No Replacement for Displacement

[aleph1]

I didn't know about the silvia rotaries. Even mazda advertises it's 787B as a 3 rotor, and claims it's a 3.9L, but it has the same displacement per rotor as the rx7.:icon18

I thought the 787B was a 4 rotor engine...

[Chingon]

you thought right, the 20b was 3 rotor.

[krazy skwerel]

My SR20DE puts out 145... the SE-R SR20DE puts out about 170 if I'm not mistaken, so Nissan is catching up.

Just a little correction for you. The sr20de was only in the older se-r's and it produced 140hp. You have the most powerful version of the sr20de in your car 145hp (2001 sentra se). 2002 was the last year they put the sr20de in any american car (G20). The new se-r's have a 2.5 liter engine in them. Sorry I can never remember the damn engine code on them. :batman

[aleph1]

QR25DE

[MrFox]

You can't create torque from gearing, you can however create HP from gearing. Torque is the base, and HP is a derivative of it, therefore if you could create the HP without the rpms, gearing, etc. needed then that will always be better. No one ever said that 100 % was a reality, it was just an example. and I wasn't talking about volumetric efficiency. 100% + volumetric effeciency is a theory, and in that theory turbos and superchargers actually add to the engine volume, therefore it's still not 100% +. And no, you can't get 100 % + from just cams and headers. remember we aren't talking about an actual engine, nor am i comparing any. it sounds as though you are biased on this matter, so a discussion based on facts is impossible.:icon18

Ohhh... Ohhh.... let me at this one.

1) You can't create torque from gearing, you can however create HP from gearing.

The whole point of gearing is torque multiplication. If you can "create" power from gearing, let me be the first to give you 1 MILLION dollars.

2)Torque is the base, and HP is a derivative of it,

Other way. Torque is the derivative of powerP=T*RPM; Therefore P'=T. (unit conversions excluded)

3)100% + volumetric effeciency is a theory, and in that theory turbos and superchargers actually add to the engine volume, therefore it's still not 100% +.

VEs are calculated based on atmospheric pressure, thus FI will produce VEs well over 100%. And how does FI add to the engine volume? They increase intake air density, not displacement volume.

4)And no, you can't get 100 % + from just cams and headers

Yes you can. It is call pulse tuning. With properly tuned headers and cams, reversion waves arrive near the closing of the exhaust ports, creating a region of very low pressure inside the cylinder which draws the intake charge in.

5)so a discussion based on facts is impossible.

:rolleyes

[C-Kwik]

tl1000sga: Ever noticed that your car accelerates faster in a lower gear? Why? Because there is more torque in a lower gear. But what you will find interesting is that if you were to take the actual wheel torque measurements in each gear for a given motor, you will find there is more torque, but when you convert that torque measurement to HP using wheel RPM's, you'll find the HP stayed the same. Save for any frictional differences and boost response differences of course.

Think of it this way. Transmissions are like levers. If you needed to lift a rock and put the fulcrum closer to the rock, it will be easier, but will require more movement to lift it a certain distance. A fulcrum that is further from the rock will require more force to lift the rock, but will not require as much movement. Think of RPM as the movement of the handle and torque as the force put on the handle.

Mr Fox summed up the rest rather well. But I will respond to the 5th point more openly...my discussion IS based on facts. If I were biased, I would be giving you opinions. The debate over displacement vs technology can be seen as opinion, but truly I am looking at output. And for the most part, HP is really what tells you about the true potential of a motor. So if I were to compare a 700HP F1 motor vs a 700 HP Pushrod 5.7L V-8, I'd say they are pretty equal in output. Put them in the same cars and the performance should be very similar provided optimal gearing for both. So I say that technology being a replacement, substitute, or whatever else you want to call it, IS fact. And 700 HP is 700 HP. Or is this biased too?

[McAdam]

hrmmm, adding more fuel to the fire. indy cars... buick had an engine, dont know last time it raced, but it was a pushrod, 2 valve engine, and becasue it was LOW TECH it was allowed more boost and a higher displacement than the other multi valve, ultra high tech engines in INDY. It still lost, and the high tech engines bumped out more horsepwower thanks to VE.

THANK YOU MrFox! i was going to jump in and say that the whole point of gears is torque multiplication, but you explained it ever so eloquently!! (sp?)

horsepower is how fast an engine can do work. Horsepwoer matters in acceleration. horsepwoer IS acceleration. Look at the S2000. not a lot of torque, 159lbs/ft at 9000rpm? but it still scoots the 1/4 in under 14. because it has high HP. as much as I hate to make a good exapmle of any honda prodct, I will give credit where credit is due.

