63 replies to this topic

[pinchevs]

Hi to everyone,
I'm new to this Forum, but not to Atlas F1.

I've decided to turn here in the hope of receiving an authoritative answer to my question of
what is the rough cost in lap time of each Kg of weight added to a F1 car.

Thanks in advance.

Moshe Pinchevsky

[Vilshöfer]

Each kg of weight costs one tenth every lap!!!!!16

[pinchevs]

Vilshöfer,

Thanks for this information (I was actually previouslly given then information that it was 0.01 sec per kg), but I was wondering how you know this?

Is there some official team site where I can get this info from or perhaps a book?

[karlth]

Originally posted by pinchevs
Vilshöfer,

Thanks for this information (I was actually previouslly given then information that it was 0.01 sec per kg), but I was wondering how you know this?

Is there some official team site where I can get this info from or perhaps a book?

0.01sec per kg sounds much more likely.

How much exactly weight affects lap times is dependent on many factors including the setup, circuit, chassis and even the driver.

[PDA]

I have read that on weight sensitive circuits (Imola was mentioned), 1 kilo would cost 1/20 second. i.e. .5 seconds per ten kilos. the press release from Michelin at the French GP at Magny Cours this year talks about the weight factor in respect of a one or two stop strategy. It proposes a slowing effect almost half of the above (for that circuit) - about .3 seconds per lap for each 10 kilos.

[Ali_G]

Dpends what type of circuit it is.

On a circuit where there are a lot of heavy braking and a lot of acceleration zones then it would be a big difference.

A lap with long corners which can be taken on flat out it wouldn't be as big.

Niall

[desmo]

One can look at the decreasing fuel load carried between pit stops for indications of how total vehicle weight affects lap times. Tire wear makes any concrete conclusions hard to draw as new tires are fitted at each refuelling. I frankly wouldn't hazard a guess based on the data I've seen.

[unrepentant lurker]

Anybody know how many kilos of fuel it takes to go the race distance?

[Ross Stonefeld]

Whats weird is ive asked this question at every level from Formula Ford to CART. At the CART level I got 10lbs/1th of a second. I imagine the lower HP you go the more the weight plays a penalty.

They dont seem to really know though, but for just rough numbers I dont know why they dont just tell me how much time they lose after adding X amount of fuel in a practice session on the same amount of tires. Ill send some emails today to some Touring and GT people and see what their numbres say

[desmo]

I would guess about 165kg based on a number of fairly shaky assumptions about fuel consumption. I am assuming that the specific gravity is similar to pump fuel and that fuel consumption averages around 75l per 100km, some people would estimate considerably higher consumption figures and a few lower.

[Schummy]

165 kg would mean 3.3s penalty at 0.02s/kg rate. It seems too much, so I asume 0.01s/kg rate would be more real (?), in a "normal" circuit.

I'm curious about the weigth lap time penalty as function of HP (or maybe is more straightforward using power/weigth ratio?) as Ross suggested.

If we suppose a simple linear relationship between Time (per lap), HP and Weigth, we'd arrive to:

T = k + b·W - a·HP (more weigth and less HP, worse lap time)

But I think a "percentage" relationship is more adequate (as usual in positive variable), so, playing with logarithms, we would get (k,a,b are not the same as above):

T = k · W^b / HP^a

In this case, varying W in a percentage h% = h·100 (h = rate per one), we will obtain W --> W·(1+h)

k · W^b · (1+h)^b / HP^a = T · (1+h)^b =(approx) T·(1 + b·h) (if h percentage h% is small)

Thus a h% percentage increment in weight makes a b·h% increment in lap time, being "b" the elasticity between weigth and time (what I don't know in empirical data). If it is approx true, it means a certain % variation in weight would produce a fix % variation in lap time, without participation of HP. Anyway a car with less HP has a bigger lap time and that fixed % of lap time increment would make a bigger increment in absolute lap time. Then, the less HP, the most impact in seconds would do one kg. Thus my (blind) guess is Ross conjecture is true

About elasticity "b" above mentioned, for instance, if we put a F1 weigth of about 700Kg and lap times around 70s (for simplicity), the 1kg is 0.14% and 1s is 1.4%. The above mentioned rate of 0.01s/kg means 0.14% variation in weigth makes a 0.014% variation in time. It would mean a elasticity of b = 0.1, what is fairly low... but who knows ;)

Sorry for this mess... I just wanted to share some thoughts

[desmo]

Don't forget that the estimated 165kg of fuel used for c.300km race distance will be divided into discrete fractions of 165/number of refueling stops +1.

