I'm sorry, but then I totally don't understand your example. You said they had "equal" torque. I assumed that to mean at any given rpm.

Do you mean that, like, the torque values are in a grab bag, and each bag is the same, but we can put them on whatever rpm we want? Like a bag with 100 lb-ft, 200 lb-ft, 300 lb-ft, and 400 lb-ft in it.

You put 400 at 1,000 rpm, 300 at 2,000 rpm, 200 at 3,000 rpm, and 100 at 4,000 rpm?

While I do the opposite, and order them 100, 200, 300, and 400?

If so, yes you have more horsepower up to 2,500 rpm. So if we had the same gearing, you will accelerate faster from a start. But it won't last very long. Your advantage at 1,000 rpm is ~55hp. My advantage at 4,000 rpm is ~230hp. Unless we race to a very low speed, or the cars have some sort of absurdly tall gearing or something, I will blow you away in the 1/4 mile.

If that isn't what you mean, well then I just don't follow. But I'm trying.

 

It is NOT false. In the unit of a foot pound, we are talking about a force being applied at a distance (of a foot). We are not referring to any movement. 100ft.lbs. can be a weight or force of 100 pounds exerted at a distance of one foot. There is no movement necessary for that to be a valid force. In order to express movement, we must introduce time. A mile, like a foot, is nothing but a distance. However, if you go the distance of a mile in an HOUR, you are expressing movement and the rate of that movement. Work is defined as a force through a distance. THROUGH A DISTANCE expresses movement. A foot pound is a force AT a distance; no movement required. Therefore, the units for work and torque are NOT the same.

RACE ON!!!

 

Well, the notion of time would indicate a rate. Work done has no notion of the rate at which it is done. If I raise a bowling ball from the ground to the top shelf in my office, I have done a certain amount of work. That work done is the same if I tossed it up there in 1 second, or if I hefted it one shelf at a time, huffing and puffing as I went. (on a related note, the power I have is different in those cases)

I'm not sure what else there is to say, except maybe use google to search for "physics work" or open a physics book? I guess maybe it's worth asking, what do you think the units of work are?

Edit: Just to be clear, I am not, and I don't believe Mr Dave is, saying that "work" and "torque" are equivalents. They absolutely are not. Just that the units used on their values are the same. "lbs-ft" (or N-m, or lbs-in, or whatever, but it's a unit of force times a unit of distance).

 

largely -- but see a couple comments below..

I think most people are more discerning than that. There are probably a few other variables to consider, like gearing. I for one "felt" my car seemed slower when I slapped on a louder exhaust, because it sounded like the car was laboring more! (go figure).

More to what people might actually feel driving these things. For fun, I went back and reviewed a lot of old R&T Vette road tests. On average, the L98's were a tick quicker to 100 ft. and 0-30 than LT5's, which were a tick quicker than LT-1's. By the 1/4 mile, this was all reversed (and more significantly) as you would expect. Not scientific, but certainly suggests the folks who post about this might actually know what they are feeling when they floor it.

 

It's also possible that these magazine guys suck at launching a car. But I hear ya.

FWIW, a buddy of mine had an '89 IROC Z28 with the L98. His car absolutely feels faster than my Aurora. His car is loud, stiff, the seats are firm, etc. But when he had it at the track, it ran a 15.1. My Aurora has run 14.8's. So who knows...

 

Let me try this.

Engine #1: Peak HP 240 Peak Torque 350

Engine #2 Peak HP 350 Peak Torque 350

Assume they both run to 6K.

Engine #2 will produce more torque lower, winning. However, the peak torque will be the same as Engine #1 Engine #2 will have a flatter torque curve since it access more of the torque, sooner.

In this case, you can access more torque because of more HP.



Assume the torque curve is the same:

Engine #1 will start falling off as RPMs go up, once the peak torque is reached.

Engine #2 will still win because it has to rev higher since, by definition, it's rated at higer HP. So it will keep making that HP after the lower HP runs out.

Basically, more HP either allows you more access to more torque at lower RPMS, or allows you to keep making torque as you spin the engine higher.

