" The World's Fastest Piston Engine in a car is a small block Chevy " !

[oldblu65]

At last fall's FIA meet at Bonneville , a streamliner powered by a twin turbocharged small block Chevy engine ( 347 c.i. - 2077 HP ) set the record at 462 MPH . The same car with a smaller ( 300 c.i. engine - 1980 HP ) went 390.709 MPH ! The teams goal is to top 500 MPH with this same combination ! A full report of this can be seen in the April 2012 issue of Hot Rod magazine and NO ... I'm not associated with that magazine in any form !

[MagicRat]

http://sports.yahoo.com/nascar/blog/...=nascar,wp5428

[Ol'Jim]

Originally Posted by oldblu65

At last fall's FIA meet at Bonneville , a streamliner powered by a twin turbocharged small block Chevy engine ( 347 c.i. - 2077 HP ) set the record at 462 MPH . The same car with a smaller ( 300 c.i. engine - 1980 HP ) went 390.709 MPH !

Something doesn't sound right about the HP-MPH #'s.
Only 97 HP difference to gain 72 MPH?
As MPH increases, the HP requirement goes up almost exponentially. From my drag racing experience, (with a heavy, 3750# car), it took approximately 115 HP increase, (from 325, to 440 HP), to improve from 96MPH in 13.4 seconds, to 110 MPH in the 1/4 mile, (12.3 seconds). That is a 14 MPH gain for 115HP.
To get same car to the 11-flat ET range, at 122 MPH, required almost 200 additional HP, (637 HP). Those 197 horses only gained 12 MPH. If those guys went from 390 MPH, to 462, with only a 97 HP increase, (1980-2077), that is remarkable.

[MagicRat]

Originally Posted by Ol'Jim

Something doesn't sound right about the HP-MPH #'s.
Only 97 HP difference to gain 72 MPH?
As MPH increases, the HP requirement goes up almost exponentially. From my drag racing experience, (with a heavy, 3750# car), it took approximately 115 HP increase, (from 325, to 440 HP), to improve from 96MPH in 13.4 seconds, to 110 MPH in the 1/4 mile, (12.3 seconds). That is a 14 MPH gain for 115HP.
To get same car to the 11-flat ET range, at 122 MPH, required almost 200 additional HP, (637 HP). Those 197 horses only gained 12 MPH. If those guys went from 390 MPH, to 462, with only a 97 HP increase, (1980-2077), that is remarkable.

This is an excellent observation, and one I missed entirely.

I am absolutely no expert on this, but I suspect there were other factors at work which improved the speed. The salt flats are less predictable than the drag strip. These guys may have tuned other things between runs, such as suspension set up, downforce, shift points etc to maximize the potential of the car. It's also possible the faster run could have occurred during more favorable weather conditions.

[maxwedge]

My pictured race car went 122 in the 1/4 at 3600# with driver it dynoed at 505 hp. Every hundred lbs weight reduction or addition cost/reduced .10 sec and 2 mph. up or down

[Ol'Jim]

Originally Posted by maxwedge

My pictured race car went 122 in the 1/4 at 3600# with driver it dynoed at 505 hp. Every hundred lbs weight reduction or addition cost/reduced .10 sec and 2 mph. up or down

Good point, Max Wedge! My car weighed 3750 without driver. At the time, I was a svelte 170#, so total weight was 3920#. With the frontal area (aerodynamics / coefficient of drag) factor probably being similar for our cars, the extra 320 pounds on my ride likely ate up about 100 additional HP to reach the same MPH. To further demonstrate your point regarding weight, I once made a pass in my mild/stock BBC Chevelle by myself, went 13.74 @ 93 MPH. It was a Friday night/play night at the track, so 2 buddies hopped in, and we went down the track about 30 minutes after my solo pass. The car slowed a bunch, to 13.98 @ 88 MPH. Darn near made me think something was wrong with it! A short while later, (with a cooled-down car and slightly cooler air temps), I went 13.72 @ 94 MPH.
So yes, your calculations are very accurate! (And it proves that removing weight is often the cheapest way to "gain" HP!!).

[Ol'Jim]

Originally Posted by MagicRat

This is an excellent observation, and one I missed entirely.

I am absolutely no expert on this, but I suspect there were other factors at work which improved the speed. The salt flats are less predictable than the drag strip. These guys may have tuned other things between runs, such as suspension set up, downforce, shift points etc to maximize the potential of the car. It's also possible the faster run could have occurred during more favorable weather conditions.

Agree with you, Magic Rat. There most certainly had to have been other factors at play, "tweaks" made to the car, (particularly to aerodynamic trim - drag/downforce - as one goes up or down, so does the other).
Another factor that I overlooked, which makes a HUGE difference, is wind speed/direction. With all other variables the same, a headwind (and to a lesser degree, a tailwind), can change my dragstrip speed by +/- 5 MPH. And Density Altitude, (Air Quality, with regard to Temp, Humidity, and Barometric Pressure), has a MAJOR effect on Horsepower output. I assumed they factored the DA into their HP calculations, but perhaps not...