http://www.azom.com/details.asp?ArticleID=1219

Heres some info on TI's wear resistance, admitadly i have no clue if it will cause a problem, but generally it is a bad choice for any friction applications. Its also quite a bit softer than iron, and considering ive seen wear rings in steel on the oil seal area of high mileage engines you might want to do some testing first. no to mention the diameter of the hub is very small so the gain will be zero small, remember an object with a radius of zero but infinate mass will have no rotational inertia...

 

Cortc, I trust your ideas but am unclear on how the pulleys will make hp, and have it be shown on the dyno. I'm not doubting you, I'm just a little bit unsure, I'm not too knowledgable in this area of physics. Could you explain to us in detail how it will work to gain power? I am really curious, 86 brings out a good point but I'm not sure I agree with everything he's said. Also, if any other physics masters on the forum could throw in their 2 cents it would be nice. I know their are a few from what I've read that might be able to bring some clarity to this argument. Shelleys_man 06, care to help us out?

 

I know Unorthodox makes horsepower claims for their pulleys, complete with at least allegedly valid dyno charts. 86, are you saying that would be because they're also underdrive pulleys?

jds

 

Oh, but it does. Power is lost through the drivetrain before it reaches the wheels. Everything from the differential to littles pulley on the front of the motor require hp to turn them. Thats why only about 80% of the hp a motor makes actually makes it to the wheels. Redue the load caused by anything that is not the motor itself in the drivetrain (weight and friction caused buy pulleys, the flywheel, the tranny, the drive shaft, the diffefrential, and the axles) and you see an increase in the amount of hp that makes it to the wheels.

Gross hp is a pointless rating that was abandoned by the auto indusrty for just said reasons. All the hp a motor makes doesn't get used to propel the car. But by reducing the weight of the crank pulley, more of that hp will make it to the wheels.

 

Thanks s13, this makes it a lot more clear. Kind of funny how something so simple is so easily overlooked. Good luck on your project Cortc, I'm looking forward to it.

 

No, its still irrelevant to the discussion of whether or not the freed-up horsepower will show up on a brake dyno. I don't believe anyone disputed the fact that reducing rotational inertia along the drivetrain can make you accelerate faster. This reasoning behind the advantages of lightened pulleys, flywheels, etc. is correct, but I think 86rx7's issue was that this freed-up horsepower can not show up on a brake dyno, and shouldn't show up on an inertial dyno since the correct dyno technique for those is designed to minimize those very effects. Other than questioning how significant these changes might be, I don't believe there was an argument with the fact that they theoretically will improve acceleration, so I'm not sure why the whole discussion turned rather nasty. Now, I'm no expert on this stuff, but 86rx7's argument seems sound. If the dynos do in fact show an improvement in horsepower, that would be an interesting addition to the discussion.

jds

 

The dyno shows an increase, it has been measured (I have seen it with myself on numerous occasions including my current testing and on other cars)... The amount of hp/energy potential measured at the engine crank and wheels goes up the more rotational or reciprocating weight is removed from the engines moving parts... Why, because it is not being used to move mass, very simple, the argument raised is an ignorant one that is based on not having a true understanding of the concepts involved... Any dyno including a brake dyno is just putting up a certain known resistance over time to the force applied by the engine; the ability of the engine to overcome this is then applied to a mathematical formula that then converts the amount of work completed into hp... Torque is also calculated at the same time... If I add weight to the engines moving parts, more energy is used in spinning these parts and therefore less is available to work against this known resistance/mass and we get a lower actual hp reading... More of the energy released during the combustion process is allowed to make an affect/action further down the drive train since it is not being used to move mass; this = a higher measured HP reading at the crank and wheels...

 

Wow, ignorance is dangerous... Engines are dyno tested on brake dynos with accessories by manufactures; even racing engines... Let's see, you need a water pump and you need an alternator and if it a production engine in an A/C equipped car you need an A/C compressor... If you reduce the amount of mass and resistance on the front of the engine then "wow" the output on the other side goes up...

Just spoke to a buddy of mine at Ford Racing (Yes the motor sports division...) and they always see an increase in hp when running lightweight pulleys on there brake dynos...

 

Cort, I may have missed it.. but any projected pricing on the group buy? I'd be interested, depending on the price.

 

I'm really getting the vibe that you either dont understand what inertia is, or how a brake dyno functions (or inertial dyno for that matter because rotational inertia is considered error here).

Inertia is resistance to a change in motion. Rotational inertia is the resistance to change of ratiational motion. If you are not accelerating (change in rotational motion) the motor, as on a brake dyno rotational inertia does not factor in in anyway.

You can see this on the front tire on a bicycle if you turn it upside down. When it is stopped, you have to put energy into the wheel to spin it up to a particular rpm, but once it is at that rpm it spins freely on its own, only very slowly slowing down due to the friction in the bearings and air. If the wheel was in a complete vacume with frictionless bearings (i wish!) it would spin forever. So, on the brake dyno, where the engine is braked down untill engine acceleration stops , the sum of the power loss from all the rotational inertia (flywheel, pullys, driveshaft, trans gears, rear end, wheels) is ZERO. They are exactly like the bicycle tire, taking no energy because there rotational motion is not being increased or decreased. The friction in the bearings of the bicycle tire would be equivelent to the drag on the motor from the things like the alternator, ac compressor, friction in the belt system itself, friction in the trans, friction in the rear end, and friction between the tires and the rollers, they do take power away from the motor when it is at a constant rpm. Now, if the pullies arnt underdriving (reducing friction in the alt/water pump etc) how are they going to make more power?

