power vs fastness? This should start some comments!
Discussion
I noticed the recent thread on drag racing.... Seemed interesting in that some of the "high powered" cars are getting 12 secs qtr miles. My baby ZZ4 350bhp carb spyder does an easy 12.4 secs - and i need to use all five gears because I only have 5,500 revs max to play with. So it seems a bit strange that the large engine cars are not doing a lot faster times? I know the recent factory Ultima did 9.99999 - which is in a whole new league, but he was only using 2 gears (I think) so thats another second saved (one shift vs 4 - 3 gear shifts in one second would be fair?) which makes it (sort of)an 11 sec car vs 12.4 secs ....so a 1.4 sec faster car for an additional 500 bhp?? cant be right?
My spyder is lighter than a GTR though... (no glass or roof at all) but unless I am reading the figures wrong......... comments?
My spyder is lighter than a GTR though... (no glass or roof at all) but unless I am reading the figures wrong......... comments?
I found it was much better with the right conditions.... EG: Shakespear raceway (proper sticky track) and during a hot july day with hot tyres, try as i might, couldnt get the wheels to spin - even in 1st! just a slight screech and away. Must be all down to slow take ups (granny starts I think they are called)
Interesting that the "slow" granny starts give the best times, but look really boring vs all that tyre smoke and spins!
Interesting that the "slow" granny starts give the best times, but look really boring vs all that tyre smoke and spins!
I did an 11.88 at RAF Honnington, can't remember the exit speed, but around 120ish
I had my pirelli street tyres on the car, and the surface was fresh, but grippy in a gravelly kind of way.
My engine's got 510, but the torque peak is perhaps a bit higher than average, at 5100 rpm, so it really pulls well once you get things rolling.
Also, I have a G50/21 6 speed, and was launching in 2nd, at about 2500-3000 rpm.
I had my pirelli street tyres on the car, and the surface was fresh, but grippy in a gravelly kind of way.
My engine's got 510, but the torque peak is perhaps a bit higher than average, at 5100 rpm, so it really pulls well once you get things rolling.
Also, I have a G50/21 6 speed, and was launching in 2nd, at about 2500-3000 rpm.
Doesn't the terminal give a pretty good idea of the actual power the car has? It should be fairly consistent, so if Mark terminals at 130, if he fluffs the start and does a 14sec run, or hooks up and does it in 11, the actual terminal speed won't vary much?
Shithotfast, what was your terminal, about 120?
Shithotfast, what was your terminal, about 120?
scuff said:
But it's not all about BHP. Torque has a large part to play as well. IMO
S
S
Torque where? At the Crank or wheel? Remember your gearbox is a torque multiplier,
I'm sure an F1 car would launch pretty well...
wikipedia said:
For example, a 3 litre F1 engine which produces 650 kw (880PS) at 18000 rpm, outputs 345 N.m. This is only slightly better than the 3 litre engine in the BMW Z4 Coupé production car which develops 315 N.m, but this is only achieved through superior aspiration.
Paul, your assumtions for time lost through gear changes are all wrong. You say you need to get as high as 5th before the 1/4 mile mark as you run out of revs. That is 5 gear changes. I'm pretty sure the factory car would be into probably 4th by the 1/4 going by the terminal speed. 3rd maybe. You do not loose huge amounts of time with a gear change as the car is still moving forward. So, although you loose say 2/10ths of power fully applied, you are still moving.
If the factory car requires 3rd before the end of the run that is 2x 2/10ths. 2/5 sec where power is not being applied. Not a huge amount in the overall scale.
Your car produces 12-13 second runs because it has a great combination of power charicteristics/gearing/traction etc. In your car this combo works. Add 200bhp and move the power 2000 rpm up the scale and you may get slower times.
Have fun
Paul.B
Edited for speeling!
If the factory car requires 3rd before the end of the run that is 2x 2/10ths. 2/5 sec where power is not being applied. Not a huge amount in the overall scale.
Your car produces 12-13 second runs because it has a great combination of power charicteristics/gearing/traction etc. In your car this combo works. Add 200bhp and move the power 2000 rpm up the scale and you may get slower times.
Have fun
Paul.B
Edited for speeling!
Edited by Paul.B on Monday 19th March 18:04
agree with Paul B on this (the shorter one!) as its more about package than power..... if you modify the power you have to also modify the rest of the package (assuming your package was optimum to start with).
From the telemetry on my car each extra gearchange cost approx 0.4's.... IMO this is one of the reasons why the Veyron produces such shocking acceleration times.
