A&Q about 350Z
Q:
I already got a nice lengthy explanation about that, but since we're talking about performance, let's get realistic, could you build a 7000hp DOHC V8? Talking dragsters here. Why do they use the engines they use?
A:
It'd depend what fuel you intend to use.
With pump gas you are severely limited and you'd struggle to get much more than the old 100 hp/l unless boosted.
When you start talking alcohol and nitrous the game changes entirely.
A:
let's say top fuel
A:
I'd never buy (most) european cars....because I do my own work.
European cars are nice to drive, no argument there. I'd commit suicide if I ever worked at one of their dealerships though. The few I'm forced to work on are enough trama for me. No thank you.
And yes, many american cars are a pain in the butt also, but on average, I still say, no comparison
A:
the F1 engine installed in a semi, with proper gearing, would make twice the rear wheel torque (power applied to the wheels) than the above mentioned semi truck engine.
To use layman terms....HP is torque adjusted for gearing. If a motor makes twice the HP, it will make twice the wheel torque....with proper gearing.
now would the F1 motor last long in that situation? Definitely not.
A:
It would need an indestructable CVT basically, but yeah it would work. The fact taht it spins at eleventy billion RPM makes up for the fact taht it would need to start at an insanely low gear ratio. But once it got into it's paper thin powerband then it would be faster than the truck.
Then again, Audi has their new diesel Le Mans racer, the R10, and it was kicking ass and taking names from what i remember... all while using less fuel and being much quieter. Lemme look some stuff up on it.
*edit* yar, Audi R10, all aluminum 5.5L V12 twin turbo TDI, >650hp and >810 torques. Pretty crazy.
A:
The biggest advantage is the low cost, which is why american manufacturers such as GM use push rod designs for their low end engines. High end engines such as Northstar/Aurora, Ecotec and HFV6 uses DOHC and 4 valves per cylinder just as most engines.
Push rod designs aren't really that compact, but this also depends on what you mean with size. A four valve DOCH engine is going to be a bit wider over the heads but that would also be the case with for example push rod hemis. How wide they are is mostly dependant on the valve angle and how the valvetrain is packaged. On the other side, if you use DOHC and 4 valves/cyl the greater flow due to larger port area/bore area and the more aggressive cam profiles which are possible to use with the direct acting cam system it's possible to decrease engine displacement and still get out the same kind of power output.
An ordinary gearbox with the proper gearing would work fine for a F1 engine.
The F1 V10 engines used earlier gave well above 200 Nm at low speeds, and since low speeds in a F1 engine is like 5000-6000 rpm that's still 150-200 hp. Remember that those speeds are only slightly above idle speed which is around 4000 rpm. At around 9000 rpm the torque output begins to increase fast, so at about 13000 you have almost the full torque availible, that means well above 600 hp. Then you have more than 900 hp at around 18-19k rpm.
The current F1 engines are a bit weaker but they can still produce about 750 hp with a decent power curve.
A:
If you made an intelligently geared 12 speed tranny for the motor, it would work just as well....actually better. The RPM of the power band doesn't matter much when its redlining in first gear at 2 mph. You'd still have double the wheel torque.
and of course its power band is short. Its 1/10th the cc's with twice the power output. That level of performance doesn't come with a free lunch. That shouldn't even need to be reiterated.
A:
Well, but now we're nitpicking reliability. How long would that F1 engine tow 60,000 lbs?
You can use gearing to multiply torque, but HP is already a function of motion. If you take an engine making 1000 lb-ft of torque at 2000 rpms, that means its making 381 hp. If you put it through a 2:1 gearbox, its now putting out 2000 lb-ft at 1000 rpms shaft speed... which is still 381 hp. The problem is the mismatch in gearing for the engine's power band.
You would have to gear an F1 engine down so far that its acceleration would be VERY subpar. You'd go through 50 gears just getting to 30 mph. First gear would literally have to be somewhere around 400:1 final drive to achieve the same speed per range of RPM.
A:
look guys, you are over thinking this.
you COULD pull a semi with a lawn mower engine if you wanted to.
what i was getting at is this...
with identical gearing, an engine with more torque and less power will pull harder than an engine with more horsepower and less torque.
yeah gearing helps, but gearing is only a torque multiplier. Hp is unchanged by gearing. (already mentioned by curtis)
if you have a honda 1.8L high strung engine, you have to rev that thing to the top of its redline before you shift to get the best acceleration. a much torquier engine can be shifted earlier and not lose acceleration.
engines with lots of torque usually come with 5 speed trans.
low torque engines come with 6.
(well not anymore... but thats how it used to be. except 3-4 and 5 respectively)
A:
no, its much simpler than that: maximum acceleration = highest HP.
That simple. The rest of the formula is gearing the motor to best take advantage of the power band. As another has mentioned, even "out of the power band" for an F1 engine, you still "only" produce 600+hp. Which is still way more than the semi engine.
Geared Intelligently, the F1 engine will accelerate that 80K pound mass way faster than a "normal" semi engine, regardless of what torque numbers the semi engine produces. This is a plain simple fact. It should be simple anyway
A:
so, according to this logic, a car will accelerate as quick in fifth as in first???
A:
was that directed to me? And if so, please provide a quote which shows I suggested such
A:
IMO, it's average to the wheels over your gear spread that counts.
If your engine puts out an average 200hp over say 3-5000rpm and you have the gears to keep it in this range. Then you can put down an average of 200hp to the wheels. You'll be faster than an engine which has a higher, but shorter power peak but lower average power over the range the gears are in.
It's a little difficult to explain. But in my definition of average power to the wheels I'm also including gearshifting time. More gearshifts (time putting 0hp to the wheels) is going to lower your average power to the wheels.
To take a 1 ton car to 30m/s in 4 seconds requires an average power to the wheels of:
P=E/t
Ek=1/2m*v^2
P=1/2m*v^2/4
= 500*900/4
=112.5 kW
Approx 150hp.
As we know, a 1 ton car capable of getting to just over 100km/h in four seconds has a peak power way in excess of 150hp. But it needs a peak that high to get an average of 150hp to the wheels during four seconds of acceleration.
The maths in her includes several assumptions (like the car being a solid block, not a collection of rotating shafts). But it illustrates the point well.
A:
I have a feeling that power drops off significantly outside of a few thousand RPM range for an F1 engine like that. The companies don't publish dyno sheets of course, but i'd think that the torque curve would be not very flat and even, and the power curve would be especially peaky.