[Yelnats]

For purposes of calculation I have assumed that in a two stop race, a refilled car laps about 1.5 seconds a lap slower with it's extra load of 55 kg of fuel. But tires have an influence on post stop lap time and if they weren't changed I would guess the car would be about 2.5 secs a lap slower.

So 2.5/55 = .045 secs slower per KG of weight. This seems reasonable and is in excellent agreement with the published figures that PDA has quoted above.

[imaginesix]

I saw an article in RaceTech or Racecar Engineering that rated the time penalty by weight increase. It was an article about strategy and game theory.

I didn't buy that issue, but I'm sure one of you has to have it (Ben?).

[Schummy]

Taking a two stop race and assuming Yelnats guess about raw lap time differential (0.045s/kg) it would do elasticity b = 0.45 in my calculations. It is close to 1/2 and it would imply lap times are proportional to square root of weigth (in my simple model above). It's to say, a 10% weigth reduction implies approx a 5% reduction in lap time and so on.

In a funny side, if Minardi usually is at about 5% slower than leaders, it would mean that with an (illegal) 10% weight reduction they can fight for poles/wins (if they are reliable!). To reduce 10% of weight is about 65kg, just the body weight of Yoong : Minardi would go faster without Yoong at the wheel!! Alternatively, they can choose racing without fuel (about 65kg also) !! (With due respect to Minardi, they are real racing people )

I think one can say safely that the worst weight repercusion in absolute lap times is in light weight low power cars (FFord, Karts, also 125cc motorbike racing) and the less effect of 1kg is in heavy powerful cars (NASCAR, Group C, Norbert Haug's Mercedes ). The horsepower influence is by "size" of lap times: more HP, less lap time, thus less time lost. Effect of 1 kg in seconds per lap would be medium in heavy low power cars (touring cars) and in light powerful ones (F1, 500cc motorbike FIM).

[Ben]

As requested (Circuit is the A1 ring):

2.6kg = 1 lap of fuel = 0.05 seconds

I think the talk of whole tenths of seconds was talked about more in terms of the new roll hoop regs which place that weight high up, so you get increased weight transfer as well as more mass to accelerate.

Ben

[Ross Stonefeld]

Can we assume that a Formua 3 or Formula 3000 car, is going to get a lot bigger penalty than .05s from 2.6kgs?

[Yelnats]

I am not convinced that less powerfull cars pay a larger penalty in lap times per Kg of extra weight.

Intuitivly, I would think a more powerfull car, ie higher lbs per Hp ratio, would be slowed more on a percentage basis from additional mass because it spends a greater percentage of the lap time accelerating the to higher terminal speeds on the straights. I.E. a F3 car tools along 50% of the straight at top speed so the additonal mass has little effect there but an F1 car accelerates the entire length of the straight a pays a penalty for additonal mass all the way along.

Of corse the F3 lap would take 20% longer so a smaller percentage loss in lap speed would be reflected in a prortionatly longer time penalty per lap and may even out the equation.

[Ross Stonefeld]

Oversimplified, adding weight would be the same as reducing power no? As far as p/w goes. So adding weight I imagine would kill some of its acceleration ability, as well as making braking zones longer and cornering speeds slower. A tenth a corner adds up over a lap.

[Ben]

I would agree with Ross, but I think it does matter what circuit we're talking about and the type of car. On a circuit with long straights you'd spend less time accelerating and probably be limited more by drag at higher speeds hence the available power. A tighter circuit with short straights will put a premium on acceleration both lateral and longitudinal hence mass (and probably low end torque rather than power).

