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Discussion Starter · #1 ·
I've been mulling this over of late and have come up w/ a few thoughts. A few facts first- the WRX sedan weighs 3130- that's w/ full fluids, no driver. The weight distribution is 59/41 f/r. Add a 190 lb driver (I'm not overweight honest) and your looking at 3320 and a weight distribution of ~ 61/39.

While not realistic to ever get a 50/50 f/r (for us anyways), lightening our load and/or redistributing our weight can be very beneficial.

We can do some easy things when heading to the "track", lightening our fuel load will shed 6 lbs/gal, going w/ a 1/4 tank sheds ~ 100lbs.

Removing the spare/jack/tool bag/cover nets another ~ 35 lbs. Floor mats ~ 4lbs.

A "typical" catless exhaust (including) uppipe will shed ~ 25 lbs, titanium even more.

Very worthwhile is to shed unsprung weight, you gain the obvious weight loss, but even more importantly your suspension works more efficiently translating into more grip.

Lightweight 16/17" rims can shed 5lbs/corner. Lighter tires can shed another lb or two over oe/corner. Lightweight lug nuts another 1/4 lb/corner. That's ~ 25lbs additonal weight gone (+ the bigger bonus of unsprung weight).

Many coilover setups are a couple of lbs/corner lighter than the oe strut/spring setup.

Brake upgrades frequently utilize aluminum calipers which can shed 5lbs/caliper front, 2-3 lbs rear. Using two piece rotors w/ aluminum hats can shed a couple of lbs as well- even when going up in rotor diameter.

Aluminum control arms only shed ~ 1lb/side, but their real benefit is being significantly stiffer than the oe stamped steel ones, still 2lbs and it's unsprung weight.

In my case (don't have coilovers, am only upgrading front brakes and have added ~ 2lbs in the rear w/ larger dia rotors), thus far I've shed right at 200 lbs, 37 lbs coming in the form of unsprung weight. That puts the weight of the car at ~ 3120 w/ driver (honest I'm not overweight at 190 lbs).

Here's the things I'm thinking about doing:

Relocating/replacing my battery w/ an Odyessey one ~ 13lbs + 2 lbs of wire and moving it to under my passenger seat. The stocker weighs 31lbs and this moves the weight back a bit further and to the opposite side.

Removing fog lamps ~ 4lbs, I do this anyways as that's where I source air for my brake duct setup-which weighs ~ 2lbs, net 2 lb loss.

Removing the subframe ~ 30 lbs and utilzing a lower arm bar, couple of lbs. This one has my head scratching as it possibly contributes to chassiss rigidity, particularily fore and aft. On the other hand the RA comes w/o the subframe (does have a oe lower arm bar) and not many complain of the handling of the RA.

Another option is the Do Luck subframe- aluminum weighs ~ 6lbs and would be as rigid (or possibly even more) than the oe subframe. This piece is a little cost prohibitive @ $500!

Either way the subframe will likely be dumped.

JDM bumper beams, weight savings of ~ 20lbs each. The front would be more benficial than the rear- distribution wise. Trade off, less protection in low speed, (0-10mph) crashes equates to more costly repair bills.

Am leaning on doing the front.

"Race" seats, can't do full blown ones need to have comfortable/reclining ones. Still can shed ~ 10 lbs/seat w/ this type (Sparco Torrino for example), obviously more w/ real race buckets.

I'm considering lightening up my stereo by relocating the oe sub under the drivers seat (my battery is going under the passenger) and attaching via velcro and taking it out on track days. Sub weighs ~ 5lbs.

What I'm not willing to do, but would save substantial weight is removing all AC components, removing all stereo components, rear seats and quite a few other "creature comforts".

Still, all in all, w/ the battery, sub removed, fogs removed, subframe removed (+ weight of lower arm bar or Do Luck), front JDM bumper beam, Sparco Torrinos- I'd be looking at ~ another 87 lbs- alot of up front.

Here's some weights of many oe items:http://www.oakos.com/wrx/weights.htm

Like to hear what others have done to lower/redistribute weight.