I'll crawl back inot my hole now. been in paint fumes all day.

McAdam

[PROJECTRB240SX]

I DISAGREE. TORQUE IS ACCELERATION, HP IS HIGHEND POWER. WHERE TORQUE DROPS OFF HORSEPOWER TAKES OVER. BUT DISPLACEMENT HAS LITTLE TO DO WITH TODAYS TECHNOLOGY. I MEAN LOOK 1250HP CIVICS, 1000HP 2.0L NEONS, 1000HP 2.8L SKYLINES, ETC. DISPLACEMENT INCREASES TORQUE, BUT TURBOS INCREASE HP. WHAT AND ENIGNE LACKS CAN BE MADE UP WITH TECHNOLOGY IN OTHER AREAS.

[McAdam]

in a sense you are right, but if you had 2 identical engines, both had the same peak torque output, but one had more HP, the one with more HP will accelerate faster. Turbos add torque, becasue displacement is torque and a turbo basically adds displacement. On a motor that already has good Volumetric Efficiency (thats what technology gets us), more torque = more hp.

ugh, I have the whole thing in my head and what I want to say, its just doesn't want to come out on the computer screen. It looks like I am contradicting myself, but in my head it makes sense! lol

McAdam

[PROJECTRB240SX]

YEAH YOUR RIGHT ABOUT TURBOS, TORQUE AND HP. BUT THEN AGAIN THE ONLY WAY THAT ENGINE COULD HAVE MORE HP IS IF IT HAS A HIGHER REDLINE. THEN WE GET INTO DOWN LOW ACCELERATION AND UP HIGH ACCELERATION. TORQUE AND HORSEPOWER. BASICALLY TORQUE IS THE MEASUREMENT OF AN ENGINES CORE POWER, HORSEPOWER IS AN ENGINE LONGTERM POWER BASED ON ITS ROTAIONAL FORCE THE FASTER IT SPINS. ALL IN ALL YOU INCREASE HP AND YOU INCREASE TOP-END ACCELERATION, YOU INCREASE TORQUE AND YOU INCREASE TOTAL ACCELERATION.

[MrFox]

THANK YOU MrFox! i was going to jump in and say that the whole point of gears is torque multiplication, but you explained it ever so eloquently!! (sp?)

C-Kwik did the explaining... I was just being a prick

THEN WE GET INTO DOWN LOW ACCELERATION AND UP HIGH ACCELERATION

TORQUE IS ACCELERATION, HP IS HIGHEND POWER.

Acceleration is dependent on the amount of FORCE pushing the rear wheels.

This driving FORCE is directly related to the amount of REAR WHEEL TORQUE applied.

However, REAR WHEEL TORQUE does not equal to ENGINE TORQUE, because of gearing.

Because of the very nature of POWER in a thermodymamics sense (cannot be destroyed, only changes form), it remains relatively constant through out the drive train, unlike TORQUE. So REAR WHEEL POWER = ENGINE POWER (minus drivetrain losses)

Now because POWER is constant, the engine TORQUE variable is now IRRELEVENT when calculating driving FORCE at the rear wheels - the true measure of acceleration.

[stutt944]

outta the blue:

Q: does a hemispherical combustion chamber technically add displacement? i.e. is a 400ci. engine's displacement increased if the heads are reworked to be hemispherical?

[C-Kwik]

I DISAGREE. TORQUE IS ACCELERATION, HP IS HIGHEND POWER. WHERE TORQUE DROPS OFF HORSEPOWER TAKES OVER. BUT DISPLACEMENT HAS LITTLE TO DO WITH TODAYS TECHNOLOGY. I MEAN LOOK 1250HP CIVICS, 1000HP 2.0L NEONS, 1000HP 2.8L SKYLINES, ETC. DISPLACEMENT INCREASES TORQUE, BUT TURBOS INCREASE HP. WHAT AND ENIGNE LACKS CAN BE MADE UP WITH TECHNOLOGY IN OTHER AREAS.

HP is not high end acceleration. Actually, HP is not acceleration. The only force you feel accelerating your car is torque. Even at high RPM, torque is what accelerates a car. Without torque you have no HP.

