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  #61 (permalink)  
Old 05-13-2010, 03:27 PM
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yes its all feel i agree, i cant look at the tack , when the cars seems to stop pulling i shift, whether its in the torgue range or horsepower range i dont know , i would assume its in or slightly after the torgue range .
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  #62 (permalink)  
Old 05-13-2010, 05:00 PM
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Quote:
Originally Posted by ap72
There are a few assumptions, but people don't like to hear "the highest average power down the track produces the fastest times".

You need the highest amount of power to the wheels, perhaps it should read-

Select gears and stall to deliver the peak amount of power to the wheels all the way down the track and you will go as fast as the engine will allow- provided you can get it to hook.
Yeah, I suppose... I guess I've always ASSumed the 'best' 1/4 mile engine would be the best compromise, AFA size vs. powerband goes. I never really thought of it as a HP vs. torque thing.
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Old 05-13-2010, 07:04 PM
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Thus the only curve you need to concern yourself with is the horsepower, NOT the torque. select your gears and stall to keep you as near to the horsepower peak as you can all the way down the track and you will go as fast as the engine will allow.
I will edit this statement to reflect current fact.

Thus the only curve you need to concern yourself with is the torque, NOT the horsepower. select your gears and stall to keep you as near to the torque peak as you can all the way down the track and you will go as fast as the engine will allow.

There...fixed, carry on.

I think this discussion should focus on why you seem to have this statement backwards AP72.
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Old 05-13-2010, 09:08 PM
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come on now guys...you all know it's not HP or TRQ that wins races...Cubic Dollars wins races. Great point chuck.
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Old 05-13-2010, 10:35 PM
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Ap72

Well all I got to say is if people would build combo's CORRECTLY, the data, results, etc will show that an engine's torque is what you really want to shoot for.

Plain example is if you have 2 identical cars lets say 300 hp on both and car 1 has 268 trq and car 2 has 333 trq you will notice that car 2 will take off quicker and harder. Getting it to win depends on the driver!!

I'm a strong believer on trq and most experienced guys do shoot for trq.
If trq was not a factor, then why would big blocks exist?
I've seen plenty of small block claiming 600hp and here comes a big block with 400 hp and eats the small block. And the car with big block almost always more.

If your going to start a thread then I think it should be for the intended purpose of gaining knowledge, and not try to contradict alot of these heavily experienced guys.
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Old 05-13-2010, 10:55 PM
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Main reason for trq

One more thing. The reason you want more torque is because more torque means MORE hp to wheels. There is a mechanical clutch theory I have saved. I have to dig it up for you. I'm sure once you read it, it will clarify why hp and trq come together and why greater trq levels produces higher fptr-force.
(take off or horse power felt when driving)
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  #67 (permalink)  
Old 05-14-2010, 12:06 AM
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Maybe this will shed some light.

I think the problem here is HP is talked about like its a physical quantity, it is not. HP is simply a measurement calculated to define a measurable quantity (torque) to indicate work done.

For example;

You could have a motor producing 1 million HP at some ungodly RPM and not be able to move a car, to be able to move the load you would need some ridiculous thousand gear transmission just to make it move. Conversely you could have an engine with 5HP but a ton of torque and easily move the car with one gear. Cars have finite numbers of gears to select from and have real mass to move...hence why high HP cars with low torque figures require more gears to move them effectively.

Why? To keep the engine in its effective torque curve which allows acceleration!

Eureka!

This is why engine builders define their engine builds by torque production under the curve, they may advertise it by peak HP but its the area under the torque curve that matters. Engine builders everywhere spend millions of hours to increase that area under the curve because torque is what does the work, HP is simply a mathematical byproduct of that effort and is used to define the work accomplished by the torque at a certain angular velocity (rpm).

Clear as mud huh?
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  #68 (permalink)  
Old 05-14-2010, 06:27 AM
How fast is fast enough?
 
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Quote:
Originally Posted by 4 Jaw Chuck
Maybe this will shed some light.

I think the problem here is HP is talked about like its a physical quantity, it is not. HP is simply a measurement calculated to define a measurable quantity (torque) to indicate work done.

