Roen

iTrader: (2)

I'd wonder what the charts would look like from a dead stop, without the cars being in their powerband? I don't think Paul covers that in his article. The higher tq at the tq peak implies a larger hp curve, given the aforementioned conditions. What car moves faster, one with a larger hp curve or one with a smaller one?

You can keep quoting articles, but if you don't have an understanding besides what someone tells you, how can your points be valid? I'm taking into consideration the article that you posted, in fact, I use it as basis for some of my arguments because I try to understand what he says instead of reading the words at face value. Please don't take this as offensive, I mean no offense, but I don't like having discussions with people who just post sources, instead of posting their own opinions and the logic to how they got to that conclusion. Think about what I just said, as opposed to just wanting to be right. That'll be the best for both of us.

sonorous7

great stuff. I just think about it too much sometimes and get worried that the mods on my car aren't "right" and that it would be better off being stock (i.e. properly tuned by Mazda engineers). But just having a highflow cat and catback can't be doing that much harm; the pros have to outweigh the cons. My other car is a 2.5L Sentra and has a header b/c the stock one failed. It's the best bang-for-the-buck mod you can do for that engine; perhaps the same is true for a rotary.

rotarygod

iTrader: (1)

There are many people who like to use the argument that Mazda designed something a certain way spending millions of dollars in the process so it must be the best way to do it. They did design it the best way they could for THEIR goals. Manufacturers need to take many things into account such as noise, packaging, emissions, economy, etc... Many of these require a compromise from some other area so what they do is usually an acceptable average of everything with just enough room to hit their projected power goals. They usually hit this and leave it at that rather than optimizing it to do more.

If you want to increase noise, sure you can get more power. The stock box exhaust manifold may rob ultimate horsepower from the engine but with it their noise levels stayed down where they needed them and they still had at least their goal power output. The intake manifold was designed with failry long runners for good low and midrange power. The throttlebody was designed to give a smoother more linear feel over just a larger single plate throttlebody. The best way to accomplish this is with the new Renesis intake as it has the optimum setup but with the technology at the time they couldn't do this effectively.

You can tell that if you want to change any one thing about the car it is easily possible to get more out of it. It will no longer conform to Mazda's original design goals for a street driven, emissions friendly, quiet, civilized passenger car though. Don't be afriad to make a change. What you want and what they wanted probably aren't the same thing. That's OK.

rotarygod

iTrader: (1)

It sounds like both of you guys understand what's going on with the horsepower/torque relationship but are trying to somehow argue different points of it with each other.

If we have 2 cars with the same average horsepower assuming the same usable rpm range, they should be the same speed regardless of their total torque. In other words if we have a car that is geared to run from 6000-8000 rpm and it's average horsepower is 200 hp, it should be the same speed as a car geared to run from 4000-6000 rpm with an average of 200 hp. The torque between them both will obviously be different but their speed should be the same. Please don't get too technical about the rpm spread and how a higher rpm will have a narrower powerband, etc... It's just an example.

If we had 2 cars that both ran with a usable rpm range of 6000-8000 and they both made the same peak horsepower of 200 but car A had more torque below this than car B, car A is only faster because it has more horsepower below the peak than car B does. It's average power over the usable rpm range that makes you faster and car A would have it. Since torque and horsepower are mathematically related, more toque must also be more horsepower. Since torque is a resistance to twist and horsepower is this same force applied over time and distance, it is the horsepower not the torque that is actually doing the work of making you faster.

The highest average horsepower not torque (as this can vary depending on what rpm we are referencing) over the usable rpm range is what makes you faster.

Aaron Cake

iTrader: (1)

I'm really sick right now, so I'm not sure I'm completely understanding what you are trying to say. Are you trying to say that on two cars that are exactly the same with exactly the same redline, the one that makes 200Ft-LBS will NOT be faster then the one making 100FT-LBS?

When you start to talk about gear changes (as the Paul Yaw article does), all of this goes out the window as we can gear a car any way we want.

And it depends on the situation too. Looking at a high HP-low torque vehicle from a street use persepctive, it becomes very unattractive. Maybe it's fine at the track where it spends all it's time at 8,000 RPM, but at 2,000 RPM on the street it's another story. Not to mention that a car with a flatter torque curve is going to make more power throughout the RPM range, be easier to drive, and probably faster.

Edit...I seem to be talking about the flatness of torque, not the total amount of torque. That's probably the difference.

Roen

iTrader: (2)

I think this was the point that I was trying to hammer in the whole time. Perhaps I could've explained it better, but thanks rotarygod for explaining it in succinct terms. My main point was that the higher tq at the tq peak implies a larger hp curve throughout the rev range, all other factors remaining constant and identical.

iceblue

The point here is not copy past. The point is each section I pasted dealt with the attribute you were trying to inquire.

