MWG

I think car A would be faster because there would be more wheel torque. Car A would get there first because it would still get to the same speed but would do it faster because of more wheel torque to be used in accelerating the car. Now if you had it so that the Car B could use gearing to stay in gear longer because of a higher rpm then Car B would win because their is distance to gain because you spend more time accelerating. Now to make myself clear Car A would win if it doen't spin it's tires. this would make a difference. Also if mazda made as you called it Mazda150 why does any one make trucks anyway. I mean there is GMC, Chevy, Ford , Dodge, I heard that Toyota is getting in to it too. I mean why don't they stop? Mazda Truck would be different which in the whole point. I would buy one. And it would make the engine be used in Another car. Also I have that book and have seen that line. But my question is it not that much heaiver. I mean look at the 3 rotor Rx-7 that people have made they dont weight much more than a stock RX-7 if more at all. Plus the 3rd gen Rx-7 is strong enough to hold up to the 3 rotor more powerful motor. If Mazda had made the 3rd gen a 3 rotor it probley would have been behind the front axle just like the 2 rotor. So I dont know what the mazda is talking about in that line. the reason 300ZX weights more is because it is bigger than the previous models That only makes sense. The 3rd Gen didnt get much bigger. One other thing I love that post you made on the other tread with beavis and butthead. I was great. One other thing car B would take longer to rev to that same point unless you had more power. Power would move the rotor or piston faster with more force to a small degree. but rotating mass makes a difference you can get a rotary to rev faster when you make the parts lighter just like in a piston engine. Take for example a Honda S2000 motor does not rev as fast as say a renesis will for two reason because of weight and because of recipating motion it take engery to fight the down motion in a piston motor. The engery required to move a rotor is not as great because the rotor are all ways moving in the same direction. You can also rev faster if you lower the amount of friction. Like in F1 Cars they only have 2 rings in the piston motor unlike a regular car that has 3 rings. I also like that wisdom you posted. Where did you hear that or did you think of that yourself and really show us all how wise you are.

Buger

Hi MWG,

The peak engine hp and peak engine torque given for the 2 cars can give us 2 points on each of their torque curves if the rpms are known. Although car A has 250 ft-lbs of torque, it can't rev very high or it will have more than 150 hp. Although the figures for the cars were pulled out of my ( * ), diesel engines have higher torque than horsepower so car A could represent a diesel car. To make a realistic curve, the rpms for peak torque will be 1700, rpms for peak hp will be 4100. Redline for car A is a little above peak hp (4400).

Since car B only has 150 ft-lbs of torque, it must make it's horsepower by higher rpms. Of course we all know that the hp/torque equation is: hp = (torque*rpm)/5252 so the hp peak must be at least 8754 rpms for the torque to still be below 150. To make a realistic curve, the rpms for peak torque will be 6500, rpms for peak hp will be 9000. Redline for car A is a little above peak hp (10000).

Both cars are geared to hit redline at the following speeds in gears:

1st gear speed at redline: 38mph
2nd gear speed at redline: 63mph
3rd gear speed at redline: 95mph

and both cars have a 3200 lb weight, 215/55R16 wheels/tires, and same everything else.

Car A has no chance against car B... The weights for the 2 cars are the same and Car B has much more wheel torque because it's higher horsepower allows it to be geared much shorter to shift at the same speeds. Below times are approximated by cartest:

Car A (250 ft-lbs peak engine torque)
0-60: ........... 9.02 seconds
1/4: ............. 17.03 @ 81.86 MPH

Car B (250 peak engine hp)
0-60: ........... 6.17 seconds
1/4: ............. 14.85 @ 95.28 MPH

What does this tell us? More horsepower is better than less for acceleration and more engine torque does not necessarily mean more wheel torque. Of course this is nothing new and I am not wise at all for explaining this to you.

I came up with the stuff about answering questions and learning because some people are more interested in talking about everything they know (or think they know) rather than listening to what other people have to say and considering it. Knowing the definitions of a few terms and knowing a few odd facts can impress people who may not know what you are talking about but all of that can be meaningless unless what you know can be applied practically. There are many people who don't know a thing about definitions and "book knowledge" but are much "wiser" than you can imagine. I didn't mean to threadjack and I think I've blabbered enough now so I will stop here.

I'll attach some graphs of the comparison below:

MWG

Hi Burger,


If what you say is true than explain how the car with more torque does not accelerate faster, your saying the gearing would be set so the redline at the same mph in each of the gears. so your saying that the Torque in the 250Ft-lb would be reduced so much that it would be like having a really tall gear ratio and lower the torque at the wheel. Instead of having a Short gear ratio that would make more torque at the wheel higher. Than why arent the lower torque cars just Zooming past all the higher torque cars? your comparison is not fair because diesel torque curve is much different that a gas car. you need to diesels or to gas car engines.

Buger

Hi GWM,

The car with more wheel torque does accelerate faster! Yes.

No, gearing will not reduce the wheel torque of the 250 ft-lb car, it increases it in the gears mentioned. The higher torque/lower hp car will have to have a much taller gear than the other car to go the same speeds because it can only rev to it's 4400 rpm redline (less than half the redline of the lower torque car). The car with the lesser engine torque/ higher hp can be geared to have much higher wheel torque than the other car.

You should be able to answer this question yourself? If the horsepower numbers were the same, the higher engine torque cars will be zooming past the lower engine torque cars. Please read this entire thread again and understand the context of your discussion. In this case, you predicted that a 150 hp car will be faster than a 250 hp car. As I mentioned earlier,

"More horsepower is better than less for acceleration and more engine torque does not necessarily mean more wheel torque. Of course this is nothing new and I am not wise at all for explaining this to you."