This can be seen specifically in the L98 examples right here in this thread.

 

FWIW don't confuse motor torque with rear wheel torque....like I said in my previous post the ONLY thing that makes the car go is rear wheel torque!!!

 

I agree with your comment of introducing time indicates a rate. I also agree that a measure of work doesn't include a rate or time. Introducing time, was a bad idea. It doesn't apply. I agree that in either method of moving the bowling ball the same amount of work is accomplished. However, in your own example, you have acknowledged that movement is necessary for work to be performed. The measurement of a force, specifically foot pounds, doesn't require movement. I guess, even though not commonly used that way, a foot pound COULD be a measure of work. Although I am nor familiar with a foot pound of work, I can see how it might be valid. I have to agree that I may be wrong. I apologize to you and Mr. Dave. I made my statement about the units of measurement not being able to be the same out of ignorance.

RACE ON!!!

 

Hey, no problem.

 

Thanks.

HOWEVER, being admittedly wrong on that side point in no way diminishes my message that HP = [Tq X RPM] / 5252. Careful consideration of that simple formula answers all of jsup's questions.

RACE ON!!

 

No need to apologize to me, although the gesture is appreciated.

I don't understand why the concept of HP and torque is so hard to grasp sometimes. Nothing to argue about that equation, because its fact. Pretty easy to look up on the web.

 

If the torque curve for both engines is the same, the HP curve is the same. As CFI has posted, HP is simply a mathmatical calculation based on the torque and RPM.

 

I hadn't read that post. I thought we were talking about the post I was responding to.

I know what a straw-man is, and I wasn't making one because I genuinely believed you were making an argument that you weren't. Upon reading what you've said since then, we both "get it," we both believe the same thing, and all we're doing is arguing semantics.

 

Time for my knowledge check.....

Torque and HP are related in that torque (force) is required to create HP. Torque is a measurement of an engine's ability to deliver force. But, buyer's want an engine's force for different reasons. A truck owner wants something that can pull heavy cargo, tow, etc... Torque is a measure to let that buyer know how much power that motor can deliver. Often, (like for towing) the power has to be delivered at a low rpm range.

Others like to know how fast a car can travel (or how fast it can get to a high rate of speed). Again, torque is required -- but for a longer period of time. And, speed is tied to the rpms of the engine (sans gearing). So another measurement was needed in an attempt to capture the ability to deliver torque over a period of time. For an engine, it's related to the speed the parts are operating.

An L98 -- with it's TPI -- appears to be a strong car because it can deliver a lot of initial force. The TPI is an intake that creates columns of air. And, those columns have the impact of forcing more air to fill the cylinders at a low rpm -- kind of like mild super-charging. If this setup had the ability to sustain torque for a long period of time -- into high rpms -- it would be a fast car. But, it's really not (at least not compared to LT1's, LT4's, LT5's, LS1s, etc....) It's not "fast" because it sacrifices top end pull for better initial pull. It has good torque for a shorter period of time (rpms) -- which translates to lower horsepower.

If you look at the graph I posted on the first page of this thread, you can see the effect of changing the stock TPI to a larger (LT) runner setup. You can also see the affect of changing to a shorter runner setup (like the HSR). From 3000 to 4200 rpm, the large(r) tube runners provide an additional boost in low-end power. (They extend ability of the motor to generate it's potential HP to lower RPMs). From 4200 to 4800 rpms, the large tubes actually increase the motor's overall HP. So, if you had 3 motors with idential drive trains (1 with the large tube TPI, 1 with the stock TPI, and 1 with a short runner setup) and limited their engine speed to 5000 rpms, the large tube runner motor would win the race. But that's not what happens in real life. All 3 motors have the ability to turn higher RPMs.

If you look what happens after 5K rpms, the short runner intake takes the lead. And, it's does it with a vengance! By looking at the area between the HSR and the LT runner setup from 3K to 5K --vs-- the area between those lines after 5K you'll see a bigger gap after 5K. With the given parts of the motor, the short runner setup creates more power -- at a faster rate -- than the LT's advantage down low. That's why the short runner car catches up and wins the race at the end.

