Maybe if they only have one gear. The big advantage of torque at higher rpm, especially in an acceleration contest, is that you do not have to upshift as early and lose your torque multiplication.

I bookmarked this link a long time ago because it is pretty handy every now and again
http://vettenet.org/torquehp.html

 

Unfortunately, that is not how it works. To really get into it, torque at the engine doesn't matter - torque at the wheels does (and is thus affected by a number of things - such as gearing, tire size, etc). Additionally, if that were
the case, then why not make an engine that made 300 lb/ft of torque at 100 rpm, gear it accordingly, and call it a day? Wouldn't that make sense? Less rpm would have a whole host of benefits?

Additionally, the car that made that power down at 3000 rpm would only accelerate faster if you made the other car start at the same low rpm. However, if optimized for the engine, the car with more power (torque * rpm) is going to accelerate faster.

The problem is torque, by itself, is fairly useless in cars. Torque * rpm is much more useful. I'm not making this up - honest! Do a google of Torque vs RPM sometime.

Yes - if you make both cars start their run at an rpm that is lower than 3000 rpm.

Once again, only if they are forced to both start at some pre-determined low rpm.

Once again....ah, nevermind. I've said it enough.

LOL. When I get home and get the time, I'll link some very interesting Tq vs HP information. it really isn't speculation - it is proven physics....but I'm sure not smart enough to recite it without the reference right beside me.

Bob

 

Oops....should have read more before I posted - that's one of the links! There is more - much more, for anybody looking for it.

Bob

 

Not sure how to read this. At the instant that both cars are making 300 lb ft, they will accelerate at the same rate (with same gearing, weight, traction, etc.). In other words, the car that is making 300 lb ft at 3000 rpm will accelerate as hard at 3000 rpm as the other car accelerates at 5000 rpm. 300 lb ft = 300 lb ft. Simple as that. As you said, torque is what is accelerates the car. F=ma. F comes from the torque working through the radius of the wheel/tire, m comes from the car, and there's your a. This is what I was talking about earlier. Of course, these days with trucks being used as cars, and not so much for getting heavy loads moving, this is probably becoming less significant. And all of this discussion is leaving out the magical effects of the torque converter (which are in 98% of pickups). A looser converter can be used to provide torque multiplication and get the engine up toward its torque peak. That's right, in the traditional "trucks need low rpm grunt" world. Those numbers are, of course, full throttle numbers, by the way. So the Ford will have an advantage (maybe not, depending on torque converter matching with the engine torque curves) right off the line, but eventually its power/torque output falls behind the Chevy. FWIW, I don't recall a magazine test in which a 5.4L F150 outaccelerated a 5.3L Silverado. BUT, hook a 7000 lb trailer to each one, and the Ford might pull it off. The added mass of the trailer means the accleration will be slower, so the engines will have more time to be working at the lower reaches of the tach before they make it to those 4000-5000 rpm numbers. The extra grunt of the Ford in those lower reaches might pay off there. As I was saying earlier, having a lot of torque output at really low rpm is ideal for getting big mass moving (which is why 18 wheelers use the engines they use). As you mentioned earlier, it is all about the curve; peak numbers are used for marketing purposes to give an indication of what the engine can do. I think the fact that the ratings are typically given as a single torque number and a single power number has confused people about what they really are.

It would be really cool if it became common to show a full load torque curve for all engines instead of just a peak power and torque number.

 

Pro Drag racers used to make as much HorsePower as possible and gear accordingly.
The engine at 5,000rpm is doing the work faster, nearly twice as fast, or in less time per revolution, making it easier to move, and has to accelerate faster..."all else being equal"...

 

Uncle. Have a great day.

Bob

 

I agree. We said the same thing.
In the real world, don't most cars start from a stoplight at idle? @1000rpms or less?
In case they don't, I put this little disclaimer in my post to cover that concept...
Yeah, I've googled and yahooed before as well... and I have several bookmarks too.
http://www.modernracer.com/tips/torquevspower.html
"For Mr Average, torque is therefore more important than horsepower, unless you spend your life racing around at high revs. "
http://www.carcraft.com/techarticles...wer_vs_torque/
"Engines don’t make horsepower; they convert fuel into torque. Torque is the twisting force imparted to the crank flange and then transmitted to the transmission and the rest of the drivetrain. To some degree torque is the grunt that gets things moving, and horsepower is the force that keeps things moving."


While getting my BSME, I spent 6 months studying automotive powerplants at UNC-Charlotte under Dr. Jerry Hill, an engine designer for Pratt-Whitney. He was on the team that developed the engines for the F14 Tomcats and F-15 Strike Eagles. I triple-minored in Math, Physics, and Computer Science during that first degree too - a result of changing my major from Physics late in my 3rd year (doh!)
I've personally built about 20-24 engines just for my cars alone since 1984, and I've raced everything from 1/8 mile brackets to autocross to full roadcourses. I've picked-up a few things over the years, and I've studied text books... and greasy fingernails... both.

