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[Modified by Cottonwoodz, 10:22 PM 10/12/2002]

 

Is this like an estimate for wheel horsepower and torque?? Why is the H22a4 so much lower than the 96-down..OBDI?? but I dont understand how this would be factored in to your formula. thanks for the info though

 

nice post,

in school for mechE eh? sounds fun!

 

Huh? Am I missing something?

Your "corrected" numbers don't make sense. It looks like you just calculated what the HP would be at the torque peak point for each motor rating and called it "corrected HP". And then you calculated what the the Torque at the HP peak rating would be and called it "corrected torque"...

If you want to get an understanding of what SAE corrected power as measured by an inertial dynometer means, read:
http://wahiduddin.net/calc/calc_cf.htm

Andrew

 

They make sense. Its not SAE corrected power, nowhere in this post it said "This is SAE corrected power" It has nothing to do with an inertial dynometer. Its just corrected HP done by using the formula
Hp= (Torque x RPM)/5252.101 ..Here let me go find some links for you to read up on.
HP = torque * RPM / 5252
torque = HP * 5252 / RPM
torque = HP at 5252 RPM
HP is not measured directly, it is simply calculated from torque.

 

"Corrected"? Corrected for what then? Again, all that you did is calculate the HP at the torque peak and the torque at the HP peak for each motor.

I'm still not 100% clear on what exactly your assertion is, but this makes no sense:
What is the significance of "155.9 HP corrected"? It has no relation, mathematical or otherwise, to 200hp @7000 RPM. However mathematically, 155.9 HP (156hp) is the HP at the crank at 5252 rpm.

What you could accurately say for each motor is something like:
99-up Prelude
H22A4
200Hp and 150.0 TQ @7000
156Tq and 155.9 HP @5252

Andrew

Edit: I cna't spll so good and clarification.


[Modified by aklucsarits, 11:11 AM 10/10/2002]

 

Question

When you convert from engine torque to horsepower, why is the number 5,252 involved?

Answer

Have you ever looked at the specs of an engine in a magazine and seen something like "this engine makes 300 pound-feet of torque at 4,000 RPM," and wondered how much power that was? How much horsepower are we talking about here? You can calculate how many foot-pounds of horsepower this engine produces using a common equation:

(Torque x Engine speed) / 5,252 = Horsepower
The engine that makes 300 pound-feet of torque at 4,000 RPM produces [(300 x 4,000) / 5,252] 228 horsepower at 4,000 RPM. But where does the number 5,252 come from?

To get from pound-feet of torque to horsepower, you need to go through a few conversions. The number 5,252 is the result of lumping several different conversion factors together into one number.

First, 1 horsepower is defined as 550 foot-pounds per second (read How Horsepower Works to find out how they got that number). The units of torque are pound-feet. So to get from torque to horsepower, you need the "per second" term. You get that by multiplying the torque by the engine speed.

But engine speed is normally referred to in revolutions per minute (RPM). Since we want a "per second," we need to convert RPMs to "something per second." The seconds are easy -- we just divide by 60 to get from minutes to seconds. Now what we need is a dimensionless unit for revolutions: a radian. A radian is actually a ratio of the length of an arc divided by the length of a radius, so the units of length cancel out and you're left with a dimensionless measure.

You can think of a revolution as a measurement of an angle. One revolution is 360 degrees of a circle. Since the circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. To convert revolutions per minute to radians per second, you multiply RPM by (2-pi/60), which equals 0.10472 radians per second. This gives us the "per second" we need to calculate horsepower.

Let's put this all together. We need to get to horsepower, which is 550 foot-pounds per second, using torque (pound-feet) and engine speed (RPM). If we divide the 550 foot-pounds by the 0.10472 radians per second (engine speed), we get 550/0.10472, which equals 5,252.

So if you multiply torque (in pound-feet) by engine speed (in RPM) and divide the product by 5,252, RPM is converted to "radians per second" and you can get from torque to horsepower -- from "pound-feet" to "foot-pounds per second."
_______________________________________
maybe this will help you out http://www.howstuffworks.com/question622.htm
HP is dependent on how much Tq it makes at peak power.The more Tq at a higher RPM the more hp the engin will produce.

