Thursday, February 28, 2013

"The One-Wheeler-Peeler", part 1

By: David Corsaro

Well, the Evo X was sold back in November to make way for an even more potent vehicle... a 2012 Toyota Yaris! 

Okay not entirely true- the Yaris is a tad slower and it wasn't meant to replace the Evo. 
This five door dorkfest is my daily driver. 

Being the SE version, it gets a good number of upgrades over a base Yaris including four wheel disc brakes, a quicker steering rack, and 16" alloys for starters.  I also topped out at over 41mpg driving to Lincoln last year... on Dunlop Star Specs. 


But can it be fun to drive? Yeah, but not without tinkering.

The first modifications were Tokico HTS shocks and struts and an Ultra Racing 23mm rear bar to help restrict the rear torsion beam from twisting. Crash bolts were added to the front struts for extra negative camber.

Almost on two wheels... let's see if I can keep it on the ground this year.
Adding the ever-proven Dunlop Z1 Star Specs in 205/50/16 on the stock 16" x 6" wheels provided much needed grip over the stock tires. 

Just these few simple changes helped the Yaris nip at the heels of a couple of very well-driven Minis at our local autocross... 0.5 to 1 second behind on a 60 second course. 

Close, but still an eternity in autocross terms.

Clearly the Yaris' biggest flaws are large amounts of body roll coupled with an open front differential. To be fast with these cars will require maintaining momentum, increasing composure and avoid spinning the inside front tire which just wastes energy and adds seconds. To do all of this however requires modifications that will bump the Yaris to one of the newest classes in SCCA's Solo program- Street Touring FWD. 

While still only a supplemental class, it has seen moderate support at the national level and a little better support at the regional level. The majority of experienced autocrossers prefer to drive vehicles that are proven winners in their respective classes. There are a few exceptions, those willing to drive cars that are considered shitboxes within the sport. I am one of those exceptions because I will race anything... but it should be fun to drive too. 

The most difficult task in preparing a vehicle for double duty is keeping a streetable ride for commuting during the week while having a competitive car for the weekend.

Having run Star Specs on five different cars since 2008, I have decided to go with Dunlop's newest creation, the ZII. I am going to start the year on shaved 225/45/16 for the fronts and will be using up my old shaved Z1s in 205/50/16 out back.
Like the Z1, the ZII maintains the ability to flipped inside to outside and consequently LF to RF, LR to RR... rewarding competitors with longer tire life. Less siping on the outer treadblocks should lead to higher grip levels than the Z1.

Ever since owning a Championship White 1998 Integra Type R several years ago, I have always had a soft spot for white cars on white wheels. Can't wait to see them on the car!

The wheels are Kosei K4Rs that I had powdercoated, in size 16" x 7.5" for the fronts, 16" x 6.5" for the rear. 
They weigh in at 13.6 lbs and 12.8 lbs respectively.

The idea behind the heavy stagger is that I did not need, or want, as much grip in the rear as it would be counter-productive in really getting this car turned in and exiting out as efficiently as possible.

 Here is what will tie it all together, literally. Cusco's trick aluminum strut tops(right) with integrated bearing and Whiteline's front control arm bushings(left).

The OEM upper strut bearing on the Yaris uses a pathetic 'bobble' strut top design, meaning that a spongy rubber-isolated bearing is merely sitting into a cup from beneath the chassis. 

Hit a bump, and the car virtually unloads itself off of the bearing since it is not in any way fastened to the car. 

Dive hard into a corner? Mush-fest, camber-loss city. 

The design of the Cuscos fasten the top of the strut to the vehicle's chassis. This will not only allow the springs and struts to do their job as God intended by it will also help maintain front camber a shit-ton better. 

Whiteline's inner bushings for the front control arm will help maintain toe settings as well as caster/camber to an extent. 

The polyurethane control arm bushings also have a side-benefit of controlling wheel hop. This is a big problem for most front-wheel-drive cars with sticky tires. 

I have already started to tackle the chore of locking down the front end by installing custom delrin inserts I fabbed up for the engine and transmission mounts seen above and on the left.

The passenger side mount(not pictured) is now solid steel. 

Next up on the list was probably the most surprising of all... aluminum pulleys. Upon receiving them I verified their total weight at 22.675 oz total. Pretty damn light. 
The steel OEM pulleys weighed in at a shade over 68 oz, so a total savings of over 45 oz or just under 3lbs. My highly calibrated butt dyno witnessed quicker acceleration from a stop and better pull in gear at low rpms. Well worth the money and time to install.

Crankshaft, water pump and alternator pulleys from NST.

In the coming weeks, I'll be continuing to remove weight legally from all areas of the car on the cheap. I have yet to share what I've done for springs and roll control but I am pretty close to getting the suspension to where I want it to be, and while it is a little unorthodox, I feel that it is capable. Think NASCAR or dirt track hillbilly stuff. 

To be continued...

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