I know you are a smart guy. I don't know your precise educational background, but I know you have your title from a few years back too... I've watched you in the rags and mags... I know you can cut a light, and I know you can gear a car to maximize it's output - you pioneered mod-motor performance for many folks a few years ago, and that was no small feat.

So tell you what... Let's come back to this another time.
We've hijacked this thread bad enough already.
Whaddayasay we agree to disagree, and write about something else for a while - more truck related... to this thread?

To the thread - in MY truck, I'll take a boat-load of Tq pellets over a sack-full of Hp any day. I have my reasons, but that's what I want in MY truck... and in fact I have just that... @580ft-lbs and about 320hp.

 

NO NO NO!!!
You can't do this!!!
I was writing when you made this post!!!


AAARRRRGGGGGHHHHHHHHH!!!!!


Seriously - I don't think we are really so far apart in basic theory, just in application. It's a thin line and we are not the only ones wavering across it.

to you.

 

Ok.

A couple of things....I launch way, way, way above peak torque at the drag strip.

Launching any manual @ 1000 rpm isn't a lot of fun, and most automatics will 'flash' significantly higher than that too.

To put torque to use, you have to do it over time. This is where we get into rpm and thus horsepower.

Car Craft is wrong. Plain and simple.

Bob

 

Nice, what sorta mill is it (if you don't mind me asking) I keep on trying to get my pops to build a 400 using the 170 E-TEC heads from Edelbrock with a nice custom hydraulic roller to take advantage of the cylinder heads at a relatively low rev range.

 

Yep - on a unloaded 0-60 run with short rear-end gears (like the 3.73s and 4.10s now becoming common), horsepower starts getting damn interesting - and of course horsepower is definitely a factor at highway speeds (assuming that the transmission ratios are well-matched to the power curve and road speed). And although I don't think it's possible to have too much horsepower in a truck (especially when trying to merge onto a busy expressway from a too-short entrance ramp when towing five tons or so), I do start to get nervous when I see people driving their half-ton trucks like they've seen in the commercials. It's a bad feeling seeing someone yanking a big boat down the highway at 75-80 MPH with their new Hemi Ram and knowing damn well that if they get cut-off by another idiot, something bad is likely to happen.

 

Me too!..I see guys using powerful "1/2" ton trucks hauling loads that a "Full" ton Dually, at the least, should be used...tailgates way lower than the front bumper, tire sidewalls bulging from the weight, and they're trying to run 75mph...like they're trying to prove something.
Especially diesels, I see them all the time, hauling Huge Cabin Cruisers around the upper lakes here.
I've personally hauled just over 2 tons of sand in my Silverado 3/4 ton, 2WD, truck bed...talk about a white knucle affair, the front was so light it wondered all over the lane, and I only went 40mph for about 3 miles. But it does show how strong these p/u trucks are.

 

You need more tire pressure, then - it shouldn't start getting "interesting" until you get over three tons in the bed. You're right about how strong a modern truck is, however - quite honestly, I've never seen anything but tires fail from overloading. Poor maintenance, on the other hand...

Oh, the hypocrisy - bitch about unsafe truck driving in one post, brag about violating GVWRs in the next.

 

Alright, here's my 2 cents.

Engines produce torque, they don't produce horsepower. Different levels of torque are produced at different RPMs.

Horsepower is a meaningful translation of torque, dictating what work the engine actually does.

One of the best examples to understand this relationship is a waterwheel. Take two waterwheels. One has "buckets" that of capacity of 5 gallons. Another has "buckets" of capacity of 7 gallons.

Since horsepower is work done by the engine, you can take the two wheels and spin them at the same RPM, let's say 100 RPMs. The 5 gallon wheel will do 5 x 100 = 500 gallons per minute per bucket. The 7 gallon wheel will do 700 gallons per minute per bucket. Now take the 5 gallon wheel and spin it at 140 RPMs. It will now do the same 700 gallons per minute per bucket as the other wheel. If you spin it even higher, it will surpass the 7 gallon wheel.

This is an explanation of torque in relation to horsepower. Horsepower is the total work done by the engine, much like gallons per minute per bucket.

In real engines, of course, the capacity of the buckets vary with RPM (as does torque - it varies with RPM), and to figure out horespower over the entire powerband of the engine is trickier. The bottom line - work done at the end of the day is what matters.

So yes, torque wins races, but more specifically, it's torque at given RPMs that wins races. Which, in turn, translates to horsepower.

And as Bob pointed out, we're talking about torque at the wheels. And vehicle mass.

 

Never before on the Internet have I observed so many people making this observation so correctly. It's quite refreshing!