torque at these low rpms and is needed to make any useable power down there with hp per tq % being so low at those rpms.
Above 5252 rpm, Hp is higher than torque, Eg. 6565 rpm = 125%, 7878 rpm = 150%, 9191 rpm = 175%, 10,504 rpm = 200% etc.. Obviously high rpm has a great multiplying effect on hp when making useable tq up here.
Rpm isn't a by-product it's an equal factor to torque in moving your car (performance), HP basically the sum of all the power strokes (rpm), the easiest way to look at rpm contribution is by hp % of torque at each rpm.
We all know at 5252 rpm hp is always 100% of torque, but it's the same at other rpms as well, the hp/tq % amount is static at each rpm, under 5252 rpm, hp is always less than torque Eg. 1313 rpm = 25%, 2626 rpm = 50%, 3939 rpm = 75%, etc..
Why people love so called torque engines (displacement) on the street cause the HP is generally gonna be less than torque at street rpm/speeds why diesel are perfered at super low rpm operation cause they make so much torque at these low rpms and is needed to make any useable power down there with hp per tq % being so low at those rpms.
Above 5252 rpm, Hp is higher than torque, Eg. 6565 rpm = 125%, 7878 rpm = 150%, 9191 rpm = 175%, 10,504 rpm = 200% etc.. Obviously high rpm has a great multiplying effect on hp when making useable tq up here.
I think maybe what Del is trying to say is, without a measured torque spec, you cannot figure horse power. In other words, the dyno doesn't "see" horse power, it "sees" torque and makes that conversion. So without torque, you won't have measured horse power. That much is right, because torque is what spins the dyno. If da beeotch don't spin, you ain't gonna get nuffin.
Newbomb Turk
Well-Known Member
And if you don’t have RPM you go anywhere. Without the two you get not very much
I Agree
I Disagree, Hp is what spins the dyno, water brake is a job and it takes power to do that job,
All power is the combined effort of rpm and torque. Yes while the engine is doing it's job a dyno can only measure torque at rpm (which is power).
Just like electricity it takes a certain amount of watts to do a job and is made up of a combination of volts and amps and all three are always present and link, just like hp, rpm and torque.
I get that. Not what I'm talking about.
What I'm trying to get through is, a dyno cannot measure HP. PERIOD. End of discussion. It MUST have a torque spec in order to "figure" HP. Torque is the DIRECT measurement and THEN the dyno "figures" HP based on torque.
Now, if you're talking about a horse pulling weight X amount of distance then that's a horse of a different color. That IS a direct measurement of HP, but a dyno cannot do THAT. It MUST see torque FIRST.
True to measure an engines work potential you got to give it a job first and see how it does, aka dyno, quarter mile, hauling a trailer etc.. But you can't measure torque without given it a job either, free revs won't tell you the torque.
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