| torque graph for '04
- Click HERE for Original Thread
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| jsavrtka |
Hey everyone.
Whenever I look at a horsepower vs torque graph, I always verify that it crosses at 5252 rpm (or at least has equal values). Maybe it's just me, but I'm funny that way.
Anyway, in the Canadian '04 MDX brochure (and I assume the US as the values are in imperial units), the two values don't match.
I've taken the liberty of stealing the chart from the brochure, and interpolating the values at 5252 rpm, attached (hopefully) here for your assessment.
So, does anyone have a correct torque graph? Maybe from the service manual. Dyno run?
jim |
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| eurohazard |
| Where did 5252 RPM come from? Am understanding you correctly........Are you saying the torque and the horsepower should be equal at 5252 RPM? |
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| DaleB |
That's how the equation works out. They are equal at 5252. Below 5252 rpm the actual torque 'number' will always be higher than the HP number. Above 5252 the HP number number will higher than the torque value.
He is using this fact to check the accuracy of the graph, which in this case has some slop.
(Torque * RPM) / 5,252= HP |
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| eurohazard |
I get it......I am a nerd. Math is a great thing. Some engines don't even reach 5252 RPMs....weird.
The graph doesn't look like it's too far off though. |
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| DaleB |
quote:
Originally posted by eurohazard
I get it......I am a nerd. Math is a great thing. Some engines don't even reach 5252 RPMs....weird.
The graph doesn't look like it's too far off though.
Let's try that agaiin.. |
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| DaleB |
quote:
Originally posted by eurohazard
I get it......I am a nerd. Math is a great thing. Some engines don't even reach 5252 RPMs....weird.
The graph doesn't look like it's too far off though.
Peak HP below 5000 was not uncommon in older engines. |
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| DaleB |
[QUOTE]Originally posted by DaleB
[B]
Triple posting.. I'm guilty!:cool: |
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| eurohazard |
I have no doubt that my Cadillac's 472 cubic inch engine has a HP peak below 5000 RPM.
In fact I just found the specs....345 HP @ 4400 RPM
500 ft-lbs @2800 RPM
I don't see the red line anywhere though. |
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| jsavrtka |
quote:
Originally posted by eurohazard
I have no doubt that my Cadillac's 472 cubic inch engine has a HP peak below 5000 RPM.
In fact I just found the specs....345 HP @ 4400 RPM
500 ft-lbs @2800 RPM
I don't see the red line anywhere though.
The formula has nothing to do with peak horsepower. An engine that can't even spin at 5000 rpm would have a torque value of zero at 5252 rpm, which would then yield an equal value of zero horsepower.
They've just got to match at 5252 rpm.
For an SUV, I don't care too much about horsepower, but I'd like the torque curve to be relatively flat. If Acura can't put accurate information in their literature, not only might that imply that quality control is lacking, but just might open up the door to claims of false advertising.
I'm just looking for the facts.
jim |
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| DaleB |
It was a big deal when engines (especially domestic) were able to develop max hp above 5000 rpm and run with everything intact!
Guess I am aging myself....:4: |
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| SteveNsx |
I have a .6 liter engine that revs to 15,500 rpms!!
About 105 rwhp and 48 ft/lbs torque!!
She is a dawg at 5 k rpms! |
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| eurohazard |
| R6 is a phat bike. A buddy just bought a R1 last year, because they couldn't keep up with the demand for the R6. |
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| ndahbar |
The mass public get excited about the max HP figure. When in fact, there is a HELLA lot more to the story for an engine.
The most important performance indicator is the torque output across the entire rev range, from just off idle till redline. Manufacturers just quote the peak figures, which is fine for gearheads cuz they can quickly visualize the majority of the torque curve in their minds just by seeing where the torque peak occurs in the RPM range vs where the HP peak does (that, along with other info like # of cylinders, displacement of the engine, etc.)
What you want, is a flat torque curve, to occur as early as possible, and to last as long as possible. Look at the torque curve of small-displacement, turbo engines. Nothing...nothing...nothing...we got a heartbeat now....ah it's slightly more....BOOOM it has swelled....still going....falling off now...falling VERY fast...redline reached.
Whereas something like a large-displacement V-12 will have a very flat curve the whole way. There are many things engineers can do to affect the curve.
But in general, this is why BMW and Honda engines in particular feel so good on the road: The peak figures aren't everything: Rather, they produce nice steady torque across a good part of the RPM range. Whereas most American engines fall flat on their face once they go to the upper rpm range (Corvettes included, except for the almighty Z06).
Look at the new BMW M3 for example. It can rev to 8000 rpm. It doesn't produce much more torque over its predecessor at all (the E36 in Europe), but it can rev a LOT higher, and here's the important thing: While in that very high rpm range, its torque output is STILL at least 80% of the max it can do (around its midrange of 4-5K). That's why it pulls and pulls and pulls, hard, all the way to 8000rpm. Whereas the similarly-powered and similarly-heavy car its racing needs to stop short at say, 6000 rpm, and shift. Of course, the BMW will walk it.
Always try to look at the torque curve from idle to redline. That formula provided of HP = (T x RPM) / 5252 should be used to calculate the horsepower OR the torque (my preference, always) at any respective RPM, based on what the graph tells you.
For example, if the MDX makes 253 lb-ft at 3500rpm and 265hp@5800 rpm, it is in fact outputting the following amount of torque at that HP peak:
265 = (T x 5800) / 5252; solving for T yields 240 lb-ft @ 5800rpm.
What does this mean? Means that the MDX has impressively-flat torque output all the way to redline. Only a mere 13 lb-ft less than at its very broad mid-range!! That is very admirable. Especially since this is also true at ~2000 rpm. |
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| eurohazard |
| Nice explanation! You're awesome. |
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