Might work though the biggest problem was that the tires heat up after few laps to over 100 degrees and stay there quite long. But I guess I won't be driving the FXR too soon again
Might work though the biggest problem was that the tires heat up after few laps to over 100 degrees and stay there quite long. But I guess I won't be driving the FXR too soon again
Try keeping the FZR's rears on the straight and narrow. It really needs pampering if you wanna make them last for any amount of time.
I like it at 22% to the front myself. A touch of power oversteer in there somewhere, feels so nice, easily controlled by playing with the front and rear power locking. Plus you'll always keep both tyres until everything on the F9 display is back to blue again (well, with sensible camber anyway).
Mahlzeit.....
About the FXR being competitiv in endurance racing.....take a look at the results of the Masters of Endurance.
The FXR is NOT gentle with its tyres.....we almost always had to pit due to tyre wear and only once due to fuel consumption. And whoever said it is near impossible to spin the FXR has never driven it fast enough over long enough stints.....trust me
CU, Sebastian
About the FXR being competitiv in endurance racing.....take a look at the results of the Masters of Endurance.
The FXR is NOT gentle with its tyres.....we almost always had to pit due to tyre wear and only once due to fuel consumption. And whoever said it is near impossible to spin the FXR has never driven it fast enough over long enough stints.....trust me
CU, Sebastian
XRR
365kW (490bhp) @ 6278 rpm
627Nm (462 lbft) @ 4782 rpm
332 W/kg (453 bhp/ton)
FZR
365kW (490bhp) @ 8106 rpm
503 Nm (371 lbft) @ 5267 rpm
332 W/kg (452 bhp/ton)
So where's this less power?
@moonclaw: You are just looking at the peak values. The XRR may have higher peak torque but the torque curve itself is quite sharp, unlike the FZR which has more torque around the peak value.
Also the turbo lag means that there is a lag when yopu push the throttle in XRR/FXR.
Also the turbo lag means that there is a lag when yopu push the throttle in XRR/FXR.
But to shag the , XRR still has more power.
More power at some specific point. Remember the peak power figure of a car is the most useless figure bandied about by anyone. Peak torque is much better, but still fairly useless. What you want is a torque curve - the only bit that matters.
Do a test - run the FZR and the XRR on the same tyres, the same gearing etc, and watch which one is fastest in terms of speed and acceleration. Sure the FZR might be a bit more aerodynamic (who can really tell if that's modelled accurately or not), but the FZR is a LOT faster than aero differences would suggest, meaning the XRR has less tractive effort, which means less torque, which means less useable 'power'.
Do a test - run the FZR and the XRR on the same tyres, the same gearing etc, and watch which one is fastest in terms of speed and acceleration. Sure the FZR might be a bit more aerodynamic (who can really tell if that's modelled accurately or not), but the FZR is a LOT faster than aero differences would suggest, meaning the XRR has less tractive effort, which means less torque, which means less useable 'power'.
Plus, the FZR is way better in getting the power on the tarmac, as the XRR has a very light rear (compared to its direct competitor)...
No.
The only reason you want that is so you can derive a power curve from it
Measuring the engines ability to do work (POWER output) is FAR more useful than knowing an instantaneous measure of force it's capable of generating. One is a measure of force over time (work) and the other is instantaneous force. More force over time is what moves cars over larger distances in less time. All a peak torque figure is good for is giving you a rough idea of what the power curve is going to look like!
UhOh everyone duck
How do you use power to calculate the performance of the car? That's right, you can't.
You use the torque curve and the gear ratios to generate the tractive effort curves, and from that you can calculate acceleration, top speed (if you know rolling and aerodynamic drag), everything you need.
Power curve is only useful for deriving a torque curve. Unfortunately people can only cope with 'power' without realising that in terms of performance it's a rubbish thing to quote.
If you can tell me when a power curve is useful, other than using it to calculate torque, then I'm all ears... I know a good estimate of an engine is if the lbft and hp figures of an engine are similar then it'll probably be a well balanced engine, and a high hp low lbft (peak figures) means a peaky engine, but thats about it.
Last time we had a disagreement we ended up with a 3 page conversation. Gulp.
You use the torque curve and the gear ratios to generate the tractive effort curves, and from that you can calculate acceleration, top speed (if you know rolling and aerodynamic drag), everything you need.
