TQ vs HP

[stevengerard]

All this roots vs centrifical reminded me of a snippet in July's Hot Rod. A former Chrysler engineer wrote in stating that in the 60's one group was promoting a manifold that was a big increase in Torque while the other group said that all that torque would only be utilized once, in 1st gear. Their statisitcal estimates suggested the hp manifold would do better at the track. The tq manifold won out for production so the engineers decided to race them both, the one that maximized hp one. The engines were identical except for the manifolds. They agreed the tq car felt peppier but the other one would win more street races.

This is the first time I have read hp over tq ususally its "tq wins races hp sells cars." Yeah, I know, our MMs are big and we have small displacement engines - its still food for thought.

[MENINBLK]

Torque is that gets your vehicle rolling from a standstill.
Horsepower is what ACCELERATES your vehicle from the present speed to a future speed.

[Smokie]

Actually the TQ versus HP debate reminds me of the primary diference between our cars and the Impala SS, in stock form I believe that we can agree the SS will outpull the MM. from a stop to about 1/8 mile, after that the MM. will catch and usually pass the SS at the end of the 1/4. The difference in trap speed at the 1/4 is usually in favor of the MM. by about 3-4 mph. SS has superior torque. MM. has superior HP.

[BillyGman]

A very interesting thread guys. I can't help but to add my 2 cents.......

I think that you cannot generalize this topic because it really depends on the rest of the components the engine in question has as well as the rest of the vehicle too. For instance, not only would the weight of the car have to be considered, but the rear end gear ratio as well. And how good or poorly did the cylinder heads flow, as well as how much displacement the engine had. All of these things factor in.

We are talking about adding something to the engine to enhance the way the car accelerates. That's the goal weather it means HP or Torque. Therefore, before someone spends their $$ for a go fast, Hi-perf part for their car, they have to consider what the weak points are currently. For instance, the Marauder's weak point is lack of displacement due it's puny 281 cubic inch engine. And this lack or deficiency is magnified by the massive weight of this car. So the point at which the acceleration suffers the most in a Marauder from a performance standpoint is off the line. That's why a Marauder out of the showroom can't even perform a burnout w/out using the brake pedal despite the poor traction capabilities of those factory stock tires it comes with, and despite it's somewhat impressive rating of 302 HP at the crnakshaft.

it has already been pointed out in this thread that Marauder vs. Impala SS will result in the Impala jumping ahead off the line, and then relinquishing it's lead to the Marauder after the 1/8 mile mark. And that's pretty accurate in most cases as loing as both are bone stock. What I've noticed about Impalas from going up against them at the race track last year, is when you begin to modify them, you get more acceleration out of them than you do out of a Marauder providing you have the same level of modifications done as the Marauder in question does. And that's a direct result of those cars having more displacement under the hood (350 engine).

An Impala SS vs. Marauder comparisant reveals both the weak points and strong points of each of these two cars from a performance standpoint.....

strong points:

Impala SS- more low-end torque resulting in better 1/8 mile times, due to more displacement.

Marauder- more high end HP resulting in a stronger finish in the 1/4 mile due to DOHC design and better flowing cylinder heads.

Weak points:

Impala SS- lacking in high RPM HP resulting in a weak 1/4 mile finish due to camshaft specs and poor flowing cylinder heads.

Marauder: Lack of off the line acceleration resulting in poor 60' times and poor 1/8 mile times as well due to lack of engine displacement.

So my point in all of this, is that when looking for greater acceleration out of any given vehicle, one has to consider what the car in question is lacking in the first place, and modify it accordingly.

[TripleTransAm]

One thing to keep in mind is that horsepower and torque are one and the same. Horsepower is just a mathematical product of RPM and torque, meant to illustrate the work doable by an engine at a given RPM.

The mathematical formula is:
hp = torque x RPM / 5252

As you can see above, the hp and torque curves ALWAYS cross at 5252 RPM.

If you have the hp value at a certain RPM, you can get the torque output at that RPM. Coupled with the torque peak at its RPM, you can plot both torque points on a graph and hopefully get a basic idea of the torque curve.

Example: a car with (a) 200 hp at 6500 RPM versus a car with (b) 200 hp at 4500 RPM.
The (a) car will be producing 162 lb-ft at 6500 RPM.
The (b) car will be producing 233 lb-ft at 4500 RPM.

Since torque is equal to force x distance from the twisting point (ie. axle) it stands to reason that the 233 lb-ft car is accelerating harder at 4500 than the 162 lb-ft car at 6500. So the 233 lb-ft car is faster, right?

