weight issue

weight issue

Postby kkapelke4 » June 2nd, 2011, 5:22 pm

As of right now I am 58lbs over the minimum weight.

How much do you think that could effect lap times?

I know it will effect, but by how much??

By the way I run at Mosport which is typically a 1:45-1:50 lap time!

I weigh 193lbs. My car is a tank!! I have a Blackhole which is an evolution of the Lynx B but it was built for formula first and we converted it to a vee.

See I have been karting for 20 years and being that much over weight will loose you about 8-9 tenths on a 40 second lap!!!

Thanks
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Re: weight issue

Postby Rolling Stone » June 2nd, 2011, 6:48 pm

193 lbs and a Blackhole around Mosport....Hmmmmmmmmmm...about 2 days for 1 lap :mrgreen: :mrgreen: ..Oh No!!thats me isnt it :P
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Re: weight issue

Postby CitationFV21 » June 2nd, 2011, 9:22 pm

Almost 60 lbs is a lot, but not as bad as you think.

If a top driver added 60 lbs to his car and then ran a fast lap, I would predict less than .75 of a second difference. So if you are not within a second of the fastest drivers - keep working on the weight, but don't neglect driving, engine, tires, alignment, etc.

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Re: weight issue

Postby hojo » July 5th, 2011, 10:44 am

its very possible to generate a competitive latp time with a significantly heavier car. how repeatable that lap time is very suspect and difficult. you'd have to be perfect in your driving and have perfect setup for conditions. when weight limit was 1050 there were plenty of top guys runnning 1070+

the big uphill straight at mosport would be the biggest killer to me. pushing 5.5% more mass uphill from low end 4th is definitely killing ya a bit i'd say and also the run from T10 to T2 a little.

unfortunately its pretty difficult to shed weight with these cars i'm sure you've looked or tried already to see what you can do.
kev if i drive your car at shannonville it will be right around 1075. that will be a good indicator perhaps. i'm a flyweight...if i go 5% faster its gotta be the weight!
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Re: weight issue

Postby BLS » July 5th, 2011, 11:06 am

Figuring that most cars are 10 pounds over for insurance against going under, your real penalty is probably about 50 pounds. Time on the track will depend upon variables related to accel and decel. 5% is 5% and that is the penalty for acceleration and deceleration (braking). You will accelerate 5% slower than the same car with 50 pounds less weight. It's the same as having about 3 hp less.

And it makes a big difference. Before the rule was changed from minimum car weight to car and driver (1976?) I routinely gave up anywhere from 7-10% to most cars. That simple rule change made a big difference.
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Re: weight issue

Postby tiagosantos » July 5th, 2011, 12:26 pm

There was a thread here last year where some clever people (Jim at SR and jpetillo, I believe..) came up with the physics behind weight differences and how that relates to a difference in "power". If I remember right, 50lbs turned out to be the equivalent of 1.2 or 1.4hp.. Then of course cornering and braking might also be affected. I guess it's significant, but probably the last thing I would worry about in making up lap time differences..

I was going through my data logs for a recent short practice session.. I did 6 laps, and 4 of them were within a tenth at 1:21.xxx, one was way off (made a 'slight' mistake hehe..) and the other was a 1:20.7.. Looking through the data, I picked up almost 4 tenths in one corner by braking 15 feet later (or to put it in perspective, less than 2 tenths of a second later..) but turning in at the same point, thus carrying more speed through the corner. I'm learning that our cars are so god damn slow that the smallest mistakes cost us a lot of time.. Same with any mechanical issues, loss of power, handling issues, etc.

My logger indicated the fastest possible lap using all the best sectors from that session was a 1:19.5, so I was all giddy looking through the traces to figure out where I could improve. Turned out that the differences between the same corners on different laps where I had been 2 or 3 tenths faster were so slight, that even though I know where I can make up time, I'm not sure I'll be able to hit those marks with any sort of consistency, at least for now!
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Re: weight issue

Postby BLS » July 5th, 2011, 1:08 pm

F=MA. Not much that can be said. 5% is going to be 5% slower accel or decel with the same force. 8)
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Re: weight issue

Postby tiagosantos » July 5th, 2011, 2:17 pm

Sure.. And my memory might be tricking me, but the calculation was done on how much extra power you'd need to accelerate a typical vee down a straight vs a car 50 pounds lighter and, as far as I remember, it wasn't anywhere near the 5% difference..

