27 replies to this topic

[slipstream]

Watching the in the camera action from KR McLaren in Australia I noticed how quickly the McLaren -Mercedes Accelerated through the gears. It went from 2nd to 6th gear in about 6 seconds. It seems that a Modern F1 car is much quicker through the Gears than a Champ car or even a F1 Car from 5 years ago . My question is what Makes the McLaren or any F1 Car so quick through the Gears ? Would it be its short gear ratio`s, Auto Gearbox, Power to weight ratio or a combo of all those factors.

[lateralforce]

I'm not the best person to answer you but I think you nailed it down when you mentioned all those factors. But I bet it is a hell lot of fun shiftin thru the gears picking up speed before you knew it a blink equals a soccer field length....

[Jezztor]

Pretty much a combination of the above...the quicker you can change gears, (or should I say the car changes gears), the less RPM you lose, the more torque you have, the more power you have and less loss of it...

A very reliable source has told me the new Ferrari F2002 can change gears in the middle of a sharp bend, without upsetting the car at all....

Jezz

[MRC]

The quicker you change the gears, the less time you spend not accelerating. Time spent not accelerating is considered undesirable. The RPMs you drop is dependent on the difference in the ratios, and not the time of the shift.

[mcerqueira]

I guess that there's always a limit defined by the gear ratios: no matter how fast you change gears you're never going to be faster than the difference in gear ratios. However you definitely can loose more RPMs if you change gears slower (the car looses speed...)

[Jezztor]

Originally posted by MRC
The RPMs you drop is dependent on the difference in the ratios, and not the time of the shift.

Incorrect. Drive your car, put it in 2nd. Change from 2nd to 3rd in 1s, and note the rev drop. Then go back, 2nd. Change to 3rd in 4s and you tell me if your revs don't drop - and if they don't, mail me, cos you got an amazing car.

Jezz

[mcerqueira]

I was wondering, do you think that with today's gearing change times (measured in milliseconds I guess) the focus is still on shaving that even further? Since the ideal would be instantaneous shifting I guess it is...

[MRC]

Jezztor, I believe you said, "the quicker you can change gears, (or should I say the car changes gears), the less RPM you lose".

Ok. Now I might have taken you the wrong way, but let's break down this statement.

"The quicker you change" - so the quickest is time=0. Correct? Yes, obviously. Can anyone or anything change gears in zero time? No. Is that what they are trying to approach? Yes.

So, with a zero time gear change, the revs still drop drastically changing up a gear.

Now, let's look at a 5 second gear change. You are in gear X. Now you begin shifting. For 5 seconds you are decelerating, and thus losing speed (unless your going down a hill or something). The drop in speed (AND the gear ratio change) that happened over those 5 seconds, is what will give you the drops in revs.

So I guess I will restate - the rev drop will be due to the loss in speed and the change in gear ratio. Time is not an issue, except for it's effect on how long you will be decelerating or accelerating (although most likely the former). So, with a very small gear shift time (ie F1) the biggest part of the rev drop is due to the gear ratio change.

Yes, I understand that a fast shift is required, and means faster lap time. This is due to less time spent decelerating.

If I misconstrued your statement, then I apologize.

[Ben]

MRC is correct.

When you shift a gear you should be at or around the engines peak torque. You then shift to a hugher gear which takes you back to the bottom of the power band to allow the car to accelerate up to a higher speed with the higher gear.

Check out Hewland.com where you can create ratio charts and adjust the rpm drops to allow you to maximise the gearing dependent on the power band and anticipated speed range. Also creating tractive effort curves using the methods shown in Gillespie or Genta is very instructive.

Ben

[schuy]

Originally posted by mcerqueira
I was wondering, do you think that with today's gearing change times (measured in milliseconds I guess) the focus is still on shaving that even further? Since the ideal would be instantaneous shifting I guess it is...

Well no, because there is a rule which states the minimal time for changing a gear.

Ciao,

Liran Biderman.

[Jezztor]

MRC - you are absolutely correct. I am aware of what you highlighted, I guess once again, wrong diction. What I meant to say (you took what I had said incorrectly because I had worded it badly) was you do 'lose' revs through changing, being relevant to time(tot) only because of deceleration. A sustained deceleration for a prolonged period of time will decrease 'revs'. I do agree however that gear ratios force a 'loss' of revs, I wasn't protesting that The time taken to shift between gears is proportional to deceleration (on a flat plane, not downhill and therefore not uphill either). ie. the longer you take to disengage gear X, and put it into gear X+1, the more your car will decelerate.

"Incorrect" was specified towards "...and not the time of the shift.", because, as you rightly said, the time isn't a factor of rev 'loss'; the deceleration is (thats where my crap wording kicked in), but time is a factor in relation to deceleration which is responsible for rev loss.

*PHEW* Hope that makes some sense.

Jezz

[MRC]

No problem. All ist klar.

[schuy]

Originally posted by MRC
No problem. All ist klar.

Wunderbar.

[lateralforce]

Originally posted by schuy


Wunderbar.

Also gut. anyway regarding the minimum amount of time to change gears, I guess CVT won't see the light in F1.....

[slipstream]

Thanks for the information , The Technical forum is my favorite Last night I watched some of my CART video tapes from last season I noticed how much slower it was through the gears than the Current F1 Cars. I know that F1 can shift very quick but it also must be the F1 power /weight ratio . The reason I asked was because a friend said that the Turbo Engine of the Champ cars would be quicker through the gears but he is wrong

[Pioneer]

The shift manually in CART. Has nothing much to do with the engine... just a less advanced gearbox.

