Kg vs HP

This topic has 12 replies, 7 voices, and was last updated 7 years, 8 months ago by rsbaron.

Viewing 13 posts - 1 through 13 (of 13 total)

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February 5, 2017 at 4:40 PM #21147

dogbone
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UK - England

Posts: 144

I’ve seen various comments regarding weight reduction and HP on various threads, so I’ve read across some basic power to weight theory to the Mk3 RS, happy to stand corrected if there are any errors.

Information read from http://www.tuneruniversity.com/blog/2012/03/power-to-weight-ratio/

Theory on weight loss and equivalent gains in hp, power to weight ratio, gives:

Factory RS MK3

Kerb weight (inc 75Kg driver) = 1599 Kg

Horse Power = 345 HP

Power to weight ratio = 0.2158 HP/Kg

Therefore:

weight reduction = 10 Kg

new weight = 1589 Kg

Power to weight = 0.2171 HP/Kg

Equivalent HP = 347.17 HP

HP increase of = 2.17 HP

So, the first reduction of 10Kg is equivalent to a 2.17HP increase.

It is not quite a linear relationship but as a rule of thumb each 10Kg improvement (from 10Kg to 150Kg) is equivalent to 2.4HP on average. In fact, the HP equivalent increases slightly for every 10Kg weight reduction, so for example removing 10Kg weight from 140Kg to 150Kg gives an equivalent of 2.61HP

I tried to attach my Excel file showing the workings out but the file type is not allowed.

The question is, what’s the best HP increase per £ spent? Tuning or weight reduction? It’ll be both aspects, particularly in the basic early stages when costs are relatively low.

Hope it’s a clear as mud 😉

Magnetic FPM375 DSC Controller Tractive suspension EBC discs with Yellow Stuff

February 7, 2017 at 10:21 AM #21344

kr1s
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UK - England

Posts: 696

I wasn’t happy with mine when I picked it up. Handling improved when I filled the petrol tank. And again with a passenger. I would not want to reduce the weight without spending a lot on the suspension.

February 7, 2017 at 2:21 PM #21356

Kenny
Keymaster

UK - Scotland

Posts: 3885

Interesting info. Someone knows their numbers.

I think best bang for buck with be more horsepower 🙂

February 26, 2017 at 8:31 PM #23611

johnybigarms
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UK - England

Posts: 1145

A bit of both seems best, 380hp is easily achieved for around £1200 (M380 for example) no brainier, then I reckon simple weight saving would be the next step, I ordered the RS with shell seats and forged wheels, the wheels save around 5kg, the shells seats should be the same at around 5kg lighter than the heavy bolstered standard, not ticking the lux pack option pays for most of that, plus saves weight, the motorised mirrors, cruise control and parking sensors all add weight, 1 to 2kg I reckon, non of it essential, removing parts like rear head rests, parcel shelf, under bonnet insulation, flat tire gunk and pump (call the AA) may be another 5kg saving, 1/2 tank of juice saves 25kg over full tank, then it gets harder, lithium iron battery would save 10kg over the standard lead acid, subwoofer removal may save a few kg (not really required unless your a head banger) so 50kg is possible quite easily (14hp power equiveant) over a fully tanked RS, not bad if your after the ultimate warrior (394hp v standard lardy 340hp) certainly feel different, should handle better too, although I must admit passenger does smooth out the ride a little

Mountune M380 package

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Mountune Hard Charge Pipes

JCR super low seat frames x 2

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February 26, 2017 at 9:20 PM #23625

kr1s
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UK - England

Posts: 696

I do like the theory but have to say that I find that weight isn’t important.

I just had over 100 laps of Brands Hatch.

Passenger and full tank sometimes

no passenger and tank nearly empty sometimes

that’s a change of over 100 kg

made little difference

not to me anyway

March 5, 2017 at 10:54 AM #24398

71-bda
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UK - England

Posts: 9187

Kr1s it may not have felt much different , but 100 kilos and a stopwatch would tell the difference, if just a few kilos means tenths of a second to a 800bhp F1 car, 100 kilos on a 1500 kilo 345bhp is quite considerable.

No nothing.

No Mods. No rockers. Just a chunky knob, thats now been replaced by an RS knob innit.

