I'm far from an expert. However, during the process of buying a 2000, I drove a number of cars that I looked at to buy or were owned by friends. by far the biggest sotp winner was the one I bought. It has 4.10 gears in it... hands down. and still runs 75 below 2k rpms on the freeway.

 

Explain what, how the different engines function? How a semi truck engine is built to produce a lot of low end torque and a F1 engine is built to run at very high rpm's. I really don't get the point of your question or why you'd ask it.


Thank you. Just what I'm saying. You could go even further and just say you just want lots of power all rpm's.

Peter

 

I was getting your goat. You seemed to be getting more annoyed and inflamatory so I was kind of fanning the flames.

I think it comes down to symantics. People who want power in the low end generally say torque and people who want power up top generally talk HP.

 

So it was supposed to be a loaded question or are you just trying to confuse people?

Say you could use both engines at their peak power all the time. The 1200hp F1 engine would accelerate the loaded truck 3 times as quickly as the 400hp truck engine could.

The 1200hp won't last 2,500,000 miles though...

My point is that saying I'd rather have torque than HP is dumb. Sadly, there are lots of car "experts" that keep pushing this idea of a torque engine vs a HP engine.

You can say I'll trade some peak HP for a flatter torque curve, which also means you traded peak HP for more HP in the lower rpm operating areas - you actually ended up with more HP where you will use it most of the time.

Peter

 

I don't think anyone here is confused, It's just symantics. You just come across as abrasive and kind of a dick b/c it annoys you that other folks explain things differently then you think they should; and you call their explanation dumb. You know what they mean get over it, you can't change the world.

 

Sorry did not mention in the specs that I am a Z51 optioned car. I spec ordered the car from the factory and did not take one off a lot so I added this option.

 

Ok,

I've been watching this thread since I created it and have learned a lot. I do want to thank all of the experts that have contributed and are willing to provide an plain english explaination between the vertures of HP and torque. So here is what I have concluded.

Changing gears will give me a flater torque curve and move the available peak HP down into the peak torque range.

If you are looking for top end you need HP. (I've been around the block a few times and know this one.) However, you need to keep that HP in the correct RPM range otherwise you are on the back side of the torque curve (thanks this is a new nugget for me, even old dogs can learn something new).

I do believe one more item applies here. Very few of you have asked me what I want to use the extra performance for, most have assumed quarter mile. This is in fact wrong. I like driving the car on the road and being able to pull hard out of tight corners. It appears that a gear swap for me would accomplish this at a lower price than HP (for now)

Note I did not say I would not increase HP I did say I could only do so to the extent I can keep the car CARB Legal. (bummer for me I live in CA). Good news for me I can drive the car 12 months out of the year.

The final question. 3.90 or 4.10. What is the RPM for each at 70/75/80 mph. If someone has the formula I'll take that and calculate it myself.

Again I want to thank all of you who have responded this has been a learning experience for me.

 

George, you got the full story on gears-for-fun, and that sounds like the initial way to go for that SOTP kick.
Regarding any engine mods that you can do in Calif, where the long tubes are a no-no:
A good smog-friendly baby cam will give a real torque kick thru the stock exhaust, if chosen properly - think Comp 265 or similar.
Add a underdrive pulley and a cold air intake, and then get her tuned. You will easily pick up 30 lb-ft all the way up, to add to that gear punch.
Then traction in 2nd gear will be your only problem.
After that, it's head mods, but I don't know how effective they would be in increasing torque through the stock exhaust. Tony would know. Of of course, the all-time torque monster - supercharger.

I did the mild engine mods above first, and now you have me longing for the gears.

DG

 

It's OK, you come across as abrasive and being a dick just because you're posting crap to be a dick. Your "dick" post even got a response because someone was hoping for an explanation.

HP and torque are directly related. HP basically measures how quickly you will accelerate. So, saying you want torque and not HP is a dumb thing to say. Saying you'd give up some peak HP to increase the torque between 1500rpm and 3000rpm makes sense. Lots of the posters do get it and lots of the comments were directed the same way. If you know better then educate someone and don't just pass on the "you want torque and not HP" line.

As was already commented on, there isn't a person here that would like to drop their gear ratio to a lower numerically number to make better use of their torque, like going from 3.42 to 2.73. Sometimes people that are traction limited might go ot lower numerical gears but that's actually to push their engine rpm's down and lower the HP they're applying to the rear wheels.


Not really. You don't flatten the torque curve or move the peak HP down. You can't change the shape of the torque or HP curve with rear end gears.

Coming off the line or cornering, you will likely still use the same gear as before, so you have tended to shift your engine operating range higher which puts you at a higher HP point. Look at the dyno graphs posted, move up the rpm's a little and you get more HP = faster acceleration.

You can also lose HP if you change the rear-end ratio so much that you need the next higher transmission gear. You then drop the engine rpm lower which likely puts you at a lower HP point.

Peter

 

For the sake of this conversation, my niave understanding is that:

Torque is rotational force

horsepower is the work that force does per unit time against some resistance.