Ben

[Yelnats]

Oversimplified? Duhh..... Sometimes the truth is that way.

Additional weight reduces a vehicle's power to weight ratio, whether it be high or low, thats pretty obvious and would increase braking zones for both types of vehicles.

[Ross Stonefeld]

Yeah but like 5kg added to an 80hp single seater is like adding 50kg to an F1 car isnt it?

[Ross Stonefeld]

er i mean in terms of power/weight. 50kg extra in a 600kg F1 car is gonna kill it a lot more under braking an in corners a lot more than 5kg in a 480kg Formula Junior (i would think)

[pinchevs]

Guys,
Thanks for your responses. It's an interesting debate, which actually took off to a direction which is closer to the reason I've asked about this in the first place.

I'm a very heavy guy (in non PC terms that would mean fat) and have been constantly moaning about it whenever Karting. However, Most of my friends think I'm just finding excuses for being slower than them. I didn't want to ask a lame question about Karting so I asked about F1.

I remember that I read somewhere in Autosport that 1 kg at Hunguroring would equate up to 0.5 sec per lap. The reason is that it would hurt cornering as well as accelaration and braking.

Since a Kart track is more like the Hunguroring than Monza, I thought that I could learn from that, but I wanted to hear other people first.

My personal question would then be, how much time am I loosing in a 80 kg Kart with about 8hp when I'm about 30 kg heavier than my friends?

[kober]

And how significant is affect of weight increase on cornering speeds?

[Schummy]

My answer, using the above mentioned by Ben F1 loss per kg of 0.02s/kg (b = 0.2) and the simple potencial model I wrote, would be (very coarsely!

Your friends total kart weigth = 80 + W ; W = weigth of your friends
Your total kart weight = 80 + W + 30
%weight increase: 30 / (80 + W)
approx %laptime increase: 0.2 · 30 / (80 + W) = 6 / (80 + W)

:yawn:

For example: if your friends weight is 60kg, your kart's running weight is 21% heavier than their's, and your lap time would be around 4% slower. If we use other values we have used here as F1 data, then effect would much greater (8%-10%). I don't know wath sort of lap time you do, but with a 30s lap, you lose 1.2s, with 60s lap, you lose 2.4s. And it is with the lower estimation...

Obviously, all this is very coarse and is a simple guess, but it could help. I suppose other people here can say more about it.

My advice: tell one of your friends to take aboard 15 or 30kg and do some timed laps. That is empirical data!

[Ross Stonefeld]

Formula Super A kart 145kgs/319lbs including driver.


40second-ish laps. 10kg is about 1/2 second

Anywhere from 30-45hp, I cant get a reliable number

[rdrcr]

When we talk about road racing, we know that they don't just accelerate, road race cars have to slow down and negotiate curves and corners as well. These operating parameters are all reliant on the manipulation of energy. It takes energy to accelerate the vehicle, the energy then must be dissipated to slow down or decelerate. Thus, a heavier vehicle has more energy to get rid of through the braking system so therefore the efficiency of the brake system or it's ability to change the potential energy (weight X velocity) into heat and get rid of it is directly influenced by the vehicle weight. In order to change the cars direction of travel we turn the wheels and the front tires work against the road surface and supply a force to push against the vehicles tendency to go straight. The heavier the vehicle, the energy the tires consume to change the cars direction. And if the tires can't develop enough grip to change the vehicles direction the vehicle has to go slower to a point where the tires can change the vehicle's direction. If you force the tire beyond it's capability it will overheat the compound on the surface of the tire goes into a temperature range that it starts to breakdown or change properties, it then cannot develop the same amount of grip this leads again to a slower lap time... If you are utilizing aerodynamic devices to help the vehicle negotiate corners, heavier vehicles need more down force, more down force is created by more wing which requires more energy to push through the air, more energy means more horse power etc.

Up until now we have been talking about overall vehicle weight but it gets more complicated because these same principals are applicable to any of the operating systems of the vehicle.

