So I was watching an Evo X review video on youtube when I heard the reviewer mention that the Evo X was so nimble despite its 3510 lbs weight. And that got me thinking, how did they manage that?

So I started digging.

The Evo X has a weight distribution (w/d) of 57/43%.

The 2015 STi has a w/d of 60/40? I’m not sure… the VA WRX is listed at 60/40% so I am assuming the STi will be around that same mark. The 2005 STi is at 58/42% and the 2003 WRX is at 59/41%. Interestingly enough my old 2009 WRX had a w/d of 57/43% and it was the most understeering car of the bunch.

So obviously w/d isn’t the only thing to affect the handling of these cars but I prefer overall neutral handling. And after a few mods to the chassis/suspension, that understeering 2009 WRX became somewhat neutral, at least until I discovered it’s ability to snap oversteer. 😦

At which point I moved on to the 2005 STi which had a tendency to oversteer as well. Rear bracing, potentially a rear diffuser, springs, and a carbon fiber driveshaft made it a great handling car. And I would be lying if I said I did those mods for the purpose of handling. I was chasing something else and noticed the added handling benefits after installation.

I have been trying to track all of my changes so far and I have a estimated w/d of… 59/41%??? WTF? What gives? That’s pretty close to stock! Well looking at my table I removed about 17 lbs from the rear of the car (exhaust, wing delete) and added 10 lbs to the front with the Grimmspeed TMIC. Doing the opposite of my goals. Now the wing delete is temporary, I am waiting for an STi wing (17 lbs) to cross my path at a reasonable price.

Item  Front (lbs) Rear (lbs) Total
Weight
(lbs)
Front
Chg (lbs)
Rear
Chg (lbs)
Front% Rear%
Stock 1820 1255 3075 59.19% 40.81%
WRX Wing Delete 1820 1248 3068 0 -7 59.32% 40.68%
Genome Axle Back 1820 1238 3058 0 -10 59.52% 40.48%
Fog Light Delete 1817 1238 3055 -3 0 59.48% 40.52%
Grimmspeed TMIC 1827 1238 3065 10 0 59.61% 40.39%
Rota Tarmac II (17×7.5) 1830 1241 3071 3 3 59.59% 40.41%
Grimmspeed LW Pulley 1826.5 1241 3067.5 -3.5 0 59.54% 40.46%
Fuel Injector Brackets 1823.5 1241 3064.5 -3 0 59.50% 40.50%
Intake Silencer Delete 1822.5 1241 3063.5 -1 0 59.49% 40.51%
Turbo Heat Shield 1821 1241 3062 -1.5 0 59.47% 40.53%
Turbo Blanket 1822 1241 3063 1 0 59.48% 40.52%
Oswald Lightweight Front Bumper Beam 1801 1241 3042 -21 0 59.20% 40.80%
Current Weight (Est) 1801 1241 3042 0 0 59.20% 40.80%

 

However moving the battery to the trunk will get me a w/d of 58/42%. And that’s pretty much where the big gains end. Not that big gains are needed to produce results in handling. The Oswald Lightweight Bumper Beam made a difference that I have already grown used to.

It also matters where the weight is located within the two halves of the car. Weight out at the ends of the car will have a greater impact than weight located in between or near the axles. Which would explain why the bumper beam and even the lightweight crank pulley had an affect on the front end’s improved responsiveness. So even if I don’t hit my goal of 55/45%, moving weight closer to the center and lower in the chassis will give the benefits I am seeking without actually hitting the numerical goal.

With that said I do plan to put my battery and washer fluid tank in the trunk. Mostly for w/d reasons but also to clean up my engine bay. The GD engine bay is pretty packed to the gills with stuff. The more stuff I can remove or relocate for a cleaner bay while improving handling is a win-win in my book.

Here is a great video explaining weight distribution and why 50/50 w/d might not be perfect for everyone. As with most car mods it comes down to personal preference.

 

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