Torque is a measurement of the twisting force the crankshaft produces.

HP is a measurement of the work the engine can do. In the automobile world, the work is how fast the engine can accelerate the car.

You always want more HP. The person who puts more average HP to the track wins the drag race. Power to weight ratio.

The old sayings about torque off the line and HP down the strip are wrong. They probably came from people who assumed torque at low RPM is more important because it is a higher number. The reality is that HP is the number that matters. I always want to put more HP to the ground, could really care less what the torque is.

One neat thing about HP is that it transfers directly through the drivetrain. 350HP at the engine is 350HP less the drivetrain losses at the wheel. Say about 15% losses then 350hp at the engine is 300hp at the wheels. If you also have the car mass then you can calculate the acceleration that 300hp causes. Same can't be done with torque, you need the gear ratios and tire diameter to come up with the force at the wheels.

Still, at the end of the day, torque@rpm is basically the same as HP. You can math one from the other. Torque without rpm is useless though.

 

Don't get caught up in TQ vs HP-------Just drive the car
TOP TIP
Ideally you want your trans to shift at " peak HP" On a stock C5 that is from 5800 to 6000 RPM's
But just as important ---- after the shift you want the RPM's never to drop below "peak TQ" typically about 4500-4800 RPM's
This is called your "power band"
It is useless to shift above peak HP as HP drops off a ton and you start losing momentum -- Only a cam can rasie your peak HP RPM level
As far as after the RPM's drop at shift --- It is easier to do with a manual trans more difficult with an auto trans
Basically only changing rear gears helps OR also a higher looser stall converter
It doesn't have to be perfect but the closer you can get it -- the more acceleration you'll see and the faster your car will become

 

Not exactly true. If you want to maximize acceleration then you want to shift at max RPM. The slight loss of acceleration from max hp to max rpm is much much less than the loss of torque going to a higher gear.

 

Is that why they keep making performance cars with more gears? It helps to keep it at it’s max powerband?

 

Yup, keeping the engine closer to peak HP can be a faster acceleration.

For a street driven car, the higher number of gears also keeps the engine rpm closer to the rpm required for the power the driver is demanding instead of having big swings above and below the demanded power level.

 

If you were watching a top fuel car you could see the forces of torque when the car launches
those huge rear tires wrinkle as torque is applied, torque of the engine twists the frame lifting the left front wheel off the ground
once the clutch is hooked up the HP of that engine runs it down the track, drop a cylinder , you lose 1000 hp, speed goes down

 

We aren't talking about boosted nitro engines here Just N/A engines--on gas---Again there is NO benefit ro revving your engine past peak HP as you arren't gaining any accekeration--Yeah the RPM;s may climb a little beyound peak HP but to slowly--In the long run your are better off to shift at peak HP so your engine does not fall on it;s *** when you shift
A Corvette C5 engine makes peak HP at like 6000 RPM maybe 350 crank HP but if you go beyond that even to only 6500 now your peak HP has been dropped to maybe 300---And now you have to regain the momentum and HP you lost by shifting it too high-- This all takes time and loses ET not much maybe --but if you are serious about getting all the performance you can get from your engine This is common drag racing knowledge--Shift at peak HP and try not to allow the RPm's to drop below your peak TQ during the shift--

 

Well, the 02 LS1 made 350hp at 5600RPM and 360lb-ft at 4000RPM.

The 02 LS6 made 405hp at 6000RPM and 400lb-ft at 4800RPM. However, they bumped the rev limit up to 6,500RPM. Why was this then if you're supposed to shift at peak power?

This was mentioned above, but this is because when you shift, you do not want the rev's to fall below 4800RPM where max torque is. If you shifted at 6000 (even though that is peak power) the revs would drop approximately below 4800RPM (max torque) and hurt acceleration from gear-to-gear

FWIW, these are general guidelines

 

Well you can keep saying it but this is totally not true. If you actually did the math you would easily see. Shifting at max RPM is much faster. Shifting to a higher gear reduces the torque to wheels by around 30%. 1>2, 2>3 and 3>4. Way more than running the engine to the red line.

 

Finding shift points is one of the few cases where it is more useful to look at torque than power. But you need to look at the torque curve, at the wheel, in each gear. Torque in this case is not a number, it's a set of curves.