This assumes a couple of things. The race, gearing, etc... is sufficiently long enough for the short runner car's top end to win out -- and -- the parts of the motor can function at these rpms w/o flying apart! Then, you also have to consider functional ability of the parts involved. Can the heads deliver increasing air flow with the higher rpms? Can the exhaust expel it? Etc....

As Aurora points out, people want to know how well their car's will fair at WOT. With the case of a TPI vs a short runner intake, the answer is mixed. For those who tromp from stop light-to-stop light, a TPI intake will provide impressive results. (After all, it's like having a mini-supercharger on the motor!) But for those who want to race at higher speeds (like the highway or race track), the LT1s and newer cars have the clear advantage.

So, if you're an L98 owner, here's what you do. Only race starting from a stop light. Then as the race nears 60mph -- which is way past the speed limit in town -- let off the gas. Give the thumbs up to that brand new 175 torque, 280 HP foreign rice burner that's starting to gain the the mirror. If you know the person, just say you let off to avoid the law (after all you should)! And, you won the race anyway.

If your opponent says they'd win in the 1/4 mile, point out that's not the way you drive to the store, work, etc... You have the fastest car that will accomplish that!!!

For me, my car is for the street. And, I do more than half of my driving off the highway. To swap to a short-runner intake would be kind of silly since I'd be taking away from the venue where it spends most of it's time. However, if I did do that, romps on the highway would be a whole lot more fun. And, I bet I'd like 3rd and 4th gear -- maybe even more than the 1st two!

So torque is what's important. (HP is too -- especially when you're talking about longer racers or one's that begin at higher speeds.) But, torque (force) is what you really want to know. You want to know where torque peak occurs, how long the torque lasts, and how it will be applied.

So, it's not necessarily silly to be happy with the L98's torque numbers. Compared to newer cars it's typically as fast or faster from light to light. That's because that low-end torque is there to serve. It may not get you from 50-100mph faster than new cars, but it can sure put you in front by 50mph!

Compared to newer vettes, it doesn't hold a candle, but shouldn't the newer ones be better anyway?



gp

 

Dang, people always shut up when I get "wordy". Did I get everything right -- and there's nothing left to be said? Naaaahhhhhh.... O.K., let's try this instead:

So when you shift to 3rd on an L98, I would assume it falls back into the "power band" of the motor -- yet it feels whimpy. I'm guessing your sitting at around 3K to 3,500 rpms with WOT. Even with a short-runner intake -- like the LT1, the torque wouldn't be any higher yet. But, I'm betting the LT1 feels better right there.

Doesn't the LT1 feel more impressive when you drop into 3rd? If so, do you think it's because there wasn't as much up til then?

gp

 

Well, I think you have the gist of it more or less, especially for what you are looking to do.

As I've said, I wouldn't say torque is what is important, horsepower is. Anything can make torque. Power shows the work something can do. At a low rpm (and at any rpm) more torque = more power. It's the more power when the engine is at those rpms that helps. Accelerating fast is about the total power experience, not just at the peak. A stout low end helps that.

If you are trying to race people to 30mph, then maybe a stout low end is for you. Your 0-60 mph example may not be so true. At that point the L98 has gone through 1st and 2nd, and experienced that weak top end twice, but the strong low end only once.

But you need to know what you want the car to do, and then decide what is the best way to do it. Generally speaking, you can't go wrong with doing what GM did. The LT1 seems to be a pretty fair trade-off from the L98. It's better at most everything (performance related, not trying to start an opti thread or anything).

Edit: Let me take back the part about saying "do what GM did with the LT1". I get the impression you are trying to decide on intakes and such. In that case, I've no idea what is the way to go. Simply that whatever gives you the most usable power will result in the most performance. Whether it's a long tube runner design or what depends on a million things probably.

 

I'm not quite sure what you are asking here? Are you suggesting the L98 feels awesome through 1st and 2nd?