No. Since hp is a product of torque and RPM: as RPM climbs, the torque has to fall faster than the RPM climb, numerically speaking. Otherwise, it would generate a higher peak hp number at that new RPM! So in general, torque is taking a HUGE dive after the HP peak RPM. So chances are the 233 lb-ft car, because of it's low hp peak RPM, will start to lose acceleration pretty quick, and you'll have to upshift to return to a meatier part of the torque curve.

In contrast, the 162 lb-ft car may never actually produce more torque than the other car, but because it manages to keep producing *some* torque until much higher in the RPM band, it can stay in a lower gear longer, and benefit from the better torque multiplication of the lower gear.

This is why a 190 hp VTEC can outrun a 190 hp V8. It's all in the RPM and how the torque curve looks.

[BillyGman]

I kinda figured that someone would hit on the specifics of Torque & HP Steve. I know that what you've said is true. I think that some people simply get a bit confused w/the math. I also think that the actual and underlying issue that most people are concerned w/about this matter is Low-end power, vs high RPM power, and more specifically, Low-end acceleration vs. Hi-RPM acceleration. What good would big #'s on the dyno be IF the car in question didn't exhibit better acceleration than it did before the modifications were performed? After all, that's why we modify our cars. In hopes to increase the car's acceleration capabilities.

[Smokie]

As you can see above, the hp and torque curves ALWAYS cross at 5252 RPM.
Hey Steve, have you noticed that we have pictures of dyno graphs all over this forum and the lines rarely cross at 5252.
I always thought math was an exact science.:lol:

[TripleTransAm]

I agree it's tough to visualize the math... if I was at home, I'd post some quickie hand-drawn graphs.

Conceptually, just remember that there is no such tangible thing as horsepower. Torque is what accelerates, whether at low RPM or high RPM. High hp simply means lots of torque at low RPM or decent torque at high RPM. Really high horsepower means lots of torque at high RPM. ;)

Because that torque gets multiplied through the gear ratio, you get a better resultant torque at the wheel if you stay in a lower gear, and better acceleration.

This is why the high-RPM breather in the original example above always beat out the torquer on the track. (given, of course, that the torque curve itself wasn't a teeny tiny little hump to begin with!).

[BillyGman]

Conceptually, just remember that there is no such tangible thing as horsepower. Torque is what accelerates, whether at low RPM or high RPM. High hp simply means lots of torque at low RPM or decent torque at high RPM. Really high horsepower means lots of torque at high RPM. ;)


This is why the high-RPM breather in the original example above always beat out the torquer on the track. (given, of course, that the torque curve itself wasn't a teeny tiny little hump to begin with!).AAAAAAAHHHHH!!!! I very good point Steve. EXACTLY! The important thing concerning optimal acceleration isn't only peak power, but a wide band of power throughout the RPM range. That's why more engine displacement will always mean greater acceleration than less engine displacement providing that all other things are equal. the bigger displacement engine provides a broader band of power throughout the RPM range, and that means greater acceleration.

The smaller engines tend to exhibit a band of torque that is narrower and covers a smaller RPM range than bigger engines do(Naturally aspirated engines in particular). So the torque curve that's a "tiny little hump" that you mentioned represents a power band that is very narrow, and that will mean less available acceleration throughout the 1/4 mile than a car w/a bigger engine will offer. Again, this is provided that all other things are equal. ofcourse the weight of the cars in question would also factor into the end result. Power to weight ratio is important. but that is perhaps another issue all together.

So if you had two cars of equal weight,traction capabilities, gear ratios, and transmission gear ratios, and one car has a peak HP of 360, and the other has a peak HP of 350, but the 350 HP engine also has a broader power band (aka "flatter torque curve") than that of the 360 HP one, and therefore has more low-end, and midrange power, the car w/the slightly less peak HP figure offers a greater portion of it's available power throughout a greater portion of the RPM scale. So it will be the winner in a race since it will offer greater acceleration.

[SouLRioT]

My brain is completly fried.....going to need to re-read this one later...after I take some advil.

[woaface]

Torque = burnouts
Horsepower = speed
:D

[rookie1]

My brain is completly fried.....going to need to re-read this one later...after I take some advil.

pass them down when you're done

[Bluerauder]

I agree it's tough to visualize the math... if I was at home, I'd post some quickie hand-drawn graphs.

