Wheel spinning

Anonymous · April 8, 2004, 23:20

had my first proper racing start tonight, i though 'ill show him in his calibra' s:twisted: :twisted: s:twisted: Took it upto 5k revs, dumped the clutch......nothing but wheel spin! it was like i was just sitting there on the line and me thinking ' so are we gonna start moving forward then?'

I thought rear wheel drive cars had lots more traction? whats the best way for a good launch?

Anonymous · April 8, 2004, 23:28

So I gather you got p155ed on s:(

s:(

Check out:

m http://www.mr2roc.org/forum/viewtopic.p ... =technique m

I think that a lot depends on tyres though

Anonymous · April 8, 2004, 23:34

well not really, it was just my mate and he was behind me. i was just expecting to power off the line, and leaving him for dead - his being FWD. it has been raining today so the road was probably cold and damp.

Oh well, have to try fewer revs next time s:? :? s:?

MRMike · April 9, 2004, 01:00

I wouldn't have expected wheelspin at that RPM unless the surface was poor/wet. I've just been out messing about with my GTECH I dialled in a few more revs this time, even at about 5800 sidestepping the clutch the car hooked up very well. Infact the results were massively impressive

0-60 feet 2.085
0-60mph 6.270
0-100mph 15.346
0-120mph 22.204
0-130mph 26.319

1/4mile 14.2 @ 98.41mph

These were all taken on a quarry road, (private). I know the speed things pretty contentious, but thought i'd share anyways. Plus despite my car having those awfull engine problems before, it seems back to rudest health.

Anonymous · April 9, 2004, 01:05

0-60 in 6.2?!?! - you're avin a larf! s:lol: :lol: s:lol: and a quarter mile in 14.2 secs, nah, cant believe that.

As for my wheel spinning, think i might put some different boots on, think ive got some shitty bridgestones on at the mo s:(

s:(

MRMike · April 9, 2004, 01:13

It is admittedly quite fast....but the Gtech doesn't lie (much!) and it's prooved very acurate in tests. This was pretty much the perfect start I hasten to add..no wheelspin..lost hardly any revs when leaving the line. I don't think i'll ever beat that again. The times are only a bit faster than those on Monkeywrench for a stock car..

The car had no perol in it, and has been lightened by a marginal amount also - spare/toolkit/engine tray

Anonymous · April 9, 2004, 01:24

does the gtech work by the user inputting the weight of the vehicle ect or does it just sense the g-forces and rpm via the fag lighter?

MRMike · April 9, 2004, 01:27

The gtech works by doing all those things s:lol: :lol: s:lol:

Well technically it only senses the RPM through the cigarette lighter.. the G's it calculates from the 3 inbuilt accelerometers, and the power calculation is calculated from the inputted weight.

Anonymous · April 9, 2004, 01:34

so how do you know the precise weight of the vehicle? have you had it weighed? did you account for yourself in the car?

MRMike · April 9, 2004, 01:43

Well firstly I approximated the weight, using m http://www.kumosport.com/component_weight_zzw30.asp m

Had it on the weigh bridge last week though as i've had a new stereo since so made sure the weight was correct

Anonymous · April 9, 2004, 01:47

what was the weight excluding tool kit and spare etc.. do you have it in kilos? i think the stock weight is 975kg without the driver

MRMike · April 9, 2004, 01:51

I've only ever measured with the driver in on the weigh bridge, so won't be much help sorry. If you take the base 975 then take away the weights on the previous weblink and add your weight you won't be far off

juansolo · April 9, 2004, 09:49

Manufactuers weights can be in Caterkilos. Basically as it's in their interests as figures (sadly) sell cars.

Caterkilos are legendary as they sell their cars on their light weight. So the figures are massaged a little. For example take the R500. According to the manufacturer they're 460kgs and 230bhp, giving exactly 500 bhp/ton. How handy. Except in the trim required to actually use the car (bearing in mind this is sold as a track car), and with fuel this actually rises to 499 kilos. This is weighed on proper cornerwieghting scales by the way. The net result is that an R500 is actually a R460. See how less impressive that seems.

What I am saying is take all figures you read with a pinch of salt, especially when it comes to weight. Firstly make sure we are talking kerb weights. Basically the car with all fluids. It's common for people to quote dry weights that are no use to man or beast, given that cars don't work without oil, water and fuel in them.