Second if someone else has already done something built something wrote something and 10x bettor then I could possible or under any reasoning reproduce myself. Well then I am not going to even try to reinvent the wheel they already created.

iceblue

We always have a little confusion in our conversations. Trying to work this out I think if the car had a wider TQ range it will be easier to get moving on the street then the car that didn’t have that. Kind of like a street bike all hp no tq but its much faster then your car. The TQ is the factor in having the ability to move something, force, but the force needs to have work applied. The more work applied the faster I can move my job. If I do not have enough tq I can not move my job. For instance my street bike can not pull a tanker up a hill under any reasoning if I gave it enough tq the motor wouldn’t have enough power. If I could get it to pull the tanker I would not do it very quickly. The factor of TQ would be to determine the amount of job I can perform, and HP the determination of how fast I can accomplish that job.

RotaryEvolution

iTrader: (30)

fact>theory

iceblue

Fact = null without theory.

You will find your self in a lot of holes without theory and physics behind you

Roen

iTrader: (2)

I'll pull an iceblue then. What does Paul's article say about this?

Funny you should say that when the difference between 200 lbs-ft of tq and 100 lbs-ft of tq at the same tq peak, with the same hp at the same hp peak, with the same redline and the same gearing and the same everything else is not apparent to you.

Hyper4mance2k

iTrader: (40)

So before people were shooting some low hp numbers. I've seen na stock ported 6 ports make 170 to the wheels with Webers, and the pix below this guy made 200whp with his custom intake and standalond on a s5 sotck port 6 port.

Also Horse power is not an actuale measureable force. IT IS NOT A FORCE it's a compairison. 1hp=1 horse can pull 100lbs up 100 ft in 1 minute. Something like that. Torque is a measureable force. more torque = faster car period. depending on where you tq band is and how long it is at it's peak and how it's multiplied through the gears is what makes your car fast. NOT horse power. Again horse power is a compairison to a beast and not a measureable force. you can have 10,000 hp and 1 ft lb of tq and you're not going to go any where.but you can have 10,000 ft lbs tq and 1 hp. and you'll move. of course those are exagerations cause hp is relitive to tq and rpms. HP=a ratio or ~hp=measureable force

ericgrau

iTrader: (1)

Oh no! This thread has degraded into the 5th and 6th hells of exhausts and torque!

Oh well. As stated:
(1) Horsepower = (Torque X RPM) / 5252
or (2) Horsepower * 5252 = (Torque X RPM)

But also:
(3) Force (lbs.) = WheelTorque / WheelRadius (feet) or WheelTorque = Force * WheelRadius
(4) WheelTorque = EngineTorque * EngineRPM * DriveTrainEfficiency / WheelRPM

Substituting in equations 2 and 3 we find:
(5) Force * WheelRadius = EngineHorsepower * 5252 * DriveTrainEfficiency / WheelRPM or
(6) Force = EngineHorsepower * 5252 * DriveTrainEfficiency / (WheelRPM * WheelRadius)
Since (WheelRPM * WheelRadius (feet)) = CarSpeed (mph) * 14.00:
(7) Force = EngineHorsepower * 375.0 * DriveTrainEfficiency / CarSpeed
and since Force = Mass * Acceleration:
Mass * Acceleration = EngineHorsepower * 375.0 * DriveTrainEfficiency / CarSpeed or:
Acceleration (G's) = EngineHorsepower * 375.0 * DriveTrainEfficiency / (CarSpeed (mph) * Mass (pounds))


It's only fair if we compare 2 cars at the same speed. No running start for one and not the other. If you can't visualize this, I can't help you.

DriveTrainEfficiency depends on the tranny. Usually it's around 85%.

Mass is your car's weight.

That leaves only EngineHorsepower. Given the same DriveTrainEfficiency, same weight, and same car speed, horsepower is the ONLY thing you need to know to find acceleration. Peak horsepower? No! Horsepower. Look at a dyno graft and find the rpms you drive at. That's your horsepower. Is torque unrelated? No. Horsepower = Torque X RPM X 5252. Knowing torque is great for calculating horsepower. Can I completely ignore torque numbers if I already know the horsepower numbers? YES.

