Ford's numbers don't add up

[Chevy Ryan]

Somewhere in the horsepower battles, Ford has overlooked some figures for the power ratings of the Power Stroke. My example is the 2002 Power Stroke with manual tranny. Ford advertises 275 HP at 2600 rpm and 520 lb-ft at 1600 rpm. All fine and dandy. But when you calculate the torque at 2600 rpm, it comes out to 556 lb-ft!! A couple of strange things here. For one, I have never seen a diesel make peak torque over 2000 rpm, never mind 2600. And two, if in fact the engine does make 556 lb-ft, why doesn't Ford advertise that figure instead of 520? Something here is fishy. Torque is calculated as follows: HP x 5252 divided by rpm. Anyone have an explanation?

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Ryan
2001 Chevy 2500HD 4x4 6.0L

[Colorado Kid]

Well,

The only numbers I could find for 2002 PSD w/ manual trans showed 275 HP @ 2800 RPM, which is 516 lb-ft.

What is interesting though, is that both that manual trans rating and the 250 HP @ 2600 RPM rating for the automatics, ignoring for the moment the other thread which shows increased torque with the Auto being released soon, anyway, both ratings show that the PSD is producing almost exactly the rated peak torque clear up at the peak power RPMs. This would seem to indicate (pretty much as has been claimed) that the fuel curve is artificially trimmed to reduce peak torque, and that peak torque, or very near peak torque, is produced over a broad plateau from 1600 to 2600 or 2800 RPM.

Incidentally, the same is true of the Duramax. 2002 rated as 300 HP @ 3000 RPM calculates 525 lb-ft. Using the 2001 numbers 300 HP @ 3100 gives 508 lb-ft. Either way, a very high percentage of rated torque is still available clear up at rated power RPMs.

Another way of saying this is that, in both the PSD and the Duramax, short of increasing governed engine speed, there is no modification that can be made to increase power that will not also increase peak torque.

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Waiting for...2002 GMC 2500HD CC D/ZF SB Summit/Graphite 2WD
Ordered 7/23/01 TPW 11/05/01 CANCELLED 12/13/01 (Day 153).
Orderred Again 1/3/02...Fire Red/Graphite this time.

Driving 1991 GMC Sierra 1500 V6 5sp 2WD LB 172,000 miles 22-25 MPG
This is not a fast truck!

[COBRAJET]

As posted above the torque curve is flat as a pancake from 1600-2800. Just perfect for a diesel. The DMAX is tuned the same way. The Cummins is a little more peaky on the low end, but no slouch either. The fun will be in 2003 when the new PSD and Cummins make it to the dealers...CJ