Lightweight rotors=less torque?!
 

Well I was bored last night looking through some old theads and came across a lightweight rotor thread and searched around on the topic and noticed that people were saying if you had lightweight rotors the motor would create less torque then what it already does, but no one ever stated why or wether it was true or not. So my question is why would lightweight rotors create less torque then the factorys?!

-Alex

Well lighter weight parts are usually associated with faster acceleration, but it would take more power to keep the rotor spinning at a certain rate. I could see how it reduces torque. Why do you ask anyway? Curiosity?

Well I was thinkin about buying a used motor and just tinkering around with machining lightweight internals down at my shop during my spare time just to, well, see what happens lol. Although it is also out of curiosity. What I dont seem to get here though, is if its lighter, why would it take more power to keep it spinning at a fixed rate?! Less momentum?

-Alex

At a fixed rate it would spin easier, but to speed up create compression a lighter rotor will need more force behind it. It's not like a light weight flywheel.

So then would it be correc to assume if the rotor was heavier it would creat less hp but more torque or am I still way off here lol?

-Alex

wouldn't it create more torque???? like a lighter flywheel....... creates great low end but lags on high end...

Thats what I originally thought also, except I thought it would create great high and low end torque and hp. I'm hoping more can chime in on this topic...

-Alex

There is a little more to it than just removing material from the rotors. The whole assembly also needs to be balanced. The only person in the USA who does this is Daryl Drummond. The whole process is $1200 for used rotors if they are within spec and can be used.

I looked into this not too long ago.

I understand that there is more then just removing material from the rotors and so on, but I think I could handle it just fine at my machine shop and do so cheaper then $1200.00 :) Granted I don't machine automotive parts but I do alot of medical, and military work that is extremly percise and have very small tolerances. The molds that I do for Bridgestone/Firestone also have very tight tolerances. The thing I'm trying to get at is if it will acctually loose torque or not.

-Alex

Why dont you ask Daryl Drummond. Since he does it and charges $1200 for it then he would know why someone would want to spend $1200 on it.

One needs to consider exactly WHAT it is that 'makes' the torque the engine puts out. In a piston engine, the movement of the connecting rods to drive the crankshaft is what creates torque. Imagine having several very long cheater bars connected to a wrench and you start to get the idea. This is why a long-stroke engine developes more torque....you have that long moment of inertia as the piston is being driven down...down....down.

In a rotary....much, much different. And quite frankly I can't even begin to calculate exactly how the forces are generated. This IS interesting, perhaps someone with true engineering knowledge of how this works can explain it to the rest of us?

Well, 1 Don't know how to get ahold of him and 2 would you be so willing to give someone details on something that your sellin for 1200 dollars?

-Alex

Very few people on this forum are going to be able to give you a concrete "real" answer on that (other than just "guessing"). Lightened rotors are usually for competition race cars like the SCCA boys. Daryl Drummond builds most (if not all) of the rotary engines for those guys. He is the best person to ask about the benefits or problems associated with using lightened rotors.

Try emailing Daryl at: fastrotary@earthlink.net

It will take him a few days to get back to you, but he will.

Thanks, I really appreciate it. I'll shoot him an e-mail and hopefully get the answers I'm looking for.

-Alex

I really think that the lighter rotors will act the same as a lighter flywheel....... :)

I for one hope so. We'll find out soon, either from Daryl or from me just simply doing it. I just have to find a low mileage block for sale...

-Alex

The exact same way they are in a piston motor. The side to side movement of the rotor as it "orbits" is how the power is sent into the eccentric causing it to rotate. This side to side movement is the rotary equivalent of the "throw" on a piston's crankshaft and also explains why the rotors turn at 1/3 of eccentric speed. If there was no side to side movement then you wouldn't be able to make compression either, you'd just have a triangle spinning inside a perfect circle and the volume above each rotor face would never change.

Lighter weight rotors do not give the engine less torque. An engine makes power due to the expansion of burning gases pushing against parts. In the case of a rotary the gases push against the rotor face which pushes against the eccentric and causes it to turn. Some of the engine's power is consumed in just accelerating its own parts. If you make those parts lighter the engine is able to accelerate more quickly. Automobile engines by nature constantly change power levels. If your tach is moving your engine is changing in power. Lighter weight parts make it easier for the engine to accomplish this because it doesn't consume as much power just accelerating itself.

