Hi

my C6 ls3 on the dyno only put out 378 Hp and 367tq


I would like to know why some car get alot more hp and the tq is must lower?

like : 526Hp 467tq ??


Thanks

 

Because it's stock? 526/427 is a very modified LS3.

San

 

the 526 prob has h/c with bolt ons or a simple blower with bolt ons

 

No sorry I mean the hp to tq number ?

My car had about the same hp378 has tq367

why do modified car have have higher hp number but the Tq is lower?

Thanks

 

A complete answer would require a couple of hundred pages of tech talk to explain the difference. Take a look at small diesel engines and you'll see just the opposite TQ/HP relationship. Lots of diesels with 450TQ and 250HP.

Simple answer;

Torque is measured, Horsepower is calculated from the Torque reading and is dependant on RPM.

Torque is dependent on displacement and compression.

Horsepower is how fast the Torque can be applied.

 

There are three ways to increase torque...increase displacement, increase compression ratio, or increase volumetric efficiency. Assuming stock displacement/compression ratio, volumetric efficiency is the only way to increase torque. This is achieved by changing intake/exhaust manifold, throttle body, MAF sensor, heads, and cam to increase flow at peak torque RPM sometimes at the expense of low RPM torque. But the bottom line is you're not going to get large increases in torque with the above parts, forced induction (turbo/supercharging) is the only way to achieve that.

HP is totally different as you can see by the equation used for its calculation...HP=T*RPM/5252. By looking at the formula, there are only two ways to increase HP...increase torque or increase the RPM at which you make torque. The cam is the "brain" for the engine and determines the peak of the torque curve as well as where it occurs. In general, cams with longer duration have a little higher torque numbers but make less torque at low RPM and more at high RPM compared to a cam with less duration but the shape of the two torque curves is basically the same...a "bigger" cam effectively shifts the torque curve to the right on the Torque vs RPM graph and a little bit up. With torque staying up at a higher RPM, the engine makes a significant amount more HP even though torque is only up slightly.

Two examples of the same engine different cams:
1) a stock cam gives peak torque of 400 lb-ft occuring at 4000 RPM, peak HP of 400 occurs at 6000 RPM which means torque at 6000 RPM is 350 lb-ft.

2) a high performance cam with all the mods above gives peak torque of 460 lb-ft occuring at 5000 RPM while torque at the HP peak of 6800 RPM is still 410 lb-ft which means HP is 530 at 6800 RPM.

The 60 lb-ft increase in peak torque translated into a 130 HP increase in peak HP because it was amplified by the increase in RPM at which it occurs at.

 

HP is measured on a Dynojet chassis dyno and torque is calculated...just depends on how you want to do it. HP is the rate at which work is done...torque is a force.