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Discussion Starter #1
where can I get or see the P$T curve for 3.5L engine? Is there any good article on transmission performance or chart for the relationship between ratio and torque or power?
 

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I see no "little problem".
Other than Crank HP means damn near nothing,
and can't be reproduced out here in the real world.

The one thing that Crank HP can show you
is the personality of the car and that is important.
The torque and HP both are of the roll on type.
Not virtually flat, like a diesle, not peaked
like a racing engine.
And that is good for a daily driver.

You can get a lot more HP and Torque
(probably) out of the engine
but it will become a "peaky" engine.
Ultimatly faster, but driveability will suffer.

Homer
 

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I don't know.


Homer
 

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Max horsepower and max torque normally occur at different RPM's.
 

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You ought to try that on a 1948 Chrysler before you make a bold statement like that.


It will never happen.


Homer:D
 

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How can they be the same at 5252 if the engine can only do 4800?

;)


Homer
 

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Horsepower is calculated by the formula:

Torque = (5252 * HP) / RPM

If the RPM = 5252, Torque = HP.

Hope that answers the mystery!
 

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hfelknor said:
How can they be the same at 5252 if the engine can only do 4800?

;)


Homer
Enforcer said "mathematically match at 5252" so the same formula applies for the low revvers too. But very clever with the 4800 rpm redline comment! ;)
 

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So, Back to THIS car and THIS chart.

What is the feeling?
Are the HP and TQ equal at 5250?

Is this a fake chart?

Homer
 

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LOL! Good one Homer.

Well, the feeling in the Z forums was yes. Why and how is still a question. There are numerous plots taken at the rear wheels from owners that had theirs on dynos though, so it became a moot point.

If you assume the abscissa and ordinate units are correct and:

Assume torque is correct (Dynos measure torque?):
maxHP=rpm X torque / 5252 = 250HP.

Or assume HP is correct (Dynos measure HP?):
maxtorque= 243lbft.

Of course it could also be that the plot is simply skewed by 400rpm and the max values are correct.

Or it could be that they measured both power and torque and the answer is in the test setups.

Could also be a conversion error, say from Nm to Lbft.

Whatever it is, Nissan advertises an engine that violates the laws of physics...and they don't have the dubious honor of being the first to do it and unfortunately, won't be the last.
 

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THat dyno chart is fishey, imo.....

the Y axis values are not to scale with the X, and you wont get that 1:1 happening (i have seen it close, many times on bike pulls, as my bike redlines at 12.5K).......

the chart does show character of a broad band of power, with no peaks (either there was a smooth factor of 6, or, ZERO wheel hop/slip, or ????) present.......

i wonder......

1)smooth factor(high indeed)
2)sae or std values(?)
3)type of dyno (std. drum or load control inertia)?
4)brand of dyno (DJ or mustang, or???)
5)correction value applied to correct for BHP or CHP?

anyone.......??
 

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esemes

Most of your questions don't count.:)

This is supposedly Crank HP, not FWHP.

This IS however how all manufacturers rate AND measure HP.


Homer
 

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Kris said:
interesting write up: tq v. HP
Good link Kris. Yes BUT...Depends on what you want to do with your vehicle. There are a lot of people you wouldn't want to tell that (better to have max torque at higher rpms) to.

Want to talk about ability to do work? Well lets just say you wouldn't want to grind flour, plow a field, heavy haul/tow, or off road with a Honda VVLTi, which is an amazing engine in the S2000 that develops max torque at very high rpms. For these apps you WANT max torque at low rpms, like a diesal.

And I don't want to start the LS versus Cobra debate here.
But don't tell that to the SVT guys that develop a butt load of torque just off of idle.

And I don't remember the specifics, but a lb of mass reduction is something like getting a 10HP boost. For rotating mass though, the affect is non-linear and results in even greater HP. So losing 1lb of rotating mass might be like gaining 20HP. Don't remember the numbers exactly but the overall effect. Basically a lighter rotating mass engine will accelerate faster than an engine with heavier rotating mass and more HP. So don't tell that to the motorcycle gurus like esemes.

To me, the key is in the area under the curve. In a race car, you want a torque curve that is very narrow and very peaky. A narrow but awesome power band, best left to the track. It may have the same area under the curve as a tractor engine that comes on strong at low rpms. For a fun sports car for the average enthusiast to get across town in, you want a curve similar to this one for the VQ, even though it may have the same area under the curve as a tractor or race car engine.

Match any of these profiles (peak low, peak middle, peak high) that have the same area under the curve to a CVT that can handle them and the point is somewhat moot. I do agree the key is in the gearing, tanks are a perfect example of that.

As was stated, the profile of the VQ is good for a daily driver and a fun sports car...as if we needed the curves and physics to tell us that. ;)
 
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