924Board.org

[Body Shop Rob]

With all the talk about body kits and performance upgrades, I just have to remind everyone that the cheapest, most effective way to increase the performance of the 924 is to lighten it. 110 HP cannot move a 2600 LB car quickly. Even forty more HP won't make your toes curl, and those HP will come at a dear price. Less is more.

BSR

[sneed21]

I agree, Does anyone know how much weight one can "effectively" removed from a 924? Anyone have any figures?,,,,better yet, has anyone done it and then had their 924 dynoed?

[AznDrgn]

Talk to applebit or look at his site, he has extensive weight drops and engine mods. I think last time I saw it he had his car going 0-60 in like 5sec.

[924 turbo]

Removing weight from your car is an effective way to increase performance in nearly all areas. Braking, handling, and speed will all be improved. However, there really isn't that much weight to take off of the car, unless you're willing to spend money to do a body kit, with a fiberglass hood, lexan windows, etc. If your car is a race car, by all means pull the carpet, insulation, and all non-essential electrics out of your car. But a daily driven car that's an empty, loud shell is a little ricey, IMO.

[shadowboy]

i disagree with the ricey comment

the idea behind a rice is a car with the look of performance without any mods to actually back it up

having a lightened car is a performance-proving mod

uncomfortable and inconvenient, yes
ricey.. absolutely not

but there are other factors:
1: can you deal with the loud, empty, uncomfortable car
2: do you have to? (ie do you have another daily driver)

[924 turbo]

[Richard]

Just to clarify one of the above posts. A dyno run on a striped car will not prove anything. the engine has same HP light or heavy. 1/4 speed or 0 to 60 is another story.
I always thought it would be interesting to make an easy to read chart ploting power to weight ratio against pounds removed. Also a chart "if you remove x pounds, your effective horsepower goes up y amount"...any math geniuses out there want to take it on and post results. How about you Body Shop Rob?

[baldwin]

For a first approximation you can assume a linear relationship between mass and acceleration time:
time=mass/C
In metric: 9.6seconds = 1070kg / C => C=111

You can do fun stuff combining torque, rpm and velocity graphs from the instruction manual and do some integral calculations and then come to the same conclusion. But then again, my math is a little rusty...I can post my calculations, if anyone's interested.

Boudewijn

[ This Message was edited by: baldwin on 2002-07-12 22:12 ]

[PORSCHEV]

I drag race in the pro class here in Nova Scotia, 1/4 mile drag strip. The rule of thumb for stripping weight for ET gains is every 100 pounds of weight stripped from the car, you will shed 1/10 of a second from your ET.
I would have to agree with the comment abouty loosing the interior for performance gains if you are running a daily driver....not worth it.

Stripping will not even be noticable at times. I put the old 79 Camaro on a diet....she lost 250 lbs or 2.5 tenths of a second. Hard to notice when you calculate all the other variables at play.

[Peter_in_AU]

if you want to look at the effects of power vs acceleration go to http://www.cartest2000.com/ and download a copy of their cartest 2000 software. The demo version does not allow you to change weight but you can change hp and torque.

The math involved with explaining weight reduction to effective power (torque I suppose) would be thesis stuff would'nt it? I mean if a 1000hp Nissan GTR can do an 8.9 quarter then a 500hp GTR will do a 17.8 quarter right? no a 500hp GTR will do low 10s (or something like that).

e=mc^2 probably explains the whole thing quite well

[shadowboy]

generally speaking.. it takes 10x the horsepower to half your time to any distance (roughly speaking... the shape of the torque curve is a factor.. as well as the shape of the body... aerodynamics become quite significant after ~70-80mph)

speaking of aerodynamics: it takes about 11HP to move a honda CRX Si along at 55mph

it takes all 108HP the car can muster to reach a top speed of somewhere around 105-110mph...

see, double the top speed, 10x the horsepower.

another way of looking at it is this:
the engine has to add kinetic energy to the car.. the formula for kinetic energy is this:
Ke = 1/2 m v^2.
in other words the velocity portion is squared. to quadruple kinetic energy is to only double your speed. (this is in addition to the same aerodynamic relationship).

but.. since the energy-mass relationship is linear, it means that halving your mass means it takes half the energy to go that speed.. so by halving your mass you effectively double the speed you can go at any given energy level.

as a quick less mathematical synopsis:
double speed = 4 times the energy input
double speed = 1/2 the weight

we all know what the relative costs of engine mods vs weight reduction.

to shed 500 lbs on a 2500 lbs car (20% reduction in weight--to make the math easier)

that 500 lbs is roughly equivalent to bringing the 110HP engine up to 171HP

bringing the engine up to 171HP is not gonna improve handling or braking either.. the weight reduction will

[coconutcowboy]

not only can the body go on a diet (i.e fibreglass fenders, hood, valance, carbon fibre bumpers ect),

the engine can go on one as well.

lighten the flywheel or go with an alloy one, knife edge the crank throws, use lighter rods and pistons, gundrill the cam, use a 4-2-1 exhaust header, lighter performance mufflers, use the lighter smaller crank pulley and a lighter vw cam drive sprocket.

also gut out or axe the cat if posible, the charcoal canister and use the lightest wheels you can find

[MAD924]

So it's like we already knew:
It'll take a whole lot of money to drop enough weight to really make a difference in straight line speed and acceleration.
And It'll take a lot of money to get a 924NA engine to put out enough power to make a big difference in speed and acceleration.
And without trying to sound too cynical, I'm hard pressed to believe that anyone really has their 924NA below the 7 second mark in 0-60. I've got an Integra GSR and a BOSS302 that can both do it and my 924NA is ways off of that pace. And that's a pretty quick pace. And my 924 is in very good running condition although bone stock at 44,000 miles. Sorry to the followers of applebit, but I've got to see it for myself to believe any of it.

[AznDrgn]

another example of a car that probably can pull a sub 7 0-60 is simsports super charged 924. He has a post is performance upgrades.

[MAD924]

Okay.
1st- The car is no longer NA.
2nd- Money and resources. He "guesses" it all cost about L3000=$4500 so I would guess it cost more. He also did the work himself with the help of someone to do alloy welding. And I would also guess the free help of some other sponsors. Specialty work is usually more expensive than parts. Sounds pricey to me.
I didn't say it couldn't be done. I said it would cost a lot of money. With enough money, one can make any car go fast. I just think a lot of people throw figures around like "0-60 in 5 secs" without any real proof. I don't believe all of the claims that some people make on this board or anywhere else. I really didn't mean to offend, but I just couldn't keep it to myself. I just couldn't.