stingray454

My '02 Z06 seems to suffer from low torque syndrome for some reason. The car always seems to turn low torque numbers, despite horsepower figures that have been about average for an '02 and with my mods.

Bone stock, my car dyno'd 353 rwhp but only 340 rwtq. Compared to other '02 Z06's, the horsepower is good, and right at the median for '02s. But I think the torque is on the weak side compared to other '02s - '04s.

Even after I modded it, while the torque numbers went up, they still lagged behind the horspower and seem to be less than what other '02-'04 Z06s get with similar mods. 380 rwhp seems to be average for the mods I have, but only 363 rwtq seems light again. It seems most cars are at least in the 370's with the same mods.

Any ideas what would cause a motor to have normal horsepower, but lower than normal torque?

If it helps in diagnosis, it looks like my torque peaks at about 5,000 RPMs, and my horsepower peaks at about 6,000 RPMs, and the horsepower and torque lines intersect at 5,250 RPM's.

Am I worrying about nothing, or is there something wrong?

rbartick

You might be getting yourself worried over nothing. Your HP and TQ are close to what they should be. It would be helpful if you posted some of the runs. You might have spark knock.

This is what I did stock with less than 1000 miles:


Click image for a larger view


This is what I did after an airbox change and some LS1Edit changes done in my garage


Click image for a larger view

stingray454

Here is the dyno sheet:

johnC5

All you need to look at is TQ, as HP is derived from TQ with a linear equation:

HP = TQ*RPM/5252

When RPM < 5252, HP is scaled down, when RPM > 5252 HP is scaled up.
HP = TQ when RPM = 5252.

If you increase TQ, HP increases linearly (e.g. double TQ, HP doubles).
If two cars have equal peak TQ, but one has more peak "HP", that means that the higher "HP" car has less TQ drop at higher RPM's (above 5252).

Peak TQ or "HP" does not determine performance, but rather the total area under the TQ curve (unless you have an CVT transmission that can keep the engine RPM at max TQ all the time). This is one of the reasons a ~200"HP" electric car can beat a ~405"HP" gas car 0-60 (electrics have a very flat TQ curve, with peak TQ at 0 RPM).

Thus, you could load your dyno curves into Excel and add up the dyno TQ samples to get an estimate of TQ curve area to compare with other cars (see also Simpson's/Trapezoid rule)).

Thud

This is true of every single car on the planet.
Well, except for ones that have redlines below 5250 rpm anyway.
The exact number is 5252 RPM.

This is because horsepower is not measured, but is mathematically derived from torque and RPM. So based on that equation, the numbers are always equal at 5252 rpm.

Of course, that number changes if you use the metric system ("Watts" and "newton meters")

stingray454

Since HP is mathematically derived from HP, why is it that my torque numbers are low but my HP numbers are normal relative to other Z06's?

johnC5

After 5252 RPM, "HP" is being scaled up from TQ: your engine has similar TQ at higher RPM's to other engines. If you compare TQ plots, you'll see that your curve is lower at lower RPM's, but similar at higher RPM's to the other cars with similar peak "HP". You could say your engine has lower TQ at lower RPM's, but similar TQ at higher RPM's.

To keep it simple, just compare TQ plots.

SAz06rEP

Well I finished my build about two months ago and got it dynoed. I was happy with the hp results but the torque was significantly low. Any idea on what would cause such low numbers. I will add my Dyno graph as well. I did have a intake and injector leak which I have fixed but I'm wondering if there could be something else contributing to these numbers.

Here are my mods
-Tsp stage 1 243 heads
-Fast 90 intake ported
-MS3 cam
-Ls2 ported tb
-.650 dual valve springs
-Comp cam trunnion upgrade
-Texas speed 7.400 push rods
-Ls2 timing chain
-Powerbond 25% underdrive pulley
-Long tube headers
-SLP loudmouth exhaust with x-pipe
-Ford red top injectors
-Ported Ls6 oil pump
-Vararam intake