A motor with (Peak)-->500Tq @2000 RPM is only makeing 190.4 HP
and a motor with (Peak)--> 100Tq @10,000 is also makeing 190.4 Hp








[Modified by Cottonwoodz, 6:05 PM 10/10/2002]

 

I am well aware of the mathematical relationship between torque and HP at any given RPM point. But I still do not understand what conclusion you are trying to draw in your original post.

Again, this statement would be more accuarately made as:
A motor with (Peak)-->500Tq @2000 RPM is only makeing 190.4 HP at 2000rpm
and a motor with (Peak)--> 100Tq @10,000 is also makeing 190.4 Hp, but at 10,000rpm

I think what you are assuming is that the torque peak will also be the horsepower peak. But this is not always the case. The torque peak is not the HP peak in any of the examples you listed above. Yet it seems like you are trying to draw some correlation between the engine's peak torque rating and the engine's peak horsepower rating. And this cannot be done knowing only two data points on the power plot...

So looking at the other example you added above, what if we took the engine that makes 500lb.ft at 2000rpm, and also revved it to 10,000rpm? What would the HP be at 10,000rpm? Well, in order to calculate that, we would need to know what the torque is at 10,000rpm. We don't know the torque at 10,000rpm so it is not possible to draw any additional conclusions about horsepower from any rpm other than 2000rpm from that single data point. The engine that makes 500lb.ft at 2000rpm might make more than 190hp at 10,000rpm, or it might make less than 190hp at 10,000rpm. But we'll never know because we have no additional data on that engine's power curve...

Another e.g.
Integra Type-R
B18C5
195Hp @8000
130Tq @7500

So in like all the other engine ratings you listed, we have two data points we can calculate. One is 8000rpm and the other is 7500rpm. As I tried to explain before, the only conclusion that you can draw from these rated numbers is:
1) At 8000rpm (this engine's rated power peak), torque= (195*5252)/8000=128lb.ft
2) At 7500rpm (this engine's rated torque peak), Horsepower= (130*7500)/5252=185.6hp

In your original post, you are misinterpreting the results of the calculations that you arrived at. And I still have no idea what you mean by using the term "corrected"...

Andrew


[Modified by aklucsarits, 8:26 PM 10/10/2002]

 

I agree. Your "corrected horsepower" information is useless & misleading.


[Modified by Daemione, 11:39 AM 10/11/2002]

 

I 3rd that. But nice try! and nifty info...though it means little more than "at peak torque teh engie pushes xxx hp, etc"

 

mmmm, pi

 

cottonwoodz, that is about the most misleading post i have ever seen.


[Modified by schwett, 9:57 PM 10/11/2002]

 

Baaahhhhhaa

[Modified by Cottonwoodz, 3:39 AM 10/12/2002]


[Modified by Cottonwoodz, 3:52 AM 10/12/2002]


[Modified by Cottonwoodz, 10:20 PM 10/12/2002]


[Modified by Cottonwoodz, 10:21 PM 10/12/2002]

 

First I'll provide you with a dictionary defintion of horsepower: "Horsepower is the imperial (British) unit of power, now replaced by the watt - the new SI unit. One horsepower is the work done at the rate of 550 foot-pounds per second and it is equivalent to 745.7 watts. Horsepower was first used by James Watt, who employed it to compare the power of steam engines with that of horses." Now that I've done that I'll move on...

I've never heard such an ignorant post... HP is a function of torque, that's a given. However, you're completely incorrect that peak horsepower is dependent on <U>PEAK</U> torque. This is 100% incorrect, since I have never seen a stock Honda engine (and there won't be one) which makes peak torque at redline. Thus saying, how do you use these formulas not knowing what the torque is at XXX rpm?

