RPM and speed

[johny]

with less drag you'll move more distance. Imagine riding a bycicle, with front wind you'll need to pedal more than without wind to complete the same lenght

[G-Rock]

Guys, guys, don' you see that this Ogami character is just jerking you around. He's just bored and wants to confuse people. His questions are so stupid that he shouldn't even be on this website.
If he can't understand that a car at full throttle can achieve the same speed as a car a part throttle (in a draft) then there is no hope for him.

[modbaraban]

Guys, guys, don' you see that this Ogami character is just jerking you around. He's just bored and wants to confuse people. His questions are so stupid that he shouldn't even be on this website.
If he can't understand that a car at full throttle can achieve the same speed as a car a part throttle (in a draft) then there is no hope for him.

Top marks for the trickery then =D>

[Ogami musashi]

G-rock, what's the matter? are you joking?

[Tom]

Don't worry, he's always like this, what's the term they use in America? my friend assures me its n00b although I thought it was just one 'o'

[Ogami musashi]

ok Tom, actually i think nobody here (maybe CAD in first instance) did get what i was asking for, that's why G-rock remark was quite unappropriate i think.


Well anyway, i'll try to ask elsewhere then.

[G-Rock]

Sorry boys, nobody else would say it so I had to. If an engineer in an F1 team had to clarify his question or solution FIVE times, then he would be fired.
I think Dave Killens had the best explanation but whenever someone (Orgasmi) isn't reading them or trying to understand them so that led me to believe that he was A - Stupid and incapable of understanding your theories or B - just being an ass and messing with your heads.

Don't shoot the messenger.

G-Rock
BTW After extensive testing, I just found the ideal tire pressure for my John Deere 4640, pulling a cultivator in loose soil. Measuring slip under full load, I discovered that the pressure of 11psi (radial tires) gave me the most traction. I'm not just some cracker sitting in front of a computer shooting off smart remarks. I live and breath engineering in real life even though I'm not one.

[pRo]

I know what draft is, what i want to know is the relation of Power to RPM and torque.

So i repeat my problem is to know why one RPM=one speed (assuming we are on the same gear shift and gear ratio).

You're correct. One RPM=one speed. Think about it. There's nothing variable between the engine and wheels, as long as you're on a same gear.
(assuming the car has traction and isn't spinning the rears)


However, rpm doesn't equal power. This should be easy to figure out. Think about driving your own car. Think about these three examples.

1) Drive on 1st gear at 2000rpm. Floor the throttle. Feel the acceleration at 4000rpm. You're using all the power you have in your car.

2) Drive on 1st gear at 2000rpm. Apply a little amount of throttle. Feel the acceleration at 4000rpm, which is less than above. You're using less power, but still got to 4000rpm. Your speed at 4000rpm was the same as above. It just took more time to get there.

3) Use so little throttle, that the car drives at 4000rpm. There's no acceleration. You're using very little power. But again you're at 4000rpm with same speed.

[Ogami musashi]

Pro:

Yeah thank you for your explanation but i was searching for more details but thank you anyway.


G-Rock: Actually i think you didn't understand a lot of the on going stuff because while members did answer trying to be helpfully they did not answer what i was asking for and if you didn't realise it then you're not so clever or at least not much more aware than i am.


In order to clarify, once i had confirmation here that one RPM=one speed (wich i understood it at the first message of Dave, that said it quite clearly) i wanted to know HOW, in details the power was modulated wich actually was not explained anywhere except for a very intuitive explanation that hopefully i nicked for myself ("release the throttle").

So thank you for you frank remark that was off topic and going from a situation where you did not understand the problem.

Next time before shouting loud please just think about the problem a little bit more.

Maybe people here know you and cope with this but i don't and "it had to be said" (to copyright you).


See you.

[manchild]

as long as you have the same speed, the same RPM will be produced.

Just change it to this:

As long as you have the same RPM, the same speed will be produced.

[dumrick]

G-Rock was being a jerk, that's right...

I actually didn't post because I couldn't find an answer for the original question: what kind of limiter is used and if engines in a drafting car can get over 19,000 rpm (altough I believe they can't).

Actually, some of the answers had small technical mistakes, like implying that for equal rpm and gear ratio, you can achieve different speeds. What you can, if drafting, is to achieve it with less engine power.

There's other thing: with a limiter, do teams choose the last gear of a car to be slightly longer than needed to allow for higher speeds while overtaking in drafting or the speed differential is achieved merely by faster acceleration of the car behind, that reaches the limiter earlier?

[G-Rock]

Yes, thankyou. I think we are all on the same page now. I hope Orgasmi is happy with our input and that the mystery of Rpm, speed and drafting can be put to rest or maybe we're not thinking out of the box. Is he is experiencing clutch slippage at high speeds which then in a draft would ease the power going through the clutch to the transmission, at which point the clutch would hook up again, thus lowering the rpms? Then when he gets out of the draft the clutch starts to slip again and voila, rpm's increase relative to road speed. This all happens without adjusting the throttle. What do you think of that?

G-Rock (jerk)

[dumrick]

Yes, thankyou. I think we are all on the same page now. I hope Orgasmi is happy with our input and that the mystery of Rpm, speed and drafting can be put to rest or maybe we're not thinking out of the box. Is he is experiencing clutch slippage at high speeds which then in a draft would ease the power going through the clutch to the transmission, at which point the clutch would hook up again, thus lowering the rpms? Then when he gets out of the draft the clutch starts to slip again and voila, rpm's increase relative to road speed. This all happens without adjusting the throttle. What do you think of that?

G-Rock (jerk)

Thanks for finding the way the revs are limited in an F1. I missed that one

[DaveKillens]

Let's assume a steady state drafting scenario, such as NASCAR at Talladega, with just two cars. Let's leave out such factors as acceleration and consideration for braking.
The lead car is running flat out, top gear. The car directly in the draft would run identical RPM, but under full throttle would close on the lead car, until they collide. To stay in station, the car in the rear would have to ease off the gas (lessen the power produced) just to maintain the same distance.
I hope that helps.

I need to correct my statement. It's true that if identical cars ran the same RPM, they would stay on station with each other, neighter gaining or closing. You were talking about a 19K rpm limited engine, while I was referring to NASCAR, where the limit is power produced. The trailing car may be running just 25 RPM quicker than the lead car, but it is going faster.


A driver modulates power by pressing down, or lifting up from the gas pedal. It's that simple... less or more gas and air.

[Ogami musashi]

Thank you dave.