Dai Yoshihara's 2018 Formula Drift Rebuild Conclusion

by Mike Kojima


So if you have been following along with our mini-series on what an end of season refresh on Pro Formula Drift car looks like, you have followed us from stripping the car to a bare chassis, to additional updates, and lastly, the final assembly of the car.

Now the car is together and has run its first event in Long Beach. So, you can now take a look at what the final product looks like!

Check out Part One

Part Two is here!


The interior is clean and simple. A Sparco Circuit seat is used with a 6-point Hans compatible harness. Dai is super picky about his steering wheel, and an R 368 wheel has the just right diameter, rim size and dish for him. 

A Wilwood Pedal box is used. Since all of the fluid lines for the dry sump system and cooling system are run on the driver's side, a double floor is used. The upper floor panel is carbon fiber for light weight.

The battery and heat exchangers, as well as the dry sump tank, have to be separated from the interior of the car by a bulkhead. We call this compartment the oven! The oven was made out of aluminum paneling, but it was redone in carbon fiber to save some weight.

Over the past few years, the car has lost about 160 lbs from when it was first built. Currently, it is only about 40 lbs overweight.


Eimer Engineering built the rear drift brake assembly and steering column. 

A Long shifter throws the super strong, fast shifting 4-speed G-Force GSR dog engagement transmission.


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Wednesday, April 11, 2018 12:59 AM
If you have a chance during testing or practice, it would be worthwhile to take some surface pressure measurements on the car, that would give you an idea of great areas do to ducting for the radiator.
Wednesday, April 11, 2018 9:43 AM
Hey, first I must say the car looks amazing!

one question I have is as you mentioned the cooling of the waste-gates, what is the thought of not running actively cooled gates? Is the only reason added complexity, I would believe that would remove the issue.
Wednesday, April 11, 2018 2:02 PM
I saw during Formula D Long Beach what looked like heavy work was being done to the car...what happened? Did the clutch go out?
Mike Kojima
Mike Kojimalink
Wednesday, April 11, 2018 5:13 PM
Ztaal3-the wastegates are air cooled, competition cars are not like street cars so the duty cycle of the wastegate is way more extreme so cooling is an issue. The diaphragm is susceptible to heat damage if the wastegate is in an area where it heat soaks badly.

Tofu-Man- We broke the tip of the input shaft where it goes into the pilot bearing. The input shaft was whipping around and made the clutch stick. It was a weird failure that none of us ever experienced. All of the dowels were in place and we can't figure out how enough side stress was generated for that to happen. We were very lucky that Kyle Mohan spun, the car was seconds away from losing its drive.
Thursday, April 12, 2018 11:40 AM
Mike- Yeah I know that it is air cooled, I was wondering if you couldn't run a watercooled wastegate to reduce the heat better. Also if there was a reason for not going with a watercooled one.
Mike Kojima
Mike Kojimalink
Thursday, April 12, 2018 11:47 AM
Ztaa13, the better solution is to move the wastegate a little like what we did so water cooling isn't needed. For race cars, you never want to add things which mean weight, unnecessary complexity and failure points unless there is no other solution.
Thursday, April 12, 2018 7:02 PM
Mike - Can you explain what you meant by header dimensions? Were you talking about runner length and diameter for exhaust tuning? If so, do you see any benefits to exhaust tuning on a turbo application? Do these benefits outweigh the added weight and increased manifold volume (response time)?
Mike Kojima
Mike Kojimalink
Monday, April 16, 2018 5:04 PM
Runner length, diameter, secondary diameters and length. Exhaust makes a big difference on turbo motors, the tuned length gets shorter with a turbo engine due to the higher pressure and temperature in the manifold. A properly tuned header actually makes the turbo response faster.
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