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With the new 600-horsepower 2008 Dodge Vipers starting to hit the streets, it was only a matter of time before someone put one on a dyno to see what kind of juice the snakes are sending to the rear wheels. That someone, in this case, is longtime Viper tuner Hennessey, and their new car made 546 horses and 516 lb-ft of torque in stock trim. According to DragTimes, if you factor in a 13% drivetrain loss, the new Viper is actually making around 615 horses. Not shabby, to say the least. Hennessey dynoed the car a second time after making some exhaust mods and was able to raise those numbers to 574.95 rwhp and 537 lb-ft. Head over to DragTimes to see the graph. We'll take one in green, please.
Thanks for the tip, Fiske!
[Source: DragTimes]
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Reader Comments (Page 1 of 2)
adam @ Dec 8th 2007 6:43PM
Why is drivetrain loss assumed to be a percentage rather than a set amount of torque/horsepower?
mastersmite @ Dec 8th 2007 6:57PM
Drivetrain loss is based on the internal friction of the driveline. The loss is a varying amount because friction is a function of the force applied and the coefficient of friction of the , thus more power is loss as the force applied increases.
MikeW @ Dec 8th 2007 10:37PM
When gears mesh in the transmission, the efficiency isn't 100%. Not even straight cut gears are there.
So in the TR-6060 power flows down toward the countershaft via the front gear pair, then back up toward the primary axis. Except for 4th, which is direct drive & reverse-with adds another gear mesh, so the parity is odd.
Then the ring/pinion of the axle isn't close to 100%. There is a helix angle, and then the shaft axes are offset (hypoid)
So for a higher drivetrain efficiency you want to keep the number of gear meshes down.
Bad Bugatti Veyron! 4 gear meshes to get power to the rear axle.
http://www.gizmag.com/go/4909/picture/17749/
If they could have sent power through the valley of the block, the could have two total for the rear, and three for the front.
MemphisNET @ Dec 8th 2007 7:19PM
Awesome. Scary!! But awesome :D
why not the LS2LS7? @ Dec 8th 2007 7:25PM
546HP / 0.87 = 627.5HP.
I don't know if I trust these guys cailbrate a dyno if they can't do math.
Mike @ Dec 8th 2007 7:34PM
615 horsepower at the flywheel with a 13% loss gets me to 544 horsepower (close enough to their 546).
615 / 1.13 = 544
SPF @ Dec 8th 2007 7:49PM
13% loss means you have 87% left, so it should be whatever the horsepower amount times 0.87, so LS2/LS7 is right.
SPF @ Dec 8th 2007 7:53PM
I meant BHP * 0.87, just to be clear.
So WHP/0.87 should equal to BHP.
Mike @ Dec 8th 2007 7:27PM
There must be some seriously restrictive pipes on that beast from the factory if exhaust mods alone can find gains of almost 30hp at the wheels!
I'm usually pretty skeptical about what comes out of Hennesshady, but nice work on the new exhaust if it's true.
Rob @ Dec 9th 2007 4:20PM
its not uncommon for aftermarket exhaust systems to free 20-30hp from stock v8 motors, so this would be in line for this v10. Its very possible this exhaust setup deletes the cats and therefore is not street legal. CAI setups often free 10-15hp on mustangs and camaros. Larger displacement engines respond number wise much better to mods like this than smaller motors. Its not like an I4 where $1200 in parts gains 11hp and 7ft-lbs. It seems like a big difference number wise but when looked at as a % gain the results are very similar.
Billy @ Dec 8th 2007 7:37PM
Ive said it once, its been said a hundred times, Hennessey is a crook.
Vivek G. @ Dec 8th 2007 8:18PM
That doesn't make the new Viper any less powerful.
why not the LS2LS7? @ Dec 8th 2007 8:06PM
Nor does it make it any MORE powerful.
Look at it this way, they set out primarily to sell add-ons here. Step one to selling add-ons to Viper owners: complement them on their car and how powerful it is. Even if you have to lie to do it.
Marketing and accuracy rarely collide.
MGBYG @ Dec 8th 2007 11:32PM
Cheaper than Remy Martin....
Taylor @ Dec 8th 2007 8:16PM
Annnnnddddd, -takes out loan-. I must have this.
Carlos @ Dec 8th 2007 8:59PM
Vipers are a POS truck engined car.....That I absolutely love
MikeW @ Dec 8th 2007 10:17PM
A truck engine with coaxial camshafts.
But only variable exhaust valve timing.
They will let the supercharged vette come out, then install variable intake valve timing.
Carlos @ Dec 8th 2007 11:53PM
I was kidding dude, I didn't know if the Avatar said enough
MikeW @ Dec 9th 2007 1:34PM
Best [odd firing V10] truck engine ever!
only engine with coaxial camshafts.
3000GT TwinTurbo @ Dec 8th 2007 10:58PM
best bang for the buck on the market today. I would buy one is a second if i had the bank (sigh).