Conceptually, just remember that there is no such tangible thing as horsepower. Torque is what accelerates, whether at low RPM or high RPM. High hp simply means lots of torque at low RPM or decent torque at high RPM. Really high horsepower means lots of torque at high RPM. ;)

Because that torque gets multiplied through the gear ratio, you get a better resultant torque at the wheel if you stay in a lower gear, and better acceleration.

This is why the high-RPM breather in the original example above always beat out the torquer on the track. (given, of course, that the torque curve itself wasn't a teeny tiny little hump to begin with!).

Here is a fairly good article that explains the torque vs. horsepower debate. It uses the L98 vs. the LT1 Corvettes as examples. Good article that describes this in "moderately plain english". Quite useful explanation. Torque and Horsepower -- A Primer (http://www.vettenet.org/torquehp.html)

[TripleTransAm]

Hey Steve, have you noticed that we have pictures of dyno graphs all over this forum and the lines rarely cross at 5252.
I always thought math was an exact science.:lol:


Interesting... could you post or PM me a link? I'm VERY curious how THAT worked out. How does one measure hp on a dyno then? Some special hp-meter that sniffs the exhaust? Measures the grin on the user's face? Divides the amount of money spent by the performance gains? ;)

[Bluerauder]

Interesting... could you post or PM me a link? I'm VERY curious how THAT worked out. How does one measure hp on a dyno then? Some special hp-meter that sniffs the exhaust? Measures the grin on the user's face? Divides the amount of money spent by the performance gains? ;)
See link above for "Torque vs. Horsepower -- A Primer". It explains clearly how horsepower is computed from dyno results using torque. There ain't no horsepower guage.

[TripleTransAm]

Here is a fairly good article that explains the torque vs. horsepower debate. It uses the L98 vs. the LT1 Corvettes as examples. Good article that describes this in "moderately plain english". Quite useful explanation. Torque and Horsepower -- A Primer (http://www.vettenet.org/torquehp.html)


WOW! What a well written article. That's one to bookmark, for sure.

And I can certainly agree with the choice of engines used, except in my case it's an LB9 (305 TPI) against an LS1. ;) I'd post the comparison numbers, but it would probably violate some sort of Geneva convention on abuse. :beatnik:

[MikesMerc]

One thing to keep in mind is that horsepower and torque are one and the same. Horsepower is just a mathematical product of RPM and torque, meant to illustrate the work doable by an engine at a given RPM.

The mathematical formula is:
hp = torque x RPM / 5252

As you can see above, the hp and torque curves ALWAYS cross at 5252 RPM.


This is totally correct! A great explanation!

Some dyno sheets do NOT show the crossing at exactly 5252 because the dyno machine is estimating the numbers....not to mention that there is plenty of room for "error" due to many variables.

If you want to determine which car will be faster, analyze the "total area under the torque curve" in the usable rpm range.

If you want to analyze how power is delivered, than you must be able to read and interpret the dyno graph. Focus on the torque curve. Look for the power delivery in the RPM band you find yourself in most of the time.

Peak HP means little without understanding the torque curve.

[Smokie]

Interesting... could you post or PM me a link? I'm VERY curious how THAT worked out. How does one measure hp on a dyno then? Some special hp-meter that sniffs the exhaust? Measures the grin on the user's face? Divides the amount of money spent by the performance gains? ;)
No way :shake: , I did a cursory search to refresh my memory and some do cross at about 5200, many don't, you want them, you find them, I know trouble is just a keystroke away.:argue: :uzi: :flamer: :lol:

[TripleTransAm]

See link above for "Torque vs. Horsepower -- A Primer". It explains clearly how horsepower is computed from dyno results using torque. There ain't no horsepower guage.


;) I was being sarcastic... see my above post with the same mathematical formula as mentioned in the article. Good link, by the way.

[TripleTransAm]

No way :shake: , I did a cursory search to refresh my memory and some do cross at about 5200, many don't, you want them, you find them, I know trouble is just a keystroke away.:argue: :uzi: :flamer: :lol:


Keep in mind some dyno sheets plot torque and HP on two different axes.

[Bluerauder]

;) I was being sarcastic... see my above post with the same mathematical formula as mentioned in the article. Good link, by the way.
Steve,
I picked up on the sarcasm and was supporting your assertion. I also thought that the article did an excellent job of explaining TQ vs HP.
Charlie/tstrat99

[TripleTransAm]

Sorry, I'm a little obtuse this evening... (my wife used to think I was acute, but the magic has faded...)

