Acceleration increase per kg lost

[jvanzyl]

Hi folks,
Just thought I'd start a new thread instead of landing on a reader's ride..
Does anyone have any kind of data on the acceleration increase per kg of weight that is lost?

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[jvanzyl]

OK I've found a nice little chart thing that I can mess with that tells me what the change is...
https://www.ajdesigner.com/fl_horsepower_elapsed_time/horsepower_elapsed_time.php

Edit: based on an assumption of 14.5 seconds with a 140 bhp engine for a 1/4 mile run with a car weighing 1000 kgs... if you shed 25kgs.. that reduces your time by 0.1 roughly or you require 0.6 less HP to do it in the same time...
erm.. this can't be right..

[StuC]

stock car
970kg with 135.8bhp = 14.6 quarter mile

or

fabled 10 second car
stock weight of 970kg = 422.7bhp!

@jvanzyl do you have a number in mind?

[jvanzyl]

stock car
970kg with 135.8bhp = 14.6 quarter mile

or

fabled 10 second car
stock weight of 970kg = 422.7bhp!

@jvanzyl do you have a number in mind?

Not so much a number... more of an "effortometer".. basically weighing up how much effort, cost, and loss of comfort against the performance increase!

[StuC]

stock car
970kg with 135.8bhp = 14.6 quarter mile

or

fabled 10 second car
stock weight of 970kg = 422.7bhp!

@jvanzyl do you have a number in mind?

Not so much a number... more of an "effortometer".. basically weighing up how much effort, cost, and loss of comfort against the performance increase!

Isn't it at this point that someone says turbo? ;-)
although it doesn't necessarily tick your cost box.

[Carolyn]

Bugger all.  In straight line, that is.

Lower weight (especially unsprung weight) will get you round the bends quicker.

Yes it's often easier to add BHP.

[jvanzyl]

stock car
970kg with 135.8bhp = 14.6 quarter mile

or

fabled 10 second car
stock weight of 970kg = 422.7bhp!

@jvanzyl do you have a number in mind?

Not so much a number... more of an "effortometer".. basically weighing up how much effort, cost, and loss of comfort against the performance increase!

Isn't it at this point that someone says turbo? ;-)
although it doesn't necessarily tick your cost box.

no you're right. FI is the way to go most clearly.. I was just interested to see how much performance would actually be gained by losing weight on the car..

[StuC]

with a 10% decrease in weight, so going down to 873kg this will only shave 0.5 of a second off. I am sure you would not really notice that in a 1/4 mile.

Perhaps a better metric would be accelerations from speed, rather than standstill?

If you lose all the NVH stuff, then it will be noisier... which will FEEL like you are going faster! ;-)

[cptspaulding]

Marty & Moog

I believe  Marty & Moog demonstrate this in the best manner possible.

Can't argue with science.

[Call the midlife!]

Isn't @M1tch going to great lengths to document his efforts on this already? Might be worth looking at his threads.


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[jvanzyl]

Isn't @M1tch going to great lengths to document his efforts on this already? Might be worth looking at his threads.


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Yeah I've been going back through his thread..

[jonbill]

0.5 seconds is quite a lot In 1/4 mile times. You won't feel it, but you'll beat a lot more cars.

[1979scotte]

I feel that apart from fitting lighter wheels the 2 is as barebones as I want it to be.
I would be more likely to add weight through bum warmers and heated mirrors.
Although if they make a lightweight seat that is also comfortable that could work.

Add more grunt that my ethos.

[StuC]

@cptspaulding love it!

[StuC]

Quick bit of research from here show that the kerb weight is 835kg with a 11.5 0-60.

They took out 100kg and the time dropped to 7.8! 3.7 second reduction in time. Crazy!

Or a with some spanky statistics...
12% reduction in weight yielded at 32% increase in performance.
I mean, you can't argue with those kinda numbers. lol

[Call the midlife!]

I don't care what any of the statistics prove, I'm not giving the pies up for a mere 30% ...


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[Petrus]

Although if they make a lightweight seat that is also comfortable that could work.

As Carolyn observed straight line acceleration is only óne area where adding lightness scores.

It also improves braking, cornering and roadholding. Oh and fuel economy.
More grunt only delivers in straigt line aand comes with worse fuel economy.

Back to seats, well there is up to say 15 kilos for grabs there but the weight sits low and central so it is the least noticeable you can shave off. Also there are no real cheap solutions.

