HF: I was born in Japan in 1952. I earned BE from Meijo University in Nagoya Japan. Before the MK III GTP work, I had engaged in the aerodynamic design and development of the Toyota Celica IMSA GTUs, GTOs, MK I GTP, MK II GTP, and ‘83, ‘84, ‘85 and ‘86 Eagle Indy cars. Currently I am working on motorcycle wind tunnel testing at AAR.
In my childhood, I had strong interest in vehicle's mechanism and competitions. These two strong interests lead me to design, build, and race with cars.
race car design engineer, my first
job was with Dome Co., Ltd. in Japan.
MC: What was your specific role in the development of the Toyota Eagle MkIII?
to the use of the first 20% scale wind tunnel models, I was designing
and external aerodynamics devices, designing and building wind tunnel
and wind tunnel testing. After the first 20% scale model wind tunnel
was completed, AAR established a model shop to build wind tunnel models
under my management.
MC: What is your design philosophy? How do you start when given a clean sheet of paper?
design philosophy are that the design with simple, effective, timely,
and with minimum compromise. When I have a clean sheet of
first I will list all ideas from existing data, experienced information
and educated guesses. Then I will make a layout drawing to
all of my ideas, within the regulations required, with my
of the regulations. Based on this layout, I will then design
specific wind tunnel model and build all the parts necessary for the
tunnel tests. The wind tunnel test results will give the answer to
design of the car. This sequence is repeated until we obtain
MC: How did you tackle the wind tunnel testing of the Toyota MkIII, what scale and in what type of facility (rolling road or fixed floor, etc.)?
we used a our in-house, closed test section and the rolling road, 10%
wind tunnel, that was originally built in 1979. The first MK
GTP wind tunnel test also utilized this same 10% wind tunnel. Then we
a 25% scale wind tunnel for the further evolutions of the MK III GTPs
20% scale wind tunnel models until end of the IMSA GTP series. The 25%
wind tunnel had an open jet test section with rolling road also.
MC: The MkIII first debuted with a relatively standard rear wing architecture (double element, low wing position, very large endplates). What was the immediate benefit of going to the "Red Baron" twin tiered, double element rear wing ala the Jaguar XJR-14?
immediate benefit was a reduction of the drag for the same level of
and aerodynamic balance. With the Bi-plane rear wing, the MK III
18% more downforce than the standard MK III (at equal aero. balance
MC: The MkIII's aerodynamic concepts are quite unique compared to many of its contemporaries. For example, the MkIII's front underbody solution was very unique and, it might even be said, inspired today's generation of LMP racecars. What were the inspirations for the design of the MkIII?
aerodynamics design of the MK III was the evolution of the accumulation
of the knowledge and experience from Indy cars, IMSA GTUs, and GTOs.
MK III’s front underbody preceded the evolutions from IMSA GTU front
AAR's IMSA GTU had small primary version front under body panel. The
version of AAR's IMSA GTO had a front underbody similar to MK
Also, the MK III's diffuser tunnel design employed the knowledge from
experience with Indy cars. We didn't miss any good ideas to
at that time but we may have further pursued development of the vortex
MC: How much downforce and drag did the MkIII generate? How did the MkIII compare the preceding MkII?
on the 20% scale model wind tunnel test data, the MK III, as debuted,
6760 lbs. of downforce and 1652 lbs. of drag at 200 mph. For
the last MK II made 6569 lbs. of downforce and 1721 lbs. of
at 200 mph.
MC: The MkIII appeared with subtle alterations over the several years it raced (1991 through 1993). How did the car evolve? Did downforce increase substantially from '91 to '93?
continuous evolution of the race cars is one of AAR's philosophy. After
the successful debut of the MK III, we were still look for more
and lower drag. The first major evolution was a rearrangement of the
package. The turbo air intake moved to the inside of the intercooler
duct to eliminate the periscope type air intake for reduction of the
The second major evolution was the adoption of the Bi-plane rear wing
front nose winglet alternations. The standard rear winged MK III made
lbs. of down force at 200 mph. The Bi-plane rear winged MK
equal drag configurations to the standard MkIII, generated 7220 lbs. of
downforce at 200 mph. Those forces figure are from the 20%
wind tunnel data, though the onboard data acquisition system data
considerably larger number than the wind tunnel data. The
winged MkIII developed 9275 lbs. in peak downforce
for a L/D of 4.42:1.
MC: It has been nearly ten years since the MkIII raced. What are your reflective thoughts about that project and that era of racing?
HF: It may be one of the most enjoy full moment in my life and it was close to my childhood dream.