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Old 07-18-2003, 12:12 PM   #1
DucatiBoy
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Default Cost of reducing STi weight

Has anyone started looking into how much effort and how much it would cost to reduce the weight of the STi. I believe the STi is almost 300lbs heavier than the stock WRX. Also what are the unsprung weights of the STi vs. WRX? For example does the STi Brembo rotor/caliper combo weigh more than the WRX brakes. Or is this offset by those trick aluminum suspension parts on the STi.
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Old 07-18-2003, 01:11 PM   #2
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it's not too easy or cheap to get weight out of wrx, and the STi was put on a hardcore diet to lighten it as much as possible, making it that much more difficult.

you're probably looking a serious $$ to get it all that much lighter. the spare tire/jack is pretty heavy, so that might be a place to start. a lightweight battery might help also. beyond that it gets tough. you can replace the bumper beams with lighter ones, but you'll be compromising safety.

also the trick aluminium suspension parts aren't that much lighter than the wrx ones, but they are a lot stiffer/stronger though.
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Old 07-18-2003, 01:21 PM   #3
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acid dip the body panels.
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Old 07-18-2003, 01:39 PM   #4
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WRX

Curb Weight (pounds) (w/Manual Transmission) 3085

WRX STi

Curb Weight (pounds) (w/Manual Transmission) 3263


The STi is 178 lbs heavier.

Remove your spare tire and jack for 42 lbs savings....
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Old 07-18-2003, 02:12 PM   #5
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Having gone to the effort of taking weight out of an old 911 for the track I can state two things: (1) it is expensive and (2) it makes a huge difference in performance. However, I think it would be very hard to get much weight out of an STI, unless you were to start stripping the interior(including sound deadening insulation), replacing windows with Lexan and using pull straps to raise and lower the windows, carbon fiber or fiberglass bumpers, trunk lids/spoilers--that's the type of thinking you would need to make a real difference. With modern safety regulations I think Subaru went about as far as they could go for a street legal car. People have remarked that the WRX (nearly 200 lbs lighter) feels lighter and more tossable, especially at lower speeds--I can believe it. Look at the Ferrari Enzo and Porsche Carrera GT--cost no consideration supercars with all the latest weight saving technology--those cars still weigh about 3000 lbs! I think Subaru has done a good job on both the WRX and STI, especially when you consider the additional weight of AWD.
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Old 07-18-2003, 02:25 PM   #6
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All the extra weight in the STi is really going towards better performance. You add suspension, you add engine, you add electronics... when you add performance you also add a lot of weight... so only 178 more than the WRX is not bad! You could also take out the rear and passenger seat. CF hood and trunk maybe? All those plus a lighter battery and no spare might actually bring you pretty close to WRX weight...
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Old 07-18-2003, 02:30 PM   #7
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Quote:
Originally posted by filbert
CF hood and trunk maybe?
the hoods already aluminum i believe so not sure how much that will help....

CF trunk lids from Vivid weight in at 9lbs, not sure what the stock trunk is...
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Old 07-18-2003, 02:36 PM   #8
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The first thing I think is worthwhile changing are the USDM bumper beams. I assume that they are similar to the WRX. Loosing the weight in those areas of the car will make a noticeable difference dynamically. Lightweight battery second. If you are serious, lose the side air bags and put some carbon fibre seats in the front.

If you got machine shop access and can get titanium stock, start swopping out steel parts against titanium - wheel hubs are a good palce to start. You can also hollow-drill all large bolts on the car.

If you want to keep a perfectly streetable car, stop there. Otherwise, get rid of the A/C and start stripping the sound deadening off the shell everywhere.

Maybe a carbonfibre dash replica would suit your needs. The only limits are saftey and your imagination.
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Old 07-18-2003, 02:48 PM   #9
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Interesting thing about the STi... There is no sound deadening in the shell.

Not in the areas I've seen at least: Passenger floor, under rear seat and the trunk floor.

Where the WRX had the typical semi flexible sound deadening material, the STi has just painted metal.

Imagine how heavy she'd be if they hadn't worked so hard on lightening her?

Russ
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Old 07-18-2003, 02:52 PM   #10
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If somebody really does do a significant weight loss job on an STI I hope they post their results on this board--especially if they keep the car looking pretty much stock. Would be a very interesting project, with tremendous potential gains in handling, braking, speed.
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Old 07-18-2003, 02:54 PM   #11
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Quote:
Originally posted by wrx what
WRX

Curb Weight (pounds) (w/Manual Transmission) 3085

WRX STi

Curb Weight (pounds) (w/Manual Transmission) 3263


The STi is 178 lbs heavier.

Remove your spare tire and jack for 42 lbs savings....
Thanks for that info.
That 178lbs is in the new 6spd drivetrain?


Other areas of weight savings would be seat replacement and more interior trimming.

I've been slowly putting my WRX wagon on a diet and just wanted to see what the current STi owners are up to.
My next step is to find a lighter battery and move it to the rear.
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Old 07-18-2003, 02:56 PM   #12
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Quote:
Originally posted by DucatiBoy


Thanks for that info.
That 178lbs is in the new 6spd drivetrain?