The only way to be absolutely sure is to weigh it yourself or have it weighed. Preferably on proper scales and with you in it.

More figures to be taken with a pinch of salt that in the scheme of things, really don't mean anything: http://www.juansolo.demon.co.uk/P2W/P2W.html

juansolo · April 9, 2004, 09:52

Perfect example, just noticed I have the weight of the Mr2 as 950 (which will have come from the interweb somewhere). Not right of course. Arses, I'll change that now.

Just because you read it on the internet, doesn't make it true s:wink: :wink: s:wink:

Anonymous · April 9, 2004, 09:55

As I understand it though, MRMike's figure for 0-60 is derived from his GTECH jobby measuring start time and time at 60 (which it interpolates from acceleration over time), and so shouldn't need the weight of the car input at all. While it's true that weighing it is the only way to get a true value, he'd only need that for a BHP figure.

juansolo · April 9, 2004, 10:01

It needs the weight to accurately figure out when it's doing 60. A guestimate of this will give you a guestimate reading.

Anonymous · April 9, 2004, 10:02

oh yeah, f=ma. Ooops, sorry.

edit (it's early in the morning, gimme a chance):

surely you only need to know the weight of the "masses" in the forcemeters in the gtech unit. That way, when you measure the force on them, as you know their mass, you can work out their acceleration... over time you can then work out the speed. So you wouldn't need to know the mass of the vehicle at all?

juansolo · April 9, 2004, 10:12

Right we're getting properly beardy here and it's beyond my very limited knowledge on the subject. These mini-dataloggers, they're not reading anything directly apart from maybe revs from the pulses going through the electrical system. Therefore any readings it takes must be coming from G-forces read from the accelerometers. This of course relates directly the the mass that's being propelled.

I'm wishing I payed more attention in Physics now...

Anyhow, this is only ever going to give you an approximation. The proper test gear they use either has a wheel on it that runs along the road and is calibrated. Or it has some sort of electronic gizmo that does the same.

MRMike · April 9, 2004, 11:23

Quote from: "juansolo"Perfect example, just noticed I have the weight of the Mr2 as 950 (which will have come from the interweb somewhere). Not right of course. Arses, I'll change that now.

Just because you read it on the internet, doesn't make it true s:wink: :wink: s:wink:

Well like I said I have subsequently weighed it on a weigh bridge...does that make the weight true? s:wink: :wink: s:wink:

juansolo · April 9, 2004, 11:31

Close enough s:D

s:D

SteveJ · April 9, 2004, 12:07

Quote from: "phil4"oh yeah, f=ma. Ooops, sorry.

edit (it's early in the morning, gimme a chance):

surely you only need to know the weight of the "masses" in the forcemeters in the gtech unit. That way, when you measure the force on them, as you know their mass, you can work out their acceleration... over time you can then work out the speed. So you wouldn't need to know the mass of the vehicle at all?

You need to know the mass of the vehicle, so that you can work out how much oomph (or BHP for the technically minded s:D

s:D ) it takes to achieve that acceleration.

Anonymous · April 9, 2004, 17:58

I have a copy of one of the first reviews of the Roadster in March 2000 Autocar.
They did their own 0-60 test and weighed it. According to them it came in 101kg over weight at 1076kg (no driver) but still made a 0-60 of 7.5 seconds.
This may not help much but confirms what Juansolo said. s:wink: :wink: s:wink:

MRMike · April 9, 2004, 18:02

Air conditioning is one item which makes a considerable difference..i'm not sure whether that would have been included on the original 975kg Toyota claims..what i mean to say is that you could have a manual car, no air con, and have an SMT, with air con, and HT. There is a considerable difference in weight between the two. As has been said ultimately you won't know unless you weigh the car.

Anonymous · April 9, 2004, 19:26

I am clueless with the gtech, never seen or used one, my question is how does it know when you reach 60mph?

MRMike · April 9, 2004, 19:38

From GTECH..

The G-Tech measures your speed and distance travelled by integrating forward (the forward direction is chosen automatically) acceleration over time. Basically, if you know how fast you are accelerating for a certain time period you'll know how much your speed changed after that time period. So if you start off from zero speed then you'll know what your speed is after every time period. These time periods are very small (a few thousandths of a second) and that's how G-Tech maintains its accuracy. However, if you don't start from zero speed your measurement won't be correct because you won't have a good reference point. Consequently, it's very important to start all of your measurements from an absolute standstill.