Hay all

How much would 100kg of weight slow a car down say 0-100km or 0400m? Just wondering how much it would make or not make any difference at all.

Kurt

IMO 100kg would make a noticeable difference.
How much depends on the original weight of the car - basically work out percentages. EG: my car with me in it is over 1700kg. So 100 kg less would be reducing weight by 1/17th or almost 6%.

for a 1400kg car going down to 1300kg, that's 1/14th saving or over 7%.

At a guess, I think that your 0-100 will improve - in the same time to get to 100kph, you'd reach say 107kph.
For 1/4 mile time, if your 14.2 is at say, 155kph, then your terminal speed at 14.2 seconds would become 165.85, but you'd have crossed the line sooner, so find out what times cars achieve with a terminal speed of ~160 - 162 and you'd be in that ballpark.
www.dragtimes.com.au will let you see actual 1/4mile times from various cars - you should be able to base your details from that.

Cheers!
Graham.

throw 100kg of junk in the car and see how much slower your 0-100 and 400m are, removing 100kg would probably be a similar difference the other way.

I used to race a 13b turbo rotary, rotaries dont like to haul alot of weight around due to their lack of torque..

Anyway, it ran consistent 11.8 seconds@111mph in street trim at heathcote raceway in VIC, a few months later we stripped 98 kgs out of it and made it a pure strip car ( all carpet, seats, stereo etc and replaced the windows with perspex) took it back to the track (a long tow from syd to vic) and found it made no difference to our times at all, 11.8s again! It did lift the front higher off the ground but that was it.

That's my experience with weight reduction, i cant see 100kgs making much difference to a V6, and if it did you would have to sacrifice a lot of luxury to do so...might use a little less petrol though!

It makes a huge difference.

The 380 had more power & torque than any 3.5 Magna, except the ralliart which had slightly more power (but less torque from memory).

Yet late third gens in 3.5 (like the TL) are as fast or faster than the 380 - the main difference - less weight.

Interesting.

I was thinking that if traction was an issue, reducing weight might not help things. In this case, shaving 100kg off the weight of your car and then putting 50kg of ballast on the driven wheels might be better for performance.??

I did a quick bit of research on-line and found a related page with interesting quotes:

http://www.hotrod.com/howto/113_0310_weight_reduction/viewall.html
"the drag racer's assumption that 100 pounds (~45kg) lost equals a tenth gained in the quarter"

and

Newton's Second Law of Motion -- "The acceleration of an object is directly proportional to the net force acting upon it and is inversely proportional to its mass..."


And another quote I found that I liked while investigating:
"How to reduce Torque Steer:
1) use a RWD car"
:D

throw 100kg of junk in the car and see how much slower your 0-100 and 400m are, removing 100kg would probably be a similar difference the other way.

oddly enough ive done similar to this with a mates nc fairlane to measure what the differance would be with him attending the casino drags with his full sound system during drag sessions ( by drag im speaking off raod fully legal, and controlled)

instead of "random crap" we went out and spend about 30.00 from a 2nd hand sports store for 4x 20kg bench press weights ( so abit off but you could compenaste by buying another weight)

i wasnt there for the actual testing as i couldnt find a babysitter for the kids, so i was only there to remove the sound equipment and space the weights over the car but from memory he did find a improvment in reducing the weight by the 80kg so logic says 100kg would further improve on his results

are you looking at local dargs, or just weighting the boot for your xmas holiday trip?

You just reminded me - years ago I went drag racing along with a car club mate.
He had a 1.0L Charade and after 2 or 3 runs, his time was consistently 15.2.
We removed his spare and tool box and I started to remove his back seat but he stopped me :(
With the junk out of the boot, his next run was 14.9 and then he bought the plates "HSV 18U". :)
At the time, the only quicker factory car from Holden / HSV stables was the GTS at 14.7.

So yes, removing weight can improve times. In his case, the little G100 Gtti probably weighed 800kg max, so removing a spare and hefty toolbox would be more %age of weight loss than 100kg from a Magna :)

If people that owned Magna's back then had been pulling low 14's, there would be a LOT more credit given.
Instead the old men wearing hats and sales reps gave Magna's the reputation of being the new Volvo and every couple of days I'd say "Bloody Magna" at some stupid driving habits.

Out of curiosity.. What tyre pressures are you running when you drag the car?