Continuing with the energy idea, consider an engine with lighter components. An engine uses a significant amount of its power to accelerate its own internal components so it stands to reason that if any of the engines moving parts are lighter and require less energy to move then there is more power available for the vehicle to accelerate. If the wheels stay in contact with the road surface the vehicle has more directional stability and ability to maneuver.

So if this "unsprung weight" is less and can react to the road surface more efficiently or more quickly to the changes in the road surface and therefore stay in more constant contact with the surface the direct result is the vehicle can be more capably maneuvered as a result of the tire staying on the road to have more net grip the cornering capabilities are higher.

Remembering that everything is a system, and looking at the overall picture, if the lighter wheels stay on the road better, developing more grip then the cornering speeds can be higher. If the car comes off the corners faster due to the higher cornering speeds it has a head start on the acceleration process that it will go through on the straight away additionally if the engine has more available horsepower to the driving wheels due to its lighter internal components then it can really accelerate the car down the straight-away, because the whole vehicle is lighter and has less energy stored that must be dissipated through the brakes system it is easier to slow down or can brake later for the next corner. But due to the higher cornering capabilities it doesn't have to slow down quite so much so the cornering speeds can be higher and so on and so on. These total energy savings add up to faster lap times on a race course.

Leading to another weight related topic, is the position of the weight or weight reduction. The position of the center of gravity or the virtual position of the weight has an effect on the whole picture as well. The weight of each of the components especially large dense parts and their relative position to the center of gravity of the vehicle has a lever arm effect that can play a big part in the way that a vehicle behaves. Cars that have the engine in the rear behind the rear axle VS mid-engine cars VS front- engine platforms all handle or feel totally different not necessarily better or worse just different... For racing purposes the thinking is still that you want the high density weight as close to the middle of the vehicle as possible to minimize the pendulum effect of the weight on the end of a lever arm.

Taking in all of this one can understand why the sanctioning bodies specify minimum weights. Weight is the easiest rule to specify, measure, and police.

To apply this to your Karting question. I know for a fact that weight is one of the biggest enemies in Karting. I weigh 188 lbs. not too bad for 6' 3" but I give up 20 to 30 lbs in a weight disadvantage to some who's karts weigh within 5 lbs. of mine but they weigh those precious 20+ lbs less. I took great pains to minimize weight in my Karts but I'm still handicapped, in the acceleration dept. especially. In larger cars, it seems that the weight still plays a significant role in overall performance but for some reason there isn't as much detriment in performance. In CSR the minimum weight is 1,300 lbs with driver. I'm a lot closer in making that one. It seems that everyone is about 100 lbs over the minimum. DSR is at 1,100 but they are proposing to improve the field participation for '02 to just add the class without the weight to make the minimum for CSR. Since both classes are within 1/10's of each other with their respective weight minimums it is thought that it would provide some interesting battles. Most are for the following:

To Simplify engine rules:
In CSR
1. Any 4 stroke piston engine to 1615cc, with 42mm venturies or restrictors, at 1300 lbs
2. Any 4 stroke piston engine to 1310cc, unrestricted air, at 1300lbs
3. Leave VW 2 valve 1835cc option intact, 37mm restrictor, at 1300lbs
4a. Leave Mazda 12A option intact, 34mm venturies, GT-3 prep, at 1300lbs
4b. Maxda 12A, non peripheral or bridgeport, unrestricted induction, at 1300 lbs
5. Any two valve 4 stroke piston engine to 1615cc, unrestricted air, at 1200 lbs
6. Allow any legal DSR to compete in CSR under DSR rules (without weight penalty)
7. For 2 strokes, leave rules as written

Logic: In CSR, mostly everyone runs either: VW 1835, Toyota Atlantic, BDA/BDD, 12A, or motorcycle powerplant.

The argument is... Why not keep the rules simple - all of these listed powerplants fall clearly within the simpler rules.

Ross, Formula A must be a Euro spec class. Are they 125's or 250's? gearbox, clutch or direct drive?