The whole purpose of this example was to make you think about how hp and torque affect acceleration. Like many people, you have the mistaken assumption that a higher peak engine torque car will accelerate faster than a lower peak engine torque car regardless of horsepower!

Whether it is a diesel torque curve or a very long stroke/short bore gas engine has no bearing at all on why the car with 100 less horsepower is slower. The curves are limited mathmatically by the simple equation that I mentioned. You have been given everything that you need to evolve your thinking. You can choose to question your previous beliefs on this subject or you can continue to rationalize away what is in front of your face.

Either way, I am at the point where I am just repeating things that I have already posted and it would be unproductive of me to continue this.

Brian

Fëakhelek

Brian,

Just want to say thanks for your posts. I have always had trouble wrapping my brain around the difference between and effect of torque and horsepower. The one equation you mentioned at exactly the right place made it all click:

(torque*rpm)/5252

I think people are assuming that a car with higher torque and the same horsepower is just naturally better. They are missing the fact that horsepower and torque are linked. I know I did. So if you have 2 cars with the same horsepower and one has higher torque then it almost by definition MUST have a lower redline. I know this is not exactly right since the curves could be strangely curved (really high pointy peak and low elsewhere) but this mental picture works for me.

What the equation implies to me is that for hp to be high with low torque then the rpms must be high to compensate. I know that this only applies at single points on a graph but again I am making the assumption that the peaks generally represent a half decent picture of the whole curve. I imagine there are some cars that have curves shaped like this: ^ where the peak numbers give a deceptive picture but in general I think that can be ignored for the sake of the big picture.

I also see now where high end torque is better. Torque at higher rpm means higher hp than if it occured at lower rpm.

I still have a way to go before I can say I grok all of this, but thanks for getting me past one major conceptual hurdle.

Hopefully this helps you to not feel that all this discussion is futile.

:D

MWG

Burger,


I have been thinking about everything you say. I'm not just stuck with my previous beliefs. I just trying to under stand what you are saying in you post. I mean I'm trying to think of a car with a higher rpm/hp peak is faster than a lower rpm/torque peak. I'm mean I see mustangs beat higher rpm/hp peak cars all the time example Acura Integra's. I know that higher/hp peak cars can be faster take for example RX-7 that are suped up will smoke a Mustang all day long. But for example I dont see stock RX-7 beating Mustang at all unless the driver is just asleep or a really bad driver. I'm mean I am just trying to understand what you are saying. I love higher rpm/hp engines. I have two RX-7 that are Examples. I mean my Rx-7's have a 4.10 rear end ratio and mustangs I think are somthing like 3.23. I guess I could make the rear end ratio higher. but then I would lose Top end speed. If the Mustang did that it would lose some to but not as much. I am just trying to understand why mustangs are allways faster than my RX-7's. You would hope that you could make the RX-7 as fast as the Mustang in 0 to 60 by gearing. but it is not that way why can't gearing make it as fast a mustang or make a mustang as fast as a Porsche. But you dont see people making them equal in 0 to 60 with gears. you all hear about more torque or horsepower. And you see that the cars are faster when they have more. I just am not understand how you say car b is faster than car A when the shift at the same speed, have the same weight,etc..... you would think that gearing would make neither car faster. Maybe you can say something that will turn on the light bulb in my head but right know with what you have posted. I just don't see your logic. Help me. any one.

MWG

I know that horsepower and torque are related but I dont understand fully the concection you are trying to make Brian. I understand if you make more horsepower at the upper rpm range you can use gearing to your avantage to stay in gear longer and be gaining power the whole time reving up. There for acclerating longer and with more force. If this is what you were trying to tell me. I knew that. but are you saying the gear in the transmission would be taller in car A and shorter in car B. I under stand that if that is true you would get a reduction in torque to use at the wheel if the rear end ratio was Say 3.23 as to 4.10 which would add usable torque to the wheel? Am I getting what you were trying to say. I really want to full understand what you were posting to see if I learned somthing new.

Jesuscookies

I canno't believe all this "Logical" discussion about the 20B into the RX 8

A version of the 20B should go into the RX 8 because it is the coolest god damn engine that ever existed!!! End of discussion. :D

I've have not seen a recent Ferrari, or a lambro with a V6. You know why? Because they are FREAKING SUPERCARS!! No holds barred, pedal to the metal, excess.... Think about what a mazda production car with a turbocharged 20B would say to the car world?

The 20B is the engine that would answer the skeptics. It would have torque, and horsepower both. And as another forum member mentioned, the cost would not be exorbitant because the RD is already there.

Building a fatter engine is a whole new unknown. Parts will not be as easily sourced from the 13B. And how fat can you make one of these engines? doesn't volumetric efficieny suffer when doing this?

Anyways, I had to throw in my 2 cents because I cannot see the logic in this approach by Mazda, never have been able to. The rotary put them on the map, and a 20B is just the next progession.

Superfan

It would say "Hi, my name is JC Cosmo 20B-REW". http://cp_www.tripod.com/rotary/pg09.htm

Jesuscookies

And I would say HI, EXACTLY!!!!! the cosmo is such a sweet ride, and was definetly ahead of its time. Too bad ours shores never saw it.

Drop a detuned 20B NA in a RX 8 with about 300HP. Now that would be sweet!! Even at 40K. I would be in line to buy one.

hogcar

Torque Torque Torque While it is nice to have, how many
John Deer's are winning at the track? Horsepower is where it's
at! And with the rotary just twist that sucker up till your teeth
hurt.