Am I Crazy: New but Quick Turbo/Supercharger Math?

[Kevin Shasteen]

Kevin,

 

1) If you want any respect for your equations..,

 

2).., these equations need to be based on something more tangible than fudging numbers around from just a few sources. You mentioned that your equations are similar to horsepower calculators that use 1/4mile times. Those equations are built from the simple F=ma equation. You have not started from an equation that governs a law of physics, but instead taken two numbers and a couple variables and figured out a fudge factor to get your solution. I am not a naysayer, but someone who holds a degree in mechanical engineering and someone who understands that an equation should be based in something other than just a few small bits of empirical data. Equations based on empirical data are extremely vulnerable to error.

 

3) .., I tried very hard to not rain on your parade last time, but I think it is time that some rain starts to fall.

 

4) .., What you have created is something that fits for a small set, with very few variables. Yes it seems to work, but you can't really say that it holds much merit.

 

5) .., And just the same with these programs as your equation, if you change the variables out of the range of what is mapped in the database, then your result is useless.

 

Zguy,

 

For starters, thanks for your input as I dont consider you or anyone else adding to the conversation as a naysayer - but, I'm not looking for the objectives you have posted as I am very familiar w/the obvious variables involved in engine modeling.

 

As Z8 alluded to, I'm looking for the unknown answers that apparently none of us can offer. I have no problem admitting when I dont know something. that is why I posted this thread hoping to get addt'l input. W/out further data from non V8 tubo/supercharger spec sheets; we have to this point chalked the 14.7 constant up to being a coincidence.

 

 

But, FWIW;

 

1) I'm not looking for respect. I'm looking for real responsive answers, not non-responsive answers. I dont care about respect as Math never cares about respect. All that we should care about is the issue at hand on a non bias approach. The question that this thread wanted is to identify, qualify, and offer a repeatable process in other and all turbo/supercharger builds relative to the constant being discussed.

 

You and others are correct in that this constant, by itself is unexplainable. That is why I posted the thread. The fact that this constant by itself is "Not Understood" is why I posted the thread.

 

2) I didnt bring up the 1/4 mile formula to make the point as to what the equation is made up of. If you think the 1/4 mile formulas are made up of only scientific variables then you would be mistaken. I brought the 1/4 mile formula point up to address the fact that anyone can use those formulas wheather you have a car or dont have a car.

 

The formula is theoretical if you dont have a car. If you dont have a car you can use that formula to obtain theoretical required hp of a theoretical car weighing [x] lbs reaching [x] mph consuming [x] amount of time through the traps.

 

These theoretical #'s give the end user real #'s relative to a potential needed to reach a desired goal..., this is not a bad thing, this is a good thing! My quest to qualify hp in as many ways as I can goes straight to this point, the more data input you have (regardless if you understand it or not) regardless if you do or dont have an actual engine or car; the more data inputs you have the closer to your objective you will actually come w/minimal R&D and less wasted dollars once your project does actually begin.

 

BUT, since you brought up that the 1/4 mile formulas being purely scientific; could you please tell me what the 5.825 and the 234 constants represent for determining:

 

HP = ((Car Weight / (ET/5.825)^3)

HP = (mph / 234)^3 x Car Weight

 

Dont try figuring out the constants as I will save you the trouble. Patrick Hale invented these equations, or was the first to admit the equations existed to the public. He claimed the constants were determined from countless hours of empircal numbers crunching. Patrick Hale was not only a drag racer he was also an engineer and a computer programmer.

 

So, if he can admit that the constants either dont mean anything scientific or, at this time are not understood; why cant other constants to other equations also be nothing else than a constant complimenting other real scientific data points?

 

I am personally thankful to Patrick Hale who "fudged" his numbers to give the world the 1/4 mile equations.

 

Another example of "fudged" constants is the overall gearing ratio equation using 335 for a manual trans and 340 for an automatic trans. That equation is:

 

Automatic Trans

Overal Gearing Ratio = ((Tire Diameter / 340) x (RPM / MPH))

 

Manual Trans

Overal Gearing Ratio = ((Tire Diameter / 335) x (RPM / MPH))

 

Larry Shepard created this equation and also admitted that he underwent countless hours of numbers crunching to empirically come up w/the 335 and 340 constants.

 

When a post implies that this thread's constant isnt understood or cant be qualified in itself is not an answer; it is a non-resposive answer. I know the negatives and am not looking for negatives. I am looking for real responsive input.

 

Somtimes science drives the issue and sometimes the little guy working out of their garage or kitchen table drives the issue.