Not only that you seem to thing that the HP freed up from this is a constant, when in fact it is not, it will exponetially decay as the speed at which the object (motor) is accelerating decreases (aka higher gears, like 5th, which you should be dynoing in on an inertial dyno)

so,.. lets just say you did see a peak 10 (!) hp increase in power at 7000 rpm on an inertial dyno done in fifth gear (ive allready established youed see a big fat zero on a brake dyno) you would have to reduce a 4 inch diameter pullies weight by 149 kg, which is ~350 pounds! That same pully that made 10 hp on the dyno in forth gear, would make ~192 hp in first gear!

or let me put it his way, if you removed 10kg (22 pounds!!) from a pully with a diameter of 4 inches, you would get a whopping .615 HP increase! not enough to to measure acuratly on a dyno.

These were calculated with an assumed engine acceleration of 500 rpm/second in fifth gear @ 7k rpm (probably a decent guess) and 1880 rpm/ second in first (3.76(rx8's first gear ratio) x 500 rpm/sec (assumed engine acceleration in fifth gear and a gear ratio of 1:1)

As you can see , on a properly done inertial dyno you SHOULD see zero (because changes so small are beyond the measuring ability of a dyno) results from just reducing the pullies weight by a few pounds.

I suggest you go think up a new theory as to how the world works...


all equations for moment of inertia, angular velocity etc used in the above calculations were taken from these two websites:

http://home.iprimus.com.au/stevebm/dyno_math.htm
http://theory.uwinnipeg.ca/mod_tech/node49.html

 

Let me clarify that im not saying that it wont show on the street. I could actually calculate how much power is freed up in first gear for you if you gave me the exact diameter, weight differance between the new and old pullies and a good approximation of how many rpm/second the rx8 accelerates at in first gear... i would expect it to be ~4ish hp in first but cant be sure unless i have hard numbers.

 

The affects/variables of the additional or reduced mass is dependent on rate of acceleration and velocity/speed of the rotating mass and its polar moment...



This is not an error, its affect is real and can be measured, that is why lightweight and under drive pulleys exist and are manufactured by very reputable vendors including Mopar and Ford Racing...



This is obviously a waste of time, so you win; that is in the little universe that you live in and since the rules in yours don't work in the one the rest of us live in I will not expend any more energy/hp on it since you are just visiting and will never understand with your superior intellect...



Take care, and after your next inevitable post, for the sake of sanity, I will not respond at all for any reason; so please leave my future post/threads alone and I will do the same to yours...

Unsubscribing now...

 

P.S. make sure the rpm per second is at peak power as this is where the most gain will show up.

 

Ok, so now it does free up/show hp gains, make up your mind... Last time I checked dynos exist in the real world and the contact between them and the engine is real...

Later...

 

1)That would proably be why i used 500 rpm/ second? And why i calculated its moment of inertia? I told you all the variables i used, you just have to plug them into the equations/ convert them to metric units,.. i didnt want to type that much, maybe if you actually read my posts and look at the equations you'd see that acceleration rate and moment of inertia are accounted for, do you think i pulled numbers out of my *** or something?

2) Im not the one living in a differnt universe, i used known equations to quantify what were talking about. You on the other hand call me ignorant and do nothing to back up your statments which anyone who toke high school physics can see are wrong. Are you assuming most of your customers never toke physics?

O, and by the way, thats right, they make UNDERDRIVE pullies, something were not talking about here. Not to mention if you actually READ my posts you would see im not disputing the fact lighterweight pullies can make a difference in first/second gear on the street, im disputing the fact that it is dynoable.

Anyone who reads this thread should be able to see that you have presented a load of bull as your argument (not even addressing the points i bring up most of the time), where as i have backed mine up with sources, and MATH. You even arguing that reduced pully weight will show up on a brake dyno shows that you have absolutly no clue what it is. I CANT wait untill people who have taken highschool level physics or greater see this thread and back me up, even though you'll never see it.

 

OK 86rx7,

Lets suppose all of your arguements have been valid - meaning that the flow of information you have presented does infact support your claims. I believe this to infact be true with your arguement. But that is only brings you 1/2 to being correct. For what you say to be correct all of your information must be sound - meaning truthful. If that were true then your arguement would be both valid and sound which would mean that it is correct and logical. However, your claim can not be logical because of the dilemma evident in the question below.

Why would a chasis dyno be able to accuratly show a loss in hp thorugh the driveline on a stock car, but not be able to show any further gain / loss in hp if a change was made to the drivetrain?


(sorry for this post, I just came from an ethics/logics class. :o )

 

I wouldn't butt in here out of fear of somehow winding up as the referee, but I'm about to go offline for a week, so the risk is low of that happening.

