[Mister Bone]

Torque is real and can be measured.

Horsepower is a mathmatical formula based on tq numbers. Can't really measure it.

I could come up with my own formula and say it gives me APF (asshole pucker factor)

It would use a math formula to give me this based on the amount of tq measured.

Does it or will it mean anything? No.....because in the end the rotating crank, the tq from it, is what does all the work.

HP is for bragging, TQ is for racing. What is under the tq curve is all that matters.


Flame suit on

 

[Mister Bone]

Who wants to tackle this one, TM?

Why can you dyno one car with low profile 19's on it and then change them out to say 16's of the same overall rolling circ. and have the hp and tq readings be different? :idea:

All else being equal and the runs back to back with only the rim/tire change. And then switch back to see the same results the other way.

And who can tell me which will give the better readings?

 

[Mister Bone]

Who wants to tackle this one, TM?

Why can you dyno one car with low profile 19's on it and then change them out to say 16's of the same overall rolling circ. and have the hp and tq readings be different? :idea:

All else being equal and the runs back to back with only the rim/tire change. And then switch back to see the same results the other way.

And who can tell me which will give the better readings?

The readings should be the same. Tire size should have no affect. On the other hand, chassis dynos do not give repeatable results. Figure an error of +- 7%. That's probably what you're seeing.

Size will be the same, circ. and width. Only change will be the sidewall height. Even keep the same compound and air pressure.

The results will change with the two sizes. I would like to hear who has what to say as to why it does.

One will give higher, the other lower. This will be repeatable, not to the exact number but in the same direction (up and down )

 

[Mister Bone]

/images/graemlins/laughing.gif I'm not touching this one! /images/graemlins/freak

because I haven't got a bloody clue :doh:

:lolcry:

But I have heard of this before - bugger it - here's an opinion then

I think the problem is that chassis dyno's are not as accurate as engine dynos - and therefore they are great for tuning but not the most reliable source for real life power. If they were dead accurate - as Eric says - there'd be no change by swapping gears or wheels. I have no idea which wheel size gave most power... which one?

And why do you think that is?

Lower profile gives a lower reading. Sizes (width etc.), pressure, compound, etc. be equal

As to why, I can't really explain it. It is beyond my ability to put into words. :bonk:

I was hoping you could tell us in simple English.

 

[Mister Bone]

I'm not sayin' you're wrong Jerome, I just don't think you're right.

I really wish I could prove this, but it is beyond my limited use of the English language. /images/graemlins/laughing.gif

Try this, think about the amount of tire sidewall flex. When you wind up that engine on the chassis dyno think about all the flex. The "wind-up" if you will.

And why do we use drag slicks with wrinkle walls ?

That is just one of the factors that make this scenario possible.

Edit:

I see TM is on to it. I knew with time he would come up with some ideas. :thumb: I need to learn to type faster. /images/graemlins/laughing.gif

 

[Mister Bone]

Ok - here's a wild stab in the dark

maybe the bigger sidewalls twist more and this twisting when it reaches its limits provides a counter force that actually helps the power - kinda like a pendulum effect... kind of...

maybe not

:help:

:screwy:

:leaving:

Sidewall flex = stored energy :nod: Think wrinkle walls

Keep goin' Barry, you are on a roll. :thumb:

 

[Mister Bone]

Jerome - if the rolling circumfrence remains constant, then the dyno doesn't know wether or not it's a lo-pro 19" or a 16" wheel/tire combo. If the total circumference is 3.14*19"= roughly 60" for both, then it should register the same. In fact, I would say that if anything, the 19" lo-pro, real stiff sidewalled tire would give a bigger reading, because of the low amount of sidewall flex and reduced loss of energy resulting from it.

But that's just something that popped into my head, so it could be /images/graemlins/bs

Clint re-read what TM and I both put up in our last few posts. Does any of it make any sense to you?
If yes, please tell me what you think about it.
If no, tell me your take on it.
Not a dig at all, just want you ideas on this.

Thanks

All this thinking is giving me a headache :bonk:

:rofl:

 

[Mister Bone]

Ok - here's a wild stab in the dark

maybe the bigger sidewalls twist more and this twisting when it reaches its limits provides a counter force that actually helps the power - kinda like a pendulum effect... kind of...

maybe not

:help:

:screwy:

:leaving:

Sidewall flex = stored energy :nod: Think wrinkle walls

Keep goin' Barry, you are on a roll. :thumb:

The dyno spins counterclockwise and the tire is spinning the opposite direction. When the operator hits it, the sidewall flex is going to pull power out of the reading because it doesn't trasmit the power as accurately to the drum.

Rotational direction has no bearing on this, the sidewalls are the "energy storage area" regardless of the direction.

 

[Mister Bone]

I'm not sayin' you're wrong Jerome, I just don't think you're right.

I really wish I could prove this, but it is beyond my limited use of the English language. /images/graemlins/laughing.gif

Try this, think about the amount of tire sidewall flex. When you wind up that engine on the chassis dyno think about all the flex. The "wind-up" if you will.

And why do we use drag slicks with wrinkle walls ?

That is just one of the factors that make this scenario possible.

Edit:

I see TM is on to it. I knew with time he would come up with some ideas. :thumb: I need to learn to type faster. /images/graemlins/laughing.gif

Actually your word picture was a lot better than mine - what you say makes sense. What we need now is wind up tires - /images/graemlins/supergrin.gif

Like this?

Not the best photo

[image]http://www.kalittaracing.com/photos/2003/03_indylc_004.jpg[/image]

 

[Mister Bone]

BTW - why is 5252 the magic number in the relationship between horsepower and torque?

Math formula. Exactly why that number is beyond me.