Shedding weight by unbolting stuff is simplest and cheapest. Obviously that is limited but 50 kilos can be scored without sacrificing creature comfort. I am on 55 kilos now and could take the rear cubby plastic out for another 5 but find that they hold back quite a lot of noise.

Apart from lighter wheels I am at the end of that road and may even add 5-6 in the form of a rear wing.
I will try weigh the car next week.

[Kaveney]

As my car is for track only I have done a chart of the weight loss like race battery light weight wheels and all the stuff removed .

[tom256]

Hi folks,
Just thought I'd start a new thread instead of landing on a reader's ride..
Does anyone have any kind of data on the acceleration increase per kg of weight that is lost?

Try to cut down low part of rear bumper. Some expert say it's working like parachute.

[Petrus]

Try to cut down low part of rear bumper. Some expert say it's working like parachute.

Mwahhh... it also plays a part in the air circulation in the engine compartment, just like the diaper. Best fit an aero divice that reduces drag behínd the bum(per).

[K T M Rider]

Hi folks,
Just thought I'd start a new thread instead of landing on a reader's ride..
Does anyone have any kind of data on the acceleration increase per kg of weight that is lost?

Sent from my Moto G (5) using Tapatalk

From my ageing back copy of Evo:

PFL MR2 Weight 975kgs, 0 to 60mph in 7.6 seconds.

Lotus Elise 111S Weight 770kgs, 0 to 60mph in 5.4 seconds.

The Elise makes a fraction more power and torque (5bhp & 3 lb ft) and er, it's a Lotus but essentially (at least where 0 to 60 times are concerned) the Elise is pretty much just an MR2 that's been on a fairly serious diet.

So, I reckon the answer to your question may be somewhere around a 0.1 second reduction in 0 to 60 time per 10kg weight reduction (assuming the sort of weight reductions realistically achievable by mere mortals, not Toyota race teams)

Just in case anyone's wondering how the guys in the video apparently did over 3 times better than that, well for a start they only went 0 to 36mph (60 km/h), and christ knows how shagged the engine was (given that a knackered engine will often struggle far more with additional weight, so it follows it may benefit more from a cut in weight)

[Petrus]

The report on lighter wheels gives a rather positive result.

Other calculations support this as they give a result of the wheel weight counting double, meaning that for accelleration/decelleration 1 kilo of the wheel equals 2 on the car.

That decelleration can not be translated to braking distance as that is limited by friction. Oh and roadholding but that is a díffrent effect of lighter wheels. So though lighter wheels give shorter braking distances, it is not because of them decellerating easier.
Ah and that also applies to accelleration; better grip though better roadholding may improve the times more than the weight advantage hence perhaps the wildly variating spint improvements reported.

[Gaz mr-s]

So though lighter wheels give shorter braking distances, it is not because of them decellerating easier.

I wouldn't like to state the technical definition, but the gist of what I've read about lighter wheels being desireable is they are easier to accelerate, - less inertia, & easier to brake, - less kinetic energy.

And a lighter weight for suspension to control means the suspension can be made lighter on a new car model.

[Petrus]

So though lighter wheels give shorter braking distances, it is not because of them decellerating easier.

I wouldn't like to state the technical definition, but the gist of what I've read about lighter wheels being desireable is they are easier to accelerate, - less inertia, & easier to brake, - less kinetic energy.

And a lighter weight for suspension to control means the suspension can be made lighter on a new car model.

Not quite.
Yes. less kinetic energy but is has véry little effect in the whole picture.
It has more effect on the stopwatch because of increased road contact.

No, the suspension cannot be constructed lighter because the weight which needs to be suspended, namely the car itself, remains the same.
Now you see that the spring rate cannot be change either as the cár is held up by it.
It is the dámping characteristics which need be adjusted; as a gross simplification; less inbound, more rebound damping.

On the MR2 any weight saved on the wheels has more impact because the unspung weight is low. One kilo off the wheel is 30% more noticeable than on a 1500 kilo hatchback.

Again; the contact between tyre and surface is increased roughly by the % of lightening of the wheel. How this translates into measurable results such as skid pad values, braking etc. involves other factors.
Regardless however, it wíll shift the limits further away; it will make the car longer controlable which imo is worthwhile. Nice argument to sell it to the wife too