And now that that's out of the way, I can say this: The Corvette's low end power sucks royally. The 232HP, 3085lb RX-8 and 240HP, 2855lb s2000 both have better 0-30 times than the 400HP, 3280lb Corvette. Having a peak torque of 400ft-lbs at 4400rpm versus the s2000's 146ft-lbs at 6400rpm apparently doesn't help the Corvette on the low rpms. But the peaky engine is awesome if you need more high end power. And I hear the engine weighs no more than 100lbs. more than the rotary. The Corvette also gets great (real world) fuel economy on the freeway, but it's as bad as the RX-8 in the city. Engine cost: $10,000.

rotarygod

iTrader: (1)

Paul is a smart guy. He says nothing that contradicts fact.

rotarygod

iTrader: (1)

100% correct. The only way it can be.

iceblue

lowryder420p3

damn im away for 2 days and this thread reaches 8 pages!!?!

anewconvert

iTrader: (1)

No matter how you look at it torque produces hp. Hp is a function the torque over time. You can t have HP without torque, but you can have torque without arriving at hp. The REASON HP skyrockets after 5252 is because its a math equation and the multiplier is now greater than one. Torque may stay roughly the same because the engine is producing the same force, but because we are doing that function of force over a shorter period of time work accomplished increases. Thats all that is happening. Torque is measured, HP is arrived at via an equation. Without consistant torque output hp wont increase. So torque is absolutely something that should be accounted for in the developement and tuning of an engine.

Lets all remember, Torque is a force, HP is an equation.


BC

Roen

iTrader: (2)

I was always under the impression that it's the other way around, where HP is measured and Tq is calculated. From basic physics, work is power, there's no other way around it. When you move something, you do work on it. Sure there's a force applied, but that's calculated from the amount of work you do differentiated per time. The best example is the lever arm example, where I stand on some lever on a fulcrum that's ridiculously long. My weight is the force acting on the lever arm, and when multiplied by the distance from where I'm standing to where the fulcrum is, I exert a ridiculous amount of tq. I'm not really doing much work, so it's not moving much and I'm not applying much power.

ericgrau, I don't think comparing three different vehicles with completely different gearing is an accurate picture of tq. Sure, it highlights tq's shortcomings as a measurement tool, but you lose the merits of measuring tq with that example.

Well stated, and here's my application of the previous post. Going back to my example of Car A producing 200 hp @ 8000 rpm and 170 lbs-ft @ 5000 rpm vs. Car B producing 200 hp @ 8000 rpm and 160 lbs-ft @ 5000 rpm, all else being equal. Being NA rotaries with similar hp figures, one can assume they'll have similar tq curves. Which car will accelerate faster? From the amalgamation of posts that have occurred on this topic, this is my take and correct me if I'm wrong. The car with 170 tq will be faster because of:

since tq is a function of hp. Whether it's a function or an inverse function can be debated later, it doesn't really matter either way. Because the higher peak tq implies a larger tq curve, power along the curve until the powerband of Car A will be greater than Car B. Accounting for ericgrau's point of Hp, not peak Hp, being the determining factor of acceleration, you can see that Car A will have an acceleration advantage.

Now, instead of giving you both a peak hp figure and a peak tq figure, what if I just told you that Car A made 200 hp @ 8000 rpm and Car B made 200 hp @ 8000 rpm, all else including the rpm where tq peaks being the same, except for the power and torque curves and the amount of peak tq each car makes. Could you really say that Car A is faster than Car B, or Car B is faster than Car A? Could you say that they're the same? Not really, it's a muddy guess with only one peak hp figure, you have no idea what the power curve looks like. At least with a peak tq figure, you have some semblance of comparison of power between two otherwise identical vehicles.

How does this not disagree with ericgrau's point of if I know hp, I don't need to know tq? Simple. My example only gives peak tq and peak hp information, like most dyno quotes (not dyno graphs) are. I make yada hp @ yada rpm and yada tq @ yada rpm. If I understand ericgrau's point, if and only if I know hp at every point along the curve, then tq is useless, which I agree with wholeheartedly. I believe that it's the point Paul was trying to make in his article also, that hp, not peak hp matters. However, given a comparison with only peak numbers between two cars, I must stand by my point that having a peak tq figure is not worthless, that tq is not worthless, because it allows you to see how power is delivered. It ties back to my previous assertion about 4-port vs 6-port NA engines, and how both produce similar power, but the 4-port makes more tq at the peak. iceblue's assertion is that it doesn't matter, and both will perform equally, and my rebuttal comes from the fact that if that were the case, why measure peak tq at all? It's because when a friend gives you a dyno quote, how often will he have a dyno graph with him to illustrate the complete curve? Chances are, not often, which is why it is important to know the peak tq of an engine if you only know the peak hp before making any performance conclusions. That being said, given the choice between the ported 4-port and the ported 6-port, I'd go with the 4-port because, in simplistic terms, it makes better low-end torque than the 6-port.

That's what I view a torque figure as, it allows me to see how the power is being delivered by the engine, since the power is doing the work of moving the car in the first place.