In drag racing many people like to use a heavier flywheel in order to store inertia. Inertia is not power and it is not torque. Since you can sit at the start line and rev the engine before dropping the clutch the engine with the heavier flywheel is able to store more inertia and therefore have slightly more energy available at the moment the clutch is dropped. The downside is that the engine must accelerate that extra flywheel weight all the way down the track. There is a happy medium in this case between how much the flywheel helps the launch at the expense of hurting acceleration down the track. This is very particular to drag racing because it's the only form of racing where you get to wind up the motor and then unleash it to the tires.

In a nutshell lighter weight rotors DO NOT give the engine less torque. The lighter weight rotors will have much less inertia and so the engine will be able to speed up and slow down more easily. If you ever plan on asking your engine to change rpm as rapidly as possible you want the lightest parts possible inside the engine.

How about a gain in torque? Wouldn't the lighter parts allow you to put down more torque at the wheels?

-Alex

Thanks Damon. I was just typing a response saying that torque in engines is affected by two things: 1) the power of the expanding combustion gases, and 2) the geometry of the crankshaft/connecting rods/eccentric shaft.

In lightening rotors, you aren't changing the geometry that converts combustion pressure into torque, so torque will remain the same. Just like lightening a flywheel.

The two things you need to watch are: removing material that changes the shape of the face of the rotor, which would affect compression ratio and the power of the combustion gases. The other is mechanical stress. As you can imagine, rotors are both critical parts and highly stressed parts. You can decide what material removal is safe by analytical (FEA) modeling, or trial and error. Whichever approach Daryl took, I imagine part of the cost is recovering the time he spent making sure the rotor won't fail due to stress.

Dave

BTW guys, any place here in the US that offers lightened rotors, goes through Daryl (yes, even Racing Beat).

torque = moment of inertia x angular acceleration.

It's all a matter of physics and inertia. An object's moment of inertia is directly proportional to its mass. So the more mass, the more torque. Think of 2 swinging doors, one heavy and one light. Which one is easier to stop? Of course, youl need more hp to get the heavier one moving....

Overall, lighter rotational mass engines may accelerate quicker (good for pure racing), but will also decelerate quicker (not good for highway cruising). A good mix of both should keep your car streetable and fast. Hope my two cents helps.

Ding! Ding! Ding! We've got a winner!! :)

I can guarantee that lightweight internals will not adversely affect torque. I have an ultralight billet crankshaft in my 396 (22 lbs. lighter than stock), ultra light billet rods (505 grams, about 3 lbs. lighter for the set of 8 than aftermarket 6.0" rods), and lightweight pistons (405 grams with pistons). Check out the effect on torque...

http://home.gci.net/~jimlab/images/E...vered/Dyno.jpg

Nada. Same as if I'd used heavier standard-issue components.

However, most people think that it's the length of the "lever" on the crankshaft, or in other words, the crankshaft's "stroke" (actually, the distance from the connecting rod journal centerline to the crankshaft centerline is half of the crankshaft's stroke) that increases or decreases torque. In part it is, but it's not quite as simple as that. Displacement is what ultimately affects torque production.

If I have a V8 with a 4.00" cylinder bore and a 3.48" stroke, I've got 350 CID. (4.00 * 4.00 * 3.48 * 8 * 0.7854 = 349.9 CID). If I increase bore diameter to 4.03" and stroke to 3.75", now I've got 383 CID. (4.03 * 4.03 * 3.75 * 8 * 0.7854 = 382.7 CID) The difference, of course is that one has a longer "lever" on the crankshaft, but as a result, the piston is also traveling farther on each stroke (the distance of the stroke, FWIW), creating more displacement. More displacement means I can burn more air and fuel on each cycle, creating... more torque.

Now, let's say that I create an "all bore" 383 with the shorter 3.48" stroke of the 350. I'd have to use a 4.18" cylinder bore (4.18 * 4.18 * 3.48 * 8 * 0.7854 = 382 CID). Obviously, the 3.48" stroke crankshaft has a shorter "lever" than the 3.75" stroke crankshaft above. Would you expect torque to differ substantially? In fact, given equal intake components and cam profiles, the two engines will produce almost identical torque curves. Why? Because even with a shorter lever, the "all bore" engine is exerting more force on that lever, because it is burning the same amount of fuel and air, but has a larger surface area (piston crown) to "push on". Neat, huh? :)

If I put 1 pound of pressure on a lever 1 foot long, I have 1 lb-ft. of torque. If I put 2 pounds of pressure on a lever 0.5 foot long, I still have 1 lb-ft. of torque. Pretty simple once you think about it.

