But again, unlike a dyno which can correct for environmental conditions, even with isolating all the other factors, we'd still be left with the same car doing really well in TX in the winter vs not so great when in Colorado in the Summer.I wouldn't say "accurate" but you could draw some conclusions.
Too many factors to be accurate (manual vs. auto, traction, starting gear and rpm, etc).
Given that some people can watch an episode of family guy in between shifts or that starting in the wrong gear or at the wrong rpm can have pretty large effects,
the most ACCURATE way to do it would be to do it JUST like a dyno pull. All cars start in their 1:1 gear and remain in that gear from 60-130. Assuming traction, the resulting numbers would be way more comparative.
Force = mass x accelerationAny chance you can break down this formula?
So far - this is really accurate. I ran 5.15 with 860 whp. The car trapped 148+ MPH on that run. That said - I found out my tune started me in 1st instead of 2nd gear - so with some luck - I may be able to get that 60-130 into the high 4's. Hoping to get to the track this Saturday - weather permitting - to find out. I will report back.It's a good metric of how quick a car is, but not necessarily horsepower. The problem with estimating horsepower from a time is that it doesn't take into account variable like weight, drag, auto or manual, traction, etc.
But for a typical mustang weight, auto, and assuming traction is fine, here is an average hp guess from my experience:
4s: 900+ (maybe even 1000 to really dig into the 4s)
Obviously that's not perfect and don't use it as a rule of thumb but it gives a general idea
The number may be smaller since the math is assuming constant power. That 485 whp is assumed from start to finish. That could be more accurate for a Tesla with 1 gear, but internal combustion engines with multiple gears will have horsepower output constantly changing as it goes through the rev range and shifting gears. Most people will compare the math above to dyno's but only fixate on peak power. A more accurate comparison would be the average whp over that interval.If you take a typical example of an s550 pulling a 7.0 second 60-130, the simplified math is:
(130-60) x 5280/3600 / 7.0 / 32.2 x 4200 x (130+60)/2 x 5280/3600 / 550 = 485 whp
I omitted drag so including it would push the number higher, but not to the ~650 it would take to hit 7 seconds. I’ve wrestled with this several times over the years; that the physics always seems to result in a smaller number. We had the same issue with the vcmscanner math.
The conclusion I’ve settled on is that a lot of power goes into overcoming rotational inertia of all the driveline parts stem to stern, which isn’t easily accounted for. Even dynojet applied a correction because they had the same issue.
I’ve found with the vcmscanner, if I make pulls in 4th (a10 with 3.55’s) I have to multiply by 1.2 to get numbers equivalent to dynojet. The correction is smaller if I make higher gear pulls.
I agree with this conceptually. I had a car once that pulled 146 mph with only 680 rwhp because it made 680 rwhp all the way down the track. However, if you look at the power curves on these cars pulling 7.0 60-130, they don’t really below 485 hp at any time after the launch.The number may be smaller since the math is assuming constant power. That 485 whp is assumed from start to finish. That could be more accurate for a Tesla with 1 gear, but internal combustion engines with multiple gears will have horsepower output constantly changing as it goes through the rev range and shifting gears. Most people will compare the math above to dyno's but only fixate on peak power. A more accurate comparison would be the average whp over that interval.