Chris_R
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| posted on 17/4/04 at 07:51 PM |
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Calculate your 0-60 time
Have been mailed a link to a site that says you can calculate your 0-60 time with a formula, weight (kg) / BHP x 0.9. The site gives a few examples
and seems to be quite acurate. Wondering how this applies to Locosts, so does anyone out there know their cars weight, BHP and 0-60 time. My
car's a long way off.
Site in question: http://www.cars-cars-cars.org/0-60-Times-Calculator.htm
Cheers.
[Edited on 17/4/04 by Chris_R]
A bit of slapstick never hurt anyone.
http://www.chris.renney.dsl.pipex.com/
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blueshift
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| posted on 18/4/04 at 01:08 AM |
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According to that, assuming 200bhp for the rover v8 vitesse and 600kg, ours should do 0-60 in 3.3s. I doubt this.
Assuming hicost is getting about 450bhp and 700kg, the calculator recons he should be seeing 0-60 in 1.7s. I doubt this even more.
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DaveFJ
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| posted on 18/4/04 at 09:22 AM |
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Hmmm
Don't forget thats all up weight...
include a driver and fuel with a realistic weight and IMHO you would be over 800 Kg which gives about 4.5 secs - about what I would hope....
Dave
"In Support of Help the Heroes" - Always
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Chris_R
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| posted on 18/4/04 at 10:52 AM |
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Ok, maybe not as accurate as they make out on that site. Does anyone know of a more reliable way, experience maybe. Anyone got a 1600 CVH and know
their 0-60 time?
A bit of slapstick never hurt anyone.
http://www.chris.renney.dsl.pipex.com/
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jmbillings
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| posted on 18/4/04 at 11:49 AM |
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Ive not looked, but how would they take into account gearing with that formula? And gearchange times etc. etc.?
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Chris_R
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| posted on 18/4/04 at 12:00 PM |
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Not sure about the gear ratios, but they do suggest that ‘gearbox technology’ (auto/manual I think) is a variable along with tyre adhesion, driver
skill, internal resistance and external resistance. They also put an emphasis on drive (front or rear) and engine position.
A bit of slapstick never hurt anyone.
http://www.chris.renney.dsl.pipex.com/
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blueshift
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| posted on 18/4/04 at 07:14 PM |
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quote:
Originally posted by protofj
Hmmm
Don't forget thats all up weight...
include a driver and fuel with a realistic weight and IMHO you would be over 800 Kg which gives about 4.5 secs - about what I would hope....
I weight about 75kg and fuel is a bit lighter than water, so 25kg of fuel is a bit over 25 litres.. so maybe around 700kg all-in. plus a few kilos of
clothes if you're not feeling too daring. 3.8s... maybe possible. just.
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mackie
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| posted on 19/4/04 at 07:49 AM |
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Playing with it a bit it does seem to approximate typical cars (between 1000 and 2000 kg) quite well but as soon as you put big power or light wieght
in it falls apart.
If it's around 5s for our car I'll be more than happy. Less would be better though 
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steve m
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| posted on 20/4/04 at 08:11 AM |
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What about wind resistance, "7s" are not exactley streamlined are they
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Mark Allanson
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| posted on 20/4/04 at 08:05 PM |
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In the early 80's when Cd factors were selling cars, they were published in What Car along with the 0-60 times - a Caterham was measured to be
0.65 with a screen.
Another formula is
t0-60 = 0.55 (Weight/Torque)
As it is torque which gives acceleration and BHP which gives top speed, it 'may' be more accurate (the 0.55 constant may need adjusting to
compensate for lightweight cars as it was probably designed for family saloons)
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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phelpsa
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| posted on 21/4/04 at 08:57 AM |
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According to your formula mark I will have a 0-60 time of 3.2 seconds, I very much doubt it.
Adam
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craig1410
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| posted on 21/4/04 at 12:23 PM |
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Mark,
I would have to disagree with you to a certain extent there as Kinetic Energy is equal to (mass x Velocity^2) / 2 and as power is the generation of
energy per second then power is what is important.
HOWEVER,
It is "average power over the rev range in use for each gear" which is important not the peak power and this is the reason why the likes
of a V8 "feels" faster than a smaller engine of the same "peak power" output because the V8 will tend to have a much flatter
torque curve which in turn yields a much more linear power curve. A peakier rally or race tuned small capacity engine will produce its torque in a
narrow range of RPM and unless you have a gearbox with tuned ratios to match this torque curve then you will fall off the cam and lose
acceleration.
The only way to predict 0-60MPH is to try it really although if you have a rolling road plot of power/torque versus RPM (even better versus MPH) then
you can determine your optimum gearchange points are (where road wheel torque in current gear equals road wheel torque in next gear) and then in turn
figure out the average power generated over this RPM range. You can then use this figure with some adjustments for gearchange times to predict 0-60
more accurately.
