HP and Torque

[wormdoggy]

This could be a silly question but I am truly curious to understand how the ZO6 has 500hp and only produces 475ft/lb of torque while the Viper produces 525ft/lb of torque with similar HP.



What causes this variation ?

Thanks
Patrick

 

[SRTRICKY]

I have no idea but maybe v8 vs v10 has something to do with it

 

[BlueGTS]

There are 100 reason's people could give as to why, as one is a small block V8 and the other is a big block V10. One thing you have to remember is the HP and TQ numbers quoted are peak numbers and do not speak to the area under the curve. This makes it hard to directly compare the two. With that said, the main reason for the torque difference is one is 7.0 liters and the other is 8.3 liters. Generally, all things being equal, the more displacement a motor has the more torque it will produce.

 

[Big Medicine]

It's not complicated.

It's the process of achieving high RPMs at peak torque output versus peak torque at any rpm. (respectively)

TQ(RPM)/5200= HP (which is b$ anyway given SIMILAR OPERATING LIMITS, e.g rpm range; effectively, the rpm becomes the second constant)

http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=UBB14&Number=503522&Forum=UBB14&Words=torque&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=6months&Main=503320&Search=true#Post503522

 

[ViperGMC]

HP is a calculation and is a resultant of torque and RPM.

Horse Power = Torque X RPM divided by 5252

So a much better comparison of a car’s power should be torque not HP. Torque is what you feel when you stomp on the pedal. The Viper is a torque monster and to me that is essence of a Viper, that is what make a Viper a Viper.

The graph of RPM and torque is where all the variation comes in as BlueGTS stated.

 

[GR8_ASP]

I am going to disagree a little. Thrust is what you feel. Thrust is (engine torque x trans gear ratio x differential gear ratio) / tire rolling radius. Therefor for a given gear ratio and tire coombination torque indeed is what you feel. But if the torque is developed at a higher engine speed the gear ratios can be increased (numerically) to provide a higher thrust at a given torque.

For comparison the new Z06 has a higher numerical differential (3.42 vs 3.07 I believe) and a lower numerical 1st gear raio. But because its redline is 7000 rpm instead of 6000 rpm, it is able to achieve 60 mph in 1st, while the SRT hits fuel shut-off 1 mph BEFORE 60, thus requiring a shift to achieve a 0-60 time (this is based on my car and may differ slightly by tire diameter and engine cal changes through the years).

So, the Z06 has a clear gear advantage everywhere. The 3.42 vs 3.07 alone makes up about an 11% difference. So we need 11% more torque just to make up for that difference. Almost the same difference between the engine speeds at peak hp. Now even with the gearing advantage the Viper still provides more thrust throughout the speed range, but the difference is not large.

 

[Viper X]

3.55's will fix that

 

[GR8_ASP]

A ratio change alone will not . The reason is you will now be in second gear when the Z is still in 1st (for another 10 mph). HP is HP, and when properly geared the car with the most HP under the curve (from shift point to shift point) will win, all other things held equal.

The good thing is that on the street it will be likely that the Z owner will start in too high a gear to keep the revs lower, and thus lose the gearing advantage.

 

[Big Medicine]

Nothing downstream of the flywheel proves anything about power developed & quoted from the flywheel.

Gears don't make a car faster; maybe quicker through the 1/4 mile trap, but I doubt it would have any significant affect in a half mile shoot out.

I've seen a lot of posts on here from guys who have swapped gears, run to the track, and experienced no change in acceleration, per the timing lights.

It feels faster is what they will tell you.

0-60 is an arbitrary number; I wish they would change it to 0-70. Isn't that a predominant speed limit in this country?

Maybe 0-75 would be a cute one since most people cheat the speed limit by 5 mph anyway. I think that's where they got 60 mph from during the 55 mph speed limit days. Someone wanted to know which car could reach cruising speed first, they picked 60.

I vote for a new testing protocol to prove the Vipers are just as fast. Or quick.