For example;

You could have a motor producing 1 million HP at some ungodly RPM and not be able to move a car, to be able to move the load you would need some ridiculous thousand gear transmission just to make it move. Conversely you could have an engine with 5HP but a ton of torque and easily move the car with one gear. Cars have finite numbers of gears to select from and have real mass to move...hence why high HP cars with low torque figures require more gears to move them effectively.

Why? To keep the engine in its effective torque curve which allows acceleration!

Eureka!

This is why engine builders define their engine builds by torque production under the curve, they may advertise it by peak HP but its the area under the torque curve that matters. Engine builders everywhere spend millions of hours to increase that area under the curve because torque is what does the work, HP is simply a mathematical byproduct of that effort and is used to define the work accomplished by the torque at a certain angular velocity (rpm).

Clear as mud huh?
You don't need a thousand gears, just a few, and a proper stall conveter. If torque was what won races then why is it some 327's aren't beaten by stock 400's? There's a lot of them with LESS torque but more power...

My phrase was worded correctly, and I think some are beginning to see that.

And as often as you talked about what hp is, you never once mentioned time (or rate)... Time is the invaluable factor that makes hp significant in a race.

One thing that must not be taken for granted though- STALL AND GEARING. If you are stalled and geared incorrectly then the peak average power to the wheels will not occur around the engine's horsepower peak- which is why it is SO important to match gears and stall to a camshaft.

Now it should be clear as mud.
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Old 05-14-2010, 06:48 AM
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All of this seems to be dandy and informative however I'm still not sure I'm understanding the point.I don't think re-inventing the wheel is going to happen here and I am fairly sure that reasearch and development for all of these big money race teams haven't overlooked anything.If they have maybe AP can get himself a good paying job telling them what to do to get down the track faster.Not trying to be an *** just asking.This only seems to apply in heads up racing.I can tell you if you do put your 327 in a heads up class against a 565" alcohol blower motor you are gonna get smoked no matter how you drive it.

Last edited by BBCMudbogger; 05-14-2010 at 06:53 AM.
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  #70 (permalink)  
Old 05-14-2010, 06:55 AM
How fast is fast enough?
 
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Quote:
Originally Posted by BBCMudbogger
All of this seems to be dandy and informative however I'm still not sure I'm understanding the point.I don't think re-inventing the wheel is going to happen here and I am fairly sure that reasearch and development for all of these big money race teams haven't overlooked anything.If they have maybe AP can get himself a good paying job telling them what to do to get down the track faster.Not trying to be an *** just asking.

being dandy and informative is the entire point of internet forums... And of course the camaraderie. You are right that most of the race teams now these things already, but some of the local Saturday night heroes do not, now they have something to think about when selecting their next converter or gear purchase.
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  #71 (permalink)  
Old 05-14-2010, 06:57 AM
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After reading all these posts I am not going to attempt to add any technical insight, although I think I know the answer and it's right along what 4 Jaw Chuck said. There are many on this board who seem to understand what they're talking about when it comes to force, torque, energy/work, and power. However, I will say that there seems to be a gap between those who have the knowledge and those who have attained understanding. A person with knowledge has studied a topic and would have read about a topic, seen it, heard it presented, and/or discussed it with other knowledgeable people. A person with understanding has applied knowledge to specific tasks and has developed confidence and comfort in the subject. High school physics is NOT a prerequisite to understanding the physical concepts discussed in this thread, nor is reading a host of articles in car magazines or online postings from 'experts' about whether max HP or TQ wins races. In my opinion, knowledge of calculus-based physics and/or thermodynamics is paramount to comprehend WHY one is better than the other. Without that you end up repeating what other people have said as if you understand it. Again, there are people on this board who do not have this type of education but they still understand it, but they did it by applying their knowledge over a period of time, not by reading articles or taking a high school physics class.

Just my $.02
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  #72 (permalink)  
Old 05-14-2010, 07:26 AM
How fast is fast enough?
 
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PontaicPhill, I don't know if you have taken calc based physics and all of that jazz, but I hope that it is NOT required for basic understanding. I will admit that when I was younger I thought that shifting from hp peak to tq peak was the way to go, and as I became more educated and understood more I began to see that this was yet another old wives' tale in racing, and there are a LOT of them.

