Reher said multiply torque from the same hp, and he is correct. I was getting at the same thing in my riddles. bill c5 got the message, but didn't quite carry it to it's conclusion. Namely, with 5% more rpm available you get to use 5% more gear and 5% more multiplication torque at all rpm within your operating range. We know that it is the torque at the drive wheels that accelerates the vehicle, right?

IOW, in riddle #3, there is a good chance the slightly lower hp engine might make the car faster. There are a number of folks who practice this, and some who don't. I'll leave it to your imagination as to who's quicker.


TRAGIC, I was trying to get folks to think out of the box. This is suppose to be Advance Performance Tech. "You can lead a horse to water"...well you know the rest.

 

I know the EXACT article you're referring to.

It used to be brought up all the time in the TQ vs. HP debates.

Basically, it's oversimplified and complete theory, but it SHUTS people up.

There are a few basic problems with the argument/idea.

1. It isn't TQ versus HP. They are the same thing. TQ at RPM IS HP. Thus the formula that people have posted.

2. The TQ vs. HP debate deals with PEAK numbers. Those are way simplified, and again, basically useless. What matters is the TQ curve and the area under it. Since most people are dumb, we use a number like peak HP to simplify this.

3. The most important concept that the article ignores: HOW you make power. It says, "HP lets you know how well you can take advantage of gearing." This is only HALF true. If you make more HP by increasing the RPM limits of an engine (cam, VTEC, etc.) for a higher redline, and shift the tq curve up in the rpm range, then YES, you can increase your gearing.

BUT, if you increase TQ across the rpm range, without increasing redline. YOU CANNOT take advantage of more gearing, but you will have more HP. A few examples, bolt on mods, Forced induction, increasing displacement. A supercharged LS1 car will not have any greater gearing advantage than a stock one, since they both redline at the same RPM.



The point of the article is that if you had a choice of having 400 peak tq at 2000, 4000, or 6000 rpm....... The higher the better, the faster you will be.

 

A perfect example of why area under the TQ curve matters, and peak HP doesn't mean crap!!

The Mercedes E320 turbo diesel.

Makes only 201hp. 369 lb/ft of tq.

Weighs 3835 lbs.

0-60 in 6.6 seconds. 1/4 mile in 15.0. Gets 37mpg.

Compared to another 200hp automatic car. 2002 Honda Accord.

Closer to 3000 lbs. 200hp. 28mpg.

0-60 around 8 seconds. 1/4 mile around 16.

Basically, both have the same peak hp. The accord weighs almost 1000 lbs less. But, the E320 CDI is significantly faster, and gets better fuel economy. TORQUE BABY!!! (which means it has more average HP). Basically, peak HP doesn't mean much.

 

Outta my area on this one. Way toooooo many variables to account for. I'll leave this debate to you gentlemen. Let me know who won. LOL

 

We are talking about two different things here. For an F1 engine, I agree with everything that is being said. For drag racing, the rules change ALOT. You want to make as much torque as possible from the starting line all the way to the finish. Especially from the start. Getting out of the hole first often determines who the winner is going to be which means that you may have to dip down below your power band. You really need to make torque everywhere. That was the point I was trying to make.

Now for an F1 engine, I can see everyones point and agree. But for drag racing, the rules change.


As far as "horsepower lets you know how well you can take advantage of the gearing". I thought it was the other way around. How you gear lets you take advantage of the horsepower. In other words, its alot easier to change gears than build an engine, isn't it

 

F1 engine designers are VERY MUCH concerned with torque throughout the entire rpm band. A few of them have published relative torque/power curves vs. lap times and discussed this subject. The engines with most average torque (area under the torque curve) are faster in the same car than the peaky engines with more max hp. The F1 start is truly a drag race with the winner to turn one often the race winner. It's a drag race off each corner every lap also. The elimination of variable intake (trumpet) length has hurt a lot.

I'd say there are a lot of similarities in how an F1 engine and how a drag engine are used.

My $.02

 

Again, that proves my point. TORQUE EVERYWHERE.

 

I guess I misinterpreted your F1-drag racing comparo.

 

Well....your the one that is trying to convince everyone that its better to make torque up high. Now you are saying that F1 guys are concerned about making good torque across the entire rpm range. Which is it? I've said all along that for drag racing, its better to make torque all across the rpm range.

I don't follow F1 racing at all, so I can't really make any comments on whether or not its better to make torque up high or all across the range (for F1 racing). I'm just taking your word for it and assuming that you know what your talking about

 

LOL! Lot's of people have made that assumption....or that mistake.

 

Very interesting thread, to say the least, understatedly...

So basically the question boils down to: where do you want to trade torque, down low or up high...?

 

More is better, plain and simple.

BUT, if you HAVE to choose.....

