1991camaro1996

Can anyone set me straight as to the differences between Horsepower and Torque? I've done some internet searches and it was either explained in a way that complicated it further for me, or ended up defining Torque as kind of a low end power, and Horsepower as kind of a top end power.

As an example, if 2 cars with the exact same 1/4 mile times raced each other, one with high torque, and the other with high horsepower, how would the race look? Would the torque car jump out ahead, and then get caught by the Hp car later in the race? Or is that just low end vs top end again?

Does a quick 0-60 time = high torque, and a quick 1/4 mile time = high hp or is there little distinction.

The reason i ask is that i feel the need to understand justify the low hp rating of my TBI Camaro. There are camrys with the same horsepower figures, and it would be nice to explain the difference.

aliceempire

iTrader: (14)

Hard to explain in an easy way. Too many things you need to understand but in the end it really is simple. Torque is work being done. HP is how fast it's being done.

HP=(RPM * T) / 5252

You and I can both push a big box 1 ft. Thats work. (torque)

You push the box in half the time I do. That's how long it took to get done. (HP) You are twice as 'powerful' than me.

Typically if an engine makes more torque at a specific speed(RPM) it'll be able to move more weight than an engine that makes less torque at the same speed(RPM). Doesn't matter the speed(RPM). The Camry makes 170 HP at (just guessing) 5800RPM. Your 305 is 170 HP closer to 4700RPM. The 305 will move more weight at 4700 but the Camry will move more at 5800. (because your 305 is out of power by that rpm.)

Again there's no simple way. Just too many things to understand to get the full grip.

FRMULA88

Without torque there would be no HP.

not a "this" versus "that" comparison.

Torque = work
HP = work applied over time

But you raise a valid concern.. why does a "newer smaller" engine make the same or more HP than your "big old" V8..

The simple answer is your engine is a by-product of the energy / smog era. They took the same SBC design shrunk the bore size, thru in a wimpy cam, smaller valves and a small 2bbl tbi system.. GM took what they had in their parts bin and de-tuned it to comply with emission standards and meet fuel mileage regulations.

Fast forward 30 years and this engine is "primitive" compared to any of the newer smaller engines engineered from the scratch to make the same HP with less displacement while burning less fuel. Being installed in a smaller chassis (lighter car) also means it will also get better MPG (less weight to move) and have a better power to weight ratio.

That is not to say the big old engine is useless because with the right parts is can make more power than the smaller newer engine. but at the same token the more HP you make the more fuel you need to burn..

DanielRicany

I see horsepower as almost meaningless in comparison to torque.

Horsepower is calculated, not measured. Torque is measured.

To calculate horsepower, torque x RPM / 5252.

So if I make 330 ft lbs at 3200 RPMs, 330 x 3200 / 5252 = 201 HP.

If I make 330 ft lbs at 8500 RPMs, horsepower is a lot more. 330 x 8500 / 5252 = 534 HP.

So if you make 330 ft lbs consistently from 3000-6000 RPMs, what's the difference from making 330 ft lbs consistently from 5500 - 8500? The only thing that is different in reality is the RPM. The HP doesn't mean anything. Both cars will be equally fast.

Torque is what moves you. Since RPM is a factor in calculating horsepower, what good is horsepower?

Torque is more important than HP, however, you want to shoot for a smooth torque curve throughout your power band.

AlkyIROC

In simplest terms, torque is the amount of work being done. HP is how quickly the work can be done.

Read this link. It should help understand it a bit better.

http://www.hardtail.com/techtips/hpandtorque.html

FRMULA88

Just because you memorized a formula harldly means you know how to apply it to the real world.
although your first example is pretty close to any small block chevy (305 TBI) found in a third gen..

A car that makes peak torque from 5500 to 8500 RPM would be useless to drive on the street.
unless you lived it the middle of nowhere ,have no traffic, or curved roads and don't need to stop to turn or stop for traffic lights. So All that HP at high RPM means nothing.