 

The purpose of this thread initially wasnt to disprove or prove the constant. The purpose of this thread was to obtain:

 

a) Why the constant exists

What the constant represents

 

In that quest if (apparently none of us can) give real answers to those two issues, then I guess it is implied that the constant is nothing more than a coincidence...until proven otherwise.

 

3) An idea isnt about posturing one's self to rain on someone's parade. But that is ok as I have a very heavy duty rain coat complimenting my very heavy duty umbrella.., rain away; all that I ask for this thread or any thread is to not posture negatively w/non responsive answers but to try to positively add to the issue at hand. If I (we) dont have a real answer then I (we) need to admit. "I (we) dont know". I dont know what this constant really means; again that is why I posted the thread.

 

4) Your point that this constant only fits a small set of variables is a good point. For you to say it has no merit is again negative. If I, or anyone, is building an engine w/those small set of paramters; then this constant is a very applicable one w/relative merit.

 

5) You just made my point for qualifying parameters w/in a specific operating range. If you are using point#5 as an argument to NOT qualify parameters, then there never would be any development of any kind. In order to "develop" someone has to alter the already accepted knowns; otherwise you have zero development.

 

At this point in time w/out any other input, I can accept the fact that this constant does only work for a small set of parameters and w/out further input have accepted the constant as a coincidence.

 

I'm still not going to give up on it; as I will be trying to obtain input from the non V8 turbo/supercharged build spec sheets as those articles present themselves.

 

Thanks for everyone's input.

 

Kevin,

(Yea,Still an Inliner)

[Kevin Shasteen]

Kevin,

 

1) If you want any respect for your equations..,

 

2).., these equations need to be based on something more tangible than fudging numbers around from just a few sources. You mentioned that your equations are similar to horsepower calculators that use 1/4mile times. Those equations are built from the simple F=ma equation. You have not started from an equation that governs a law of physics, but instead taken two numbers and a couple variables and figured out a fudge factor to get your solution. I am not a naysayer, but someone who holds a degree in mechanical engineering and someone who understands that an equation should be based in something other than just a few small bits of empirical data. Equations based on empirical data are extremely vulnerable to error.

 

3) .., I tried very hard to not rain on your parade last time, but I think it is time that some rain starts to fall.

 

4) .., What you have created is something that fits for a small set, with very few variables. Yes it seems to work, but you can't really say that it holds much merit.

 

5) .., And just the same with these programs as your equation, if you change the variables out of the range of what is mapped in the database, then your result is useless.

 

Zguy,

 

For starters, thanks for your input as I dont consider you or anyone else adding to the conversation as a naysayer - but, I'm not looking for the objectives you have posted as I am very familiar w/the obvious variables involved in engine modeling.

 

As Z8 alluded to, I'm looking for the unknown answers that apparently none of us can offer. I have no problem admitting when I dont know something. that is why I posted this thread hoping to get addt'l input. W/out further data from non V8 tubo/supercharger spec sheets; we have to this point chalked the 14.7 constant up to being a coincidence.

 

 

But, FWIW;

 

1) I'm not looking for respect. I'm looking for real responsive answers, not non-responsive answers. I dont care about respect as Math never cares about respect. All that we should care about is the issue at hand on a non bias approach. The question that this thread wanted is to identify, qualify, and offer a repeatable process in other and all turbo/supercharger builds relative to the constant being discussed.

 

You and others are correct in that this constant, by itself is unexplainable. That is why I posted the thread. The fact that this constant by itself is "Not Understood" is why I posted the thread.

 

2) I didnt bring up the 1/4 mile formula to make the point as to what the equation is made up of. If you think the 1/4 mile formulas are made up of only scientific variables then you would be mistaken. I brought the 1/4 mile formula point up to address the fact that anyone can use those formulas wheather you have a car or dont have a car.

 

The formula is theoretical if you dont have a car. If you dont have a car you can use that formula to obtain theoretical required hp of a theoretical car weighing [x] lbs reaching [x] mph consuming [x] amount of time through the traps.

 

These theoretical #'s give the end user real #'s relative to a potential needed to reach a desired goal..., this is not a bad thing, this is a good thing! My quest to qualify hp in as many ways as I can goes straight to this point, the more data input you have (regardless if you understand it or not) regardless if you do or dont have an actual engine or car; the more data inputs you have the closer to your objective you will actually come w/minimal R&D and less wasted dollars once your project does actually begin.