The rambler aka Big Sky
 

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Complete glove box assembly-10lbs(easy to do)

Rear seats and seat belt tensioners- 40-45lbs

Completely gut trunk of add. carpet,side panels, and insulation-10-12lbs + other trunk items you mentioned.

I've been contemplating a cage and figured out I could shed the xtra weight by doing the previous along w/ the other items you mentioned. I removed the glove box assy. today to access the filter and was amazed at how much it weighed. Some cages require removal of glove box anyway. 5min to do.

:)
 

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Big Sky:

Recent careful research indicates that 60 lbs saved (on our general class of vehicle) equates to 1/10 sec reduction in the quarter (not 100 lbs as postulated for the old Detroit musclecars).

Incidently 4hp also equates to a 1/10 sec reduction in the quarter.

For every 10 degree F increase or decrease in temperature (predicated upon a standard day of 68 F) 3hp is lost or gained.

Anybody know the correction for altitude and or air density?

And yep, weight really is the enemy of speed. :cool:
 

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Big Sky WRX said:
I've been mulling this over of late and have come up w/ a few thoughts. A few facts first- the WRX sedan weighs 3130- that's w/ full fluids, no driver. The weight distribution is 59/41 f/r. Add a 190 lb driver (I'm not overweight honest) and your looking at 3320 and a weight distribution of ~ 61/39.

While not realistic to ever get a 50/50 f/r (for us anyways), lightening our load and/or redistributing our weight can be very beneficial.

We can do some easy things when heading to the "track", lightening our fuel load will shed 6 lbs/gal, going w/ a 1/4 tank sheds ~ 100lbs.

Removing the spare/jack/tool bag/cover nets another ~ 35 lbs. Floor mats ~ 4lbs.

A "typical" catless exhaust (including) uppipe will shed ~ 25 lbs, titanium even more.

Very worthwhile is to shed unsprung weight, you gain the obvious weight loss, but even more importantly your suspension works more efficiently translating into more grip.

Lightweight 16/17" rims can shed 5lbs/corner. Lighter tires can shed another lb or two over oe/corner. Lightweight lug nuts another 1/4 lb/corner. That's ~ 25lbs additonal weight gone (+ the bigger bonus of unsprung weight).

Many coilover setups are a couple of lbs/corner lighter than the oe strut/spring setup.

Brake upgrades frequently utilize aluminum calipers which can shed 5lbs/caliper front, 2-3 lbs rear. Using two piece rotors w/ aluminum hats can shed a couple of lbs as well- even when going up in rotor diameter.

Aluminum control arms only shed ~ 1lb/side, but their real benefit is being significantly stiffer than the oe stamped steel ones, still 2lbs and it's unsprung weight.

In my case (don't have coilovers, am only upgrading front brakes and have added ~ 2lbs in the rear w/ larger dia rotors), thus far I've shed right at 200 lbs, 37 lbs coming in the form of unsprung weight. That puts the weight of the car at ~ 3120 w/ driver (honest I'm not overweight at 190 lbs).

Here's the things I'm thinking about doing:

Relocating/replacing my battery w/ an Odyessey one ~ 13lbs + 2 lbs of wire and moving it to under my passenger seat. The stocker weighs 31lbs and this moves the weight back a bit further and to the opposite side.

Removing fog lamps ~ 4lbs, I do this anyways as that's where I source air for my brake duct setup-which weighs ~ 2lbs, net 2 lb loss.

Removing the subframe ~ 30 lbs and utilzing a lower arm bar, couple of lbs. This one has my head scratching as it possibly contributes to chassiss rigidity, particularily fore and aft. On the other hand the RA comes w/o the subframe (does have a oe lower arm bar) and not many complain of the handling of the RA.

Another option is the Do Luck subframe- aluminum weighs ~ 6lbs and would be as rigid (or possibly even more) than the oe subframe. This piece is a little cost prohibitive @ $500!

Either way the subframe will likely be dumped.

JDM bumper beams, weight savings of ~ 20lbs each. The front would be more benficial than the rear- distribution wise. Trade off, less protection in low speed, (0-10mph) crashes equates to more costly repair bills.

Am leaning on doing the front.