No tackiness.

Std as Ford intended, but with a space saver wheel and jack and nuts and wheel brace. oh.. and flaps, a man has got to have flaps.

Innit?

March 5, 2017 at 11:53 AM #24408

kr1s
Participant

UK - England

Posts: 696

Hi Mike yes I’m sure you are correct

changing weight

It has to alter acceleration and braking

but wouldn’t the stopwatch be running through the bends?

what does changing the weight do to the handling ?

if the weight goes down it may need different springs and damping .

And the current suspension may suit extra weight in this road car with fixed springing and just 2 damper settings.

I know little of F1

but this fantastic RS car has a crude suspension system

my “other vehicle” has 10 clicks of rebound alteration, 10 on high speed compression, 10 on low speed compression, and infinitely adjustable preload

I wish I could be bothered to keep playing with it ?

now if all these adjustments could be controlled from the dash in the car we could talk an F1 comparison maybe

March 5, 2017 at 12:04 PM #24410

johnybigarms
Participant

UK - England

Posts: 1145

I must say the ride does get less jiggly with a passenger in the back, so losing weight wouldn’t help ride quality that’s for sure

Mountune M380 package

Mishimoto throttle Pedal Spacer

Mountune Hard Charge Pipes

JCR super low seat frames x 2

DSC Suspension Controller

March 5, 2017 at 7:49 PM #24462

71-bda
Participant

UK - England

Posts: 9187

KR1s less weight is always going to improve cornering speed, the tyres will have less work to do. you say the handling improved when you filled the tank? thats not handling, i suspect you mean comfort? weigh any car down and it always makes the suspension seem softer. I ve never heard anyone say their car handled better when laden up, I know if I was to go round a track in mine, i would not go with 3 passengers and a full tank, just me and half a tank would be the way to go. I was worried that the car may be over damped, but now Ive had it a few days, i love it, one thing is for sure, as cars get older they only get softer and more compliant so, maybe you will like yours more with a lot more mileage on it!

No nothing.

No Mods. No rockers. Just a chunky knob, thats now been replaced by an RS knob innit.

No tackiness.

Std as Ford intended, but with a space saver wheel and jack and nuts and wheel brace. oh.. and flaps, a man has got to have flaps.

Innit?

March 5, 2017 at 8:48 PM #24471

kr1s
Participant

UK - England

Posts: 696

Hi Mike.

You’re joking, right?

If less weight really does improve cornering speed then your F1 cars have their wings upside down.

Downforce? Weight?

Didn’t you put paving slabs in your boot back in the day?

March 6, 2017 at 8:16 PM #24582

rssam
Participant

UK - England

Posts: 61

I’m with you Mike weight is the enemy of a performance car less acceleration longer braking distance slower cornering. If your car has a mass of 3000kg and you have a wing that gives you 500kg down force your car still weighs 3000kg so you get the advantage of same weight but now pressed on to the road with 500kg of downforce better cornering,better braking ,similar acceleration top speed If you take the same car and put 500kg of load in it people slabs etc I think you can guess what happens

March 7, 2017 at 9:59 AM #24617

71-bda
Participant

UK - England

Posts: 9187

@ Kr1s . no pal, I think it is you having a laugh ! people used to put bags of cement or a paving slab in things like 3 litre capri mk1s to try and get the “BALANCE” better! Car weight reduces grip when cornering fast as the weight tries to transfer to the outside of the car, aerodynamic downforce is perfect as it pushes the car into the tarmac vertically down. By your reasoning every F1 team is wrong making their car as light as the regs allow, I guess if you owned an F1 team, you would have the heaviest and slowest car in the pits!

No nothing.

No Mods. No rockers. Just a chunky knob, thats now been replaced by an RS knob innit.

No tackiness.

Std as Ford intended, but with a space saver wheel and jack and nuts and wheel brace. oh.. and flaps, a man has got to have flaps.

Innit?

March 12, 2017 at 7:39 PM #25260

rsbaron
Participant

UK - England

Posts: 93

@Dogbone . Mmmm interesting. I for one am going to try and loose some of my “Junk in the Trunk” down the gym. I have a gym membership and this costs me no money. If I loose 2 stone we should be good 🙂 Simples….
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