Anyway, always worth going on a diet. I can hook you up with some great fat free vegan recipes if you'd like :mrgreen:
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Re: weight issue

Postby smsazzy » July 5th, 2011, 2:38 pm

I have always been told that every 18 pounds overe is like being down 1 HP.
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Re: weight issue

Postby BLS » July 5th, 2011, 3:24 pm

18 pounds is effectively 1.8% and 1.8% of 60hp is 1.08hp. 50 pounds is 5% or 3hp. Unfortunately, you cannot get around the very basic equation of F=MA.
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Re: weight issue

Postby tiagosantos » July 5th, 2011, 5:23 pm

You most definitely can't.. But since our cars don't operate in a vacuum, or run on frictionless surfaces, I don't think the equation applies to the real world in such a simplistic way!

Either way, the offer to share recipes still stands! :lol:
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Re: weight issue

Postby kkapelke4 » July 5th, 2011, 7:34 pm

we will have to see!

I know one of the top runners over here weighs in the same as me and he is fast!!!

Oh yeah and Andrew if you drive my car and you are faster your damn straight its the weight!!!! Lol

11 days until shannonville... I am pumped and feeling very confident of the upgrades we have made!!!
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Re: weight issue

Postby jpetillo » July 5th, 2011, 11:48 pm

BLS wrote:18 pounds is effectively 1.8% and 1.8% of 60hp is 1.08hp. 50 pounds is 5% or 3hp. Unfortunately, you cannot get around the very basic equation of F=MA.

Like Tiagos says, we're not running in a vacuum. A lot of the force is eaten up with just aero drag, and some to mechanical frictional losses, etc. The more aero drag you have (and other losses) the less M matters, that's why 1.8% weight gain does not equate to an equivalent 1.8% loss of HP. I think we guessed less than 1/2 that and then backed it up with some calculations. This is very track dependent of course, but at our tracks we are mostly between 50-100 mph. If we ran between 0-50 mph, then mass would affect us more like you mentioned. John
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Re: weight issue

Postby BLS » July 6th, 2011, 12:03 am

I'll drop it at this point with one last comment. The equation does not care if you are in a vacuum or not. The greater the mass, the lower the acceleration rate. The fact that air is present will not change the equation. Try adding 50 pounds to your car and see what the effect is...
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Re: weight issue

Postby jpetillo » July 6th, 2011, 12:28 am

Yes, of course you're right, but there are other terms in the equation that matter. Those other terms are also what the engine has to provide power to drive as well. The equation is more like...

F_engine = MA + F_aero + F_spin_up_tires + F_mechanical_losses + F_other_things

For example, at 110 mph you have almost no more acceleration. That's because those other force terms equal the force that the engine can provide when you reach max velocity, and the mass matters very little, then. Yes, you're right, adding 50 lbs is not a good idea at all and will definitely slow down acceleration, it's just not as bad as losing 3 HP for the average speeds we typically run at. I have run 50 lbs over, and I have not seen a correlation with my lap times. Actually, I was a bit faster with the added weight. But, that's mostly because I'm not that good a driver and the correlation was erroneous. A good driver will notice it more. John
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Re: weight issue

Postby smsazzy » July 6th, 2011, 12:38 am

Then the effect of additional mass is even greater. If you are using 50 HP to push the air out of the way, and you only have 5 HP left to accelerate the mass, then the additional weight is hurting even more than if you were in a vacuum.
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Re: weight issue

Postby BLS » July 6th, 2011, 1:05 am

OK, one more. Once at top speed the additional mass will not hurt, until you have to decelerate, which will be the same effect. So, if you have reached the maximum speed, the point at which aero drag and all mechanical resistance is balanced by the available force, then the additional mass doesn't matter, except when you turn or slow down. As long as you are changing speeds or direction the additional mass will have the same effect...
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Re: weight issue

Postby Rolling Stone » July 6th, 2011, 10:16 am

kkapelke4 wrote:we will have to see!

I know one of the top runners over here weighs in the same as me and he is fast!!!

Oh yeah and Andrew if you drive my car and you are faster your damn straight its the weight!!!! Lol

11 days until shannonville... I am pumped and feeling very confident of the upgrades we have made!!!