Power curve is only useful for deriving a torque curve. Unfortunately people can only cope with 'power' without realising that in terms of performance it's a rubbish thing to quote.
If you can tell me when a power curve is useful, other than using it to calculate torque, then I'm all ears... I know a good estimate of an engine is if the lbft and hp figures of an engine are similar then it'll probably be a well balanced engine, and a high hp low lbft (peak figures) means a peaky engine, but thats about it.
Last time we had a disagreement we ended up with a 3 page conversation. Gulp.
Having programmed just that thing in GRC, I can assure you all that Tristan is correct. The power curve is just some pretty you can draw once you're done with the performance estimations. Power is only really useful for a quick top speed analysis.
@ Tristan (edit2: & Bob too)
As you're well aware, torque at the drive wheels is what matters (which you alluded to above). Due to gearing, the vast majority of the time wheel torque is higher at the engines peak power output than it is at the engines peak torque output.
As far is power calculations being useful:
P = net horsepower
F = the sum of the longitudinal forces at the driven tires.
V = velocity
P = F * V
or
F = P / V
Therefore we achieve maximum torque at the wheels if you maximize your POWER at any given velocity.
Yes this is simplified since I am at work and could not resist replying, but the math still holds true.
I enjoy this topic despite the inherant futility of debating whether two pieces of data derived from each other are relevant or not... It's still just ... fun.
EDIT: Bah, beaten by BOB.
As you're well aware, torque at the drive wheels is what matters (which you alluded to above). Due to gearing, the vast majority of the time wheel torque is higher at the engines peak power output than it is at the engines peak torque output.
As far is power calculations being useful:
P = net horsepower
F = the sum of the longitudinal forces at the driven tires.
V = velocity
P = F * V
or
F = P / V
Therefore we achieve maximum torque at the wheels if you maximize your POWER at any given velocity.
Yes this is simplified since I am at work and could not resist replying, but the math still holds true.
I enjoy this topic despite the inherant futility of debating whether two pieces of data derived from each other are relevant or not... It's still just ... fun.
EDIT: Bah, beaten by BOB.
Actually, if you look at a tractive effort curve (the force or torque at the wheels) it will peak always at peak engine torque, but at varying speeds due to the torque multiplication of the gears.
Power doesn't really come into. Your equations are wrong - peak torque occurs at peak torque, peak power occurs at peak power. The peaks are not at the same time.
Power doesn't really come into. Your equations are wrong - peak torque occurs at peak torque, peak power occurs at peak power. The peaks are not at the same time.
It would be nice if someone actually would measure the the torque curves of some of the cars. Would it be this simple:
1) create a simple autocross layout on BL car park with possibility to do more than just one "laps". All it needs is a long straight.
2) take a car, put the tire pressures to full and take all the aero away from the setups. *
3) Make simple acceleration&engine braking tests so you could get the acceleration&speed values (curves) between the clutch bite rpms and the red line.
4) Save these "laps" from the replay in raf and open it in F1perfview. Also check the tires size and transmission ratios.
5) calculate&draw
6) publish the result
7) put flamesuit on
8) do it again just to prove it works!
9) well...
So it would a very simple job actually. Comparing the acceleration/time curve to the rpm/time curve and taking the right values... And vice versa for the engine braking to get the power train "friction" values, rolling resistances and air resistances.
Of course I can't do it myself because I need to learn some 3d-modelling
*I think LFs shows the forces (drag) in the setup menu, the speed slider thingy? Just write down the values in 5m/s steps and it should be fine
1) create a simple autocross layout on BL car park with possibility to do more than just one "laps". All it needs is a long straight.
2) take a car, put the tire pressures to full and take all the aero away from the setups. *
3) Make simple acceleration&engine braking tests so you could get the acceleration&speed values (curves) between the clutch bite rpms and the red line.
4) Save these "laps" from the replay in raf and open it in F1perfview. Also check the tires size and transmission ratios.
5) calculate&draw
6) publish the result
7) put flamesuit on
8) do it again just to prove it works!
9) well...
So it would a very simple job actually. Comparing the acceleration/time curve to the rpm/time curve and taking the right values... And vice versa for the engine braking to get the power train "friction" values, rolling resistances and air resistances.