Anyway, as far as the rotary is concerned, there are no connecting rods, obviously. Instead, the rotor exerts force directly on the journals of the eccentric shaft, and the "stroke" of the eccentric shaft (offset of the rotor journal centerline to the centerline of the eccentric shaft) is what applies leverage to the eccentric shaft. Once again, it is displacement that dictates the amount of torque produced.

Since we're talking about turbocharged rotary engines here, you can see from a dyno sheet that once the turbo spools and you're creating more "displacement" by pressurizing the intake charge and forcing more air (and fuel) into the engine, torque rises dramatically. Below that point, the engine doesn't make much torque because A) it has very little displacement, and B) the offset of the rotor journal centerline to the eccentric shaft centerline isn't very large. (look at a a picture of an eccentric shaft some time).

Lightening the rotors will not change the amount of torque the engine produces unless material is removed from the rotor face, affecting displacement. Only changing the eccentric shaft offset (impossible without changing the size of the housing and rotors because of the precise pattern the rotor must travel) or combustion chamber size will affect the amount of torque the engine produces, assuming all other factors (port size, etc.) stay the same.

Even with the rotary engine, displacement ultimately determines torque. A rotary engine with lightened rotors will spin up (rev) faster and slow down faster because it takes less energy to spin it up to a given speed and there is less inertia or stored energy in a lighter part when you stop applying power. However, none of that will affect torque in the slightest.

Merry Christmas! :p:

Actually, you can think of that equation as the portion of torque lost in accelerating the drivetrain.

Reducing the moment of inertia (which is the real point of lightening a flywheel or rotor) will allow more of the torque to be used on the wheels, and the angular acceleration will go up a bit.

Dave

This is starting to get me quite intreged. I think I'm going to go ahead with this as soon as I can find a low mileage block and a few bad rotors to tinker with. Hopefully all will go well and I can atleast be the second in the US capable of doing this. What had got me all confused was people saying you'd have virtually no torque with lightweight rotors, yet I have never seen any ill effects with lightweight internals with a piston motor as Jim stated.

-Alex

Gotcha Dave, you're right.

jimlab, consider me schooled :worship:

Excellent post, Jimlab! :bigthumb:

Jimbo is always....da MAN!

As said, light rotors will act like a light flywheel, and make more power available at the wheels IN THE LOWER GEARS. No gain unless the tach is sweeping quickly.

Light rotors may allow a higher redline, and more hp.

jimlab: good job on clearing up long stroke = more torque. but ... "Lightening the rotors will not change the amount of torque the engine produces unless material is removed from the rotor face, affecting displacement."

don't think a face job changes displacement. would dished pistons change yours?

-------------------------------------------

Originally Posted by bajaman
"In a rotary....much, much different. And quite frankly I can't even begin to calculate exactly how the forces are generated"

As DamonB said.

Another view: It's like a piston directly connected to the crank arm. Watch a rotary animation ... slowly. The fired face creates a "force vector" that passes through the rotor center and also the apex seal on the far side. When the rotor rotates about 45 deg from the fire position, it's "force vector" is nearly at a right angle to the e-shaft pin, and is creating the most torque.

If I recall right, the pockets on each face of the rotor give it more displacement. If you was to machine the pockets larger it should add displacement, but will also change the compression ratio from what I've gathered. Enlarging those pockets is another idea I have in my head.

-Alex

Good point. The swept volume of the combustion chamber is what's being calculated, and it's assumed that the piston has a perfectly flat top for that calculation. Adding a dish or a dome to the piston changes the compression ratio and technically affects the volume of the cylinder, but it's not factored into the displacement calculation which is only concerned with swept volume, or in this case, 8 perfect cylinders the height of piston travel and the diameter of the cylinder bore.