Yes I would call installing a 1600 engine an UPGRADE..also MCd=A&W=Harveys x No MSGx root beer=+3 Horsepower according to my high school old papers......and Andrew was talking about if he goes faster in your car "BACKWARDS" its the weight LMAO....Just kidding Kevin:>)
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Re: weight issue

Postby hojo » July 6th, 2011, 10:53 am

my last race was october 2009 so obviously i'm a little giddy to get some exercise. hopefully it doesnt take too long to get into the groove of things, more importantly the car prep side of things between sessions.
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Re: weight issue

Postby jpetillo » July 6th, 2011, 10:57 pm

smsazzy wrote:Then the effect of additional mass is even greater. If you are using 50 HP to push the air out of the way, and you only have 5 HP left to accelerate the mass, then the additional weight is hurting even more than if you were in a vacuum.

Steve, we can look at the equations in many ways, and pull out lots of information. I think what matters, though, is time to distance. What the equation shows is that the difference in time to distance is less when adding weight than by subtracting the same percentage of HP when the other factors are included in the equation. If we ignore all the other terms, then the direct percentage rule works perfectly.

BLS is also correct. Adding weight always hurts in the ways that were mentioned - no one will argue that.

That the mass difference is equivalent to a HP difference by percentage is not quite the case in reality. That was the only point I was trying to make. It's not too difficult to calculate by how much, which I've done. I'd be happy to discuss it with anyone who cares to listen to my drivel - PM me.

I'm siding with Kevin from here on out - nice job! John
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Re: weight issue

Postby fvracer27 » July 7th, 2011, 11:22 am

When I was racing Karts on year a bunch of us in the off season ran a indoor karting league karts were I believe 13hp so they were similar to our Vees all momentum very little power. I was the heaviest driver with about 55lbs heavy. When I lost everyone told me I needed to loose weight when I won then said I have more traction :-/

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Re: weight issue

Postby problemchild » July 7th, 2011, 3:12 pm

Looking back over three decades of racing FV and FF, I drove cars that were 40-50 lbs overweight on a regular basis. I never had "good years" when driving in such rides. The best years, when I won races and championships, had strong Run-offs, etc, were when I was within 10-15 lbs of minimum weight. While there are many factors that go into a competitive package, there is no doubt that being overweight is a severe handicap, and is under valued by many. For the past decade or so, the ability to be within range of minimum weight, was the single biggest factor in selecting my race car. I can buy fast parts and fix anything on the car ..... but a heavy car is just a waste of time for those that want to be fast. Show me a fast driver that is significantly over minimum weight ..... and I'll show you a really fast driver if he was on minimum weight!
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Re: weight issue

Postby lbaconll » July 7th, 2011, 4:07 pm

I agree with Greg! As a "large " driver 250+ # who has on occassion run with the West Coast "National" fast guys and ran with them well. My current car and i come in at 1100+#. Probably going to drive Me out of Vee as i have several 2nds and close calls but have yet to score a win in a regional in 16 years. I know I can drive (2 wins with Russell Formula Mazda Series), and despite a rather nasty crash in 06, I still regularily run in top 3-5 here on West Coast. No whining , just frustrating to have a class I really like, but since I am never going to be 200# I;, 6'4", Fst or F Mazda calls. That being said, watch for a COMPLETE vee package coming up soon with Mysterian M2 set up for tall, portly driver, a total of 5 National Engines 4 Ron Chuck, 1 Peak Performance, years worth of spares and all the drawings-body molds for what was Mysterian Formula Vee! :mrgreen:
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Re: weight issue

Postby lbaconll » July 7th, 2011, 4:08 pm

I agree with Greg! As a "large " driver 250+ # who has on occassion run with the West Coast "National" fast guys and ran with them well. My current car and i come in at 1100+#. Probably going to drive Me out of Vee as i have several 2nds and close calls but have yet to score a win in a regional in 16 years. I know I can drive (2 wins with Russell Formula Mazda Series), and despite a rather nasty crash in 06, I still regularily run in top 3-5 here on West Coast. No whining , just frustrating to have a class I really like, but since I am never going to be 200# I;, 6'4", Fst or F Mazda calls. That being said, watch for a COMPLETE vee package coming up soon with Mysterian M2 set up for tall, portly driver, a total of 5 National Engines 4 Ron Chuck, 1 Peak Performance, years worth of spares and all the drawings-body molds for what was Mysterian Formula Vee! :mrgreen:
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Re: weight issue

Postby SR Racing » July 7th, 2011, 6:55 pm

If you do the math on just the acceleration issue: If both are putting down 52HP to the rear wheels (typical Vee area) A 1050 lb car will out accelerate at 1100 lb car from 70 to 90 mph by about .2 sec. In HP that equates to around 2 . This of course ignores aerodynamics, gear shifts, etc. As pointed out there are more issues with cornering and braking.

No matter how you cut it though, weight is a big issue.
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