 

BUT, since you brought up that the 1/4 mile formulas being purely scientific; could you please tell me what the 5.825 and the 234 constants represent for determining:

 

HP = ((Car Weight / (ET/5.825)^3)

HP = (mph / 234)^3 x Car Weight

 

Dont try figuring out the constants as I will save you the trouble. Patrick Hale invented these equations, or was the first to admit the equations existed to the public. He claimed the constants were determined from countless hours of empircal numbers crunching. Patrick Hale was not only a drag racer he was also an engineer and a computer programmer.

 

So, if he can admit that the constants either dont mean anything scientific or, at this time are not understood; why cant other constants to other equations also be nothing else than a constant complimenting other real scientific data points?

 

I am personally thankful to Patrick Hale who "fudged" his numbers to give the world the 1/4 mile equations.

 

Another example of "fudged" constants is the overall gearing ratio equation using 335 for a manual trans and 340 for an automatic trans. That equation is:

 

Automatic Trans

Overal Gearing Ratio = ((Tire Diameter / 340) x (RPM / MPH))

 

Manual Trans

Overal Gearing Ratio = ((Tire Diameter / 335) x (RPM / MPH))

 

Larry Shepard created this equation and also admitted that he underwent countless hours of numbers crunching to empirically come up w/the 335 and 340 constants.

 

When a post implies that this thread's constant isnt understood or cant be qualified in itself is not an answer; it is a non-resposive answer. I know the negatives and am not looking for negatives. I am looking for real responsive input.

 

Somtimes science drives the issue and sometimes the little guy working out of their garage or kitchen table drives the issue.

 

The purpose of this thread initially wasnt to disprove or prove the constant. The purpose of this thread was to obtain:

 

a) Why the constant exists

What the constant represents

 

In that quest if (apparently none of us can) give real answers to those two issues, then I guess it is implied that the constant is nothing more than a coincidence...until proven otherwise.

 

3) An idea isnt about posturing one's self to rain on someone's parade. But that is ok as I have a very heavy duty rain coat complimenting my very heavy duty umbrella.., rain away; all that I ask for this thread or any thread is to not posture negatively w/non responsive answers but to try to positively add to the issue at hand.

 

If I (we) dont have a real answer then I (we) need to admit. "I (we) dont know". I dont know what this constant really means; again that is why I posted the thread.

 

4) Your point that this constant only fits a small set of variables is a good point. For you to say it has no merit is again negative. If I, or anyone, is building an engine w/those small set of paramters; then this constant is a very applicable one w/relative merit.

 

5) You just made my point for qualifying parameters w/in a specific operating range. If you are using point#5 as an argument to NOT qualify parameters, then there never would be any development of any kind. In order to "develop" someone has to alter the already accepted knowns; otherwise you have zero development.

 

At this point in time w/out any other input, I can accept the fact that this constant does only work for a small set of parameters and w/out further input have accepted the constant as a coincidence.

 

I'm still not going to give up on it; as I will be trying to obtain input from the non V8 turbo/supercharged build spec sheets as those articles present themselves.

 

Thanks for everyone's input.

 

Kevin,

(Yea,Still an Inliner)

[zguy36]

Kevin,

 

By raining on your parade, I wasn't trying to be negative, just truthful. What you are in a quest to achieve is something very difficult, if not impossible. Lets turn this conversation around and I'll try to be a little more helpful in what I am trying to explain.

 

 

Lets go back to your 1/4 mile horsepower calculator.

 

Using your equations on my setup, you get very different numbers.

 

HP = ((Car Weight / (ET/5.825)^3) ==> ((2700/(13.8/5.825)^3)=203.1

HP = (mph / 234)^3 x Car Weight ==> (109/234)^3 x 2700 = 272.9

 

This equation uses empirical data that fit a set of numbers. Now looking at this setup, it seems as though my data would be an outlier. When this equation was made, it as based on a set of data that most likely included a set of drag race vehicles. Now you put my data in there, from a car with suspension and tires not set up for drag racing, and your numbers come out screwy.

 

If your vehicle is properly set up for drag racing, then these equations will come out very close to yielding the same answer. The worse your vehicle is set up for racing, the worse the spread will be.

 

 

 

Now, there are much better equations to calculate horsepower. Using simple kinematic equations you can very accurately calculate horsepower. Products such as g-tech use an accelerometer and these equations to do this.

 

To accurately calculate horsepower without a dyno, use this equation

 

d=vit+1/2at^2 Apply this equation to a small section of time when the vehicle is at a rate of around forty mph, which would have negligible wheel spin (for most vehicles) and little drag. This gives you a much more accurate answer.