It's been interesting reading all of your posts. As weight reduction (everywhere) is often the most sought after fix in racing. The most common recommendation by the mechanics is put the driver on a diet.

[imaginesix]

Originally posted by pinchevs
My personal question would then be, how much time am I loosing in a 80 kg Kart with about 8hp when I'm about 30 kg heavier than my friends?

Just give any of your friends 30lbs worth of balast to race with, and compare their lap times before and after.

[birdie]

Anywhere from 30-45hp, I cant get a reliable number

Hi Ross, continuing our IM conversation, the lowest it could be is 35hp, I have a strong feeling it's something like 40. Based on the fact that I know Rotax Max and ICA figures (28hp) and I know roughly how they compare.

Thing is 1) Europeans just don't see the relevance of hp in karting as much as americans so there's no figures. 2)They don't go around telling people the revs either. God knows why, you'd think it would be good advertising

Ross, Formula A must be a Euro spec class. Are they 125's or 250's? gearbox, clutch or direct drive?

I ain't Ross but I know more than him. He's learning though ;)

Formula A isn't a spec class, it's an open international class. 100cc, direct drive no gearbox. Any rotary valve 2 stroke homologated by the FIA for the class. Front brakes only.

Formula Super A is similar, same engines, bigger slide carb.

Both are 145kgs including the driver, the karts tend to weigh about 75kgs on their own.

[rdrcr]

Birdie,

Perhaps my use of the word "spec" was misleading. Is it a European class? I haven't heard of it here in the US under the IKF rules anyway... and a quick search of WKA doesn't show it either.

Just curious.

Thanks for the info on what it is though. I'll bet it's a pretty competitive deal.

[birdie]

It's administered by the FIA, so basically Europe, Oceania, Asia and South America all run Formula A or a very close variation. FSA is World Championship level only as of 2001. Both used to be run as part of the North American Kart Championships but that seems to have fallen by the wayside in recent years, apparently because Randy Kugler of WKA doesn't feel it's his core business and has done no promotion.

[Ross Stonefeld]

We used to have Formula A back in like 98 didnt we?

[rdrcr]

Maybe on the pure sprint tour like Adams and Amago but not in Region 7 road race... not that I can remember anyway. I don't follow the sprinter action too closely though. You young guys are out for too much blood. I've seen some of the races at Adams, the guy ahead has a name - dead meat.

The 125 Pro class that runs Region 7 is the same way... the top 8 guys you could throw a car cover over at any given moment during a race... with draft bumping and stuff like that going on... Those guys haven't been on their heads enough to know the difference.

I just remembered... you're in WI somewhere right? That's WKA. We haven't run under them since the big rift with Bill Huth at Willow back in 90 or 91.

[Ross Stonefeld]

Toyota F1 feller Ryan Briscoe was North American Formula A champ recently so it existed at some point. All the Yanks over in Europe atm came out of that field. I think whats happened is Skusa has really pushed its national format and especially with the CART linkup they are the more organised and easily identifiable series.

[birdie]

Toyota F1 feller Ryan Briscoe was North American Formula A champ recently so it existed at some point. All the Yanks over in Europe atm came out of that field. I think whats happened is Skusa has really pushed its national format and especially with the CART linkup they are the more organised and easily identifiable series.

And even they've started adding FIA classes...

Rumour has it that new org. NAKA (which seems to have taken over SKUSA's CART links) will be running a more European-style programme as opposed to MX based shifters

rdrcr - do Americans roadrace 100s then? If you tried it with these things I can see them blowing up like grenades

[rdrcr]

It does appear that there are changes a foot with SKUSA...

birdie, the 100cc divisions were the mainstay of Karting until the Gearbox classes gained popularity. I may note, out of a certain amount of pride, that I and some of my close pals and some racing acquaintances helped change the face of karting here in the road race divisions in Region 7 back in '93. We were running 100cc open at the time and under the rules you could run a max 105cc with a gearbox on gas & oil. We took 80cc Kawi motors and put 105 kits on them and kicked everyone's ass. They blew up quite a bit, but it was the start of turning the tide. Once Hollis Brown moved on as Race Director that really opened the door to the gearbox classes. So often the problem was the conflict of interest when you have people in the organization of events building motors etc. Happens a lot...