I did this for my old Fiat Uno Turbo ie which I had on a rolling road (115 BHP IIRC) and then predicted 0-60MPH to within a couple of tenths.
By the way Blueshift, I'd be surprised if you can keep the car weight down to 600Kg's. I reckon that I am looking at closer to
700Kg's plus driver minimum.
Cheers,
Craig.
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the man with a plan
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| posted on 2/6/04 at 11:32 PM |
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I know this thread is pretty old, but i was doing some research myself, and found that the coefficient of 0.9 seemed about right for similar(ish)
cars.
Craig, I would like to disagree with you, if that is ok?
0 - 60 times is basically a representation of acceleration, and from N2 F = ma. Torque is effectively the rotational force of the engine, so F = ma
applies.
Whereas top speed is obviousle a measure of speed, so bhp (from ke = 0.5 m v^2) is more appropriate.
Please correct me if I am being a twat and am talking out of my arse.
Cheers
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craig1410
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| posted on 3/6/04 at 12:08 AM |
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The man with a plan,
I had to read my own post to remind myself what this was all about...
I'd have to disagree that you are disagreeing with me (if that's okay...  )
I think we are all just talking around the same stuff from differing points of view.
Instantaneous torque and instantaneous power are directly linked at any given RPM. Something like Power(BHP) = Torque(lbf.ft) * RPM / 5252 if I
remember correctly.
However, I feel more comfortable with the view that to accelerate my vehicle from rest to 60MPH, I need to produce a certain amount of energy and the
more power I have the quicker I can achieve this speed with all other things such as mass being equal. But there is no point in thinking that if my
car has a peak power output of 200BHP then this is the figure I should use in 0-60 predictions because my RPM and therefore power output will not be
constant during the run. In fact, assuming a linear power curve and assuming that each change of gear will knock the RPM back from 6000 to 4500 RPM,
the power will go from 200BHP to 150BHP with an average somewhere in the middle, say 175BHP. This just happens to be 0.875 of peak power which is
maybe where the 0.9 estimation comes from.
If you try to perform the estimation using torque figures then you need to adjust for each change of gear whereas with power figures the power output
only depends on RPM and this is readily available from a rolling road trace. Rolling and transmission losses obviously apply to both.
One final thing I'd like to point out again is that these estimations will vary considerably depending on the engine type with the extremes
being BEC and V8 (or even diesel) and with the gearbox ratios.
In short, you'll be lucky to get an estimate within 1 second of the figure you will achieve in practice so stop guessing and start building
then you can nip down to Santa Pod and find out for real...
Cheers,
Craig.
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the man with a plan
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| posted on 3/6/04 at 12:41 PM |
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Ok, I (more or less) stand corrected. I admit I did forget to consider revs and gear changes.
That said, it wouldn't surprise me if a much more accurate model for 0 - 60 involved both functions of power and torque and would be dependent
on the power curve.
I must agree, the best way to work out your 0 - 60 time is to go out and just do it. I cant wait!
Anyway, its pretty interesting
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craig1410
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| posted on 3/6/04 at 06:22 PM |
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Yes I think you could come up with a fairly accurate model but I think the starting point would have to be a rolling road power plot of power at the
wheels. Using this along with gear ratios you can work out the best gearchange points and then use this to come up with a decent estimate of 0-60. You
will still need to fudge the figures to take account of gearchange times and clutch/tyre slip during take off. This can be very significant once power
to weight ratio's get to a certain level. Perhaps the 30-80MPH test would be easier to estimate but then aerodynamic effects need to be taken
account of...
Santa Pod it is then...
Cheers,
Craig.
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Dale
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| posted on 23/6/04 at 04:48 PM |
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Take a look at "street dyno" which will with some work allow you to measure and get a hp/tourqe curve. I am pretty sure that the dash
seven will have this capability at some time - I hope
Dale
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Bob C
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| posted on 3/9/04 at 12:33 PM |
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Download "cartest" off the web fellas, type in your car's details & let it work it all out! It does all sorts of losses, gears
& everything, simulates 1/4 mile, 0-60 and performance round various tracks (where you can race against a mclaren F1).
BECs watch out - it don't do revs over 10k - I divided rpm by primary reduction ratio to make it all work. I'll post a picture of an
output page later tonight.
cheers
Bob C
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stressy
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| posted on 4/9/04 at 08:20 AM |
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Nice one bob
A friend of mine from a few years back used to use this along with a desktop dyno to toy with drag cars and spoke highly of it. I could not remeber
the name of itbut you found it.
I ran a couple of cars i know well through it and the results are supprisily accurate for them. you need to remember to put in the high cd for a 7,
and to use the fuel plus driver weights ( add a passenger and you may get better traction). Ive just run my car through it as she is in the garage
today and it gives 5.9 seconds. Not unreasonable at all.
Good bit of fun.
Chris
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