Here, knock yourself out. /images/graemlins/laughing.gif

If you would like more math to rack your brain just say the word. :nod:

************************

Formulas for brake horsepower

horsepower = rpm x torque / 5252

torque = 5252 x horsepower / rpm

brake specific fuel consumption = fuel pounds per hour / brake horsepower

bhp loss = elevation in feet / 1000 x 0.03 x bhp at sea level

Formulas for indicated horsepower & torque

horsepower = mep x displcement x rpm / 792,00

torque = mep x displacement / 150.8

mep = hp x 792,000 / displacement x rpm

mep = hp x 792,000 / displacement x rpm

mechanical efficiency = brake output / indocated output x 100

friction output = indicated output - brake output

taxable horsepower = bore2 x cylinders / 2.5

 

[Mister Bone]

Ok - here's a wild stab in the dark

maybe the bigger sidewalls twist more and this twisting when it reaches its limits provides a counter force that actually helps the power - kinda like a pendulum effect... kind of...

maybe not

:help:

:screwy:

:leaving:

Sidewall flex = stored energy :nod: Think wrinkle walls

Keep goin' Barry, you are on a roll. :thumb:

I feel like the constipated mathematician who worked it out with a pencil...

I've got a firm grip of the turles head - but the bugger won't come out...

I think the roll has come to a stop - I can't go beyond the stored energy released bit - but on that basis - a drag slick must really store some energy!

Coffee now - head hurts /images/graemlins/freak /images/graemlins/surrender

Like you would not believe. :nod:

Have you seen the pics of slicks on Fuel cars when they go "flat" coming up the backside?

I will see if I can find a pic of this too.

Did you happen to see the pic I posted above?

 

[Mister Bone]

I got it!!!

Jerome - pick me pick me

please pick me

ok - I think that if we look at the drag slick pic then we see the story.

It takes a lot of power to twist those babies - that will suck up a lot of energy and power...

BUT

once the limits of that tire are reached - that energy has not been wasted or lost - a lot of it is stored and then released.

If that happens on a dyno - that will definitely add measurable hp at the wheels during that process - I'd think that a Top Fuel slick twisted up to the max would unleash enough torque to move a small car.

Am I right?

Or do i get the bozo prize?

I knew you would come up with some answers. :thumb:

We are getting there. :cheers:

You can carry on, my head does hurt bad. Not from this......I don't think. /images/graemlins/laughing.gif

There are so many variables with these things that we could be here forever talking about them.

 

[Mister Bone]

Yes Dean, but which way are we going with this? I got lost during the trip. :bonk:

 

[Mister Bone]

Fair enough Mark - but by your figures - how many hp would it take to shoot a 2200lb dragster 6" from a stop in 0.5 seconds running the gearing they run?

I submit it is measureable - and that maintaining that deflection on the tire on a rolling dyno will pick it up...

Wouldn't prima face' evidence be that others have done just that?

Seeing how they 60 foot in under a second and reach over 100MPH before that mark it is one hell of a lot of power. :nod:

The tq sensors on Doug Kalittas (to rear dif) car has shown approx. 8000 HP. I forgot the tq numbers.

Shit I am straying here... :bonk:

 

[Mister Bone]

If there wasn't a lot of useful energy stored in the tire sidewall, they wouldn't need beadlock screws to keep them from slipping on the rim. You can either do it with screws, or internal pressure. The correct engineering term for this phenomenon is "rimpull."

OK, this is true. I was saying that about stored energy before.

But I got lost in what your point was...sorry but I am about brain dead right now.......too many things going thru my head.......must go back and re-read this.

 

[Mister Bone]

By the way Barry, that stored up energy in the tire isn't ever released as power measured on the dyno. That's because as that tire flexes, it remains flexed althrought the run; the power transferred the the wheels increases and increases throughout the run and the tension on the sidewall isn't released until after the power is disengaged at the end of the run.

That stored energy in the sidewall doesn't show up on the dyno.

Ah but yes it does.

Remember we are not talking race slicks so the amount of wind-up will be very small, but enough to have an effect.

God I wish I could explain this. :bonk:

 

[Mister Bone]

Ah but yes it does.

Remember we are not talking race slicks so the amount of wind-up will be very small, but enough to have an effect.

God I wish I could explain this. :bonk:

You can explain it fine. What are you talking about, a Viper on a dyno or what?

I forgot wtf I as talking about /images/graemlins/laughing.gif

Oh ok....Tire rim size in general and how it effects dyno readings.

Take a Viper, dyno with 16" wheels and 19" wheels and see which give the higher numbers. Both same OD, width, compound, tread design, and pressure.

 

[Mister Bone]

Same OD (and weight) = same reading by laws of physics.

However, I think your point was that due to the greater sidewall flex of the 16" combo, the reading will be different. Assuming you pump up the 16" combo adequately, the flex will be neglibible and the difference will be lost in the noise of any series of dyno pulls. And if you did not pump up the 16" combo, the reading would be less, because energy is wasted in the tire flex instead of being transferred to the drum (there is no traction issue here like with the dragster from rest).

Well I don't have a dyno, rwd car, and two sets of rims/tires so I can't prove this. But I have seen it in person, I try not to talk out my ass, but well at times... /images/graemlins/laughing.gif

But how about I throw another kink into this /images/graemlins/laughing.gif

Rotational mass and its location between the 16's and say 19's again :doh:

Same stats as the above equation.

Discuss

 

[Mister Bone]

I am going to let you guys take it from here. I need to find a better way to say what I need to say. And maybe dig up more info on this.

Too bad my friends shop has an engine dyno cell. No chassis dyno. Getting to the chassis dyno is expensive around here. And I no longer have a rwd car to use.

Carry on....