 

 

 

To make your equations more accurate, start holding some variables as constants. You seem to be on to something for normally aspirate engines. Hold this as a constant. Also, make some assumptions to reduce the variables. Assume that the exhaust is sufficiently large to not cause backpressure issues. Also, assume that the intake is sufficiently large to not cause breathing issues. Now, you have an equation that fits a large set of engines and weeds out the outliers.

 

My point is that to extend this equation to turbocharge engines will be impossible. Since there are many good setups that are so different, you won't be able to map them with an equation. Keep to the NA engines and you might go somewhere.

[Kevin Shasteen]

BTW, X64v; thanks for the CFM chart for the I6 Datsun head.

 

Zguy,

 

Thanxs for sharing your hp equations; I am an equation junky! I too think the 60hp spread is too much and because of that have refined my approach to the performance engine parameters for a specific level of performance desired.

 

Btw; I do have the normally aspirated hp thing down pretty tight. This is why I was kind've shocked when this 14.7 turbo/supercharger constant jumped out at me; as my exposure to turbo/superchargers is one dimensional (very little knowledge base). That is why I asked for your/others input - knowing there are some pretty smart cookies floating around on Hybridz.

 

FWIW; one variable in helping me to quality the foundation of any performance engine is in qualifying the size (small, medium, large) of the cyilnder heads relative to the cylinder. Once that qualification has been made I can then factor in the relationship to the Combustion Chamber as this is relative to the DCR SCR relationship. I touched on this in an earlier post but didnt really give details, is to convert the Cylinder in the block to a cc measurement. Then take that number and divide it into the Cylinder Head's Intake Port cc. This gives a constant, a relationship if you will between the cylinder head and the the cylinder. Once you have done this a few dozen times you will see a pattern. This is basically the process I follow when analysing any build.

 

You can then take that Cylinder Head/Cylinder constant and categorize it into a certain level of performance. This process works for all levels of performance regardless of pump gas or race gas. The problem I have w/this process is that very few engine build up spec sheets/dyno print outs, found in articles or how to books, hardly ever give the VE% column.

 

I still agree w/you and understand the nuances of subtle modifications in the variables; such as suspension changes, ect. How I see any theoretical is that its purpose is not to give absolutes. Their purpose is to get the end user close to an objective.

 

The equations given as examples were not my equations; they are equations that have been used for a few decades now. In understanding any theoretical, the end user must understand "the spread" will always be at a low, medium, to high potential for success.

 

I would add to your posts that a rule of thumb when choosing to participate in any level of performance competition, regardless if it is full race, street/strip, or hot to mild street engines; is that a certain set of parameters will apply to each category of perfomance.

 

For instance, the Do it yourselfer, will most often build a NA engine in the 1.00 to 1.35 hp/ci range, while most of the Do it youreslfer turbo/supercharger set ups will fall in the 1.35 to 1.65 hp/ci range. So, w/those parameters in mind, if you had access to a couple hundred, complete build spec/dyno sheets; you could evaluate the outcome and come up w/numerous patterns which would help those w/out experience when building their engines in the future. Talkking to a lot of enthusiasts, most dont understand how to qualify power output, much less that their car-engine belongs in a category all together; and when modified - will find itself in transitioning into another category; and so on, and so on.

 

Attempting to transpose the equations, regardless of the variables, to any engine build has become a past time of mine in the past few years. As your vehicle (body, powertrain, suspension, steering, braking) takes on a progressive transition - it will eventually move from one category to another. From talking to many a performance enthusiasts, I have discovered that most enthusiasts doent understand that different levels of performance even exist. IMO, this is where the confusion, relative to understanding the performance engine, begins and ends.

 

As far as the difference in the HP equations going on the low, medium, to high expectations I dont like a 60 hp spread either, but knowing that this is just an equation; I could accept it in the low high ball park spectrum. I dont really use these equations, I only pointed them out to make the point that they use a constant that was derived by empiracal means.

 

I like my approach when it comes to normally apirated engines. Qualify the cyhlinder head to cylinder relationship, as this further qualifies the level of performance that engine will fall in. Once you have qualified that relationship; with that relationship so too will the DCR to SCR relationship and this will further point the end user in the right direction for an intake/exhaust set up.

 

Thanks for the suggestions; this is what I was looking for, real input, real diablogue, along w/real progress. Even if the progress was to come to the conlusion that we dont know what the constant means.

 

I would still like to get my hands on a hundred different non v8 turbo/superchager builds to see if the constant changes w/displacement; and if/why?

 

Kevin,