DCCD too maybe?
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Old 07-18-2003, 02:57 PM   #13
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Rather than approaching performance gains from a typical tuner perspective (i.e. more power), wouldn't it be nice to see a tuner concentrate on weight reduction performance enhancements. I'd much rather shell out for 300 lbs. lost weight than 100 extra horsepower in an STI. I think I know which one would be harder to achieve, too......
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Old 07-18-2003, 03:38 PM   #14
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Quote:
Originally posted by rlavalle
Interesting thing about the STi... There is no sound deadening in the shell.
Interesting and neat. I guess that's why some people whine about transmission noise in the STI.

Just tells you how hard they worked on the weight issue and how close we must be to a spec C shell. It will definitely make it harder to lose significant weight beyond stock, as there is not much excess.
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Old 07-18-2003, 03:40 PM   #15
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Weight reduction serves you best, when its from rotating mass. IE wheels and tires(often overlooked), brake discs, half shafts, driveshafts.

1) you save on drivetrainloss
2) your car weighs less
3) Life is easier on the transmission

Weighing less also is very important when it comes to cornering and braking. Which is why people love RX7s and miata's

I would start with lighter wheels and tires. 1, you get better looks, and hopefully better cornering from the tires(Toyo TS-1s will probably save you 3 lb per tire, and light wheels may save you 5 or 6). You will definatly feel 35lbs off your drivetrain(More than you would saving 100lbs in the car), esp on an AWD car.

You can probly sell your STi wheels+tires to WRX owners for $800 or so. So a lightweight wheel/tire combo would run $1200 or less(after $800 from selling your wheels)

Upgrading your discs to a drilled 2 piece will save 3-4lbs per caliper also. I think AEM will make them in the future. Best guess $350 per pair.

Half shaft and drive shafts will probably be made by someone in the future. But you should be weary that changing those could cost you your tranny warranty
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Old 07-18-2003, 03:56 PM   #16
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Selling the STi wheels will probably get more than $800. They are BBS Wheels that are pretty desirable. I know of one guy who sold his for $2300!

Russ
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Old 07-18-2003, 03:56 PM   #17
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I say you kick the bitch out of the passenger seat. That'll save you a couple.
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Old 07-18-2003, 03:59 PM   #18
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These are all very interesting suggestions.

One thing that happened to me as I was purchasing aftermarket performance parts for my WRX was that some of them tended to be heavier than the part that they replaced. For example I purchased a free flowing stainless muffler to find out it weighs a substantial amount more then the stock muffler. Still using the aftermarket muffler but now looking for something lighter. May have to get a mild steel or spring for the expensive titanium. Problem is many manufacturers of exhaust systems and other performance parts don't post how much their products weigh.
This is odd since weight is such an important parameter for all around performance.
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Old 07-18-2003, 04:12 PM   #19
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Titanium exhaust no cats will save atleast 25Lbs. only run 1/2 tank of fuel. I do not know what fuel weighs but I am sure it is around 8Lbs. a gal . Empty your intercooler sprayer and windshield washer that is probably another 3Gal. of liquid (24Lbs.)
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Old 07-18-2003, 04:13 PM   #20
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My ScoobySport Stainless Steel Muffler weighs 2 lbs less than the stock STi muffler.

Stock is 20 lbs. ScoobySport is 18 lbs.

Russ
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Old 07-18-2003, 04:26 PM   #21
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Quote:
Originally posted by DucatiBoy
That 178lbs is in the new 6spd drivetrain?
Also the extra half liter engine... and the LSD... and the DCCD and larger brakes and larger wing and additional body braces to reduce flex.
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Old 07-18-2003, 05:01 PM   #22
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The AVCS should be the only thing that adds wieght to the engine. The extra displacement is meaningless wieght wise as its still an EJ motor.
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Old 07-18-2003, 05:13 PM   #23
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The bigger engine should subtract weight from the STi. Bigger holes in the block = less metal.

Run on empty. Full tank of gas will weigh ~100 pounds.
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Old 07-18-2003, 05:22 PM   #24
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The transmission (R180 rear diff, DCCD+6MT) are the heavy bits.
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Old 07-18-2003, 05:34 PM   #25
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When reducing weight always try to get 2 positives out of a part instead of a + and a sacrifice with weight reduction.

I wouldn't hesitate one second to spend the extra money for a full Ti catless exhaust. This should save about 20lbs + add about 25HP

SS headers can also save weight from the heavy cast OEM parts + arguable HP gain

lightweight wheels, I lost about 2lbs per wheel with my volks (8lbs off of drivetrain)

lightweight pully. The STI has even more weight bolted to the crank pulley compared to the WRX (there are 2 different views to this though) 6lbs savings

lightweight rotors. stockers are extremely heavy, but no light replacements available now

lightweight battery located in trunk

Outside of these, it is very hard to justify the money / sacrifice.
If you are willing to "race prep" the interior then go right ahead, but you are probally only looking at about 70lbs savings with a huge sacrifice. Traveling without a spare is always a gambling proposition.
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