Horse Power and Torque

[Lextreme II]

For the 4.0 liter, some members dyno with great torque and some dyno with greater hp. Is there an explaination of these outcomes? What does it mean when the dyno shows more torque than HP and what does it mean when HP is greater the torque? Would the NA and FI have different ratios or would a supercharged system be different then a turbo system?

 

[verylost]

Is it mathematically possible for torque to be greater than horsepower?
Horsepower is a mutlple function of torque and engine rpms, therefore I think the absolute number of torque will always be less than the absolute of horsepower.

Then again its 4 am. Math is fuzzy right now.

 

[0sb0rne]

erm... look at almost any diesel car... you generally find the torque is higher than the hp... but then I also guess it all depends on your units of measurement... (lb ft/rpm for torque and hp for horsepower I'm refering to)

Andrew

 

[Zuffen]

If you dyno more horsepower than torque you have a dyno Queen.

If you dyno more torque than horsepower you have a much more driveable car.

 

[Pro]

amen to that.

"grunt" (torque and power for this argument) under the curve - torque being a big factor of that - wins races.

ask any boat, off road / rally or tarmac racer.

 

[Nightsabre]

Unless I am mistaken, HP is in units of ft-lbs/min and Torque is in ft-lbs. So HP would simply mean how fast it is able to apply the torque (or force), of course the faster the better. And torque would simply mean the force applied, regardless of how long it would take. Perhaps torque is important for those who are towing and such, as it requires much force, but the time is unimportant. I will assume horsepower would be required for acceleration, as the faster it is able to apply the force, the quicker you go. Any confirmations on this?

 

[Lextreme II]

Lets stick with the 1uzfe (4.0) with different dyno results. One example would my torque numbers are always higher then my hp. I know few guys with 1uzfe have high HP then tq. I was just wondering if different FI system make a difference. Or perhaps the restrictive exhaust or intake would determint the differences.

If you look at this pdf http://www.clublexus.com/forums/attachment.php?attachmentid=59169 Looks like the 4.0 liter (GS400) with supercharger gets more hp and turbo gets more tq.

 

[Toysrme]

Isn't the RMM supercharger centerfugal? You'll never get earth shattering torque (That's not in your upper rpm band) out of that - without something like stepped gearing.
If RMM = ceterfugal, then that explains why it has good top end & nothing (Compaired to a big blower, or descently picked turbo) under that.

 

[verylost]

Is it mathematically possible for torque to be greater than horsepower?
Horsepower is a mutlple function of torque and engine rpms, therefore I think the absolute number of torque will always be less than the absolute of horsepower.

Then again its 4 am. Math is fuzzy right now.

Now that it's 2 PM, I've figured out mathematially how torque can be greater than hp.

And Nightsabre has the best explanation.

 

[Lextreme II]

So if HP is ft-lb over time. Is that mean supercharger get quicker spool or power quicker due to less lag? It like strength vs. power in weight training. Strength would be how much you can left and power would be how much you can left at a given time. For example, if subject A can bench press 100 lbs and takes me 2 seconds. Subject B can press 75 lbs at 1 second. So subject A would have greater strength and Subject B would have greater power.

So i would assume the supercharger get better respond and require less time. What do u think?

 

[Toysrme]

Now you're getting into what type of supercharger + what size supercharger VS what is the spool time & powerband of the turbo.

 

[WDoherty]

yeah a screw or roots type supercharger is going to give you an instant response, but probably less overall hp. That's why cobras and lightnings run such low 1/4 mile times.

 

[WDoherty]

oh, and lex, you did your pull in 2nd gear so you may have had some torque multiplication going on. I don't know about the LS but the SC has an overdrive off button so you can do 3rd gear pulls which are pretty much industry standard.

 

[jibbby]

When measuring peak torque engine performance on a dyno sheet curve it is where the torque curve is measured at it's highest curve peeking point and then at what rpms it hit thst point at to determine if the engine is setup up for lownend, mid or high range torque..... Cams, turbo's, superchargers, bore strokes, etc..can change the peak torque reading and at what RPM's it peaks at, if I am not mistaken... I see this on the dyno sheets but when I think of torque I always think of torque at the wheels and not the engine or crank.

As you know torque at the wheels can be changed and or transfered with the drivetrain, torque converters, tranny gearing, diff. gearing, etc..... Being a former 4X4 junky I always fell in love with the low end torque or grunt over mid range and high range all day long.. Performance street cams always took away the lowend grunt while the RV cams turned the engine into practically a power stroke Diesel...This was when I worked on building the CHevy's.. On a steet racer Lex like ours probably a good long steady torque curve shown on a dyno would be better in comparison over a sharp peaking torque curve is my guess. Am I right in saying this? So torque has many variations to consider. Would a long drawn out torque curve that is shown on a Dyno be better then a fast peaking and fast droping curve that reaches a slightly higher curve peek? For a street racer?....Am I making any sense?