I did understand it after I took a lot of physics and engineering classes but I would like to think that it is not required for most to understand it- again I'll never know for sure. Maybe you're right though, all of the guys I know that grasp these ideas fairly easily are pretty well educated, either through college or a lot of self reading and instruction...

Maybe that is the point of all this, reducing the need for "education" when trying to understand a fairly simple concept. "Simple" can mean something entirely different though depending on your current level of understanding and that is something that I have a habit of taking for granted.
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Old 05-14-2010, 07:43 AM
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ap72, I could not tell you the best way to run a car down the track. I just don't have the experience to know one way or another. You are absolutely right, there are a lot of old wive's tales going around, like "Pennzoil is good for cars with high miles". Ultimately, the best thing for you to do is go out and experiment with your shift points and determine experimentally what gives you what you want. Shifting one way might give you the best ET in the 1/4mile, and if that's what you want then dial that in and stick with it. Then you might do some research to try and explain WHY those shift points work the best. Sounds like you have already done the research, so it's time to go out and test your theory.

As far as my education, I will only mention because you ask and I in no way mean to say my education makes me more intelligent than anybody else (just ask my wife ). I have taken way too much calculus, physics, thermo, machine design, etc. BSME from Nebraska, just got my Engineering Masters from K-State. Getting ready to take the PE exam this October (just mailed the application yesterday... ). Although these expensive pieces of paper can be a strong foundation for understanding, they are no substitute for years of experience and they are not necessary to win races. Most of what I do professionally involves structural design, but knowing what I know about power systems tells me that without a strong knowledge base in physics it can be difficult to comprehend things like energy and power.
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Old 05-14-2010, 07:50 AM
How fast is fast enough?
 
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Quote:
Originally Posted by PontiacPhil
ap72, I could not tell you the best way to run a car down the track. I just don't have the experience to know one way or another. You are absolutely right, there are a lot of old wive's tales going around, like "Pennzoil is good for cars with high miles". Ultimately, the best thing for you to do is go out and experiment with your shift points and determine experimentally what gives you what you want. Shifting one way might give you the best ET in the 1/4mile, and if that's what you want then dial that in and stick with it. Then you might do some research to try and explain WHY those shift points work the best. Sounds like you have already done the research, so it's time to go out and test your theory.

As far as my education, I will only mention because you ask and I in no way mean to say my education makes me more intelligent than anybody else (just ask my wife ). I have taken way too much calculus, physics, thermo, machine design, etc. BSME from Nebraska, just got my Engineering Masters from K-State. Getting ready to take the PE exam this October (just mailed the application yesterday... ). Although these expensive pieces of paper can be a strong foundation for understanding, they are no substitute for years of experience and they are not necessary to win races. Most of what I do professionally involves structural design, but knowing what I know about power systems tells me that without a strong knowledge base in physics it can be difficult to comprehend things like energy and power.
I sit for mine in October too! Good luck!
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Old 05-14-2010, 08:31 AM
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Originally Posted by ap72
I sit for mine in October too! Good luck!
Good luck to you too! Everybody tells me the application is harder than the actual test. Took me a week to fill it out the flippin' thing.

As far as TQ vs HP, my computer is sitting here crunching on an FEA, so I had some time to think about it. I would say that torque is a bigger factor in road races (which was Mr. Shelby's area of expertise, correct me if I'm wrong), where HP may be more important in drag racing. Here's why:

When you're going through chicanes and constantly accelerating/decelerating, F=ma tells me that torque to the rear wheels will get you up to speed quicker than the other guy. In a road race you are not granted the luxury of keeping the engine at peak power output all the time. Accelerating from one turn to the next will result in a lower lap time.

When it comes to drag racing, HP may be more important because more energy converted from fuel energy in the engine to kinetic energy of the car equals faster MPH and ET. I believe the area under the HP curve, NOT the torque curve, gives total energy output (since horsepower is energy per unit time, and integrating the HP curve multiplies energy/time by time. Integrating the torque curve would give units of lb-ft-s^2 ), integrating the HP curve gives total energy output during that period of time. The kinetic energy of your car is 1/2mv^2, so to maximize the velocity you would want to maximize kinetic energy, which we now know is done by maximizing the area under the HP curve. If I was a drag racer I would probably want to use a CVT, and I would set it up to keep the ratio such that the engine is constantly at peak power output, NOT peak torque.
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