It doesn't have to do with it being a V8 so much as the length of the stroke. Sure, if a V8 is set up with the same stroke as a honda (which would mean it WOULD have more power because it would be the equivalent to the honda's 4 cyl but it would have 8) then the engine could be set up to run at that RPM. ALSO it depends on the quality of the engine balancing. A poorly balanced (read: most production car motors) engine will have a much harder time running at higher rpms as the rotating masses start vibrating and shaking due to the imbalance. The advantage rotaries have is the fact that it doesn't rely on a reciprocating motion to make power. So the rotors just spin faster and faster until usually what happens (atleast, this is what I've read happens) is that the eccentric shaft flexes too much and the rotars slam into the rotar housing. But look at it this way when you're looking at V8's, long strokes, and why they have a hard time reaching higher RPMs:

If you have a V8 piston that has lets say a 4" stroke from Top Dead Center to Bottom Dead Center. And you compare it to a 4cyl engine (or whatever engine) that has been designed with a 2" stroke from TDC to BDC. When the short stroker is running at 5000rpms it has to move that piston up and down 2" at a certain speed per second. Now, if you have a long stroking engine running a 4" stroke it has to travel TWO TIMES AS FAST (and I'm talking the speed of the piston moving upwards) as that 2" stroker. Which means that probably atleast TWO TIMES as much strain is being put on the engine at that RPM. So if you're understanding this (because I dunno if I'm being very clear here) the reason MOST V8's don't run at high RPM is because they're designed with a longer stroke to make more horspower in the low RPM's. (This is caused by a crankshaft with a longer stroke which allows for more torque and therefor more horsepower). Now if you take a V8 that has a LOOONG Stroke and thus LOTS of low end power and hook it up with the right camshafts, theoretically you could make LOTS of power in the high end. However, the real world will step in here and your engine will blow. Probably due to cracking a rod or spinning a bearing or something (dunno what EXACTLY will happen but something like that) and so THAT is why I usually refer to V8's having more power in the low end. Now as I understand it the new mustangs make pretty good horsepower around 5000-6500rpm which is great, good for them. As far as I can understand it, they probably used a shorter stroke than say my friend's Nova's 350. (which redlines at 4500rpm). I'm not knocking long strokers, I just prefer short stroking or rotary engines because more often than not their power band is much less peaky, which is advantageous in road racing (atleast as I see it...)

Hope I cleared something up without upsetting anyone

 

The main thing that will destroy an piston motor is piston speed. I hate to use someone else as a reference but I will. My buddy rob has a 1980 chevy malibu with 454 in place of the garbage 305 that was originally in there. He has stock heads, crank, rods, valves, and lifters. He does however have ARP studs in the bottom end, forged alluminum pistons, roller rockers, and a cam. His motor makes good power from 3K to 6500rpm. There are plenty of people who have very similar setups. Your freinds nova with a 350 must have a very low lift/duration cam. I have a set of double hump 1.94/1.50 cylinder heads that can be found on stock novas and corvettes from the 60's, and early camaros. These heads flow upwards of 515 lift stock. With that much lift, the motor will be making power well into 6K rpm possibly 7, and the bottom end will hold it. I am still going to get arp studs, and forged pistons as a safety precaution, plus I want to raise my compression, but the fact is that it can be done and has been done for years. The new modular ford motors are actually not that tolerant of high revs.

 

Piston speed and long stroke are related, but piston speed doesn't destroy the motor, the rod angle does. A long stroke will have proportionally higher piston speeds because per rpm the piston has to travel a greater distance and speed is distance divided by time. However, this speed doesn't affect the durability of the motor, it is the angling of the rod at TDC that pushes the piston against the cylinder wall thus stressing the motor. With a longer stroke that angle is exacerbated as opposed to a shorter stroke, hence they can run higher revs. The advantage of a longer stroke is bigger displacement for more low end torque. But for strict racing engines a shorter stroke is still the best because you can make up for the loss of displacement with a higher redline. In fact highly oversquare motors like F1 engine redline at 17K rpm. Another benefit is slower piston speeds which cause an increase in pressure, thus you can actually suck in more air for a given revolution.

 

Well said FDRacer I completely agree

 

True, that is why people destroke 350's to 327s and 454s to 427s.

 

*nod* again, this is true I love agreeing with people. It makes my life easier. Although, a good argument is always fun too.

