Hmm.. how do you figure slippage then?

 

If its an A4, maybe so due to crappy tranny ratios and random shift points. But it would be tough for me to believe that for an m6.

Really the only drawback in my opinion to gears with a m6 would be gas mileage and possibly top speed in 5th (6th doesnt have enough power to overcome 160+).

 

Well then, here's a little education for you:

http://www.vettenet.org/torquehp.html

Dan

 

Actually HP and TQ both accelerate a car.....your both wrong. They work together one influences the other.

I have an auto and love it so back off

 

You want to explain that?

Dan

 

Im really glad you can use google, its a great skill to have. This guy makes some shady points. Let me explain.

"Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)"

Now one would think that this sounds right, but he fails to point out that peak HP is at a higher speed (vehicle speed) than peak torque. A car accelerates MUCH harder at slow speeds. Try this same experiment at 50 mph in 2nd (peak hp) and 50 mph in 3rd (peak TQ) and then feel the difference.

HP accelerates a car, not torque.

Ok think about it this way. Imagine a car engine as a rocket and the rocket's engine could only fire in bursts (somewhat like a cars). Now the rocket could fire adjustable bursts and vary the rate at which it fires them. Now the acceleration of the rocket is going to be roughly proportional to the ammount of total work that is done by the engine. If the rocket's engine only fired HUGE bursts at a slow rate, it would not accelerate as fast as it would at twice the rate and 3/4 the bursts power.

An engine is similar in this same respect because the engine is creating explosions that create torque. The rate at which this is done will affect how fast the crank (and consequently the car) will accelerate. Each rpm will accelerate the crank, and more torque will accelerate it faster.... but the more often the cylinders fire, the more often the crank has a chance to accelerate. Thus accelerating the car faster.

(sorry for all the rocket refrences, thats what i do)

 

basically each gearing will react different at different speeds.........do you want to pull harder at 120 or at 25 or anywhere in between? It's all in what you are trying to accomplish.

But we all agree here that getting the car moving takes the longest amout of time. That is why you run the 3.73's. This is where races are won and lost most of the time.....the line so pulling a .5 off the line on a car is better than gaining .2 tenths on the same car half way down the track........proven time and time again

So if you are going to be crusing around the freeway at 70-80 i would get the 2.42's

All IMO of course

 

Ferrari Modena...
3100lbs
311 rwhp, 237 rwtrq
Generates the HP at a rediculous 8400rpm or something like that...
1/4? 12.8 @ 113mph.

 

Torque is what gets you off the line, Horsepower is what gets you down the track. This is the easiest way to think about it.

 

It's accelerating more in 2nd because of the torque multiplied by 2nd gear is higher than the resulting TQ multiplication in 3rd. It has nothing to do with speed. It's all in the gearing.

Not true.

A car can't fire HUGE bursts at a slower rate.(different Octane fuels may affect this though)

The speed of the crank is proportional to the force applied to the piston which creates TORQUE. The cylinders are able to fire more rapidly because the force on the piston created more TQ which spun the crank faster.

That's cool. I'm a Mechanical Engineer, who has worked for GM designing powertrain components.

I understand a little how you are conceptualizing HP and TQ, but the fact remains that TQ accelerates the car, not HP.

HP is a FUNCTION OF TORQUE. That means the HP results from TQ. HP=RPM*TQ/5250 like you have stated. A car that makes 300 ft lbs of TQ from 1000-8000 rpm will have only 57 HP at 1000 RPM and 457 HP at 8000 RPM. You think that car has 8 times as much acceleration at 8000 RPM, even though it has 300 ft lbs of TQ at 1000 RPM? The fact is, that car will accelerate at the same rate from 1000-8000 RPM. No matter where you step on the gas in that RPM range, you will get the same belt in the back(disgregarding wind drag)

I really don't want to keep arguing about this. I suggest that you read a few more articles like the one I linked to. Eventually, it will makes sense. It is a concept that MANY, MANY people get wrong.

Dan

 

The huge bursts at a slow rate was relating a fully filled cylinder at low rpm. Smaller burst would mean less air in the cylinder.

And as far as im concerned, with a flat torque curve between 1-8k rpm an engine will accelerate 8x faster at 8k rpm than 1k.

How else can you explain why Formula 1 cars are geared for 18k rpm and not for torque?


Hey, if you worked for GM..... wanna hook up a poor aerospace student with a job?

 

That's funny. It seems that whenever I mention on this board that I was an engineer with GM, they ask for job hook-ups.

I'm in the chemical industry now. The automotive industry is fun for a while, but not where I wanted to spend my entire career.

Formula 1 go to such high RPM so that they can take advantage of the TQ longer in each gear.

Sorry, I can't help out with the job right now. The best way to get a foot in the door is to get an internship or co-op. That's how I started out, then was hired when they liked my performance.

Dan

 

rwtq accelerates a car. If you have low HP, then you cannot maintain high rwtq at high speeds.

In theory, you can have 50lb ft of torque, and 1000 HP at the flywheel if that torque can be maintained at a high enough rpm (say 50lb ft at 100,000rpm, pure theory here). In order to realize that HP, you would need a big enough gear to multiply that 50lb ft flywheel torque into serious rwtq. The ability to rev to 100,000 rpm will allow you to shift at normal shift points despite the wacky gear ratio. You should be able to do 9second quarter miles with this motor.

I hope that makes sense. This is in oversimplifcation because Im discussing peak HP without taking torque curve into account.

You will pull harder in 4th gear with 3.7s then you do with 3.23s, only because 4th gear is slower in the 3.7 than in the 3.23. HP = torque x velocity. The slower you go, the harder you pull.

Gears do not increase HP, so generally speaking they should not affect the pull you feel at say 70mph. 70mph might = 2nd gear with the 3.23s but 3rd gear with the 3.73. The question should not be, which car pulls harder in 3rd gear, but if 3.73 pull harder in 3rd than 3.23s pull in second. i.e. which car pulls harder at 70mph? And that has been discussed already.

 

Dan

 

correct me if im wrong, but wouldnt that prove that 50 lbs torque at 100,000 would accelerate faster than 50 lbs of torque at 5000 rpm.

In order to put this torque to the ground you would need a rediculious gear ratio for the 100,000 rpm thus multiplying the torque put to the wheels (because HP is higher).

So with 50lbs at 100,000 rpm with 1000 hp, it would put down more rwtq than the rwtq at 5000 rpm (50 hp).