Dai Yoshihara's 2018 Formula Drift Rebuild

by Mike Kojima


After 3 years of Formula Drift competition, our team had pretty much developed the BRZ chassis to where we were satisfied with its performance. After some post-season testing to try out a few new ideas we decided that with the development stable, it was time to completely go through the car, repair some minor damage incurred during three seasons of hard use and to rethink the car's layout.

Our goals were to make the car simpler, stiffer, easier to maintain and repair and possibly lighter.  To do this the right way required that we strip the car down and clean things up from the ground up with a fresh group of eyes.

We decided that we were completely satisfied with engine development and no changes were being made except for some minor changes to improve oiling to the top end. The MotoIQ Garage derived engine has proven to be very reliable with great power and response and a very wide powerband. All the work will be focused on the chassis.


Eimer Engineering first stripped the car to a bare shell and sent the unibody out to be chemically dipped. 

Dipping involves soaking the shell in tanks of various stuff. Dipping completely removes all paint, undercoating and seam sealer. This can end up weighing a significant amount. 


After being soaked in a tank of stripper, the unibody is washed then soaked in a neutralizing bath, which deactivates acids found in the stripper. This is needed to prevent the unibody rusting from the inside out.

After neutralizing, the unibody sits in a tank to get iron phosphate coated. This is a surface conversion process where the steel gets covered with a layer of iron phosphate. This is somewhat corrosion resistant and has a toothy surface that is good for the paint to stick to. It also welds decently.  

In some areas, a little bit of chemicals continued to seep out and cause the white staining, but we used a bottle of the phosphating solution to neutralize and clean it up.


Previously, the unibody had been cut back to the limit of the rules and the quarter panels cut back to the limit of the rules to install overfenders. 

Doing this makes the car much easier to repair if there is incidental contact during competition. No changes here, except for welding up the holes for the nutserts for the overfenders so new nutserts could be installed in fresh holes. The edges of the 1/4 panels had gotten a little bent over the years, so they were straightened out with some minor sheetmetal work.

Dai drives really well, so there was little damage to the unibody. The framerails were dented in a few places under the sideskirts, and the quarter panels dented under the overfenders in a couple of spots. Chris Eimer spent some time repairing these areas either with a little sheetmetal work or cutting the damaged areas out and welding in new sheetmetal. 

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Thursday, February 08, 2018 7:41 AM
With the car stripped down like this I thought it was a Mustang at first.
Thursday, February 08, 2018 10:25 AM
haha, me too!
Thursday, February 08, 2018 12:32 PM
"Dipping completely removes all paint, undercoating and seam sealer. This can end up weighing a significant amount. "

I'd be curious if this car was weighed before and after to see what the difference was and then after it was painted again to see the difference.

in the chase for saving every last ounce possible from a car build i'm curious if this kind of treatment is worth the cost over removing the sound deadening the old fashioned way.
Thursday, February 08, 2018 1:30 PM
It's at the very least worth the cost of inhaling the horrible fumes of seam sealer while stitch welding a chassis. I wish I could find a place in New England that did this. We can have things media blasted but I'd rather a chemical bath if it were an option.
Mike Kojima
Mike Kojimalink
Thursday, February 08, 2018 1:47 PM
Our car is overweight for the tire size classification by about 50 lbs so we were not worried and hence didnt weigh the car unibody
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