I would rather have the car that made less HP but had peak torque in range that I can actually use.

at 6000 RPM, your 330 torque example makes 377 peak HP. which is pretty similar to mild 350 SBC build.

midias

Not true at all. I very much enjoy driving gen 1 S2000s and they make peak tq at 7500 and peak hp at 8300. The gen 2s were also fun but made peak tq between 6500-7500 depending on the market.

Orr89RocZ

iTrader: (20)

Yeah alot of built imports make peak trqs over 6500 rpm.

A v8 sbc making trq that high would mean large heads and cam with a hp peak closer to 8000. That would be a wild combo to run on the street. I think thats what he meant

But the more torque you make at high rpms, the more hp is created. And as explained hp is what accelerates the car over time. More hp means more mph in the 1/4 mile and usually lower ET. A motor making 330 lb ft to 6000 rpm would be slower in the same weight chassis than a motor making 330 lbft to 8000 rpm, as long as you gear to match the power bands.

We all talk hp for builds but really just making trq and placing it in different places along the rpm range. Cams and heads effect where those peaks are because peak trq is actually peak air flow and volumetric efficiency. Street cars are ok with trq peaks in the 3500-4500 range. Most sbc shorter runner intakes make broad curves. You start getting peak over 4500, thats getting into peak hp rpm of 6500+

FRMULA88

if that's what you enjoy good for you, but it's not a third gen.

FRMULA88

[QUOTE

A v8 sbc making trq that high would mean large heads and cam with a hp peak closer to 8000. That would be a wild combo to run on the street. I think thats what he meant

QUOTE]

Correct

redneckjoe

so how much torque does my 5 HP briggs and stratton make on my mower?

hmmmmm?

redneckjoe

if you've ever been on a fast street bike, you can feel HP. torque IMO, gets you off the line,...but HP, man, it just never stops pulling.

redneckjoe

to complicate matters worse;

why do HP and torque numbers always cross at 5,252 RPMs on a dyno chart?

its a constant.

but you could build 2 totally different animals and yup, 5,252 cross.

Fast355

iTrader: (2)

It crosses because of the formula used to derive HP from TQ.

HP =TQ x RPM/5252. 5252/5252 = 1 at which point HP = TQ

That being said I am not a HP junkie, much, much prefer torque. Torque will launch you off the line and get you moving. Broad torque curve > High peak HP number. Honestly why I am not a fan of the 4.8 and 5.3 engines in a truck or SUV. The older 5.7 engines do a better job of moving them and towing in 95% of the real world driving conditions.

yaj15

iTrader: (3)

I have driven a couple of the full size Chevy trucks at my work, 2009-2010 with the 5.3L engine & 4-speed automatic drivetrain. There is no torque with that motor until you get to 4,000 rpm. Once you are there the motor comes on the cam and carries that power to 6,000 rpm. That power band would be great for a lighter car but in a heavy truck used to carry tools, equipment, tow loads to job sites - 95% of the time the motor is running under 4,000 rpm - so most of the time the truck is a dog to drive. Would help out performance if it had at least a 3.73 rear gear instead of the highway 3.08 gears even with a stock stall converter.

Orr89RocZ

iTrader: (20)

Lsx motors in generall dont make alot of trq but usually have a broad curve.
Now the 6.0-6.2 liter trucks pull really good, esp the vvt 6.2.

redneckjoe

so,.....
if we take the camshaft away,.....
what parts of a build affect HP & torque?

it is interesting.

FRMULA88

Displacement,cylinder heads, compression ratio, (NA or power added) but the camshaft is the heart.

But, to make the best HP & TQ for your particular build you need to concentrate on all of these 3 components..There is no silver bullet.. how many people have you known that throw in a big cam and do nothing else... then they wonder why the engine runs like crap.

AlkyIROC

At the track and all things being set up perfectly, torque will affect your ET. HP will affect your MPH. Since more HP means torque is being done faster, we always tune for more HP. Watching your MPH while doing things like jet changes, ignition timing etc will tell you if the change makes more or less HP by how much the MPH changes. ET is dependent on traction. Spin off the line and ET slows down but MPH will stay roughly the same at the 1/4 mile.

You can also play around with the powerband by playing with valve timing. A camshaft installed straight up normally works fine. Providing the camshaft doesn't have any advance built into it, if you advance the cam, you move the powerband lower which is good for a street car and is why many street type cams already have advance built into them.