1. If you can only have 200 peak tq. The higher in the RPM you have it, the better.

2. Even better than scenario 1. Having 200 tq all the way from 1000 rpm to redline. (flat tq curve).

3. If you can only have 200 peak HP. Ideal situation would be to have 200 hp from 1000 rpm to redline (this would mean 1050 tq at 1000 rpm, 525 tq at 2000 rpm, etc).


Either way, the end result is the same, MORE AREA UNDER THE TQ CURVE.

Peak numbers are useless for comparison.

 

No where.

But, if you HAVE to trade..... Losing down low and trading it for up top will make your car faster at full throttle (slower at part throttle/daily driving).

This is why.

TQ at Rpm is the acceleration that you FEEL. Punch the gas in any gear, how hard you are pushed back in your seat is a DIRECT result of the torque curve. You will feel greatest instantaneous acceleration at peak tq.

If you lose 50 lb ft of TQ from 2000 to 4000 rpm and gain 50 lb ft of tq from 4000 to 6000 rpm (for example).

Your overall acceleration in 1st gear at full throttle will be IDENTICAL to before you made this magical switch.

HOWEVER, in a race, in 2nd, 3rd and 4th...... You will never dip below 4000 rpm, so you won't feel the loss, but will feel the 50 lb ft you gained.

At PART THROTTLE, or full throttle, any time you are between 2000 and 4000 rpm in any gear, you will be that much slower.

What would you do in this hypothetical situation??? If you're racing, drag, or otherwise, it would be a great switch. For daily driving, bad idea.

 

 

Let me try to think here.

You are assunming that the shift points are increasing with the higher peak RPM, sorry I missed that one. I used the numbers you provided and assumed that all other conditions are the same.

Increasing Peak RPM will then decrease dy/dx and you get more area relative to the higher rpm peak HP .

By the way does anyone know where the water is?

 

The water is in my Pappy Van Winkle bourbon...

Plot the engine torque curve multiplied by overall gear ratio vs. mph (instead of rpm). That's the torque accelerating the vehicle. Area under the curve is a good visual for how well this is done.

Now increase the rpm 5% with case 3 (slightly less peak hp), and multiply the similarly shaped torque curve by new (+5%) gear and plot on the same axis. Assume max speed will be the same, because hp is about the same.

You should have more area under this new rear wheel torque curve. The difference should be additional available rw torque for acceleration. Well that's how I visualize it.

 

That seems to work. Of course this is all theory, since most people who increase power and rpms do not gear the exact same amount.

I still think the area under the tq curve concept seems the simplest to visualize and understand.

Area under the tq curve is why an S2000 is still quick with 240hp and only 150 lb/ft of tq. It's also why the same car with a 240hp GTP motor (3.8 supercharged) would be slightly quicker at full throttle (ideally geared for both setups) and significantly quicker at part throttle.

Area under the tq curve is why I like a LARGER displacement engine with a lot of low end tq in my daily driver versus a smaller engine with the same peak HP.

At full throttle, they may accelerate almost the same, but at part throttle (where I spend most of my driving) the larger displacement torquey engine shines.

 

Was the orginal question after runner lengths, wavelengths..stuff like that ? Any ls specific info would be interesting.

 

Think about 205 mph Pro Stockers. All the top folks are running within less than a mph, have about the same areo drag, so the horsepower is pretty much equal. If someone was able to extend their max hp rpm 5% from say 10,000 to 10,500 and keep the hp number the same, and even though torque at 10,500 was down, theoretically they could increase the gear by 5%, and have more area under the torque curve at the wheels. That might give them the win.

I can't prove to you that folks have done this, but theoretically it's possible to go quicker but not faster this way. A foot at 205 mph is .0033 seconds. It doesn't take much.

 

Let me provide a little different take. It isn't peak anything that matters (unless you have a CVT transmission), and it isn't the torque curve per se, it is the area under the horsepower curve.

Now this is related to the torque curve, since it is hp is a linear function of torque and engine speed. But not quite the same.

Let's used the Accord vs MB Diesel example earlier. I'd like to change it to the MB gas vs MB diesel, since I actually worked the numbers on this in '04. At the time the gas engine had 221 peak hp, the diesel 201. However, the diesel had a flat power curve and the gas engines was constantly rising. When accelerating at WOT, the diesel would average around 195hp, the gas engine in the high 180s.

Although the diesel had nearly 50% higher peak torque, it was largely irrelevant for maximum acceleration. It occurred at 1800rpm, and the engine was way beyond that right away and never would drop below the low 3000s after a shift.

How, here is a little math game. Take a car going any road speed; 60, 100, 120, 150mph...you decide. Pick any tire size. Any gear ratio. Any engine speed. Just as long as the ratio of vehicle speed to engine speed gives the desired road speed.

If you say the engine makes a specific horsepower it will always have the same force accelerating the car. 720hp @19000 rpm from an F1 engine would be the same as 720hp @2400rpm in a truck engine. Don't believe me; work the numbers for yourself.