For a given speed in a given gear, the amout power required to overcome the resistance is roughly the same and is reflected by the torque required at the rpm the engine is turning. The amount of torque that is avaiulable above that required to overcome resistance (ie per the engine dyno curve) reflects how quickly you can accellerate at that point. So broad flat torque curves, give a much more constant, continuous rate of accelleration that peaky engines with a tighter powerband and peak horsepower.

For maximum speed against resistance (ie top end speed) if geared properly, peak horsepower is going to determine the top speed. That's why a lot of bikes for example are faster in 5th gear than in 6th because the lower gear ratio puts the rpm for maximum speed closer to peak horsepower.

so the bottom line is that you want BOTH torque and horsepower, and with all other things equal, you want to keep the engine in the range from peak torque to peak horsepower through each gear to give the best overall rate of accelleration... yes?

 

Yes, so if HP is the work done then don't you really want HP?

Your point about the broad flat curves is true, they do give a long steady acceleration in each gear. But, you could gear that peaky engine so it accelerates faster down the drag strip than the broad flat torque curved engine. Think about how peaky most full-out drag car engines are.

Well ya, since torque and HP are directly related you get both, doesn't matter if you want both or not...

The shifting from peak torque to peak HP could be argued to provide the highest average HP during your acceleration run and the highest average HP will produce the fastest acceleration. However, you don't shift down to the torque peak to make use of the torque curve until you get back above 5250rpm so you can make use of the HP curve again.

Peter

 

By your own explanation the terms are interchangable, you increase one you increase the other by the same percentage. So why get all bent out of shape if someone chooses to say I want to increase torque?

The torque curve is the dominant part of the graph below 5250rpm, when focusing on building power in that range it's natural to look at the torque curve. When someone says, "I would rather have torque than HP." They are simply focusing on the part of the graph below the 5250 RPM range, and you know and understand what they mean but you can't accept it b/c of your, "I'm smarter than you b/c I'm an engineer," mentality. You're acting like a professor who can't understand or accept the meaning of a student's paper b/c of a few grammar errors.

Generally engine builders use the term "torque engine" b/c it's instantly recognizable. It's simply easier than saying, "I want to build an engine that is high in power in the low RPM range," Not b/c they are niave or stupid.

 

From your responses it appears you didn't really read what I posted and you openly posting that your are baiting me so personally you really hold no credit here and you are certainly not worth wasting any more time on.

Peter

 

Wow case closed.

After reading all the arguments and examining all the evidence, I've concluded I'd rather build a torque engine for a street car

 

Proportional and interchangeable are quite different terms.

 

Agreed, but since torque and hp increases are proportional you can use either term to describe or explain a change in an engines output.

 

not exactly...

torque is rotational force - which translates into the ability to accellerate.

since horsepower is torque x rpms, and represents the amount of work that can be done, there is a distinct difference between thw two.

300 ft pounds of torque at 5000 rpms will aloow the same rate of accelleration as 300 ft pounds at 1000 rpms, but at 5000 rpms the engine is turning over much faster and you're doing a lot more work (ie going faster).

They're both important terms.

 

well make since of this, after my cam my car makes 411 rwhp and 352 rwtq. Car ran the same times/mph down the 1/4 after/before the cam. Why is my torque so low. Yes I know factory cars make more tq than me. My mods are kooks 1 3/4", high flow cats, GHL exhaust, vararam, ported tb, and the cam of course 22x/22x, 58x/56x on a 116.

 

Oh goodness

I started an argument with one guy now everyone wants a piece
Not true, what you just said that is....

If that were true a cars ability for max acceleration would be in the bottom part of the graph where the torque curve is the highest, but we know a car accellerates the quickest where the HP is the highest.

Hence the earlier example where lionelhutz so elequently pointed out that an F1 engine making 1200hp and 280lb/ft would accellerate a load three times faster than the semi engine making 400hp and 1000lb/ft if both engines were operating in thier peak power range.

BTW, I don't disagree with lionelhutz on his facts or science they are true; I just can't get him to agree with me. I guess you catch more flys with honey; I should remember that next time

 

To add to the drama.....LOL

You dont get a one to one gain in torque and horsepower and its not even proportional in the sense there is no constant multiplier.

At 3000 RPM's you only get about 6 HP for an increase of 10 ft/lbs of torque.....take the same 10 ft/lbs and add it at 9000 RPM and its worth 17 HP.....quite the difference. After 5250, you get more than one HP for every ft/lb gained based on the RPM divided by 5250 which keep turning into a larger multiplier.....thats how an F1 engine can make crap for torque but make insane HP.....it carries the torque so high the multiplier effect is huge. Same argument with high performance liter bikes.....the only make 70-80 ft/lbs of torque (at the tire) but can generate close to 200 HP (at the tire) due to the same reason.

FWIW I think Lionelhutz has a very good understanding of the whole HP/Torque relationship (which is all mathematical) and I think his explanation helps a guy that might be confused potentially understand it a bit better. I have spoken with many people that don't quite get it (including people in the industry) and its potentially one of the greatest misunderstood things on the Net in my opinion and I'm talking about on these performance automotive message boards. Hell....Ive spoken with "shops" who think they should try to keep the engine closer to peak torque for the best dragstrip results.....scary stuff

Now should we discuss chassis dyno "percentages"

Don't even get me started on that one

-Tony