"Race" seats, can't do full blown ones need to have comfortable/reclining ones. Still can shed ~ 10 lbs/seat w/ this type (Sparco Torrino for example), obviously more w/ real race buckets.

I'm considering lightening up my stereo by relocating the oe sub under the drivers seat (my battery is going under the passenger) and attaching via velcro and taking it out on track days. Sub weighs ~ 5lbs.

What I'm not willing to do, but would save substantial weight is removing all AC components, removing all stereo components, rear seats and quite a few other "creature comforts".

Still, all in all, w/ the battery, sub removed, fogs removed, subframe removed (+ weight of lower arm bar or Do Luck), front JDM bumper beam, Sparco Torrinos- I'd be looking at ~ another 87 lbs- alot of up front.

Here's some weights of many oe items:http://www.oakos.com/wrx/weights.htm

Like to hear what others have done to lower/redistribute weight.

The rambler aka Big Sky


Thats alot of weight to shed. what about lexan?
 

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well, i'd rather run a 13.1 with a full interior than 12.99 with a stripped interior, no AC and no power steering
 

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Shibby said:
well, i'd rather run a 13.1 with a full interior than 12.99 with a stripped interior, no AC and no power steering
Agreed. Or even better, a 12.97 with full interior...and hey...how about no weight reduction?;) Better yet, how about a 13.1 with baby seat in the back?:eek: Yep...did that too.

I admire the amount of thought that goes into the weight reduction issues. I'm assuming you are considering this for road coarse/solo II running? One question though. Why not move the battery all the way to the trunk? Wouldn't that allow for better weight distribution? Oh...almost forgot....here's one my dad used to joke with...helium in your tires!!:tongue:
 

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Excellent post Big Sky.

I haven't done ANY weight reduction really. Intake silencer removal, and turboback ;). I have done any addition either though :).
 

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Shard said:
:rotfl:

That would be cool if it worked.
Technically...it does. Worth the hastle though? Doubt it. Plus, I believe helium expands and contracts more with temp diff...so would be harder to adjust. look at me...discussing the physics of helium in a tire....sheesh...time for bed!!
 

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YBNormal07 said:
Technically...it does. Worth the hastle though? Doubt it. Plus, I believe helium expands and contracts more with temp diff...so would be harder to adjust. look at me...discussing the physics of helium in a tire....sheesh...time for bed!!
haha, no joke, good NIGHT.
 

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Discussion Starter · #12 ·
Yes- my weight goals are aimed towards track/autox, although I do have the goal to hit a new 1320' track nearby this year, just to say I've done it.

Moving the battery clear to the back would help more w/ distribution, but you also trade off the weight of additional wire (remembering that the further it has to travel the heavier the gauge needed).

As I live in a very cold clime, this battery would only serve in the spring/summer/early fall- I'll have quick disconnects on it so I can easily take it out/put it in.

As this is a daily driver (the boss's to boot!;) ), I have to temper my weight reduction w/ reality. At some point I'll get her a new car (she loves Mini's), then I'll be dedicating this more seriously. At that time I would consider the Autopower four point roll cage as well.

Speaking of glass, evidently some STi trims came w/ much lighter glass in the rear- where there is little to no chance of rocks getting it. There is an outfit that sells Lexan pieces that fit our car, no idea on price, but the rear compartment and rear window would be viable places to consider. Lexan scratches pretty easy, thus not a real option for front or front sides (for me anyways).

neverending mods- are you talking about some metal in the glove box or getting rid of the glove box entirely- mine would have to stay, but I have heard of some metal pieces in the center console and glove box that would shed a few lbs.

Big Sky
 

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Hey Im not sure what class you are running now in soloII but putting the battery under the passenger seat is illegal in SP and ST classes I believe. You can relocate them but it has to be out of the passenger compartement(AKA behind the rear seats).
 

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Well I looked it up http://moutons.org/sccasolo/Rules/street_modified.html Says all street prepared mods are legal plus what is listed on that page. The SP ruling is it has to be in the trunk.

