kozman

Got a question, trying to figure out what it all means..

My stock 89, 305, TPI auto puts out about 190 hp with about 290+ of torque according to the specs. I have read about how the TPI's are "torque monsters" , maybe someone can explain that to me. There have been arguements that horsepower is king and torque is a redheaded stepchild.I'm not at all a machine head so I'm a little inexperienced what this all means to my car.

I have always seen that horsepower and torque mostly run parallel to each other, for example on cars - 425 hp with 420lbs of torque. So why is the torque and hp spread so wide(190-295) with TPI's?. Is this a good thing or bad thing and what and if are the benefits of having torque higher than hp.

School me....

mnorton

Torque is the ability to get a mass moving. It's the seat of the pants feel you get when you step on the gas. It's what spins the tires. Horsepower is the a unit of work that comes into play once the mass is moving. It's what gets you up to 100 MPH at the 1/4 mi. TPI cars are low HP because the don't rev high well.... The newer cars on the market have higher HP numbers because they are higher reving engines. Look at the peak HP and TQ RPM numbers for a new Mustang and you'll see what I mean.

Sonix

iTrader: (1)

HP would be the red headed stepchild if anything...

HP is a fictitious number (when talking about engines, not so for electric motors...). It's a derived number from the torque (the actual measureable amount of "power" that your car produces) at a certain RPM.

HP and torque will cross over at 5252RPM. If the torque number continues to grow after that, your HP will be higher then your torque. If your torque is falling off, then the HP will be lower.
diesels, and low RPM engines have higher torque vs HP. If it's a high revver, it'll have more HP than torque.

Depends on what you're after. Smaller engines that have high HP and low torque (*cough honda cough*) produce low amounts of torque, but it keeps producing it high up into the RPM band, therefore it makes a large amount of HP. That's why they feel so lazy and sluggish until you rev the bejesus out of them and get it going.

sap

As already noted, HP is really just torque at some engine speed. The torque is what makes you go.

The advantage you get from high HP (specifically producing torque at high revs) is that you can gear it down to put more torque to the wheels.

For a greatly simplified example, if you're putting down 300 ft.lbs. of torque at 3000 RPM through 1:1 gearing and your buddy's car makes 200 ft.lbs at 6000 RPM through 2:1 gearing then he's putting down 400 ft.lbs. compared to your 300 ft.lbs.

http://www.vettenet.org/torquehp.html

Rob Wade

Torque is especially useful in heavier cars as its torque that gets the boat moving! TPI motors generally aren't big horsepower producers but the long runners in the TPI intake create gobs of torque.

Apeiron

The scientific definitions of torque and horsepower are different from the uneducated pedestrian usage. People say an engine "makes torque" when its power curves peak at low RPM, and that it "makes horsepower" when it peaks at a high RPM.

8T9 BANDIT

HP sells cars and TQ wins races.

my fav quote.

Duts87ss

iTrader: (10)

Actually, at any RPM above 5252 HP will be greater than torque no matter what the curve look like.

HP=(TQ*RPM)/5252

Fast355

iTrader: (2)

Which is exactly why I am running a TPI with vortec heads in my fullsize van. 400+ ft/lbs of torque @ 3,000 and 300+ HP @ 5,000.

DukeofHurl

So on my car which is pretty much stock, and the upgrades to the TPI will be slow coming, would I be better off swapping on shorty headers instead of longtubes since I will mainly be benefitting from torque at this point? In other words, will a trade-off for HP be cutting off my nose in spite of my face since the factory plenum, runners, manifold can't generate much upper end power?

Apeiron

I'd put shorty headers on for fitment reasons alone.

sap

You're right of course, but I assumed that me meant if you maintain decent torque past 5252 your peak HP will be greater than your peak torque.

But yeah, below 5252 the torque is always higher, above 5252 the HP is always higher.

Street Lethal

iTrader: (16)

Horsepower is calculated torque, it simply cannot be generated without any force (torque) being applied to turn the prop. As for the differences in torque and horsepower numbers at particular RPM's, this is because of the ever changing numbers being calculated in the equation. The numbers in the TPI example are off because the valvetrain symmetry was never really ideal from the factory....

iroc.86

torque is how much work can be done and measured in a rotational movement!

horse power is how fast that work can be done and measured in a straight line!

racing geek

iTrader: (5)

That is exactly why I bought my car instead of the something such as a civic... torque is fun!!!! When I do turn my focus to the engine, I'll be building it for torque.

RedHawkLB9

and HP will come with it plentyfull

please...alota ppl say tpi suks blah blah blah..a well set up 305 or 350 TPI car can b a killer on the street...and even lil on the strip

bjankuski

I like this quote!

HP under the curve where your engine operates is what is important. The highest HP at any given RPM will also have the highest torque number. Torque at low RPM will have a low HP number and the car will be slow. Torque with no RPM is 0 HP. In other words no work will be done. This concept often gets confused but here it goes, two cars with the same peak torqe reading but different peak torque RPM points will not drive or feel the same. If the torque peak on one of the cars happens at 2000 RPM and the other car has a torque peak of 4000 RPM the car with the peak at 4000 RPM will have twice the HP and it will be faster. The maximium acceleration for both cars will be the same but the car with the higher power band has the ability to keep accelerating in any one gear while the lower RPM car has to shift (to maintain the same speed) which causes it to loose torque to the wheels (in other words acceleration).