There still are a number of 100cc, 150cc rotary and reed valve classes but they are not the most popular these days. They hold together pretty well. I don't know what the preferred engine is now-a-days but when we ran them the TKM was the hot unit. They weren't cheap either and you always needed two of 'em in case you blew one up. We twisted those engines over 13 grand (there were reports of much higher RPM's) and nothing lasts for a long time under those conditions. Recently, over the past 5 years, the 125 sit-up classes are at the forefront for training and exposure to other / higher forms of racing. The IC 250 single class is also very popular. We have about 20 entrants in that class at our events. The Anderson chassis & Rotax 258 engine are the choice pieces. There is some really beautiful equipment running these days. It's very competitive and everyone keeps their wits about them as it's a slightly older crowd that participates.

[pinchevs]

Guys,
You are all talking of Karts / racing cars, which are way more powerful than the karts I race on.

I'm trying to think of what would be 30 kg, but still small enough so that my friend would be able to easily carry it with him on the kart. perhaps a gold bullion ;)

[Pioneer]

Lead is considerably cheaper than gold and nearly as dense.

[Yelnats]

Originally posted by Ross Stonefeld
Yeah but like 5kg added to an 80hp single seater is like adding 50kg to an F1 car isnt it?

An 80 hp car pulls its 400 kg around a given cirquit 25 % slower than a 800 hp F1 car, not 10 times as slowly which is what your theory implies. Why is does the first 400 kg of weight result in a much smaller penalty than the next few kg? The speed penalty of weight is more closely related to the overall weight of the car, not the horsepower.

[birdie]

I'm trying to think of what would be 30 kg, but still small enough so that my friend would be able to easily carry it with him on the kart. perhaps a gold bullion

if you find out, let me know ok, 30kgs is the ballast I need to race a Rotax Max kart

[rdrcr]

Originally posted by pinchevs
Guys,
You are all talking of Karts / racing cars, which are way more powerful than the karts I race on.

I'm trying to think of what would be 30 kg, but still small enough so that my friend would be able to easily carry it with him on the kart. perhaps a gold bullion ;)

It doesn't matter how "powerful" the vehicle is really.

An 80 hp car pulls its 400 kg around a given cirquit 25 % slower than a 800 hp F1 car, not 10 times as slowly which is what your theory implies. Why is does the first 400 kg of weight result in a much smaller penalty than the next few kg? The speed penalty of weight is more closely related to the overall weight of the car, not the horsepower.

This is what I was trying to say in my long winded descriptions...

Thanks -

Lead ballast is commonly used. Secure it to the frame around the seat.

Like I commented before, the mechanics all try to take weight off the driver.... it might do some good in all aspects.

[Ross Stonefeld]

On strictly power to weight ratio, is it a direct ratio? Is 50kg in an 80hp car going to affect its acceleration the same as 500kg in an 800hp car? (assuming identical chassis and conditions).


Somehow I graduated from High School with no physics credit

[birdie]

Me too, can't concentrate unless it's strongly related to something I'm interested in. Feel I missed out though so I've started lurking in this forum.

rdrcr (thanks for the ikf scene insight btw) we have major problems trying to find places to bolt on 30kgs (66lbs for the yanks) of lead...

[Pioneer]

You could strap a SCUBA diver's weight belt around the driver. I dunno if that is legal though. Probably not.

[birdie]

I feel really stupid but what's the kW/HP conversion?

[Wyatt_Burp]

I horse-power (PS) = 746 watts.

[pinchevs]

"SCUBA diver's weight belt"

That's a great idea! but does it weigh 30kg?

[Yelnats]

Jimmy Hoffa's did!

[Pioneer]

Originally posted by pinchevs
"SCUBA diver's weight belt"

That's a great idea! but does it weigh 30kg?

The belts in and of themselves weigh very little, but they have pockets that you slip lead slugs into to control bouyancy.

Simply add 30kg worth.