As for more weight reduction, you could do hollow swaybars, take out some sound deadening, the front jackpoint under the engine serves no other purpose, CF trunk/no wing, get steeringwheel with no airbag, and take out all the little metal peices in various areas of the car(as in behind the glove box, under the center console, crossbeam under steeringwheel etc..) Oh and I have not found anything that says the subframe is for structuall ridgity. If you take it of you can actually flex it in your hand, AFAIK its just for crash protection and the car handles just fine without it.
 

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Discussion Starter · #16 ·
I read the SP rule and was probably "stretching" the SM rule that says drivetrain, "ignition"- free, battery = ignition= stretch probably.

While the subframe is flexible, you can bend the U. It probably prevents some fore/aft movement as it is tied into the front cross member. Gary S has retained his, as this was his thought on the subframe.

I have since found out that the JDM STi (and WRX) has the subframe, but the RA and spec C do not. This could be done for weight savings (as many of these cars are detined for rally and will be seam welded anyways), but on the other hand I haven't heard of anyone complaining on the handling of the oem RA either.

It doesn't take that long to remove it, it would be worth doing some testing w/ it on a track- lap times and pyrometer readings should reveal whether it's worthwhile to keep it or not. Unfortunatley for me, the nearest road track is 800 miles away.

Big Sky
 

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YBNormal07 said:
helium in your tires!!
While I realize that this was a joke, helium would go right throught the rubber in your tires. You'd have to refill your tires often.

As for, "Incidently 4hp also equates to a 1/10 sec reduction in the quarter.", this suggests that a 40hp increase will give you a second in the quarter and that with an 80 hp increase, you will be in the low 12's. I'm guessing that you need more than 4hp for a 1/10th reduction in the quarter.
 

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Discussion Starter · #18 ·
For the drag guys it appears that 50 lbs loss yields ~ .07 in time lowered.

This also equates to ~ 5 hp for every 50 lbs shed.

This is using a car at our weight and ~ 300 hp crank.

3320 lbs w/ 300 hp (crank) ~ 13.8
3270 lbs ~13.73
3220 lbs ~13.66
3170 lbs ~13.59
3120 lbs ~13.51

3320 lbs w/ 305 hp ~13.72
3270 lbs w/ 305 hp ~13.66
and etc

3320 lbs w/ 320 hp ~13.51 same as 3120 lb car w/ 300 hp


The relationship seems to hold pretty good.

Here's a site you can play w/ (make sure to add drivers weight):

http://www.discountpartcenter.com/milecal.html?lbs=3320&hp=320&submit=Get+Results

Big Sky
 

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Big Sky and Rich 10:

Hmmmm....interesting. Here is what we know with a fair degree of certainty:

A 3085 lb Rex with 227 hp typically runs the 1/4 in 14.4
A 3263 lb STI with 300 hp typically runs the 1/4 in 13.2

So...assuming same driver weight, the Rex has a 178 lb wt advantage or (at 60lbs/1/10 sec) for the same 1/4 time the STI is going to need 12 hp more or 239 hp to run with the Rex.

The STI, of course has 300 hp; therefore 300-239=61 hp so
61 hp divided by five hp per 1/10 second = 1.2 sec.

Therefore 14.4 - 1.2 = 13.2 seconds for the STI which is exactly what it does. So 5 (flywheel hp) per 1/10 sec is more accurate than 4 hp per 1/10.

However, as 1/4 mi times drop into the elevens and twelves the equasion seems to lose a fair amount of it's accuracy. :cool:
 

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Geekqualizer said:
However, as 1/4 mi times drop into the elevens and twelves the equasion seems to lose a fair amount of it's accuracy. :cool:
It seems that tuned TurboXS Stage 4 cars that have near 300whp (lets estimate 350 crank hp) are running mid to high twelve's. Since they have approximately 120 crank hp more than a stock wrx, the original formula would have them running a quarter mile time three seconds less than a stock WRX. This would be a time of low 11's.

Even a TurboXS stage 3 which has a claimed crank hp of approximately 80 more than stock would run low 12's according to the formula. I believe that they are running low 13's.

I don't know what the accurate figure is or at what point the equation would change. I just thought that the formula seemed to suggest too great a quarter mile benefit for a given hp change. YMMV.
 
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