 

[bango]

Really depends again what is "Street racer",short sharp bust of speed from lights to lights?Or the "drift" style racer..The long smoothtorque curve achieved as soon as possible be my aim...and at good fuel econ too cough..cough..hehe

 

[jibbby]

I am thinking if your engine can rev to 6000-7000 rpm's and your racing in let's say the quarter would it be more beneficial to have a long consistant torque and horsepower curve show up on a dyno test let's say as apposed to a higher peaking and sharp curves with a dramatic climb and drop? HP and Torque?

Example -

A) A 400whp reading with a long consistant dyno curve throughout the 6500RPM's?

or

B) A 450rwhp with a sharp climb and drop off curve shown on a 6500RPM dyno sheet?


Woulldn't (A) out perform (B) on the same cars in the quarter? I would think so....this always puzzled me when looking at different dyno charts...I am not a dyno pro so if I sound ignorant please understand I am only trying to learn....

 

[UZZ30-Québec]

Having a bigger torque than HP only means that your engine breathes better overall beyond 5252RPM and more HP than torque means your engine breathes better over 5252RPM

when you're talking of blower/turbo, it's all about the cams, and how the engine can breath boost.

the more your engine breath, the more HP it will produce for the same torque (higher RPM)

 

[cjsupra90]

UZZ30... put pit very well. Just to add to it, its all about where the engine produces torque in the RPM range of the motor. Horsepower is really not a readable number, only torque is and horsepower is nothing more then a mathmatical equation bases on torque and rpm.

In all honesty, horsepower really means nothing except for a number to brag about. Its really the torque and the torque curve that shows how well an engine performs.

 

[JBrady]

I have given this topic a LOT of thought so any dissagreements to my following statements should be given THOROUGH consideration before posting:

Horsepower is simply a way to quantify work output of an engine. You can also use kilowatts, BTU, calories or ANY conceivable unit of measurement. I use the term POWER to simplify. To say that horsepower is unimportant is a misunderstanding of what POWER is.

POWER or the work performed is inseparable from torque (FORCE) in a running engine. There is a HP and a TQ measurement for every RPM point. TQ is always more below 5252rpm and HP is always more above 5252rpm due to the math that calculates HP.

Used in a vehicle with gearing it is POWER that is most important as you can MULTIPLY torque with gearing but you cannot multiply power.

Davids question is really more of WHY one engine will have a higher peak TQ number vs. one that has a higher peak HP number. Notice I said PEAK because peak can be deceiving on how an engine performs.

When you are talking supercharging (both "turbochargers" and "superchargers" are in fact superchargers) it comes down to the BOOST curve and the boost quality. Boost is not boost. Boost is a reading of the resistance of an engine to inhale a given amount of pressure from a compressor as measured (usually) between the throttle body(s) and the intake valves.

Boost curve is based on how a supercharger (SC) is powered and its relative capacity. Turbochargers are centrifugal superchargers as are Vortech, Powerdyne, ATI Procharger and several others. Centrifugal SCs do not produce boost linearly. They operate at a relatively high compressor rotating speed.

A belt driven centrifugal SC usually does not make any low RPM boost. Most start making boost above 2500rpm. Due to the belt drive you do not make peak boost until engine redline.

A wastegated turbocharger can make boost well below 2000rpm and reach peak boost well below engine redline and maintain peak boost to redline.

 

[Anaema]

I have given this topic a LOT of thought so any dissagreements to my following statements should be given THOROUGH consideration before posting:

Horsepower is simply a way to quantify work output of an engine. You can also use kilowatts, BTU, calories or ANY conceivable unit of measurement. I use the term POWER to simplify. To say that horsepower is unimportant is a misunderstanding of what POWER is.

POWER or the work performed is inseparable from torque (FORCE) in a running engine. There is a HP and a TQ measurement for every RPM point. TQ is always more below 5252rpm and HP is always more above 5252rpm due to the math that calculates HP.

Used in a vehicle with gearing it is POWER that is most important as you can MULTIPLY torque with gearing but you cannot multiply power.

Davids question is really more of WHY one engine will have a higher peak TQ number vs. one that has a higher peak HP number. Notice I said PEAK because peak can be deceiving on how an engine performs.

When you are talking supercharging (both "turbochargers" and "superchargers" are in fact superchargers) it comes down to the BOOST curve and the boost quality. Boost is not boost. Boost is a reading of the resistance of an engine to inhale a given amount of pressure from a compressor as measured (usually) between the throttle body(s) and the intake valves.

Boost curve is based on how a supercharger (SC) is powered and its relative capacity. Turbochargers are centrifugal superchargers as are Vortech, Powerdyne, ATI Procharger and several others. Centrifugal SCs do not produce boost linearly. They operate at a relatively high compressor rotating speed.

A belt driven centrifugal SC usually does not make any low RPM boost. Most start making boost above 2500rpm. Due to the belt drive you do not make peak boost until engine redline.

A wastegated turbocharger can make boost well below 2000rpm and reach peak boost well below engine redline and maintain peak boost to redline.

some belt driven centrifugal SCs can reach peak boost before redline. the best example i can think of is the twin Rotrex SCs in the new Koenigsegg CCX. they are designed to produce about 1 BAR of boost at 2500 RPM, the redline being about 8000. ill try to find a link.