From the telemetry on my car each extra gearchange cost approx 0.4's.... IMO this is one of the reasons why the Veyron produces such shocking acceleration times.
deadscoob said:
Doesn't the terminal give a pretty good idea of the actual power the car has? It should be fairly consistent, so if Mark terminals at 130, if he fluffs the start and does a 14sec run, or hooks up and does it in 11, the actual terminal speed won't vary much?
Shithotfast, what was your terminal, about 120?
Shithotfast, what was your terminal, about 120?
yes, and did notice sometimes the terminal speed could be slightly higher, yet overall time higher? I think 125mph was the highest with a 12.8 but only 120 something (lost the slip) with 12.4 which was my highest......
andygtt said:
agree with Paul B on this (the shorter one!) as its more about package than power..... if you modify the power you have to also modify the rest of the package (assuming your package was optimum to start with).
From the telemetry on my car each extra gearchange cost approx 0.4's.... IMO this is one of the reasons why the Veyron produces such shocking acceleration times.
From the telemetry on my car each extra gearchange cost approx 0.4's.... IMO this is one of the reasons why the Veyron produces such shocking acceleration times.
No it doesn't COST 0.4 seconds either. You are still moving towards the goal. You loose 0.4 seconds where you are in full acceleration but you gain time every time your engine is in it's optimum "power band".
andygtt said:
If the gearchange had been instant it would have been 0.4s faster as the car was not accelerating for 0.4's.... if I had had the Veyrons box I could have got down the quarter in 10.6's.
I think it's more complicated than that. If it takes 0.4 seconds to change gear you've 'lost' 0.4 seconds worth of acceleration. Supposing you're averaging 10 mph per second, that's 4 mph worth of acceleration lost. You then have to work out how much time that extra 4 mph would have saved you over the remainder of the run i.e. a gear change at the start of the run makes a hell of a lot more difference than one just before you cross the line. On the other side of the equation, changing gear more often will mean you're closer to peak power more of the time which works to your advantage.
andygtt said:
If the gearchange had been instant it would have been 0.4s faster as the car was not accelerating for 0.4's.... if I had had the Veyrons box I could have got down the quarter in 10.6's.
No, your car doesn't stand 100% still for those 0.4 seconds that the shift takes. Maybe you loose 0.1 seconds or someting like that. It's very difficult to calculate. Most cars will have a better 1/4 mile ET with a closer range gear box (more shifts).
OK good point I can see that you are specifically talking about quarter mile times.... wereas I was talking about acceleration to a set speed which just isn't the same measure and thus wouldn't translate to a saving on the quarter mile time of the same amount.
Hard to judge how much time this would loose on the quarter time but I agree definatelly not as much as I thought.... I'd venture to guess that the speed of the 1st to 2nd gearchange would probably have the most effect on the time.
Hard to judge how much time this would loose on the quarter time but I agree definatelly not as much as I thought.... I'd venture to guess that the speed of the 1st to 2nd gearchange would probably have the most effect on the time.
Right, you lot, can people get me diff and gearbox ratios for Ultimas please 
I'll get them fed into Cartest 2000 and create an Ultima model (or few)
www.cartestsoftware.com/cartest2000/index.html (have a nosey, very detailed)
and get some numbers out for Ultimas (obviously having to specify power etc first), as its currently missing from the database.
It is interesting to see the affect of gearchange times on 1/4 mile, its true the Veyron uses its gearbox to offset its weight, as does the F430 Ferrari reasonably well too.
The software has a optimum launch, which calculates the best get away, for a heavy 4*4 Lambo its very high revs, but for a V8 TVR its less than 2k !
RichardD said:
Right, you lot, can people get me diff and gearbox ratios for Ultimas please I'll get them fed into Cartest 2000 and create an Ultima model (or few)
www.cartestsoftware.com/cartest2000/index.html (have a nosey, very detailed)
and get some numbers out for Ultimas (obviously having to specify power etc first), as its currently missing from the database.
It is interesting to see the affect of gearchange times on 1/4 mile, its true the Veyron uses its gearbox to offset its weight, as does the F430 Ferrari reasonably well too.
The software has a optimum launch, which calculates the best get away, for a heavy 4*4 Lambo its very high revs, but for a V8 TVR its less than 2k !
I have most of the gearbox ratios for G50 & some G64 but they are at home so will post them this evening.
Steve
steve_d said:
I have most of the gearbox ratios for G50 & some G64 but they are at home so will post them this evening.
Steve
Good stuff, Would be best to have a few Ultimas in I think, 400, 500, 600 and 700 bhp versions, or a range of real PH'ers cars
. Out of interest anyone know the drag coefficient (not matter too much for 1/4 mile, but would if want a top speed figure) ?
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