Basically, you don't want to pay the torque-at-the-wheel penalty of shifting to a higher gear until it's absolutely necessary. Which means that you want to stay in gear until the torque-at-the-wheel in that gear drops so far that it meets the torque-at-the-wheel in the next gear. It's generally a mistake to trust intuition for this stuff - you just have to plot the curves (aka "shut up and calculate") because the results depend on the shape of the torque curve and the differences between the gear ratios.

I barely skimmed this article, but the pictures illustrate the idea really well:
http://teamghettoracing.com/tech-inf...change-points/

 

Awesome. Well done.

 

What oil should I use to maximize hp? What about to maximize torque?

 

Whatever is best! Same oil works for both.

Bill

 

Everyone is entitled to their opinion and every combination my be different-- BUT I have 30 years of drag racing history and was taught by the best N/A tuner/driver in world Harry Holton NHRA record holder in B stock automatic Also by Frank Hawley
There is NO math for throttle response or acceleration or shift points Only trial amd error--- so your opinons are just that --opinions--After 2000 passes under my belt i haved tried several shifting sequences--- Nothing ever worked better than what I have learned---and shifting the way I was taught many years ago
Why would you want to shift when the engine HP drops OFF ??? That makes no sense as then your engine has to regain that lost HP and like i say that takes TIME and slows your ET

 

Excellent stuff. It shows how to put the most HP to the track during the acceleration.

 

You'll generally have better results continuing beyond the power peak because torque at the wheels is what gives you acceleration and shifting reduces torque at the wheels. You'll accelerate fastest by shifting at the point where staying in gear would cost more torque than shifting will cost. Or until you hit the rev limiter, which may happen first.

If you're looking at the power curve to choose your shift point, you might get the right answer, but only by coincidence.

 

When talking about a base C5 vs Z06, you cannot compare shift points because the gearing in the trans is very different. In a car with the MN6 trans shifting from 6000 rpms puts you in second gear about 4000 rpms which is peak torque area. In a Z06 shifting at 6500 rpms puts you about 4800 rpms. Which makes it look like GM knew where to put the red lines and rev limiters at.

 

The base C5 is not significantly different from the C5Z even though it has a different motor and a different transmission gearing. As NSFW said in the post above, its not just about where you are on the dyno power curve. You need to see the curve in every gear at the wheels. And it is significantly different because of gear ratios. When you shift from first gear to second gear you immediately transition to a curve that is the gear ratio less by 1.78/2.66 = 0.67 (MN6) or 2.07/297 = 0.7 (MN12). In second gear you have 33% (or 30% for Z) less torque at the wheels than you did in first gear. Similar gear ratios are found comparing 2/3, 3/4 etc. So comparing 6000 RPM vs 4000 RPM on a dyno sheet is meaningless. It is not telling you the power at the wheels. You can feel this effect in your car. Try accelerating from 2000 RPM in every gear. What happens? You are at the same point on the dyno.

 

Gordy: Gearing doesn't change the starting force or starting (clarified) power, it changes the torque (by increasing the distance in the equation). So if the redline was raised on the Z06 to shift past peak power (which remember was quoted at 6000RPM) it is because the shifting RPM drop is now at peak torque (which was quoted by GM at 4800RPM)

Regarding GM's role: Transmissions don't shift to a redline without being programmed to do so. They didn't take the base engine, convert it to an LS6, swap the gears, and leave the ECU alone with a 6000RPM redline. If they did, and with shorter gearing, you'd be in 2nd gear earlier but without dyno-ing the motor, you have no idea what torque and power it makes. They did not also raise the redline to 6500RPM soley to make it shift "the same" as the base model and get lucky with how the peak torque was exactly at 4800RPM. Designing an entirely new cam with different intake duration, exhaust duration, LSA, etc. was also not a coincidence lining up with the other changed figures of the car.

Same reason the C6 Z06 redline was 7,000RPM even though peak 505HP was at only 6300RPM. The peak torque was at 4800RPM, which again, would not have been reached in a shifting RPM drop if the redline was lower.

The reason we want to shift-drop into the highest torque (even if this means carrying past peak power in a gear) is to give the next gear the highest starting-torque number for HP to multiply off-of . This gives up faster acceleration

 

No. When torque is reduced power is also reduced. And thereby acceleration. There are mathematically bound together.

Ok. Here is a table showing acceleration for a car similar to a C5. More power with similar gearing. You can see that at every shift except maybe 4 to 5 you will loose acceleration after shifting. When gears are so far apart this will happen in all cars.