As an example, I have 5cc valve reliefs (clearance) in the crowns of my pistons, but it only affects the compression ratio and not the rated displacement of my engine.

http://home.gci.net/~jimlab/images/Pistons/PB140037.jpg

Yep. Pressure on the connecting rod journal (and therefore torque) also rises and falls in a piston engine as the angle of crankshaft rotation changes.

http://science.howstuffworks.com/fpte4.htm

Theoretically it seems like it should create less torque at the wheel... but thats not what's producing the power and therefor not what you need to look at. A lighter rotor will let the drivetrain spin the wheels at a faster rate, if any noticeably difference, and therefor create more torque. The unsprung weight on cars is harder to explain... sorry if that explanation sucks.

It's easy to explain. Unsprung weight, flywheel inertia, rotor inertia, they are all like throwing sandbags on the back of the school's star running back. He has the same 'torque' (running power) as before, it just slows his acceleration and ability to change direction. And theoretically, suspension and drivetrain are best with zero response time.

Dave

Lightweight rotors are what the RX-8 has. They are BETTER due to less inertia, just like lightweight flywheels.
Combustion physics has to do with rotor shape, injection rates, sparking, intake & exhaust timing (port shaping) and other things like 100 octane racing fuel vs the 91 octane crap they sell out West, but NOT heavy vs light rotors. "Light is right", in rotors as well as pistons. So good combustion characteristics along with light rotors is the ideal.
Lightweight flywheels, if TOO light, can affect street drivability due to not only fast spinUP but fast loss of RPMS (spinDOWN) too. Rotors affect this much less so. The power gained by having less weight to push around during combustion is better, now worse.

I think many of you are missing the forest for the trees. The weight of rotors/flywheel (i.e,. rotating assembly) does not change the torque or power PRODUCED by the engine, it just changes your perception of it, because it changes the INTERTIA of the assembly. The mass of the flywheel, other than providing a physical surface for a clutch assembly to grip and a ringgear to crank the engine with, is used for one thing...storage of energy. Same goes for the weight of the rotors themselves (again, other than their obvious physical properties and shapes). The more mass, the more energy you can store. This energy is sapped off the energy the engine produces during combustion. IF an engine with infinitely lightweight internals could make 500hp at the crank by transmitting ALL of it's generated power straight out, then that engine would make less as measured at the flywheel with a massive RA. Because some of that energy was invested into the RA's mass to begin with.

This helps you with low end driving. That energy is removed and transmitted to the drivetrain when load is introduced. When you introduce a load from the drivetrain and weight of the car, you drain the engine of energy at the crank. The flywheel, and to a degree, the entire RA's mass, has stored some energy to counteract this shock, so that it's easier to drive the car and maintain smoothness between shifts. Without this, you'd kill the engine every time you tried to pull out, and your revs would drop instantly during shifts, making driving a bitch.

The less mass the RA has, the less energy it stores, and the more energy gets transmitted directly to the drivetrain. It doesnt mean the engine is PRODUCING any more power because of the less massive RA, just that more of it is being transmitted to the car rather than into the RA. The less energy available to combat the effects of load being applied, the more you feel the effects mentioned above.

As a real world illustration, if you take a stock car with a 25lb flywheel (like an s4 t2) and install a 9lb flywheel, and do back to back drives, it'll feel like you have gained hp. IN reality, your engine is identical as before, and is producing teh same power via combustion. Just that less of that power is tied up in rotating assembly inertia, and thus a bit more is transferred to the wheels, so the car feels faster. By the same token, at a stoplight or a hill, less energy is stored in that lighter flywheel, so when it comes time to present a load to the engine, you feel more of a shock and tendency to die because of that.

There is one big difference between reciprocating angines and rotary engines. The reciprocating engine has to stop and start the weight of rods and pistons every revolution and that work is directly subtracted from torque/HP. That loss starts small at low RPM but increases at the square of the RPM (or is it cubed?). Rotary weight has no effect on a constant RPM, it only slows down acceleration.

The weight in a rotor also places stress on the bearings that have to keep it moving in the right direction. That weight will affect max possible RPM.

Since rotating weight only affects rate of acceleration, it really only affects the lower gears. It only really matters in gears that you can run through in less than 3 or 4 seconds. A lightened flywheel or light rotors doesn't really affect 4th and 5th gears. Probably not 3rd gear either unless you have a lot of HP on tap.


I would suspect that the SCCA guys want the lightened rotors not for any change in torque but to allow them to make the big HP that comes from running at higher RPM.

ed

What's your justification for this statement? Do you not accelerate in higher gears also? And in fact, with less gear multiplication in higher gears, the heavier you make the components of the rotating assembly, flywheel and clutch assembly, or the rest of the drivetrain, the slower you will accelerate.

