HP/TQ Graph

[kenkillsr]

Tech's;
I recently read an item in TL wherein the tech stated; "the most efficient operation, {sweet spot}, is where the HP and TQ curves intersect."
Since reading this, I've been searching for the chart/graph relating to my 2005 E350 6.0L PSTD.
Anyone know where I can find one or more?

 

[tonkadoctor]

Might as well give up that idea... on the 6.0 they dont intersect. In fact they don't even come close until after 3500 RPM.

This pic is from a 2003 Ford 6.0 service manual WARNING... The entire manual is 65-68 MB..... NOT dial up friendly

You must be registered for see images attach

 

[argve]

I read that as well and it's geared more towards engines that are not so one sided (like gassers) on the torque (building torque at low rpms)

with a V8 diesel if you can keep them around 2k they normally do pretty well on fuel mileage vs hill holding power.

 

[tgatch]

HP and TQ is ALWAYS equal at 5252 RPM's hence the equation of

TQ * RPM
------------------ = HP
5252​

Or

HP * 5252
------------------ = TQ
RPM​

Peak volumetric efficiency for ANY engine is at TQ peak.

 

[rubberfish]

We fiddled around with that formula at the
last dyno event, and the results were not
consistent or accurate. For example. A 12V
at 400rwhp makes 1000lbs of torque. While
a 24V is up at 500rwhp to make the same
amount torque and about 600rpm lower too.
It's about as accurate as one of those online
"how fast is my car in the 1/4 mile" sites.

 

[tbirdfiend281]

maybe im just not very well versed on this subject, because i haven't been keeping up with my science's lately, but i don't understand how 'HP and TQ is always equal at 5252 rpm's of a motor'? like whats the theory behind that? it seems to general to pertain to every engine out there

 

[tgatch]

We fiddled around with that formula at the
last dyno event, and the results were not
consistent or accurate. For example. A 12V
at 400rwhp makes 1000lbs of torque. While
a 24V is up at 500rwhp to make the same
amount torque and about 600rpm lower too.
It's about as accurate as one of those online
"how fast is my car in the 1/4 mile" sites.

It's not accurate on a chasis Dyno. Get an engine load dyno and you will find that it is accurate. Drive line loss, torque multiplication through gearing, plus different tire diameters, wheel weights rotational mass differences and you've just added a TON of variables that will skew the results.

 

[tgatch]

maybe im just not very well versed on this subject, because i haven't been keeping up with my science's lately, but i don't understand how 'HP and TQ is always equal at 5252 rpm's of a motor'? like whats the theory behind that? it seems to general to pertain to every engine out there

Horsepower is 33,000 foot-pounds of work per minute. By this measure, one horse can raise 33 pounds 1,000 vertical feet in a minute, or 330 pounds 100 feet in a minute, or 3,300 pounds 10 feet in a minute, and so on.

I will quote from How Stuff Works:

There is a direct relationship between horsepower and torque. You can convert torque to horsepower with the following equation:

HP = Torque * RPM / 5,252

That 5,252 number, by the way, comes from dividing 33,000 by (2 * pi). Imagine taking 33,000 foot-pounds and walking it around in a circle rather than a straight line.

Read the whole article here

Physics are physics boys. Just because a Chasis dyno doesn't match up doesn't make it not true. As stated before a chasis Dyno is not as accurate as a true engine dyno where one eliminates transmissions, clutch/torqueconverter , rear end ratio, differing tire and wheel weights, etc...

 

[tgatch]

Just some dyno's to prove a point:

A rotary engine from an 86 RX7

You must be registered for see images

A 454 Dyno:

You must be registered for see images

I'd like to find a diesel dyno of over 6000 RPMs. But you would have to agree that a rotary and a 454 Big Block are about as opposite as it gets and their HP and Torque lines cross at pretty dang close to 5252 RPMs

 

[tgatch]

Here is a printout of a Crate LS7 Engine Dyno chart:

You must be registered for see images

at 5200 RPMs it is making 539lbs-ft and 533 HP.

Any further questions about HP and TQ being identical at 5252?

BTW pick any RPM and you will find that the equation works FLAWLESSLY as this was an ENGINE DYNO.

 

[gamudslinger88]

I'd like to find a diesel dyno of over 6000 RPMs. But you would have to agree that a rotary and a 454 Big Block are about as opposite as it gets and their HP and Torque lines cross at pretty dang close to 5252 RPMs

The way the equation is set up all dyno pulls are the same at 5250 rpms. If im not not mistaken.

 

[tgatch]

The equation is set up that way because that is how horse power is figured out.