My ham fisted mathematics says dropping 100kg, from a stock TJ 4spd auto, would be equivalent to an increase of 10Kw (in standard trim)

Standard Kg:Kw - 1468 / 150 = 9.8kg per Kw
Less 100kg Kg:Kw - 1368 / 150 = 9.1kg per Kw

Same Kg:Kw in standard trim - 1468 / 9.1 = 161Kw

Some brainy math genius will correct me I'm sure, but this is how I see it. Not 100% sure, but shaking 100kg could be less expensive than chasing an extra 10kw. And would probably yield a more tangible result.

Real world results like 0-100 or 1/4 times, not sure. Improved fuel consumption stands out though. Simple fact the professionals are always chasing more power and less weight tells me 100kg wont be missed. Just don't go nuts and spend a squillion dollars, and countless hours, turning your daily driver into something you hate driving due to lack of comfort.

I would point your attention to the Lamboghini Gallardo Superleggera. Lamborghini stripped 100kgs out of it, and gave it an extra 7kW, and it dropped the 0-100km/h time by 0.2 seconds, 3.8 -> 3.6.

It will give a small difference all other things being equal. Maybe 0.1 or 0.2 to 100km/h and about the same for the quarter mile.


Yet late third gens in 3.5 (like the TL) are as fast or faster than the 380 - the main difference - less weight.

Rubbish. My 380 is much faster than my TL. Almost 2 seconds to 100km/h.

Rubbish. My 380 is much faster than my TL. Almost 2 seconds to 100km/h.

Mine isn't.
My 380 has the galant intake and straight through muffler.
My TL has straight through muffler.
Both manual, both have 50-55k on on the clock - times IDENTICAL.

Mine isn't.
My 380 has the galant intake and straight through muffler.
My TL has straight through muffler.
Both manual, both have 50-55k on on the clock - times IDENTICAL.

Auto vs Auto 380 should win. Manual vs Manual. 3.5l wins.

I think we could be talking manual v auto here.

flyboy is comparing manual against manual, Disciple is comparing auto against auto.

Comparing like against like you wouldn't think there would be much difference, but maybe the 380 auto is different in some way to the late 3rd gen 5 speed auto?

I've had a couple of 'tests' in my lightly modified manual 380 against similarly lightly modified manual TL/TWs, and there is bugger all in it from a standing start.

The lighter TL/TW gets off the mark a bit better, then by the time I hit 3rd gear (90km/h) the extra torque of the 380 catches up with the TL/TW and starts to pull away.

I think we could be talking manual v auto here.

flyboy is comparing manual against manual, Disciple is comparing auto against auto.

Comparing like against like you wouldn't think there would be much difference, but maybe the 380 auto is different in some way to the late 3rd gen 5 speed auto?

I've had a couple of 'tests' in my lightly modified manual 380 against similarly lightly modified manual TL/TWs, and there is bugger all in it from a standing start.

The lighter TL/TW gets off the mark a bit better, then by the time I hit 3rd gear (90km/h) the extra torque of the 380 catches up with the TL/TW and starts to pull away.

If anything, the extra torque of the 380 should help low end pull rather than high rev acceleration. The extra weight must negate this.

Kurt, weight loss is your biggest friend in chasing those low 1/4 mile passes. I reckon with drastic weight loss (200kg plus) and select mods should drop the time to a very low 14, maybe a 13.9. It should be doable. Problem with the magna sedan though is the firewall, this makes weight loss more difficult. As others have said start losing the weight by having some lightweight 17s or even 16s!

If anything, the extra torque of the 380 should help low end pull rather than high rev acceleration. The extra weight must negate this.

Kurt, weight loss is your biggest friend in chasing those low 1/4 mile passes. I reckon with drastic weight loss (200kg plus) and select mods should drop the time to a very low 14, maybe a 13.9. It should be doable. Problem with the magna sedan though is the firewall, this makes weight loss more difficult. As others have said start losing the weight by having some lightweight 17s or even 16s!

My old TE 3.0 manual (extractors & Unichip & free flow exhaust) was a lot easier to get off the line than my 380.
The extra torque of the 380, especially combined with the short final drive ratio in the manual 'box, makes it very hard to get a good launch.

I agree treeadeyman. Getting the power to the road in the 380, especially the manual, is very VERY hard. I think the traction control was built around the auto, because it certainly doesn't seem to help me get off the line and still allows some long periods of wheel spin before it kicks in. I generally turn it off.
Perhaps the 380 dumps a lot more weight onto the rear than the TL/TW during launch.


combined with the short final drive ratio in the manual 'box, makes it very hard to get a good launch.

Yes... but it makes for a hell of a lot more fun from about 40km/hr through to about 120!

