Simviation Forums

Anyone here a car person?
Thing is, I'm doing Aerospace Engineering but we have a silly little report due on a car we're supposed to make with this silly little game (Racing Academy, from Lateral Visions, available for free).
So I'm writing my report now, which is due in two weeks, and came across something I'd like to talk about in my report but have no clue about.
In an ideal engine, what would the Torque/RPM characteristic be like? I had the idea that Torque would be independent of RPM but I'm completely unsure. I'd hope that someone here would know or I'll just leave that part out altogether...

Post in the 'Autos' forum and I might help.

Cars are useless. I want a report on something with wings...  ;)

F1 car?

Torque is dependent on RPM and work generated by the equation:

In SI units -  Work out [kW] = (T * n)/9549 where T = torque [Nm] and n = rotations/min [RPM]

In English units - Work out [hp] = (T * n)/5252 where T = torque [ft-lb] and n = rotations/min [RPM]

Hope that's what you were looking for.

[quote][quote]
Cars are useless. I want a report on something with wings...

In an ideal engine, what would the Torque/RPM characteristic be like? I had the idea that Torque would be independent of RPM but I'm completely unsure.

Torque can be independant of RPM. Let's say a 200 lb person puts a one foot long wrench on a bolt and applies all their weight but the bolt doesn't move. There was still 200 lb-ft of torque applied but with no RPM (rotation). Torque(lb-ft) = Force(lb) x Distance(ft), or 200 lb x 1 ft = 200lb-ft.
One other thing that has to be accounted for is gear ratio. A 3:54 ratio will apply more torque (do more work) at the wheels than a 1:1 ratio, but the 3:54 ratio would be less efficient at speed.  
In the internal combustion engine peak torque will always occur at a lower RPM than peak horsepower. This is because torque is dependent on cylinder efficiency; Less air/fuel = less torque. And since HP = Torque x RPM the rate that horsepower will fall off depends on how fast the torque curve drops off.
What a designer has to do is study the horsepower and torque curve. The peak effeciency will fall somewhere between these two curves. In the big picture parasitic loads also have to be taken into consideration. Confused yet?

Which is why all heavy plant and HGV's are diesel powered.

Now you have me interested...

Searched on the internet and found out a bit...
It has to do with the way the combustion occurs in a diesel engine, giving it
a longer stroke length, meaning a longer "lever arm" and more torque.
Pretty cool to know. So why don't all cars use diesel?

Because it is an RPM limiting factor?

[quote]Searched on the internet and found out a bit...
It has to do with the way the combustion occurs in a diesel engine, giving it
a longer stroke length, meaning a longer "lever arm" and more torque.
Pretty cool to know. So why don't all cars use diesel?

[quote]Now you have me interested...