Corvette Z06 Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
206 Posts
Discussion Starter #1
Whenever there is a Car A vs. Car B discussion, and Car B happens to have lower a lower Horsepower but produces more Horepower for the displacement of the engine, you see the comment "Car B is more technologically advanced! Just look at its HP/Liter ratio!!"

I have all kinds of respect for high revving engines. But ultra high HP/Liter ratios just aren't all they're cracked up to be.

These engines have low torque. Why? Because toque comes from displacement. Period. How do you get horsepower?

HP =Torque*RPM/5250

What the people who love to think that their HP/Liter ratio is the best thing since sliced bread, make their car uber fast, and technologically advanced don't know is that their car produces crap HP until 5250 RPM. This is what explains the low 0-60 and 1/4 mile times.

Torque is everything. The "technologically advanced" engine can't defy physics. We know that gobs of low end torque means gobs of HP which all adds up to mind blowing acceleration.

Any other thoughts on this issue? Why do so many people rant about their 100 HP to Liter ratio? Just needed to vent and see what other people think about this.

:cheers:
 

·
Registered
Joined
·
384 Posts
My wife has a Honda S2000, with a 120Hp/L engine. The car is an amazing technological feat considering how docile it is for an engine that will rev quite happily to 9000rpm, but in order to have some fun in the car you have to really abuse it.

With the low torque output the only way you can get a decent start is to dump the clutch around 7000+rpm. I dumped it once at 6000rpm and all it did was severely bog. I since haven't tried dumping higher as several driveline components can be easily broken by this kind of treatment. All and all it is still a wonerful car, and the build quality is fantastic.

I would still like to see the Z06 rev to 7k or 7.2k, I think that the 7k threshold is separates the average street car from a race car. Please note that I am not calling the Z06 average in any respect, I just think that it would ad to the package.
 

·
Registered
Joined
·
2,486 Posts
I think HP is very overrated. The next time you get to look at a dyno sheet.....look at where the LS6 or even the LS1 for that matter, start to enter the peak area of its torque curve and look how long it stays there...... Now thats impressive!!!!!!!!!

One of my favorite things to do is to show those ricers my rear tail light to their front bumper ratio:cheers::lol: :lol:
 

·
Registered
Joined
·
422 Posts
I don't have experience with big displacement V8 engines but I don't think that smaller engines necessarily lack in torque. Here's why -- Until recently I used to own a Mitsubishi Eclipse GSX. It came with a turbo-charged 4-cyl, 2.0 liter engine and full-time all-wheel-drive. The stock power rating was 210hp (6000 rpm) and 214lb-ft of torque (3000rpm) at the crankshaft. Redline was at 7500rpm. No big deal, right! Well, after some modifications I was seeing over 300hp at the wheels and 280lb-ft of torque (on 91 octane pump gas). See http://www.geocities.com/arao99gsx for the list of modifications.

With proper tuning a car with similar modifications should
have gotten to 350hp and 350 ft-lb of torque on pump gas.
A similar car but with a bigger turbo-charger dynoed at 401
hp at the wheels and 390lb-ft of torque, again on pump gas.

The best part is that despite all of these modifications the car was a daily driver and never once broke down or had any problems. On the freeway you could easily get upto 160 and car would still pull (didn't dare go any faster on the local highways). I had no trouble taking on a Porche 911, M3 or a Corvette (yes, including a 2001 Z06) from the line, thanks to the AWD system (with my race clutch I could launch at 6000rpm. It is a real sight to see all 4 wheels spinning for an istant and then you are gone).

So a properly set up car can produce big power and gobs of torque reliably despite engine size.

Its another thing that I lost the car when a speeding idiot on a local freeway lost control of his car and ran me into the median wall, resulting in a total loss. It was a real shame because 2 years of hard work was lost in an instant, but I am lucky to be alive. I am now planning on getting a 2002 Z06, and someday I hope to thow 2 turbos on it. Stock performance (on any car) will never satisfy me for long. :)

-Anil
 

·
Registered
Joined
·
803 Posts
Contrary to popular opinion, there is a substitute for cubic inches. It's called boost pressure. A small motor can produce big motor numbers on boost because: Equivalent CID = CID x ((boost pressure + 14.7)/14.7)

Blown is better! :D
 

·
Registered
Joined
·
206 Posts
Discussion Starter #8
Torque is quite limited by your engine size friend.