Retarding a camshaft moves the powerband upward which is good for high reving race engines which stay and work in those high rpm ranges.

4 degrees of cam timing which is the normal retard/advance setting is worth around 2-300 rpm powerband movement. You won't change the peak power, you just move it around in the rpm range.

As for the 5252 crossing point, I've never had my engine on a dyno but I'd estimate it makes over 800 pounds of torque at around 5000 rpm. As HP increases and crosses at 5252, my torque curve doesn't really start to drop until after 6000 rpm. By then, my converter is in full lockup and brute HP is moving me down the track. The torque got me off the line and moving quickly down the track. When I shift gears, the rpm drop range puts the engine back to where HP is doing the most good. I shift at 7400 and the rpms drop to around 6400. That range is where my HP is highest. At that speed, torque has dropped off and isn't needed as much.

Since the original question asked about HP and TQ in a race application, using a street car theory doesn't give the full potential of what torque and HP will do. I launch my race car at 4500 rpm and the converter stalls at 6000. Shifting at 7400 rpm only gives me about a 3000 rpm operating range but that range is where I'm making the most torque and HP. Launch at or around full torque to get you moving. Shift at the top end of the HP curve to get you down the track as fast as possible. If the tranny gears have a nice ratio, the rpms will drop to the start of the peak HP curve so you can stay near the top of the HP curve all the way down the track.

Sure I'm driving around the pits or coming back up the return road at a couple of thousand rpms and making more HP and torque at those low rpms than most street cars do at high rpms but my race car isn't designed for low rpm driving.

Orr89RocZ

iTrader: (20)

Power curve is set by head size aka port volume and area and intake runner length. Intake runner length has a tuned effect that will determine volumetric efficiency and where in the rpm range that occurs. Long runners move torque and hp down to lower rpm values. Short runners move it up high.
Head port volume determines velocity if air charge. Air speed needs to be correct for the rpm range you are targeting. Too small port will have air speed to high to reach your desired rpm. It will stall/choke. Power will fall off. Too large a port, air speed is too slow. You dont get as good cylinder fill and have to rev higher and higher to gain airspeed. Power is down in your target rpm range.

Fast355

iTrader: (2)

6.2 is decent, not great. There are other trucks with less HP that tow equally well especially with a few minor changes to them. Like an Intake/Exhaust/Tune. I have a 2014 Titan 4x4 with the tow package 3.36 gears, intake, headers, exhaust, tune that will hold overdrive at 1,600-2,000 rpm (60-70 mph) with ~6,000 lbs behind it. I have had 9,000 behind it and it will hold 60 mph with ease in 4th gear at about 2,000 rpm. The older GMT400 trucks with the L31 350 do a great job towing as well. I have had 4 different L31 setups and none of them struggled with up to about 8K behind them. My 97 Express van was rated to pull 7,500 lbs and I am sure I have been over that a few times and even stock it would pull a loaded trailer as fast as I wanted to go.

Fast355

iTrader: (2)

^^^

LSx ports are huge and intake runners relatively short, hence why they need to rev to make power. The 5.3 and LS1 5.7 both have longer strokes than the old 5.7, I am sure in an attempt to keep some low-end torque.

Orr89RocZ

iTrader: (20)

Havent been in any other trucks except my friends dodge hemi pulling my car on his trailer. Truck felt strong, no issues. Havent pulled anything with my 6.2 but have no doubt it will perform. I see what my friends 5.3's do and they have no issue.

My truck is a 1500 with trailering package that gives it the same rating as the 2500. 10500 lbs i believe. Also has 3.73 gears. I just know it feels very strong off the line and pulls great thru 3rd. Much more torquey than the 5.3 trucks! Night and day difference. I have no doubt it will tow anything i could ever want to tow and it needs no mods to do so. Its dyno tuned and made additional 25 whp. Dyno 330 thru 14 bolt 6l80/90e and 31" tire

Fast355

iTrader: (2)

I have no doubt it will tow well!