(horsepower x 5252)/rpm = foot-pounds

(Foot-pounds x rpm)/5252 = Horsepower

For reference, here's a dyno of a stock '97+ Prelude



Now, first off I'd like to know how you got your numbers... Let's see here (I'm only going to compare it against the 5th gen Prelude, same processes can be proved for all) Using the dyno as a reference, the motor reaches it's max torque at ~5252.

Let's do the calculation..

(Foot-pounds x rpm)/5252 = Horsepower
SO
(156 tq x 5252rpm)/5252 = 156 HP (nice of you to round down)

Ok, we just found the horsepower at 5252 rpm on a H22a4 engine. Now, let's use the dyno plot's torque to approximate WHEEL horsepower at the max HP point which you listed as 7000 rpm. Of course some of these are appoximations upon the graph.

(Foot-pounds x rpm)/5252 = Horsepower
(118 ft/lbs x 7000rpm)/5252 = 157.3 HP

And look at that, doing absolutely nothing to the car a stock H22A4, using a VERY modest 15% drivetrain loss, it just gained 25 HP over "stock!" If you want to tell me this isn't a stock dyno, please let me know how how you setup the equasion to find out your numbers. Here it is again (since you drove it in our faces)

(Foot-pounds x rpm)/5252 = Horsepower

If I actually thought like you (and I don't) and thought peak torque and peak HP coinside I would of at least thought of this...

(156 lb/ft x 7400 rpm)/5252 = 219.8 HP

7400 RPM came from the H22A4 redline BTW.

I'm sure that anyone that can do junior high math can figure out how all the rest of the numbers are just as much garbage as the ones that I just proved wrong.

Now, I hope that I put an end to your BS and hopefully you will think before start spewing this complete garbage again. I think I can rightfully say that you've lost a lot of respect with this post and your attitude toward the board members. I can't believe that you're ignorant enough to call everyone sheep. What does that make you now?

 

I don't see how that link will help me out any more since you copied the entire text of the link over. I actually (for a second) thought you had a spark of enlightenment, but I was wrong. You still don't fully understand what you just copied over. But at least you're getting the concept.

PEAK torque means absolutely nothing other than it's the highest torque point. Anyone who has passed pre-algebra can fill out the equasion with 2 of the 3 data points. I don't understand your obsession with PEAK torque. It only gives you a horsepower data point at the peak torque RPM level. Your calculations above should read 190.4 HP @ 2000 RPM, and 190.4 HP @ 10,000 RPM respectively. All these stats do is give you an idea of the personality of the engine. The first would have the low end torque that H series (for a Honda 4 cyl motor) share. The second shows that the car has to revved to extremely high RPM's to get any power much like a S2000 motor. Thus saying that the H series engines are a more 'streetable" (read: lower RPM needed for getting around town generally) than an S2000 motor.

I'm glad to see that you've modified every single one of your earlier posts since they were, as Schwett said, "the most misleading post i have ever seen." I still think a few apologies are in order for your earlier conduct of yourself. In the future, please regulate yourself. Most of the people on this board know what they're talking about and you should take that into consideration next time.

 

OH MY GOSH!!!!!!!! at first i thought it was pretty cool.. seeing all the hp #'s for the different engine types..and then all the corrected.. but then a few days went buy. it was getting a little more deep.. then i check it today (bout a weekend later) and i find myself dumbfounded... this is way to deep for me.. this is more like some debate ... like one u watch on tv between congressmen.. (im falling out)((arrrhhh)) then i just scroll and scroll.. so much #'s.. so many big words.. im not trying to make it sound like im stupid.. but im just a simple guy.. like simple things.. like i dunno.. random #'s here.. 200hp @ the flywheel and 175 at the wheels... now i know u guys will tell me thats probally wrong.. wich i dont doubt.. just random like i sed.. but anyway.. something like that.. thats simple.. y cant we keep it like that.. all u guys went through, that was like being in school all over agen. just on h-t.. whewww... i neeeda break.. hahha.. brain overload... c'mon guys.... i just now forgot what my point was .. but i thank u fellas for that.. hehehe...