Gear ratios are different from the Third Gens to the 380;

380 5spd Auto / 3rd Gen 5spd Auto;
1st - 3.789 / 3.789
2nd - 2.162 / 2.057
3rd - 1.421 / 1.421
4th - 1.000 / 1.000
5th - 0.686 / 0.731
Final - 3.325 / 3.684

380 5spd Man / 3rd Gen 5spd Man (3.5)
1st - 3.333 / 3.583
2nd - 2.105 / 2.105
3rd - 1.407 / 1.407
4th - 1.031 / 1.031
5th - 0.804 / 0.761
Final - 4.111 / 3.722

(Sources; Mitsubishi 380 marketing PDF, and, Third Gen Workshop Manual)

Differences show up mostly in the final drive ratio. This could attribute the 3rd Gen auto appearing to be as quick/quicker than the 380. Whereas the 3880 Manual has lower overall gearing, which would give it a much quicker 0-100 time given the bigger engine as well.

Doesn't make sense that they'd run such a low ratio in the 380 manual though?

My thought is it's in the gearbox. My TL was a 4 speed auto, where as the 380 is a 5 speed auto.

Looks like your much better off chasing the extra 10kws..

There is a lot of safety and comfort built into your Magna, intrusion bars, air bags, sound deadener etc, which of these would you first strip without making the car illegal or very hot and noisy on the inside? And your certainly not going to go running perspex instead of glass...and all for what? a .2 time difference on your mates stop watch or 1/4mile on a perfect run??? Not worth it, you quickly hit a dead end when looking to remove weight, where as if chasing horsepower the sky's the limit!:badgrin:

Sorry Work Hack, but that's just too much negative talk for me.

Sure, the sky is the limit in chasing more power, but it also gets expensive fast.
And the amount of power needed for a 12 second 1/4 mile on a 1500kg car will be a heck more expensive than a 1200kg car.

Sometimes the best compromise is to chase a little HP and a little weight loss. End up with the best possible performance for the smallest outlay, even if that performance is just for bragging rights and not really representative of on-street performance.

Strip out the back & passenger seats, spare tyre, jack, tools, run with 1/4 tank of fuel
My estimation: seats 30kg, spare 20kg, jack + tools 10kg 20L of fuel instead of 70L saves about 40kg, 30+20+10+40=100.
So at my guess, you've saved 100kg right there and you can see how much of a difference it makes.


One thing to remember for any nay-sayers, drag racing is a sport - some people will be described as crazy for spending money to go fast, but IMO it's a great learning experience - the ingenuity, skills and knowledge etc are all valuable things to have.
But yes, you do have to be a bit crazy to want to go fast :)

Looks like your much better off chasing the extra 10kws..

There is a lot of safety and comfort built into your Magna, intrusion bars, air bags, sound deadener etc, which of these would you first strip without making the car illegal or very hot and noisy on the inside? And your certainly not going to go running perspex instead of glass...and all for what? a .2 time difference on your mates stop watch or 1/4mile on a perfect run??? Not worth it, you quickly hit a dead end when looking to remove weight, where as if chasing horsepower the sky's the limit!:badgrin:

You obviously dont know kurt!

I have been also looking at weight as i did a few 1/4 mile runs a couple of weeks ago in the magna on stock size tyres, and want to get into the 13's next time

My 1st couple of runs was with my girlfriend and spare tyre in the car. I ran aprox 14.46-14.48
The next few runs was without girlfriend and spare tyre and I was running 14.04-14.06 with a best of 14.034
she weights about 55kg. Spare tyre 19.2kg so that 74kg added .4 of a second to my 1/4 time

I have also been weighing some wheels. This is from memory but should be pretty accurate.

16x7 tj sport wheels with 80% tyre 215/60/16 bobjane allrounders (current rear wheels) 18.4kg
16x7 bobjane wheels 5 spoke with 90% diamondback from kmart 215/60/16 tyre (current front wheels) 18.2kg
17x7 enkei rallairt with 40% stock size tyre 18.8kg
15" steel wheel with 40% stock size tyre 19.2kg
17x8 evo 9 enkei with new federal 235/45/17 rs-r 21.8kg
17x8 evo 9 enkei with used 90% 225/45/17 yokohama tyre 20.4
17x9 sparco racing with new 275/40/17 mickey thompson street drag tyres 24.4
16x8 wed wheels with worn 255/50/16 mickey thompson street drag tyres 17.8