My 2WD 2012 dyno'd 296/388 on a Mustang dyno with only intake/muffler swap, and a hypertech tuner and didn't have headers on it. Have seen these trucks gain 30 RWHP with headers and matching tune.

4.03 x 3.73 must be a nice gear to get rolling with from a stop!!

My 3.89 x 3.36 is not bad itself.

Then again even with the 2.48 x 3.73 the Express is still no slouch.

Orr89RocZ

iTrader: (20)

Awd launch is a blast. If it had 3200 stall it be deadly from a dig in a short race. Its a blast

Fast355

iTrader: (2)

4HI launch in the Titan is pretty fun too. I have chirped all 4 tires from a dig a few times. The factory converter flash stalls about 2,700 rpm and peak torque is ~2,900 rpm. Its quite a rush to get off the line quickly in a 5,800 lbs truck.

I know we got a little off topic, but it is amazing how well an engine can run if it is kept properly in its powerband.

Orr89RocZ

iTrader: (20)

Yeah thats one point i like to make. Doesnt matter where the power band is as long as you can get to it. If motor needs to turn 8000 rpm, run 4.88 gears and 6000 stall lol get up into the rpm range. It will run hard!!
If tpi 4500 rpm setup, you can use 3.08-3.23 gear and 2800 stalls. Its all matching the powerbands

8Mike9

Ya'll might be talking about newer 5.3's. but my '03 Chevy runs at will, plenty of torque, I pull a 4 horse trailer (maybe 2500 pounds max) with 2 horse's and loaded with gear, never a hint of a bog/lug.

I've pulled many a car trailer and pickups on the trailer with it as well, mostly older trucks in the 3500lb range, no idea on the trailer weights, and never felt like I needed more.

But as mentioned to stay a bit on topic, Tq does work, HP is a measure of how fast it can be done.

Fast355

iTrader: (2)

5.3 might be ok with a lighter trailer, but really struggles with some weight. I am not one for towing 45-50 mph in the slow lane. If the trailer is adequate I will run 70-75 mph with traffic.



I had no issue pulling this at 70 mph down the highway.

rusty vango

trorqe is what moves the car down the road, horsepower is what determines how fast it moves down the road, got it? OR torque is what determines how far through the wall you go. horsepower is what determines how fast you hit the wall

8Mike9

Here in ca, speed limit is 55 max when pulling a trailer...I could pull the weight faster, but I'm old enough to run things as the law allows.

I took my loaded truck, extended cab, with 4 of us in it, a crap load of weeks supplies in the bed, two horses in the trailer, the trailer geared up with tack and 3 bales of hay and a 55 gallon barrel of water, up over the grapevine (some parts a 6 percent grade) to Pamona for a horse show...just hit that little tow button thingy on the shifter, cruise on, AC going...just under 60 the whole way.

How that is "okay at 45 to 50"..not sure, but had to be pulling/dragging and hauling 5500 to 6Klbs there, with out issue..sure, it's not a 1 ton Dodge with a Cummings, but my Peterbilt will pull 10 of them in the wrong way too

Thirdgen89GTA

iTrader: (5)

How did I miss this post? Thats exactly how my GTA is. Peak torque is right around 5300rpm, with peak HP near 6800. Totally the opposite of a street power band. I built a race engine, its not just happy at pedestrian highway speeds.

I let a friend borrow the GTA once. He hadn't driven it since it got the cam/heads upgrade. He complained about how sluggish it was at low speeds, and that it didn't feel fast. I asked him where he was shifting at and he told me below 5000.

I took him out for a ride again. I slowly ramped the car up to 60mph in 2nd (~5000rpm), and then asked if he was ready and stabbed it. His eyes bulged out of his head and he clenched the armrest for dear life. What had felt like a sluggish, slow car transformed into a angry rampaging beast.

QwkTrip

iTrader: (22)

You probably didn't miss it back in the year 2014

Thirdgen89GTA

iTrader: (5)

hmm, now I realize I thought I was responding to another thread.

I see how it happened.

I rolled through a current post to a "related thread" and missed the change from the current thread to an old thread.

I hate the related thread feature.

WildCard600

You can turn it off in the user control panel. First thing I did when I rejoined the forum.