Sorry for the long winded reply, but I feel that there's a lot of either miscommunication or people trying to hammer in the same point from different viewpoints and a lot of that needs to be bridged before any side understands what the others are talking about. And whoever said tq being a force and that force matters, lever arm example, and if that's not enough, read up on the basic definition as to units of work. Let me give you a hint, it's not lbs-ft.

ericgrau

iTrader: (1)

Yep, car A will likely be faster b/c it makes 160HP @ 5000rpm while car B makes 152HP @ 5000rpm (I'd imagine the rest of the horsepower curve follows the same trend). Or since the torque numbers are at the same rpm, you can simply compare torque directly like you did. Horsepower = torque x rpm / 5252. Comparison problems come when 2 cars have peak torques at different rpms. Then you have to break out the calculator and figure it out. Really it would be more useful if they gave you horsepower at another rpm, not torque. The torque number is somewhat misleading until you convert it to horsepower. Then it's useful b/c it gives you another point on the horsepower graph.

A 6 port N/A with 200HP (peak) is faster than a 4 port N/A with 200HP (peak). The auxilary ports close at low rpms to provide max low end power while they open at high rpms to provide max high end power. Opening the ports at lower rpms, or having larger ports in a 4 port motor, actually makes you lose low end power. The 6 port provides better power across all rpms, whereas the 4 port is likely to be more peaky. However, the 4 port TII has a clever spooling trick on the turbo to maintain low end power without sacrificing the high end. I don't remember the details.

anewconvert

iTrader: (1)

[QUOTE=Roen]I was always under the impression that it's the other way around, where HP is measured and Tq is calculated. From basic physics, work is power, there's no other way around it. When you move something, you do work on it. Sure there's a force applied, but that's calculated from the amount of work you do differentiated per time. The best example is the lever arm example, where I stand on some lever on a fulcrum that's ridiculously long. My weight is the force acting on the lever arm, and when multiplied by the distance from where I'm standing to where the fulcrum is, I exert a ridiculous amount of tq. I'm not really doing much work, so it's not moving much and I'm not applying much power.
QUOTE]


hp = (Tq * Rpm)/5252


Torque is the force being generated. Hp is the work being generated by that force in an arbitrary time frame. In this case 1 minute. In order to get hp you have to know torque and give it a time frame. In order to get torque the time frame is inconsequential. Torque can be directly measured. HP has to arrived at via math.


BC

iceblue

It would not be faster the car would only be capable of pulling a higher load.

HoLsTeR

you can count the weight of the car itself as a load. the car with more torque will pull more easily meaning chance is that its faster if they have the same hp, weight, and gearing.

Roen

iTrader: (2)

I agree, with you, given that the stock NA tq increasing power systems are in place. However, the 200 hp 6-ports that I've seen, they all require work that eliminates many of those systems (5th and 6th port actuation, VDI, etc.) Kahren's 6-port engine made 195 whp with a custom intake manifold and sleeve removal. I belive that means all 6 ports are always open. It's his opinion that a ported 4 port will make similar whp but more tq on the low end. With those systems unable to function to make that kind of power without using a bridgeport, it's the tuner's opinion, which i believe, that the 4 port will be faster than the 6 port, because of the porting and functionality changes. Sorry that I didn't mention that before, it didn't occur to me.

Like I said, I'm lazy, so low end tq is synonymous with low end power. (For me)

You're right, I just realized, work isn't power, it's energy. Power x (or intergral with respect to) time = energy. Energy is what moves a vehicle. However, let me be the devil's advocate for a minute. To get work from force, it's the integral of force with respect to distance = energy. However, I never understood the implications if that force was on a lever arm, aka torque. As I remember it, torque isn't the intergral with respect to distance, it's the dot product of force and distance instead. What is the conversion of tq to energy (work)?

Also, regarding the whole inverse function/function point is it really

hp = tq x rpm / 5252 = f(tq)

or

tq = hp x 5252 / rpm = f(hp)

I always thought it was hp and f(hp) rather than tq and f(tq).

What are you referring to? If you're referring to my example, it's not hard to see, more tq = more hp, break out your calculator or look at ericgrau's post on the previous page if you don't believe me.

It's not the torque, but the increased power implications that the increased torque figures have that make the car move faster. I can see that these days, most ppl confuse hp with peak hp as opposed to other forms. I just like to use layman's terms and say it's because of the tq rather than it's because of the increased power that comes from the larger tq graph.

iceblue

Tq is always in the equation. However we have to revert back to the facts of physics. Tq does not do anything on its own in any way at all. When we are talking about acceleration, the time it takes to travel a distance from point A to point B the determining factor is HP.

Now we need TQ to perform certain applications of course, TQ has to always be considered for what you are doing. TQ just has no relevance to acquiring or determining acceleration.