The evo 9 enkei are my new daily wheels but they add 11.2kg to the weight which i read somewhere is effectively doubled because is rotating mass.(like putting 22.4 kg inside the car)
I am going to do a few runs on these as I would like to do a high 13 on my daily wheels/tyres(i have done a few little mods to the car so its slightly possible) otherwise i will change to the bobjane wheels on the rear and weds on the front for a guaranteed high 13's

Good post, VR4 squared! :)

You inspired me to hit the garage with some scales and weigh up my factory TJ2 sport AWD 16x6 rims with 215/60/16 tyres:
2x nearly bald BF Goodrich Sport tyres weigh in at 17.4 & 17.6Kg -
2x with plenty of tread (60%?) Gemstone 1000 tyres weigh 16.8 & 17.4 kg.

The lightest one doesn't have any balancing weights on it, others have around 20g? of weights. I don't know why there's such a big difference.

My goal was to get some 195/40/16 tyres put onto these rims at some point. I wonder how heavy they will be then :)
I'd hate to think what my 245/35/18 combo weighs.

I also learned that these factory wheels are by ROH, and that a plastic bag with 20 factory wheel nuts weighs about 1.5kg.
I found a set of Alloy wheel nuts that claim to weigh 380g for a set of 20. So if you want to save about 1kg of weight (double it because it's rotating mass) there's one way to blow $50-100. :)

Cheers! Oggy.

Rays light weight carbon steel nuts are 22grams each

Dang - I'm sure my nuts are heavier than that!

I kmow right. TZABOY has them on his red car. They are insanely light and very very strong

As an estimate: (Figures based on a FWD vehicle, and using flywheel power, and race weight being car and driver)


180 Kw @ Flywheel and 1450 kg race weight = 0-100km/h in 6.4 sec quarter mile in 14.43

Strip out 100KG's
180 Kw @ Flywheel and 1350 kg race weight = 0-100km/h in 6.1 sec quarter mile in 14.11

OR add another 10 Kw @ Flywheel
190 Kw @ Flywheel and 1450 kg race weight = 0-100km/h in 6.2 sec quarter mile in 14.13

OR do both
190 Kw @ Flywheel and 1350 kg race weight = 0-100km/h in 5.9 sec quarter mile in 13.83

Just for comparison sake i ran my magna in full street trim including spare wheel and subwoofer and all interior trim bits and got a 14.2. Ben (TJTime) took his backseat, spare wheel out of his Sports and ran the same time as me in my VRX which also has all the bodykit pieces as well which wouldnt count for much more weight.

Both of us were running (before ben put the wavetrac in) pretty similar setups but I think it comes down to the driver in most cases.

Just for comparison sake i ran my magna in full street trim including spare wheel and subwoofer and all interior trim bits and got a 14.2. Ben (TJTime) took his backseat, spare wheel out of his Sports and ran the same time as me in my VRX which also has all the bodykit pieces as well which wouldnt count for much more weight.

Both of us were running (before ben put the wavetrac in) pretty similar setups but I think it comes down to the driver in most cases.

This!

I assume Kurt is asking if he removes 100kg from his car how much faster will it be with him still driving.

So assuming we have same car, same driver, same tyres/traction etc, if Kurt takes 100kg weight out of car his 0-100km/h his time will potentially drop .3 seconds, as will his 1/4 mile time.

The best thing about weight reduction for a run down the quarter is that a lot of it just needs time to remove stuff, which can usually be replaced again after the event if done sensibly.

The exception in regard to cost is lightweight wheels which are expensive but can save 30-40kg alone if you compare 4 average quality 19"aftermarket wheels/tyres with a set of lightweight 16" or 17" rims and tyres. However with lightweight wheels you can use them everyday on the road as well, and they improve handling greatly, so these are one of the best performance mods dollar for dollar.

If you can remove 100kg of weight for free (except for the cost of your time to do so), in the case of your average Magna you are basically getting a similar benefit of around extra 10Kw for free.

How do you get 10Kw out of a Magna?
In a FWD drive Magna you could fit some new extractors for $700+ fitted (less than 5 Kw surely)
Get a tune for anywhere from $300-$700 (maybe more than 5Kw but unlikely more than 10Kw)
Fit Ralliart/380 cams, buy them for $400 and $300 install (maybe 10Kw max?)

The benefit is that all these, while costing $'s, are a permanent increase in power to weight.

However if all you want is a one-off time slip for bragging rights no other modification compares to weight reduction when you look at it as dollar to dollar.


i reckon FTW, do both and run 13's!