Of course I can't do it myself because I need to learn some 3d-modelling
*I think LFs shows the forces (drag) in the setup menu, the speed slider thingy? Just write down the values in 5m/s steps and it should be fine
You might be able to do this with the g-meter in LFS, or in F1 perf view. If you know the mass of the car and the acceleration of it you can derive the torque at the wheels (ignoring drag of any sort, so keep the speeds low). And if you know the gear ratios, the dynamic wheel circumference (pi*r^2 will do though) and the torque you can easily work out engine torque at certain rpms.
I'll have a lookie at the weekend (work commitments til then
) but maybe someone will beat me to it...
I'll have a lookie at the weekend (work commitments til then
) but maybe someone will beat me to it...I knew I should've waited till I got home to reply :doh:
Why? P=Fv is a common formula!
Let me ask you this - when is the most energy being produced by an engine - at peak torque or peak power output?
The more energy produced, the more energy expended on moving the car therefore the faster it will accelerate.
The very definition of power speaks for itself: the ability to do work. Doing work on the car is what we're concerned with. I don't care how much force you apply to the crankshaft, rather I am concerned with how quickly you can apply the given force, with the end result being work which takes power to accomplish, of which force (torque) is only a component.
If this is wrong (which would seem to contradict a lot of physics, but I'm open to learning) then someone needs to tell me exactly why time is not important in this debate, since acceleration occurs over time - and force is an instantaneous measurement, whereas power takes this into consideration providing what would seem to me to be a much more relevant indication of the potential of an engine.
Why? P=Fv is a common formula!
Let me ask you this - when is the most energy being produced by an engine - at peak torque or peak power output?
The more energy produced, the more energy expended on moving the car therefore the faster it will accelerate.
The very definition of power speaks for itself: the ability to do work. Doing work on the car is what we're concerned with. I don't care how much force you apply to the crankshaft, rather I am concerned with how quickly you can apply the given force, with the end result being work which takes power to accomplish, of which force (torque) is only a component.
If this is wrong (which would seem to contradict a lot of physics, but I'm open to learning) then someone needs to tell me exactly why time is not important in this debate, since acceleration occurs over time - and force is an instantaneous measurement, whereas power takes this into consideration providing what would seem to me to be a much more relevant indication of the potential of an engine.
Also, dont forget that the FZR responds nicely to the EXPLOIT, so once the patch is out it will level things that little bit more.
Okay, do we agree that the acceleration will be greatest when the force at the wheels is highest. It's a simple F = M x a problem. For a fixed mass, the greatest force will result in the greatest acceleration.
So below is a graph of tractive effort at the wheels (force at the wheels, in Newtons) against engine speed for 5 gears. As you can clearly see the tractive effort curves are squashed torque curves, and the peak occurs at peak torque in any gear, where the most acceleration is to be had. Also the top speed of the car is shown by where the drag line (red) intersects the tractive effort curves.
It also shows when to change gear - when there is more force in the next gear than the current gear, and in this graph it is where each line crosses the next.
The second graph is the same as the first, but I have also put on the power derived forces using your equation. Power in watts = Newton meters per second, and I converted the speed for the calculation to meters per second, so the end result is in Newtons. As you can see, it shows peak accelerations at the point of peak torque NOT peak power. Quite why the two lines don't coincide perfectly I'm not sure, and I can't be bothered to inpect it, but it's probably just a poor conversion between units or something.
Hopefully this will answer your questions. Peak acceleration ALWAYS occurs at the point of peak torque. The car in question in this graph has a peak torque of 100lbft at 5700rpm, and a peak power of 117hp at 6700rpm.
Feel free to ask more questions, but you won't win this one
So below is a graph of tractive effort at the wheels (force at the wheels, in Newtons) against engine speed for 5 gears. As you can clearly see the tractive effort curves are squashed torque curves, and the peak occurs at peak torque in any gear, where the most acceleration is to be had. Also the top speed of the car is shown by where the drag line (red) intersects the tractive effort curves.
It also shows when to change gear - when there is more force in the next gear than the current gear, and in this graph it is where each line crosses the next.
The second graph is the same as the first, but I have also put on the power derived forces using your equation. Power in watts = Newton meters per second, and I converted the speed for the calculation to meters per second, so the end result is in Newtons. As you can see, it shows peak accelerations at the point of peak torque NOT peak power. Quite why the two lines don't coincide perfectly I'm not sure, and I can't be bothered to inpect it, but it's probably just a poor conversion between units or something.