86r is right on this one, since his whole point is that the torque that is freed up by lightweight non-underdrive pullies is is freed up when the engine RPM's are changing (just like the torque that's freed up by light flywheels, light rotors, light e-shafts, light brake rotors, light rims, light lugs/nuts, etc.). Reducing spinning weight in the powertrain frees up power for accelerating the car, but only while the car is accelerating. When maintaining constant speed/revs, there is no relief on engine loading because there is no work being done by the engine to keep things spinning at the same rate (except for internal friction, which isn't really affected by just lightening parts; you'd need a change to bearings/lubrication to change friction).

This means that at any given constant RPM, pulley weight doesn't affect the power output of an engine, since lighter pullies only reduce internal "load" when the engine (and therefore the pullies) is revving up. In the case of a car, this applies to all rotating mass from the engine block to the tread on the tires. Reducing this rotating mass (or more precisely, the rotational inertia of that mass) will allow the car to accelerate more quickly, since less work is required just to spin up the powetrain and therefore more is available to increase the linear kinetic energy of the whole car.

However, this also means that any system which measures the power output of the engine (or by extension, the car/powertrain) at a "static" RPM/speed should not be able to detect the difference from changing pulley/flywheel MoI, because there is no internal reduction of load at a fixed RPM.

 

Because the whole of that loss is not rotational inertia, its also friction in the bearings and meshing of the gears and even the tire on the roller. A huge loss of rotational inertia, like lightening all the wheels by 20 pounds each, or changing the flywheel from a 30 pound one to a 9 pound one (both of these items have a large radius) will show up on a inertial dyno as a small gain, which can be magnified the lighter the dyno roller/ the more powerful the car (aka the faster it can accelerate) . The fact that inertial dynos can measure this is considered error, many dynos (especially motorcycle dynos) try to factor this out with a correction factor. A 1:1 gear is used when dynoing to A) try to reduce the friction in the drivetrain to a minimum (The 1:1 gear usually has less gear meshing and such to go through) and B) to make the car accelerate slowly as to not show the loss from the drivetrains rotational inertia.

On a brake dyno however, only the sum of the friction in the drivetrain will be measured so something like lightened pullies or a flywheel wont show up.



Thank you for the support bgreene

 

So are you saying that the 20% average drop in power loss from the motor to the wheels is almost entirely from the friction of the gears in the tranny and diff?

If that were so I would think using Royal Purple or Redline gear oils would show a noticable gain in hp on a dyno because they reduce/optimize friction and reduce heat. However, from my own personal experiece with with such oils I can honestly say that my gain from them I could not feel whatsoever.

HP, by definition, is a measurement of how quickley torque is produced. By reducing rotational mass on an object of any diameter that is connected to the crankshaft will alow an engine to rev faster - thus produce its torque faster which by the definition of the term HP means that more HP will be produced. If this were not true i would expect to see only dyno printouts from pulley companies to show an increase in HP with their products. But that is not the case. Independent magizines that dyno aftermarket parts always show a gain in hp when testing an lightweight pulley, unless the pulley is so light that it effects the ballance of the engine which should only happen if a motor isn't internally balanced or has a seperate harmonic balancer connected to the crank.

 

Well, I wouldn't say that the synthetic gear oils are going to make make that huge of an effect on that power loss. It should help, but in the overall scheme of things, I would imagine the difference would be extremely slight.

As far as the other pulleys for which you've seen dynos, are you sure they're only lightened, and not underdriven? Off the top of my head I can't actually think of any others other than cortc's which are lightened only (not saying they don't exist). Personally I've never been too thrilled about underdriving accessories on what is (at least for me) still a street driven car 100% of the time.

jds

 

I'm not sure how the data sesors that feed into the machines that make dyno charts work specifically, or how the tests are really constructed or run in any specific instance, so I may be way off base with this but....

In theorey, power output can be calculated based on RPM and Torque. Measuring RPM is relatively simple in the automotive world (and is necessary for any dyno chart using RPM for one axis).

If the test setup only measures torque (and calculates RPM based on that reading and RPM), and torque measurements taken in a dynamic situation (engine spinning up, for example), then the test result would indicate an increase in HP, because there is an increase in output torque with less rotating mass in the powertrain.

If the test were configured to measure torque at fixed RPM points, with the engine simply maintaining that rate for some time (only 1-2 seconds would be necessary), then there should be no increase in HP, because the lighter parts only free up torque during acceleration, not while "cruising".

This is why it's important to make sure you're specific about what is being tested for, when reading charts (and if possible, know how the test setup/environment is configured in order to know if a given independent variable is really being tested for). Muddling/witholding much of this kind of information is one of the more common tactics used in marketing (or by anyone else who tries to use some small bit of data to prove a much larger point)

 

Ok FYI everyone, I have it on impeccible authority that the UR pulleys are officially shipping next Friday, October 29th! Flywheel will probably get a ship date after we get back from the SEMA show in Las Vegas (November).

 

"after we get back"?!?!?! you going to sema?

 

LOL, I wish! I mean after THEY get back. :D