I can't speak to the LT1, but I have owned an L98 for about 4 years. And I absolutely had fun owning it. But once you get past about 4,000 rpm that thing really lets you down. I don't care what gear you are in, though it's certainly worse as you climb up them. I had a 4+3 and by 4th it was pretty bad and by 3rd overdrive (low 100's if I recall right) it was really nothing to brag about except that you are going quite fast and the car is still pulling. The thrill was the speed not the acceleration.

But horsepower is horsepower, regardless of gear. And unless you live in Manhattan or something, I'm sure you can run through 1st gear pretty often if you want.

I would think an LT1 would be more fun in 1st and 2nd gear, as well as in 3rd. The notion that there "wasn't as much up til then" would seem to be disproved by the 0-60mph times of the L98 vs LT1, which is the first 2 gears.

 

Every motor has less acceleration in higher gears as compared to lower gears!!!!! This is not unique to the L98!!!!

Basic explanation is that in the lower gears you have a higher (numerically) ratio that gives a higher torque multiplication....so more torque at the rear wheels gives more acceleration!!!

What is unique about the L98 compared to the LT1 or LT4 is it has less horsepower!!!!

An LT4 will smoke a L98 just as much in 2nd gear as it will in 3rd gear(plus remember when the L98 is in 3rd gear the LT engine will still be in 2nd gear due to its higher rpm power band)...the only place a L98 will pull harder is in first gear until you get up to a high enough speed that the LT engines are up in their power band.....plus you will have to shift sooner in the L98 (lower rpm capability) and after that the LT engine will be in its power band with MORE horspower and it is all over for the L98....

Clear as mud, but think about what I am trying to say...

 

Interesting....

So the real advantage of the L98 is really gone by the end of 1st gear? I didn't say it was impressive thru 2nd, but it's enjoyable. The second I drop it into 3rd (during a romp), I think to myself "What's the point" and let off.

When I was driving my 91 6-cylinder Jeep home from work tonight, I tromped it -- as an experiment. Actually, it has a good weight to HP ratio @ 600 lbs less than our Corvettes! (I stared and stared at the manual when I found this. A friggin Jeep is lighter than a vette. That's the XJ models).

Anyway, I always thought it accelerated quite well for what it is. Tonight, I realized it really pulls much better top -- compared to my Corvette. I don't really mean it's faster overall, I mean it doesn't hit that TPI "wall". And, that makes the "acceleration experience" quite a bit more impressive.

When you super-impose the HSR dyno on top of the stock TPI, it's disgusting how much of the top end the TPI chops off. What's really sad is how little it gives back at the bottom. It can't be more than 10-20 HP.

Maybe us early C4 owners really need to "wake up" and realize the TPI is a glorified mechanical rev-limiter....

In the TPI's defense, I will say this. If you super-impose the dyno of a larger tube TPI next to an HSR/mini/LT1 runner, there's about 40 more HP to gain from 3200-4200 rpms. I'm not sure if that's enough to throw your head back a little after shifts or whether the top end is really what I'm after. I'm also sure that extra 40 HP in mid-range torque would go along way toward gaining an insurmountable lead in shorter races.

And, this is what led to the creation of this thread. I was trying to figure out if there's something magical in gaining the torque necessary to feel an impressive pull at shift-points. I thought the car's ability to pull dimished as speed increased -- but I realize I've gotten too used to the lame top-end of the TPI.

gp

Edit: I reread my post above. I did say impressive. MY BAD!!!!

 

This statement is the answer to the original poster's question. When you shift to third your motor is back in it's powerband, but the power to the rear wheels is substantially less than the car that is still in second gear and still in it's powerband, due to the gearing, which is leverage. (rear gears, trans gears, wheel size, etc.) When you shift your TPI car you are getting back into your powerband, but it is your ENGINE'S powerband. The power at the rear wheels is substantially less because you lost alot of leverage when you left 2nd.

These threads on hp/tq and some of the contributions that are offered up always make me laugh. Some people just never get it.