TQ vs. HP which is more important. . .

[dizuster]

Sorry not sure which forum this should be in but. . .

How important is HP. I know that's a strange question. But for example if you have a motor that makes an average of 500ft/lbs from 3500~6000. Or you have a motor that make the same average 500ft/lbs from 4500~7000. How much improvement does that motor make in the car. I know this is kind of an ambigous example. But if the low RPM motor was geared/CSA/cammed correctly, would it be just as fast as the higher RPM motor correctly geared/CSA/cammed?

My gut, and experiance tells me no, but why? Torque is the force that moves the object. HP is the rate at which it happens. I reallize that TQ is just the potential for work. But I wonder how important HP really is.

From what I can tell, a given motor size, and a given compression will always make the same TQ if the VE% is constant. If that happens at 6000,7000,8000, whatever. . .is that correct?

So if you had a 3000lb car with the 2 motors, both producing the same TQ, how much faster is the car that has 1000rpm higher range?

[OldSStroker]

As you said, torque at the drive wheels is what accelerates a vehicle.

Use your own examples and calculate drive wheel torque. The 500 lb-ft (flywheel) average will be multiplied by about 1.167 in the 4500-7000 rpm engine vs. the 3500-6000 at every mph if you gear for a given top speed. Think 205 mph ProStock cars and gearing vs. avg torque and rpm band. Could you possible go quicker with a higher rpm band and actually less avg. flywheel torque? With races won by .001-.005 seconds, it leads to interesting some ideas.

Of course, 500 lb-ft @7000 is 666 hp, but only 571 @ 6000, again the 1.167 factor.

[Unkl Ian]

What application ?

[maxracesoftware]

i usually stay far away from a TQ -vs- HP Post

what gives you the potential and ability to run the fastest
in any MotorSports form is = (Torque times RPM) which is HorsePower

..for Professional max-effort applications=
you want the greatest amount of Torque
at the highest RPM you can achieve
(which is HorsePower)


just a quick look at Formula 1, NASCAR, ProStock....
RPMs are increasing ...no one's going the opposite way to lower RPMs.

Formula 1 + NASCAR + ProStock should all be capable of
achieving the same peak Torque at much lower RPMs if they wanted to.
Example, Formula 1 could achieve same peak Torque at 5000-6000
or less if they desired to ....but instead move the same amount Torque
to 16,000+ RPM .

another example
600 Lbs Torque @ 5000 RPM = 571.2 HP
600 Lbs Torque @ 9000 RPM = 1028.2 HP gains = +457 HP

its pretty obvious how important (Torque times RPM) = HP,
is !!! .... i'm certain you won't see any Formula 1 engine being designed
to run 5000 rpm or less, likewise NASCAR or ProStockers,
instead they'll all keeping searching for ways
to move their Torque Curves higher and higher
to achieve more HP which is just TQ times RPM.

[67RS502]

A comparison would be a crotch rocket with say 60tq @ 8000 and 120hp @ 14000,
and a Harley with 60tq @ 4000 and 60hp @ 5500, assume the race wt. is the same the
crotch rocket would still smoke the Harley - it wouldnt even be a race, because the hp difference.
I think that example puts it in perspective for most people.

Hp is where its at, but you should shoot for the most tq in the useable
rpm without sacraficing hp.

[Ken_Parkman]

The most acceleration is with the most wheel torque. This is achieved with the most hp in conjunction with the correct gear ratio. A car will accelerate far faster in low gear at a higher power (rpm) than in second at a lower rpm and therefor power, even though the engine torque may be higher.

Power is where it is at, as long as the drivetrain is right and keeps the engine in it's powerband. A mid range torque curve is what feels good in a street car, but is for the most part irrelevant at the dragstrip.

[Darin Morgan]

i usually stay far away from a TQ -vs- HP Post

what gives you the potential and ability to run the fastest
in any MotorSports form is = (Torque times RPM) which is HorsePower

..for Professional max-effort applications=
you want the greatest amount of Torque
at the highest RPM you can achieve
(which is HorsePower)


just a quick look at Formula 1, NASCAR, ProStock....
RPMs are increasing ...no one's going the opposite way to lower RPMs.

Formula 1 + NASCAR + ProStock should all be capable of
achieving the same peak Torque at much lower RPMs if they wanted to.
Example, Formula 1 could achieve same peak Torque at 5000-6000
or less if they desired to ....but instead move the same amount Torque
to 16,000+ RPM .

another example
600 Lbs Torque @ 5000 RPM = 571.2 HP
600 Lbs Torque @ 9000 RPM = 1028.2 HP gains = +457 HP

its pretty obvious how important (Torque times RPM) = HP,
is !!! .... i'm certain you won't see any Formula 1 engine being designed
to run 5000 rpm or less, likewise NASCAR or ProStockers,
instead they'll all keeping searching for ways
to move their Torque Curves higher and higher
to achieve more HP which is just TQ times RPM.

I am not one to shy away from this discussion. I get asked this question a lot and its simple. Larry already hit the major point here. But I think I will rehash it a bit. TQ*RPM/5252=HP

Just look at the equation and work with it and you tell me which is more important.

TQ is twisting force but NO WORK IS BEING DONE.

Once you incorporate the RPM component you are then doing work over a period of time.

You don't go faster from A to B with more twisting force. You go faster from A to B by doing MORE WORK.