If anything, lightweight components are even more critical in higher gears and at higher speeds, where the available torque at the axles is far less and the weight of the car, drivetrain losses and rolling/wind resistance have far more effect on the rate of acceleration.

"If I have a V8 with a 4.00" cylinder bore and a 3.48" stroke, I've got 350 CID. (4.00 * 4.00 * 3.48 * 8 * 0.7854 = 349.9 CID). If I increase bore diameter to 4.03" and stroke to 3.75", now I've got 383 CID. (4.03 * 4.03 * 3.75 * 8 * 0.7854 = 382.7 CID) The difference, of course is that one has a longer "lever" on the crankshaft, but as a result, the piston is also traveling farther on each stroke (the distance of the stroke, FWIW), creating more displacement. More displacement means I can burn more air and fuel on each cycle, creating... more torque.

Now, let's say that I create an "all bore" 383 with the shorter 3.48" stroke of the 350. I'd have to use a 4.18" cylinder bore (4.18 * 4.18 * 3.48 * 8 * 0.7854 = 382 CID). Obviously, the 3.48" stroke crankshaft has a shorter "lever" than the 3.75" stroke crankshaft above. Would you expect torque to differ substantially? In fact, given equal intake components and cam profiles, the two engines will produce almost identical torque curves. Why? Because even with a shorter lever, the "all bore" engine is exerting more force on that lever, because it is burning the same amount of fuel and air, but has a larger surface area (piston crown) to "push on". Neat, huh?"

I find this very interesting and I have to admitt that it makes sense. Any chance of posting some SIM'd torque curves?

great post, Rob

Torque available at the wheels is less at higher speeds but the POWER available at the wheels is the same. Power is what accelerates the car. The rate of change of the RA's angular velocity is very low at higher speeds.

At higher speeds the car isn't fighting accelerating the mass of the car. It is fighting the wind drag *and* where I believe I went wrong in the other thread was the increased rolling resistance from higher weight.

Torque at the wheels, or more accurately, thrust at the tire contact patch (drive wheel torque divided by the rolling radius of the tire) is what accelerates the car. Torque available at the axles is not the same in higher gears, which is why you accelerate much more slowly in 4th gear than you do in 1st.

F = ma

a = F/m

Mass (m) is a constant, so as force (F) decreases in higher gears, acceleration (a) steadily decreases also, until the car cannot accelerate further.

Not necessarily. If you're cruising at 1,600 rpm in 6th gear (a valid example in the Corvette world), it's going to take much longer to get the rotating assembly and drivetrain to spin up if you just step down on the gas, despite the fact that you're already going 75-80 mph. You must downshift and increase gearing multiplication (and engine rpm) to spin up the mass of the rotating assembly and drivetrain faster and accelerate more quickly.

Rolling resistance and aerodynamic drag do increase at higher speeds, but those losses affect force, not mass. The available torque or thrust at the drive wheels is still fighting to accelerate the mass of the car further.

As you can see in Newton's formula above, mass is a constant, and you're still wrong.

It's the RATE of acceleration that makes all the difference. If you can run through a gear in less than 3 or 4 seconds then your rate of acceleration is very large.

You should run through first gear in about 3 seconds and second gear in about 3 seconds. but it takes you much longer to run through 4th gear. It takes me about 25 seconds to run through 4th gear up the back straight at Watkins Glen. That's not a very high RATE of acceleration. Flywheel weight doesn't matter much there.

As an extreme example, a heavy flywheel will not affect your terminal velocity. At that point your wind resistance is perfectly balanced by your HP and you have no acceleration.

In really rough numbers:
In second gear you are accelerating by about 1000 RPM/second If you lost 1/2 second that would be a .000125 per 1000 RPM per second. Running fourth gear in 25 seconds is about 160 RPM per second. So ->.000125 X 160 X 25= the same 1/2 second lost over the entire 25 second distance.

You still lose in the upper gears, just not that much.

ed

Flywheel weight does matter, because heavier drivetrain components slow your rate of acceleration in every gear. It may not be as noticeable in 4th because the rate of acceleration in 4th is much lower than in 1st, but it's still there. Note the green line in the chart below representing drivetrain losses through the gears.

https://www.rx7club.com/attachment.p...chmentid=88046

About as much as in any other gear.