[Ben]

I would have thought a champ car V8 (turbo of course) with a 15k effective rev limit would have a broader torque curve and hence be tolerant of wider spacings between gears.

Indeed if they do (as claimed) produce 900hp they do have more torque so that would explain it.

Ben

[Aubwi]

I'm sure the most important factor is simply the top speed that is reached on the circuit. At Monza for example, the top speed is much higher than at Monaco, so the gears are further apart and it takes much longer to get to top gear.

Unelss we're just talking about how long the gearshift itself takes, but I didn't think that was the original question.

[lateralforce]

Question guys: If F1 uses CVT then theoretically they can shift in 0 time right? (well....if there is such thing as 'shifting' in CVT)

[Christiaan]

One of the 1st ten topics on this BB discussed this topic, back in the days when the internet was in black and white.

I remember that at the time Ferrari had a legal traction control system running in their car that only switched on for about 200milliseconds, which was the time that the engine and wheels were disconnected. Something about FIA's rules being interpreted as to allow TC if the wheels are not being driven.

I asked on that thread about revving your enine as high as possible during a gear change to reduce the lost revs. If you had a high performance clutch and a sizeable flywheel I think it would make a difference... or would it?

[slipstream]

A Light Weight Clutch and Flywheel makes a big difference in Acceleration through the gears. A light Clutch and Flywheel is much better than a heavy one. A found this statement in one my F1 books . Steve Bryan AP`s chief Engineer says " Every gram of mass you can reduce in terms of rotating mass saves energy each time the driver accelerates through the grears. This means the Engine can reach its max rpms faster , and the car accelerates more quickly . "

[Pioneer]

Originally posted by schuy

Well no, because there is a rule which states the minimal time for changing a gear.

Ciao,

Liran Biderman.

No there isn't.

[schuy]

Originally posted by Pioneer


No there isn't.

Sorry, my bad.
I seemed to remember, there was a suspicion Ferrari employed a very clever TC since it's gearbox was so fast, and they used the rest of the time to get to the minimal time required to change gears to regain lost traction.
I just went over the regulations again, nothing like this is closely stated there.

Liran Biderman.

[schuy]

I just read a group test by Autocar, from April 3 2002.
The test included the new Lamborghini Murcielago, the Pagani Zonda C12 and the B.Engineering Edonis.
The Lambo has 571BHP over 1819kg.
The Pagani has 555BHP over 1250kg.
The Edonis has 708BHP over 1400kg.
But, look at this 0-60mph information.
So, from this data, you would the Edonis would kick ass, and the Pagani will probably be better than the Lamborghini Murcielago.
But, both the Lambo and the Edonis do 3.6s, whilst the Pagani does 3.7.
I think this is very strange.
The Edonis is geared for high-speeds(226mph), but still, it is supposed to kick ass, because a long first ratio would mean it doesn't have to change gears until 60.
Perhaps the Edonis is having trouble, because it has to wait until it's quad-cam turbos kick in, as max torque is at 3,750 rpm.
The Edonis has more BHP than the McLaren.
Maybe just clever mechanics by the Lambo crew?
Thism is their first 6-speeder.
But, what is really strange, is how the Pagani didn't clock a better time.
Maybe bad traction then?

Liran Biderman.

[Ursus]

When you've got that kind of power, 0-100kph times is greatly affected by how well you can put down the power. The lambo may well have 4 wheel drive (didn't later model diablos have this?) and so can use it's power better and keep up despite it's unholy weight.

[Janzen]

I would think that F1 cars are not optimized for accel from zero. Since this only happens at the start. Without out checking i think in Brazil they take the slowest corner in 80km/h or something in first gear. The most impressive in F1 is probobly the accel from about 100-250 and.

[schuy]

Originally posted by Ursus
When you've got that kind of power, 0-100kph times is greatly affected by how well you can put down the power. The lambo may well have 4 wheel drive (didn't later model diablos have this?) and so can use it's power better and keep up despite it's unholy weight.

Yes, that's very true.
I can't believe I forgot that.

[benrapp]

Originally posted by schuy
I just read a group test by Autocar, from April 3 2002.
The test included the new Lamborghini Murcielago, the Pagani Zonda C12 and the B.Engineering Edonis.
The Lambo has 571BHP over 1819kg.
The Pagani has 555BHP over 1250kg.
The Edonis has 708BHP over 1400kg.
But, look at this 0-60mph information.
So, from this data, you would the Edonis would kick ass, and the Pagani will probably be better than the Lamborghini Murcielago.
But, both the Lambo and the Edonis do 3.6s, whilst the Pagani does 3.7.

Liran Biderman.

0-60 is about balancing traction and torque curve against inertia: spin the wheels and you go nowhere; don't spin the wheels, the engine bogs (because it's geared to do 1000rpm at 10mph or whatever) and you go slowly. The Lambo is naturally aspirated and large capacity (i.e. good low-end torque) and has 4wd but is heavy. The Zonda is rwd, but big-cube nat-asp and light. The Edonis has the worst of all possible worlds: small(-ish) capacity turbo, rwd only and not the lightest. Remember also that the Edonis as tested as down on power, producing only about 680bhp.

It would be better to measure 30 to 90 if you want a 60mph increment. This still avoids the zone where drag becomes the overriding issue.