Ok, here's the deal. I drive everything using the tachometer. Yep, even my
2.5L TJ. I determine shift points according to torque rating for the engine.The problem is, I'd like to get my hands on a Torque vs RPM curve, - or tables. Usually, the manufacturer published a composite graph, showing Engine Torque and Horsepower vs Engine RPM.
Not Jeep. Jeep doesn't even know what I'm talking about.
Anyone out there have such info?
Thanks Matt
97 TJ 2.5L 5 spd
Jeepers are not fond of Dyno's my theory is that we are sooo cheap that Dyno's would show us how little we gain modding our I6's (and especially the 4 bangers) that it would ruin our favorite pass time.
And before you think I'm purely joking look at all the claims of 40 horse power for the 4.0 head swap (into a 4.2).
Bill:
Do you have a link to a similar torque curve chart for the Jeep 3.7L V-6 and/or the 3.8L V-6 used in the '07 Wrangler?
Tom
Hang on a mo, Power and torque curves always cross at 5252 rpm !
Dave Milne, Scotland
Yep, that is probably why Jeep isn't publishing the charts for the V-6's
Hi Bill,
No, I meant that power and torque are mathematically linked..
Torque = Force x Radius Power = Force x Distance / Time
Given that the definition of 1 Hp is the ability to of a horse to move
33,000 lb ft / lb in a minute, we can divide that by the circumference of a circle (2 x pi x r) to get the number of times a horse could move 33,000lb round a circle of diameter 1 foot in a minute. That is 33,000 / (2 x 3.1415926 x 1) = 5252.So that's true for any engine.
Dave
Read it carefully - I said 5252 rpm. Although I made a small mistake - I said a circle of 1 foot diameter and I meant a circle of 1 foot radius. As to whether an engine will rev that high or what type of cam it uses to get there is immaterial ; it just means that the power and torque curves WILL NOT cross each other.
Dave
Well they won't cross if the engine won't rev to 5252 rpm !!!
Dave
Bill, you are right in that this makes apples equal to oranges, because torque and power do not even describe the same physical quantity. Dave's
5252 rpm is an accident of the units used, and has no physical significance whatsoever. By proper selection of units or system of measurement, one could say that "torque is always equal to power at XXX rpm" where XXX is any number!If you convert to the SI (International System) and use rotational velocity instead of rpm, you come up with the relation
W = T * r
where W is power in watts, T is torque in newton-meters, and r is radial velocity in radians (a dimensionless quantity) per second. Under this system, the graphs cross when r is equal to 1.
SI units are explained at
see kids, I told you higher math was usefull for common everyday life...
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