Hopefully this will answer your questions. Peak acceleration ALWAYS occurs at the point of peak torque. The car in question in this graph has a peak torque of 100lbft at 5700rpm, and a peak power of 117hp at 6700rpm.
Feel free to ask more questions, but you won't win this one
You can get the torque curves of the engine much easier than that, I did it in S1 days. Just drive the car from rest at full throttle (no wheelspin) until you hit the rev limiter, output the RAF data from the replay, use F1perfview to output to the longitundal force on the drive wheels to CSV, sum this in Excel, divide by total gearing reduction (look at 1st/final drive ratios in setup used) and tyre diameter, then adjust drivetrain losses until peak torque matches up. Voila and you can plot the torque curve. A little more work and you've the power curve too.
OK so it's not a one step process.
-------------------------------
To the debate:
"Therefore we achieve maximum torque at the wheels if you maximize your POWER at any given velocity."
Yes, but that is coincidence - I mean, you don't need to know anything about the power curve. Just look at the wheel torque in every gear and you'll end up straddling the rpm peak power anyway.
Tristan: peak acceleration IN ANY ONE GEAR certainly happens at peak torque. By making use of multiple gears, acceleration will be a constantly dwindling number once you hit peak torque in first. The point is you are only at the rpm of peak torque, unless you gearing is over spaced, changing down will decrease engine torque output but increase torque at the wheels.
It is best to only think about torque and not power though - by optimising torque you'll be optimising power anyway.
OK so it's not a one step process.
-------------------------------
To the debate:
"Therefore we achieve maximum torque at the wheels if you maximize your POWER at any given velocity."
Yes, but that is coincidence - I mean, you don't need to know anything about the power curve. Just look at the wheel torque in every gear and you'll end up straddling the rpm peak power anyway.
Tristan: peak acceleration IN ANY ONE GEAR certainly happens at peak torque. By making use of multiple gears, acceleration will be a constantly dwindling number once you hit peak torque in first. The point is you are only at the rpm of peak torque, unless you gearing is over spaced, changing down will decrease engine torque output but increase torque at the wheels.
It is best to only think about torque and not power though - by optimising torque you'll be optimising power anyway.
I think it's the best to use a slightly taller 2nd gear. Accelerate from the low clutch bite rpms to the redline and lift off the throttle and let the car slow down by engine braking and air resistance + all the other "resistances".
Then just separate the raf output into two parts. The acceleration and the deacceleration part. The latter gives the info you need to reduce the resistances from the acceleration curve and therefore you don't need to calculate them by yourself.
The result is a torque curve from the axle of engine (or how do the london people call it )
Then just separate the raf output into two parts. The acceleration and the deacceleration part. The latter gives the info you need to reduce the resistances from the acceleration curve and therefore you don't need to calculate them by yourself.
The result is a torque curve from the axle of engine (or how do the london people call it
)I prefer the XRR, mainly because I haven't taken the time to learn the FZR better. Even then, I still like the XRR the best, and the XFR second best.
And, would it be a bad thing if I've beaten FXRs with the XFR? (Allthough I'm definately sure he was a shoddy driver.
And, would it be a bad thing if I've beaten FXRs with the XFR? (Allthough I'm definately sure he was a shoddy driver.
Thank you!
Since most lamen off the street can't relate to "wheel torque in each gear", and it's not published in magazines (hehe maybe it should be, can you imagine seeing tractive effort curves in auto rags ROFL, people would be like "WTF?") Ahem... Right then, since they're NOT, peak hp/tq values are both relevant IMO.
I still disagreee. I've done a number of programs and spreadsheets for predicting perfomance of various race cars we've owned over the years, and not once has the power curve or any power figure been useful. All you ever need for any performance calculation is the torque figures.
And Bob - I don't get what you mean by straddling the rpm peak power anyway... it's perfectly possible that the optimum gear shift point of a car is BEFORE peak power. It just depends on your gearing. I don't see what that sentence means, although BBT ^ seems to think it proves him right. Maybe it does, but can you clarify your sentence.
And Bob - I don't get what you mean by straddling the rpm peak power anyway... it's perfectly possible that the optimum gear shift point of a car is BEFORE peak power. It just depends on your gearing. I don't see what that sentence means, although BBT ^ seems to think it proves him right. Maybe it does, but can you clarify your sentence.
about gtr's
(131 posts, started )
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