Cosworth F1 20000rpm engine makes peak TQ at 17600rpm with 270ft/lbs. At its HP peak its making 246ft/lbs at 19600rpm.

246*19600/5252 = 918HP

The V6 in my wife's car also makes about 246ftlbs at 4200rpm

246*4200/5252 = 196HP

This demonstrates the equation pretty dramatically. You cant keep increasing VE (max BMEP or TQ) but you can take peak VE and move it up in the rpm range to produce more power.

And if you wanted to make 918HP and do it for $1,178,000.00 less than the F1 engine, all you have to do is build a 555cid engine.

689ft/lbs * 7000rpm = 918HP


Why do you think all ET calculators use HP as the primary variable to determine ET and MPH?

[Robert Kane]

Thank you, thank you, thank you, Larry and Darin. I have been growing hoarse discussing this point for years. I say if I have a bucket that hold 5 gallons (representing torque) and I can carry 4 buckets (representing RPM) and my brother also has 5 gallon buckets (same torque) but only carries 3 of them in the same amount of time, (lower RPM) then I have done 33% more work, or have accelerated more mass in the same time ( or same mass in less time - lower e.t.).
In fact you can run faster/ lower e.t. with more RPM and less flywheel torque and apply more wheel torque with proper gearing. Get me through the RPM's and into high gear as quick as possible and let my final ratio picked for best acceleration through high gear. If it's lazy in high gear it's never gonna run the numbers.
Now a jet drag boat is a different animal.

Robert

[Darin Morgan]

Thank you, thank you, thank you, Larry and Darin. I have been growing hoarse discussing this point for years. I say if I have a bucket that hold 5 gallons (representing torque) and I can carry 4 buckets (representing RPM) and my brother also has 5 gallon buckets (same torque) but only carries 3 of them in the same amount of time, (lower RPM) then I have done 33% more work, or have accelerated more mass in the same time ( or same mass in less time - lower e.t.).
In fact you can run faster/ lower e.t. with more RPM and less flywheel torque and apply more wheel torque with proper gearing. Get me through the RPM's and into high gear as quick as possible and let my final ratio picked for best acceleration through high gear. If it's lazy in high gear it's never gonna run the numbers.
Now a jet drag boat is a different animal.

Robert

Actually, a jet boat is not another animal. Its exactly the same principle but with a catch 22 thrown in.

A jet boat will go faster with more HP just so long as the HP occurs at max pump efficiency. If you have a pump that is maxed out at 8000rpm and you put an engine behind it that makes peak power at 8900 or 9000rpm, it will be a dog. We did an engine for a jet boat called Head Over Heals. In his class everyone was buying older Pro stock engines that 1200hp at 9000rpm and then they stuck them behind pumps that where done by 8100rpm. We built and engine for half the cost of a Pro Stock engine that only made 1120HP but did it at exactly 8100rpm. The exact point where the pump was most efficient. He then proceeded to massacre the field by 3 tenths for over five years and he is still doing so.

The trick with a pump jet is putting peak power at peak pump efficiency but you are still working off of peak Horsepower not Torque.

[Cammer]

Good posts!

[Jay Allen]

After you have determined the engine's operating range, it is the highest column average of HP you can achieve in that range.

Thanks.

[EngineTech1]

It's definitely not about how many power strokes you make. The fastest 1/4 mile cars in the world make very few total revolutions or "Power Strokes". Certainly much less than the fastest pro stockers. As a matter of fact the slower the car the more total power strokes it will make in the 1/4.

[EngineTech1]

As a matter of fact I can't help but wonder how many times this topic can be brought up and still have so many people who believe all the crap that's thrown out there about how "Torque is what wins races, Hp sells engines" I've actually seen that quote in an ad for an engine shop.
Torque at the wheels isn't what wins races, it's power, and not just peak either, it's average through the usable rpm band.
I'm glad Darin and Larry would speak up and make some good examples because it really seems that few people can see past all the garbage.

[Robert Kane]

Darin, I am with you 100% on the jet boat. I should have clarified my statement. We found exactly what you said. anything above what the pump wanted wasn't getting used. We never found anything worked much higher than 8000 -8200 when we ran it 1:1. We mopped up those guys who thought they could throw lots of rpm at it and all they did was never reach thier powerband, or cavitated the pump and wasted the power they made. We first used old Lenco sections to underdrive the pump and keep the engine where it made power, and worked on keeping it loaded throughout the run. The boat owner actually built a pump "dyno" to test in his swimming pool so we could study the discharge and film the intake underwater. I would have rather gone comp, or top sportsman racing, but I don't have the nuts big enough to go that fast on water!

[Joe Mendelis]

People need to not treat torque and horsepower like they are two totally unrelated things.

I would look at the column average. That doesn't mean the highest column average will win the race. Making the same average power doesn't mean the same e.t.. The slower you are going the more you add to your et/ lap time.

Two cars go 10 miles. 5 miles there, 5 miles back. Car A goes 75 mph for 5, then 25 mph for the trip back.
Car B goes 50 mph the whole time. B is faster.

If one engine makes more power for more of the time where the car is going slower (right after launch or corner accel.), it could go faster than a car with the same column average but steeper curve/ different shaped curve. For what that's worth.

Torque and RPM are equally important in going fast, right? Just look at HP because it gives you both in one figure.