Proof:

HP = (Tq x RPM)/5252HP = (0 x RPM)/5252HP = 0/5252HP = 0

While the equation can work the other way if you plug in 0 for HP, you have to understand that a motor does not create HP. HP is a derivative of torque that represents the potential power of a motor. It adds into the equation, the RPM factor which tells you alot more about what a motor can do. A 150 ft-lb at 6000 RPM torque motor does the same work as a 300 ft-lb at 3000 RPM motor at those respective RPM's. Why? Because you can use a gear that is 2 times lower with the higher RPM motor and achieve the same torque, at the same wheel speed.

HP1 = (150 x 6000)/5252HP1 = 900,000/5252

HP2 = (300 x 3000)/5252HP2 = 900,000/5252

As you can see they make the same HP.

So why is HP such an important number? Because it tells you what the motor will do through a transmission(gearing). Take the two motors described above. And apply a gear that multiplies the 6000 RPM motor's torque by 2. Say the gearing and tire combo puts the car at 30 mph at 6000 RPM. And lets say the 3000 RPM motor hits 30 mph at 3000 RPM. They will have the same torque at the wheels at the same wheel speed. So they will be accelerating exactly the same at 30 mph. While the torque of one motor doubles the other, the HP is the same and the performance is the same. So you can tell a lot more about how fast a car actually will be by looking at the peak HP number than looking at the torque. HP is just more realistic of what is being done at the ground. It's much harder to quantify torque at the ground since there are too many variables and it changes with each gear.

That being said, to build a faster car, you can increase torque, maintain the same peak torque but have it occur at a higher RPM, or increase torque and have the peak occur at a higher RPM.

This debate (HP vs Tq) is so misconstrued by so many people, and the internet makes it 10 times worse. But trust me, once you get it, it will make perfect sense.

[C-Kwik]

outta the blue:

Q: does a hemispherical combustion chamber technically add displacement? i.e. is a 400ci. engine's displacement increased if the heads are reworked to be hemispherical?

No. Displacement has only to do with the area of the bore and the length of the stroke. If you think back to science class in high school and measuring the volume of a odd shaped object, the easiest way was to fill a container with a known volume to the top. Then drop the object in the container. Some of the water will come out. Then you measure the amount of water that is left, and subtract it from the volume of the container and it will give you the volume of the object. To apply it to a motor, you don't look for the volume of the piston itself, but think of it as how much air it pushes out of the cylinder between bottom dead center and top dead center. This amount of air is similar to the water that flowed out of the container when you dropped the object into the container. This volume is that cylinder's displacement. The easier calculation is to take the bore and divide it by 2 to give you the radius and then use the formula for the area of a circle(pi*R6^2) Then multiply it by the stroke.

[stutt944]

aight.

[tl1000sga]

Ohhh... Ohhh.... let me at this one.

2)Torque is the base, and HP is a derivative of it,

Other way. Torque is the derivative of powerP=T*RPM; Therefore P'=T. (unit conversions excluded)

:rolleyes

If HP = torque X RPM, then HP is derived from torque. Hence Torque is a base, HP is a derivative of it. How's that foot taste?

:boink

Oh, C - Kwik, my appollogies, you obviously are discussing facts, I don't know what I was thinking that night, must've been :alcoholic

[MrFox]

If HP = torque X RPM, then HP is derived from torque. Hence Torque is a base, HP is a derivative of it. How's that foot taste?:boink

Looks like someone haven't taken calculus yet.

It probably tastes like chicken. Let me know.

[tl1000sga]

Actually I'm in math 153 (calculus III) right now. Is there something I'm missing?:icon18

[MrFox]

Then you understand differential calculus, and derivatives.

You probably meant horsepower is a function of torque.

Sorry to have ragged on you, I was bored at work.I'll stop being an arse. I promise! :icesangel

Peace?

[tl1000sga]

Oh, of course, peace

You really had me worried that I was missing something.

I just stared at the screen repeating that quote for like 5 min. racking my brain. LOL:thinker

[prigo]

When considering power to weight, and real world vehicles, we should also mention the documented road course and 0-100-0 test between the Suzuki GSXR1000 vs. ZO6.

The Gixer lapped the 2.5 mile Willow Springs track 7.8seconds ahead of the ZO6. The Gixer went 0-100-0 before the ZO6 hit 100mph.

A for example: Force equals mass times acceleration. The Gixer, with 170lb rider on it, pushes only 4.2lbs for each horsepower. The ZO6 has to push 8.1lbs.

"The 'Vette can only manage 120mph as it sweeps toward Turn Nine, and it's relative pork forces Schwantz(driver) to turn in almost 250 feet earlier. The Gixer, meanwhile, launches to an eye-watering 156mph: At one point the bike is going a stupifying, even to us, 53mph faster."

