At 01:29 PM 2/7/05, you wrote:
>--SNIP--
>Anyhoo, my brain went "does not compute" on me; there's probably a
>simple explanation, but I had to check. I'm assuming the numbers
>weren't a typo, so are the DragTruk times out of date perhaps? I
>would have expected 13.70s out of a 4300-4400lb truck at that power
>level. -Jon-
I've been a little puzzled myself after seeing lots of very impressive peak
numbers on all the Dakota forums with higher than expected ETs.
I know that the shape of the power/torque curves and where the peaks occur
are more important in projecting likely ETs than the actual peak numbers alone.
"Area under the curve" to ex-Math teachers :-)
Also, the type of dyno used and, probably even more so, the person who is
behind
the wheel on the dyno can have a fairly significant role in the numbers.
I have read quite a few times that the "Mustang" dyno gives higher numbers
than the "Dynojet" and, even with the Dynojet, numbers can be different
depending upon which software is being used. How the vehicle is strapped
in by the operator can have a pretty huge influence on the numbers as well.
I used to have my dyno done at a shop in Toronto who, I found out a couple
of years later, had a reputation of being on the high side by at least
10-15 rwhp.
Generally speaking, peak rwhp of 260 to 265 should translate into just
breaking into the 13s. When I first broke into the 13s (13.98), that's
where my peak rwhp was (263 @ 5800) but the curve was
pretty broad and flat. Peak torque was not an impressive number (250 @ 4800)
but its curve was broad and flat as well.
When I advanced my cam timing by 3 degrees, I was expecting to raise
the low and mid range torque some but also at some cost to high end hp.
Performance literature suggested that nothing would be added to the
peak numbers. Sure enough, my 60' times dropped to be in the 2.03-2.04 range
consistently, 1/8th times went from 9.0x to 8.8x times and 1/4 times
went from 13.98 to 13.76. I ran the bottom 1/8th in 4.95 when I did the
13.98 and 4.94 after advancing the cam timing so fortunately it did not cost me
after the 1/8th :-) I suspect another dyno. session would reflect this.
Going to drag radials many, many years ago from my all-season Dunlops
gave me a 3/10th drop.
Where I've found to be invaluable about dynos. is that it's a pretty good guide
in seeing/confirming where improvements are needed so that you have
a pretty accurate idea what mod is needed next for improvement and
whether it will complement your existing mods. That's just been my
experiences.
The best mod for our trucks which have the aerodynamics of a shopping mall
is a huge tailwind :-P
Bob
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