I'm not sure if this is directed to me as far as you thinking I'm looking for an increase in torque from doing this, or if your just talkin in general, but I'm really not looking for any increase. I just simply had the idea of doing this and while I was searching through some old threads (2-3 years old) I noticed they all stated you would loose torque. Obviously I wouldn't want to do this and have a loss in torque since its not what our cars have alot of. I have decided to go through with this and am searching for a slightly used motor to mess with so I guess we'll all have an answer as to what will happen soon. As "RotaryResurrection" stated there won't be any gains from a lighter flywheel or lighter rotors at the crank. There will be a gain in the rear wheels though since less power is lost through the drivetrain due to lighter components. On another note, I really don't see lighter rotors making an extreme effect on daily driveability unless an extreme amount of weight is taken off. Obviously it will change the driving characteristics of the car but I don't see it being anything the driver couldn't adapt to pretty easily, like a lighter flywheel.

-Alex

I'm with Jimlab on this one, how could you justify an increase in acceleration through lower gears, and then the increase in acceleration go away in 3rd and up. That simply doesn't make any since at all. An increase in acceleration wouldn't just vanish in higher gears, it just may not be as noticable, but it would def. be there.

-Alex

Your wrong here Jim.

Torque available at the axles is NOT the reason you accelerate much more slowly in 4th gear than you do it 1st.

Look at your own "losses" graph and see that there is a dramtically increasing drag force, [I]that[I] is why you accelerate much more slowly in 4th vs. 1st. Weight/rolling resistance increases roughly linearly.


HP is what moves the car. Torque does not move anything. POWER moves things.

Like I said, torque at the rear wheels is less in the higher gears, HP available at the wheels doesn't change much at higher speeds.

Rotational inertia does slow you in every gear but the amount is related to your rate of acceleration. Your graphs appear to be showing frictional losses not inertia losses. That graph does not show rate of acceleration anywhere. It could be equally valid for 10 seconds or 10 minutes.

Losing 1/2 a second in 3 seconds is a much bigger deal than losing 1/2 second in 25 seconds. When you reach terminal velocity the inertial losses go to zero.

ed

i read through this whole thread and it made me think of two things. first, what would happen it the rotor face was cut into like that piston crown on page 2. also, what if there was weight added to near the tips of the triangles to add centrifical force?...i imagine it would lower the amount of power? that your engine needs to keep itself running when driving on the highway, but then you would be pushing your brakes and the engine wouldnt be able to slow itself down in stop and go traffic.

From what I've gathered changing the pockets on the rotor faces will add displacement, but will change compression ratio. Its something else I have in my mind but 1 step at a time lol. I've also been thinking of a way to loose weight in the rotor and add/shift weight to the corners of the rotor. I'm not sure exactly how that will effect the motor either, and like I said, one thing at a time. I dont want to start altering everything at once and not be sure wich process made had it go all wrong. Once I get the motor I'll be able to tear it apart and see exactly how the rotor is constructed and I'll also find some bum rotors to cut in half to see how much room I have to play with and what not. I would rather not pull the motor out of my car and tinker with it since its in perfect running condition and less than 28000 miles lol.

-Alex

Sorry Jeff, you are.

Have you ever seen a graph like this?

https://www.rx7club.com/attachment.p...chmentid=88059

Correction, that is only part of the reason you accelerate much more slowly in 4th vs. 1st. See above.

Wrong again Jeff. A vehicle's rate of acceleration (g-force) follows the engine's torque curve, not the horsepower curve. Maximum acceleration is at torque peak in first gear, not horsepower peak. Do some research.

Horsepower is merely a calculation based on torque and rpm. If we converted torque at the axles to horsepower at the axles, you'd still see the same drop in POWER in higher gears.

Good point, the graph does show frictional losses of the drivetrain, not inertia losses. The program isn't that detailed.

I haven't seen anything that proves me wrong yet.

Torque does not move anything. Power moves the car, power in our case is torque x rpm. Plain and simple, PERIOD. Buy a Physics book and read up.

Where did that graph come from? What are the units? LB? That isn't a measurement of power.

550lb*ft/sec is one HP IIRC.

So take another look at the graph, make the units so they actually reflect POWER, to me it looks like your trying to show the *thrust* unit. That is NOT a correct way to characterize acceleration.