While you can increase an engines torque with mods. (Supercharger/Turbocharger) you will hit a ceiling.

Torque is a product of force and distance. Supers and Turbos increase force, but the force increase is limited by the amount of boost you are able to run through the engine. The only way to increase the distance is to modify the engine block for a longer stroke (or replace the engine).

Bigger displacement gives you much more distance to work with, and therefore more torque. The LS6, a natually aspirated engine, has 400 lb-ft of torque, compared to the 350 to 390 lb-ft that the 2.0 liter engines produced with turbos. Look at the dyno charts for some 800+ HP heavily modded toyota subra turbos. The torque is stuck at around 500 lb-ft because of the small displacement. Slap a supercharger on a vette, and you will easily see 700+ crank HP and torque. Revving the engine higher and adding boost can only get you so far, more displacement.

The main "technological advancement" of high HP/Liter is that the smaller engine block costs less and the manufacturer gets to pocket the savings!
 

·
Registered
Joined
·
206 Posts
Discussion Starter #9
Roger Ramjet said:
Contrary to popular opinion, there is a substitute for cubic inches. It's called boost pressure. A small motor can produce big motor numbers on boost because: Equivalent CID = CID x ((boost pressure + 14.7)/14.7)

Blown is better! :D
Hahaha, you wrote that just as I was writing my post! I did know that boost increases torque before reading your post :lol:
And I totally agree, but you're still limited by the amount of boost you can run, thus a smaller dispacement engine has a much lower torque ceiling, which was my one of my main points all along :)
 

·
Registered
Joined
·
2,388 Posts
Roger Ramjet said:
Contrary to popular opinion, there is a substitute for cubic inches. It's called boost pressure.
Yep ... turbos make the MEP of the engine increase, which produces more torque at all RPMS. More torque at all RPMs = more HP at all RPMs, since HP = (T X RPM)/5252 ... BTW, its "5252, not 5250 ... close enough I guess.

Yes, its torque (actually the force between the tire and ground caused by the torque) that moves the vehicle. BUT, in order to move the vehicle at a fast rate, you need HP. Sure, alot of low end torque helps get off the line (if you can keep the tires from going up in smoke), but once your moving the HP factor becomes the real player. If you have the correct gearing for the 'peaky' motor and if you stay in the peak power band its going to haul ass just as good as a hiigher torque, lower reving engine, assuming both have the same peak HP rating.

How many non-turboed F1 cars that rev to 15,000+ RPMs have alot of low end torque compared to their peak HP ... none. In the end its HP that wins races, not torque :D.
 

·
Registered
Joined
·
206 Posts
Discussion Starter #11
But its much easier to produce all that HP with more torque :)

After all, Horsepower is just Torque applied over time.

It takes time get to your power peak. The quicker you can get to it, the better. It takes more time to rev high when you have less torque. The drivetrain components hold you engine back when the cluth is engaged (obviously), so with more torque available an engine can more easily overcome the resistance of the drivetrain and quickly rev to its power peak. Go torque go (literally!)! :cheers:
 

·
Registered
Joined
·
206 Posts
Discussion Starter #12
One more thing, I'm all for an intercooled supercharger or turbocharger, though I think I like superchargers more.

Turbocharged vs. Supercharged discussion anyone?

(I'm sure there has been quite a few going on around here, but I'm pretty new and haven't seen one yet) :)

Anyways, I'd love to talk about the advantages of one over the other. I'm always lookin to learn something :)

Maybe I'll start a new thread on that soon, but I'm having fun with this one :D
 

·
Z06 Power Adder Authority
Joined
·
3,265 Posts
I think HP/TQ to weight ratio is more important than HP/L.

However, I am with ZeeOhSix. HP wins races. Otherwise, we'd all be driving around with turbo-diesel truck motors that produce 600ft/lbs of TQ, but make relatively low HP (for the torque rating) b/c they don't spin any real rpms.

You want a pretty flat torque curve no matter what the displacement is. This is where variable valve timing comes in so handy. If this technology was used in American V8s, it would be insane.

Obviously, more displacement means more potential for HP/TQ. This isn't profound and has been stated several times in previous posts.