[David Morton]

Hey Steve, have you noticed that we have pictures of dyno graphs all over this forum and the lines rarely cross at 5252.
I always thought math was an exact science.:lol:I think he chose a bad word. He means they match. 350 ft/lbs tq @ 5252 rpm = 350hp @ 5252 rpm.

This formula is SAE specification for HP and is stated correctly. So 350 ft/lbs tq @ 10,504 rpm = 700 hp @ 10,504 rpm.

We may be at a slight disadvantage with a 281 cid engine but we have technology in our favor. A DOHC engine is always going to outwind a pushrod and rocker arm engine. I'm waiting to see a good reciprocating assembly for this engine coming out of one of these suppliers that can get us 9,000 rpm. I'd even settle for a de-stroker, say 3.25 in, like the venerable 327 has if it will get us 9 grand. Then we can start talking serious camshafts and 4.88 gears, 1200 rpm idle speeds and 3500 stall speed convertors. Then we'll be talking some serious HP, N/A that is.

[SergntMac]

I did a cursory search to refresh my memory and some do cross at about 5200, many don't.
Just my .02c here, Javier, and I think that for some new to this high performance arena, a dyno graph of their MMs performance is a Playboy centerfold to them.

Once a dyno has collected the data from the pull, any dyno computer can print any of that data in any form or style you wish. Only a few of those reports will show the 5252 RPM intersection, but it's there nonetheless. Owners not knowing much about their choice of graphs could easily snatch up the wrong graph and post that here. Likewise, owners who do understand all that, can manipulate the report to highlight what data they desire highlighted. Dyno tests and tunes are good stuff, but tell only part of the performance story.

Graphs are good for the quick visual, but you really need to understand what you're looking at. The true 411 is available in the column/row report of all the all data, every every step of the test...IMHO.

Back to the question at hand, you can never have too much torque. But, you can run out of resources to manage it.

[Bluerauder]

No way :shake: , I did a cursory search to refresh my memory and some do cross at about 5200, many don't, you want them, you find them, I know trouble is just a keystroke away.:argue: :uzi: :flamer: :lol:
FYI. Check HwyCruiser's Garage. Three dyno runs on one sheet just posted. All cross at "exactly" 5252 RPMs. Specs out at 275 rwhp @ 5200 rpm / 295 rwtq @ 4200 rpm SAE

[BillyGman]

There must be some truth to what MAC said, because my car speced out at a 5200 RPM cross over also when it was N/A but when I S/Ced my car, it didn't. They were two different Dyno places that I brought it to each time which have different type of Dynos, but wether that has something to do w/this or not I dunno.

[MENINBLK]

FYI. Check HwyCruiser's Garage. Three dyno runs on one sheet just posted. All cross at "exactly" 5252 RPMs. Specs out at 275 rwhp @ 5200 rpm / 295 rwtq @ 4200 rpm SAE

Here is an article that talks about the formulas and relationships of Torque to HP...
http://articles.domestictunerz.com/article.php?ID=167

I just realized that this is the same article that tstrat99 linked to but this is on the Domestic Tuners website.

[TripleTransAm]

There must be some truth to what MAC said, because my car speced out at a 5200 RPM cross over also when it was N/A but when I S/Ced my car, it didn't. They were two different Dyno places that I brought it to each time which have different type of Dynos, but wether that has something to do w/this or not I dunno.


Was any of these dyno places where they tied your car down by the shocks? :lol:
:nono:

[BillyGman]

oh man, don't remind me of that please!!!!! But anyway it just so happens that the place that did that is the place I had the car Dynoed when it was N/A and also when the cross over was at 5200 RPM. But I'm done w/that place. You can bet on that.....

[TripleTransAm]

Dyno shops are to be taken with a grain of salt. Actually, with an entire truck load of salt, the kind they use in the positively absolute worst snow storms in the NorthEast, the kind that are accompanied by 25 mm of freezing rain followed by ice wind and 12 inches of snow, then more freezing rain... then .... (you get the point?)

Case study: a supposedly reputable speed shop in Eastern Toronto... name splattered ALL OVER the F-body mailing lists and message boards, TONS of happy campers hopping all over the place with nice meaty dyno charts. Okay, so there were a few customers with small issues (excessive oil consumption, catastrophic engine failure, inability to put down some good numbers on the track, etc.) but come on, the dyno numbers were THERE!