"It's clear, especially here, the bike's advantage involves more than power; it also has a far-superior response-to-speed, not to mention weight-to-traction ratio, whether it's on the brakes or at full lean, knee-smoking cornering. The bike's minimum speed in Turn Nine is 98mph; the car, turning in much earlier, is forced to slow to a finger-tapping 76mph."

0-100: Gixer in 5.32seconds; ZO6 in 11.19seconds

0-100-0: "The car made it's run in 16.41 seconds. The Gixer did it in 11.01. Which means--looking back at the Vette's 0-100 time--that the bike had scorched to 100mph and had already stopped before the car ever hit 100mph."

--Motor Cyclist, April '02

Yeah, but Willow was DESIGNED for motorcycles (not that bikes arn't faster)

[stutt944]

Looks like someone haven't taken calculus yet.

And it looks like someone haven't taken grammar yet.

:pface :icesangel

[MrFox]

Damn you, you bastard guy! LOL

:dunce

[jamesr20det]

You're right, I am not saying that V8's rule everything. There is deffinately a time and a place for a V8, as with every other engine. I just don't think that technology is a direct replacement for displacement, I think it comes in a close second. But, then again, I wouldn't dream of putting a V8 in my S14!:hitit

I have to agree with this. There is a time and place and that time has passed. I grew up with a 69 dodge charger 440 magnum with two 1100 holley's and a road runner with 383 and they were great cars then but at 8 to 10 miles to the gallon who can afford to drive them, not me. not trying to piss anyone off but i look at it from a power/liter viewpoint and i chose to make big power with little displacement and save my $$ for something other than gas.

[D-UNIT]

But you need fuel to make power! If you could make as much power as those NA v8's I'm sure you would be using just as much gas. A tank of gas doesn't last that long in my car when I blasting it. Nor do I make Half as much power as a stout v8.

You see it's not fair to compare the gas milelage of a Carbuerated NA v8 to an I4 turbo car. Because unlike a turbo engine were the engine purrs like a kitten till , you open the throttle body boost builds then that little 4banger turns into wastegate regulated gas drinking beast. Well a raunchy growling gas sucking NA v8 can't turn the boost off. It can't turn it's always on vtec solenoid off. They don't have to tech of E.F.I. so they need to guzzle fuel to make power. I bet if you had a moderately modifed NA I4 with the rowdyest cams you could find and an agressive fuel map , you would have horrible gas mileage too.

[tl1000sga]

A very good point that I'm sure a lot of people don't realize. The civic I just built for my friend gets awesome mileage "until" you put it in the wind with that v-tec kicked in. Then it gets crappy mileage, so bad that I would say it's worse than my 327ci S-10 at full throttle. Of course, the S-10 actually gets around 26 mpg in the city, I still can't get over that.:icon18

[jamesr20det]

But you need fuel to make power! If you could make as much power as those NA v8's I'm sure you would be using just as much gas. A tank of gas doesn't last that long in my car when I blasting it. Nor do I make Half as much power as a stout v8.

You see it's not fair to compare the gas milelage of a Carbuerated NA v8 to an I4 turbo car. Because unlike a turbo engine were the engine purrs like a kitten till , you open the throttle body boost builds then that little 4banger turns into wastegate regulated gas drinking beast. Well a raunchy growling gas sucking NA v8 can't turn the boost off. It can't turn it's always on vtec solenoid off. They don't have to tech of E.F.I. so they need to guzzle fuel to make power. I bet if you had a moderately modifed NA I4 with the rowdyest cams you could find and an agressive fuel map , you would have horrible gas mileage too.

I am aware and that is why i chose to go with the sr20det small displacement = good gas mileage when cruisin around town and on trips and when i need it i kick it down and the turbo gives the extra power i need. That is the beauty of it to me efficient till I open the can of woopazz

[stutt944]

good point.

[tl1000sga]

Pretty much the best of both worlds, Thats what I liked about my 327ci S-10, it got great mileage around town and just cruising. I never would have guessed it though when I was building it.:icon18

[C-Kwik]

Yeah, but Willow was DESIGNED for motorcycles (not that bikes arn't faster)

Save for cars with crazy aerodynamic downforce, a bike will likely own a car on any road course. While a car will ultimately have more stability and lateral grip than a bike, a bike is much smaller and will have more room to straighten out the turns. The overall turning radius will be wider since the bike doesn't take up as much width of the track. Therefore, bikes can carry a higher speed through a turn. The fact that most bikes will out accelerate just about any car certainly helps too.