 

yup, that's why i'm destroking my drag s14 240sx from the stock 2.4L to 2.2L. should be sick, expecting 800rwhp w/ 9.5K rpm redline.

 

Tight!!! Get some videos online when you get it running! I love the S14's and a 9.5k redline? Sweeeet!

 

Trying to sum up the importance of torque vs horsepower for the "fun factor" or "seat of your pants" dyno. It seems to me that

1) f=ma. Acceleration is the fun factor, what sucks you back into your seat, into the door, or into the steering wheel! The force you feel on your body is due to acceleration of the car. Acceleration of the car is inversely realted to the mass of the car.

2) Power = Kg*m/s. Force (in Neutons) N=Kg*m/s^2. Neither torque nor power alone gives you acceleration. Rather the rate of change of power does (F=Power/s). At top speed you are using alot of power but feel no acceleration.

3) Acceleration. You accelerate when you have more power available than you need to maintain your current speed. You don't accelerate because of torque. Torque doesn't suck you back into your seat.

4) Gearing matters, obviously.

High torque means nothing by itself. High power means nothing without considering the weight, speed, and gearing. You have to measure the torque to know the power, and know the speed, weight, and gearing to determine the acceleration, or "fun factor" you will get out of that power.

My 2 cents.

 

Well said. It ALL about thye FUN FACTOR

 

A wonderful use of physics to illustrate a point! Very well done mcguire

 

I hate to bring dissent into this but.....

I guess rod angle may also contribute to 'stressing' the engine, but the main thing is piston speed and the piston trying to separate from the rod while its decelerating during the top half of the stroke (ie, from 90 btdc to 90 atdc).

You can make more power by stroking or destroking- it just changes at what rpm you'll want to make the power at.

And BTW, F1 engines are over 18krpm now.

 

yeah, so why doesn't everyone just go rotary

 

"We have peak horsepower at 8200 and it’s about 600. The problem with rotary, and why they don’t keep up with say a Lazzono Ford Riley & Scott, at that point is torque. The old saying goes, “Horsepower sells cars and torque wins races.” They have somewhere in the neighborhood of 560... 70... 80 foot pounds of torque, or pounds feet as the technical people like to call it, whereas we’re running in the 410 range. So we have good horsepower and top-speed, but we don’t get off the corners as well" - Jim Downing

 

Doesn't sound like he really knows what he's talking about....when I read that he sounded like some slack jawed yokle with 3 teeth an 1 eye. But then, they don't really need a driver to know how the car works, they just need him to run the track in the shortest time.

Nice Avatar by the way

 

Do you even know who the hell Jim Downing is?!

 

Some hick who agrees with me about torque? Anyway, he doesn't drag race, so he probably doesn't know what he is talking about.

 

Lump me in with the slack jawed yokels

 

Thats a big difference in power....not just torque. That would explain the performance difference. If the two cars had the same rwhp at 8200 then they would also have the same tq at that level. The reason one doesnt perform as well as the other is its just under powered.

Also if they have 560 lbs of tq at 8200 they would have a WHOLE lot more than 600rwhp. Thats more like 875rwhp. This tells me thier high tq figure is down low, if he's running 600rwhp at 8200 then he only has 384lbs of tq at 8200. Who cares about down low tq on a course with curves, you just gear the car and tranny to always stay in the power band, thats whay a gear shifter is for.

Sounds like the comparison of performance isnt based on apples to apples or something.

STEPHEN

 

An engine in a V arrangement is going to have much more torque relative to hp than a rotary. Especially as the cubic inches go up.

 

To elaborate on a few answers:

How fast a car is cannot be measured by a single number. Depending on the speed, different issues are most important.

From a standing start, the primary issue is traction and torque. The ideal is to get maximum traction, and enough torque to push right to that traction limit. High torque = quick off the line. Torque is just plain pushing potential. That's why someone said torque gets you going.

As the car gets moving faster, other forces start affecting the speed - mostly drag due to air. So to acheive higher speeds, you can cut down on drag (low drag coefficients (Cd)), or provide more to resist the drag. Engine horsepower is what you need to meet the increasing drag force when accelerating at higher speeds. The top speed of the car occurs when the engine horsepower is pushing against all the drag it can handle.