Outcome: after some nasty ugliness that lasted a few months, it was discovered that the head tuner was 'overtuning' the customer cars, to the point where they would put down decent dyno numbers, but would eat themselves up over a short timeframe (and the customers would come back for a fix, thinking they had just overstressed stock parts with all that power).

Best of all, the dyno curves themselves were bogus... the 'tuner' would turn up the heat inside the car, and the dyno software would pick up on the incredibly "high" ambient temperature, and during SAE correction to a standard temperature, you'd get TREMENDOUS results. While it might have been 70 degrees in the garage, the interior of the car might have been cooking at 85 degrees or more.

Dyno curves are nice to have, if anything to compare between mods on the same car. But for absolute comparison... there's that grain of salt again.

I was present during the dyno session where my WS6 put down 310 at the rear wheels in late 1999, and I know that no such shenanigans were happening. Among the entire crop that tested that day, the conscensus was that the results were accurate if not a little low. I know my WS6 puts down the power considering my trap speed. But my car is stock... if I was to extensively modify my car and get it dyno'ed at the shop that did the work, I'd be very worried about the results, as I'm sure they'd want the customer to feel they got something for their money. (incidentally, the same shop did some cam and rocker work on a fellow GTA owner, and they only got 7-11 rwhp increase. They are working extensively with the owner to try and find the lost hp, but at least they are being fair and honest about their results.).

[BillyGman]

I know what you mean about the possible dangers of bringing your car to get it dyno tuned Steve. And it's for precisrely that reason that I wouldn't have my car tuned by anyone other than Lidio since it's him that burns the chips for the Trilogy S/Cer kits.

Keep in mind that the dyno places that I've brought my car to so far have only dyno TESTED it. NOT dyno TUNED it. I just don't trust them around here to be messing around w/the fuel/air ratios and the ignition timing advance curve on my Marauder since it's S/Ced.

[SergntMac]

/Steve flushes out a good point to keep in mind, the "Earl Schieb" dyno.

A dyno costs big money, and it takes up valuable shop floor space. If the owner can't make the machine pay for itself, that's more overhead he has to make up elsewhere. The tendency, or, temptation to "enhance" a customer's performance is there, and I am sure some shops take advantage of that. Likewise, if it's a shop tool that doesn't get a lot of dyno business frequently, the dyno operator may be honest, but out of sync with how to run a good dyno test. End result can be the same, a worthless dyno report.

My very first dyno on an MM brought many issues to the front. A poorly maintained machine, a poorly educated operator, and a lack of business for the shop. They told me, with reports to back it up, that my N/A MM, with an early Reinhart Stage 1 kit, had 385 RWHP...WTF?

This didn't live long thanks to my friends here. One of the good things about our mutual interests and 411 exchanges here, is that we learn more about good and bad. BTW, one night, Zack and I went to our local dyno, and asked Mike to help us "fool" his Dynojet machine. We learned a lot about what can be done, and what cannot. But, here's one trick y'all should know about.

To advanced your numbers to their highest possible with your mods, just inflate your rear tires to 50 PSI. You'll get the highest readings possible with rock hard rear tires. This isn't really wrong, as long as you use the same PSI everytime you dyno. You'll have honest consistency, which is the point of any dyno test. OTOH, if you want to be the leader of the pack at any dyno day, just overinflate your rear tires. Likewise...If someone at your local dyno day shows some really unusual numbers, well...Check his rear tire PSI?

[Smokie]

I think I am going to draw my own draft, no dyno. I will use my ET and Trap Speed to estimate HP & TQ. I will be conservative:

TA DA : Results, 259 hp and 272 tq

My numbers I assure you are accurate and beyond reproach.:lol:

[Marauder]

Does HP get you moving and TQ pulls the weight?

What about those little Hondas with 300hp but only 180 ft-lbs of TQ? Put 4 people in that car and ours and see who wins... :D

[stevengerard]

Does HP get you moving and TQ pulls the weight?

Other way around.

[MENINBLK]

Does HP get you moving and TQ pulls the weight?

What about those little Hondas with 300hp but only 180 ft-lbs of TQ? Put 4 people in that car and ours and see who wins... :D

Torque overcomes the resistance of weigh to stay at rest and gets it in motion.
Horsepower ACCELERATES the rate of increase of motion.

Torque will get your car to MOVE off the line.
Once your RPMS start climbing, then HP takes over and increases your rate of Acceleration.

Think of it as a Stage 1 and Stage 2.
Stage 1 is your Torque and Stage 2 is your HP.