But if you gear the vehicle appropriately (thus increasing torque multiplication and keeping the motor in the "sweet spot"), you can make up for less low-end TQ.

It's all about "HP under the curve"...certainly this is just a function of the effective TQ curve. They go hand-in-hand. Fortunately, GM did a great job with the LS1/LS6 powerplant. :)
 

·
Z06 Power Adder Authority
Joined
·
3,265 Posts
zurmagus said:
One more thing, I'm all for an intercooled supercharger or turbocharger, though I think I like superchargers more.

Turbocharged vs. Supercharged discussion anyone?

(I'm sure there has been quite a few going on around here, but I'm pretty new and haven't seen one yet) :)

Anyways, I'd love to talk about the advantages of one over the other. I'm always lookin to learn something :)

Maybe I'll start a new thread on that soon, but I'm having fun with this one :D
I'm game. :D I can offer some pros and cons for each. I've been running centrifugal blowers on several vehicles for over a decade.

Start another thread and I'll jump in.
 

·
Registered
Joined
·
155 Posts
HP/Weight it is!

First of all, HP/L or specific output should only be considered a criterion for normally aspirated engines - increasing volumetric efficiency with forced induction skews the HP/L figure abnormally, making comparisons largely invalid.

That said, HP/l is a number purely for bragging rights and has little real world significance. It is generally accepted that DOHC engines have higher specific output than the OHV designs. But the penalty paid is in the form of greater mass and poorer packageability. Take for example, the S54 motor in the new E46 M3: producing 333 hp from a 3.246 liter normally aspirated inline six, it is a tue engineering marvel. However, the LS6 motor is not only lighter but also more compact than this high-tech M powerplant. The true measure of specific output thus is hp/weight not hp/displacement!
 

·
Registered
Joined
·
7 Posts
Torque at the wheels is what matters. And peak HP numbers give you a better idea of that than peak torque numbers. You can make power with torque or rpm's. Torque matters when you're looking at the curve. What you want is a high peak HP and a flat torque curve. Even the z06 would have a much lower peak torque number compared to it's HP if you could somehow make power all the way to 10,000 rpms. Something like an F50 which makes 500+ HP and "only" 300 ft-lbs of torque :)
 

·
Registered
Joined
·
2,486 Posts
Screw High HP and low torque. HP wont pull an 8000 pound fishing boat up the side of a mountain in the snow.

Torque will drag it up by it's [email protected]#king balls.

For the technically challenged............(no finger pointing please)

Torque = "How much work is being done"

HP = "The rate at which the work is being performed"

:cheers: TO ALL :cheers:
 

·
Registered
Joined
·
384 Posts
If you are tuning an engine for track use you would try and maximize the output of the engine between the minimum and maximum rpms that would be seen during track event. In these cases alot of times rpms are raised to get more HP as HP is a result of rpm and torque, ala F1.

This works great on track only race cars where you gear the transmission and rear end to work the engine in its desired HP producing range.

On the street its a totally different game, most of the time you will be driving well below the engines torque peak when you need acceleration. On the street I believe that area under the curve is what matters the most. The sooner your engine reaches 85 or 90 % of its torque peak and the longer it maintains it the more drivable and FUN your street car will be.

The Vette engine may appear to be nothing but an old world antiquated muscle car V8, but if you look at the area under its Hp/Torque curve and its Hp/Ltr rating I think that it is just as Hi-Tech as any engine out there, its just super tuned for the real world not certain number achievements.
 

·
Registered
Joined
·
2,388 Posts
Area Under the Curve

Yep, I agee that the area under the HP curve is actually the best way to determine vehicle performace (for a given vehicle weight and gearing setup of course).

As others have said, the best engine will have a high and flat torque curve which will give near linear power throughout the RPM range. Obvioulsly, the flatter the torque curve stays at higher RPMs, the better breather the NA engine is. Engines that have good low end torque don't need to have as spot on gearing to maintain good road performance and are easier to drive and make accelerate in situations that require frequent gear changes (ie, road course).

I also agree that the LS6 is a very well breathing engine, and makes lots of torque and HP, which makes it great for what we all like to do ... drive it :D.
 
1 - 20 of 30 Posts
Top