Dave

 

**** it, I'm tired of this argument cluttering up my e-mail. And no, I don't know who Jim Downing is, so no, I don't give a **** about what he has to say. On top of that, whenever someone says

"or pounds feet as the technical people like to call it, "

They sound like a dumbass. It's Foot pounds, thats how its written, thats what the technical people like to call it. The technical people also figured out what makes a car go foreward. So start listening to "the technical people" not "Dale Earnhardt Jr." not "Mr. ******* president" I don't give a rats *** if your gym teacher says torque wins races, unless they have this "technical" background then they just go with the flow. The flow says "Horsepower sells cars and torque wins races" well I guess we can throw math out, hell physics too. ****! Why don't we start building cars out of legos and superglue. Then we'll use our arms and some long levers to create massive amounts of torque to propel us not only down a drag strip, but a racetrack as well. **** gears, we just need power in the low end. RIGHT??? Cuz that whole horsepower doesn't mean **** right? Yeah, course those damned Semi-trucks with their MaD QwiK Diesel engines will probably smoke us (all that torque you know) and we'll win EVERY RACE! CUZ TORQUE WINS RACES BABY YEAH! Sounds like we've got one great big ****** winner there.

SPOauto's knows what he's talkin about. But this argument just keeps ****** going on and on. And what the **** is with the personal shots hmmm? I know I didn't start em, I've tried to keep **** clear. But whaddya know, I try to make a simple joke about slackjawed yokels all in good fun and this is what I get:

Oh yeah, I measure EVERYTHING by drag races, thats why I bought a ******* RX-7, so that I could DRAG RACE. ****, why am I suddenly being confused with the "Daddy just bought me a neat sports car that goes reawwy reawwy fast" crowd? Hmmm? I'm workin my *** off to pay for my car. I'm researching everything I can about RX-7's and cars in general. I'm going to the people who REALLY ******* KNOW WHAT THEY'RE TALKING ABOUT (i.e. the people that DESIGN THE **** THAT MAKES CARS GO FOREWARD) And here it is, folks, the first step towards my demise. I've got the crowd goin against me already.

No and I believe I already ******* said that when someone mentioned it earlier when someone quoted the "torque wins races" crap. Or did you only read the last few posts?

On a THIRD note (or is it fourth or fifth or whatever) I'm STILL ASKING FOR HARD EVIDENCE. Believe me, if someone would enlighten me with some real honest to God evidence I'd love it. Then I could go back the mechanical engineer and phyicist and say "Well then how come someone proved this?" and continue on with the goddamned learning process. Instead I have people quoting GOD KNOWS WHO and saying "look look look, a race car driver said that torque wins races" well guess ****** what, Dan Quayle spelled potato wrong and AL GORE claims to have invented the internet. Is everyone right? No. This is why I would LOVE to have someone use some good old fashioned MATH or PHYSICS or some sort of VALID DOCUMENTATION to prove me wrong. I'm not saying I'm the high and mighty of knowledge, but I'm sick of hearing (in many different forums/threads/day to day basis) people say "Nuh uh you're wrong" and then having NO evidence to prove it. So please, for the love of heaven or hell someone come up with something....but then again I hope this stupid thread dies RIGHT NOW because I'm sick and tired of writing the same responses OVER AND OVER AND OVER AND OVER again. I apologize for all the yelling, I know, I'm flaming people, I know I'm being a ******* ***** but my car (that yes, I've yet to really drive/OWN) is STILLL IN THE FUCCKING SHOP AND MY SCHOOL IS TRYING TO PULL THIS "Oh you never earned those credits, you can't graduate..." **** ON ME AND A BUNCH OF OTHER CRAP! I'm about to go down to my local post office and show them how it's really ****** done.....ok, no I'm not (disclaimer)


Let's just all forget about the anger and let me sleep or something. Bye.

 

HaHa

damn dude, you need some prozak (sp?)

I hope you got some sleep and feel better this morning lol

STEPHEN

 

Black Dragon, Torque wins races for sure !

That is why I am entering my "hand powered go cart" into the NHRA funny car finals this year. I will have a 2 mile long bar swinging of a ratchet system directly driving the rear axel providing me with around 4 million foot pounds of TORQUE

Man, thats got to win ?

 

Black Dragon,

It really is POUND-FEET, not FOOT-POUNDS.

I was confused for years, and then took a Physics class. So go argue with my professor.

Jim Downing is a rich ************. He is very smart and probably more technical than any of us. He doesn't have to give exact hard numbers to be reputable, it was probably some walk-by comment or quick interview, not a ******* spot on Larry King! It was a generalized statement. Not one to be poked and probed for validity! Get over yourself!!