「A 500+ hp Diamante Appears!」Highway Battle Scars Reveal the True Intensity of This Expressway Runner! [OPTION Back Number]

Published : 2020/03/20 23:56 Modified : 2020/03/23 00:06

This is one of those mysterious cars that creep out from the woodwork at midnight to play on the Tokyo Metropolitan Expressway loop. It is an attack machine based on a rare Mitsubishi Diamante. It has been modified to be a true highway monster. (Excerpt from OPTION Magazine, August 2001 Issue)



An FF machine with over 500hp! A serious C1 highway runner built by super tuners JUN!


Using ultra rare parts that are all out of production?!


This Diamante boasts an amazing 500+ hp in an FF setup. The front bumper pockmarked by road debris tells the story of this speed demon. This car debuted during the bubble era in Japan when manufacturers were producing high-end sports sedans. The owner originally wanted to buy a Celsior but when faced with a seven month waiting period, he chose this Diamante which was immediately available.


The car was capable of more than sufficient speed after removing the limiter, but after getting defeated by a Porsche on the Wangan, the desire for heavier tuning was hard to shake. The owner then brought the car to super tuning factory JUN for a power-up.



There were little to no tuning parts available for the Diamante and it was said that JUN initially refused to accept the job. However, when only the turbo setting was done by another shop, the tuning potential was higher than expected and JUN agreed to take the challenge.


The base engine is a 2972cc 6G72 V6. GTO 91.6φ oversize pistons were incorporated to bring it up to 3005cc and cams were machined to provide high lift. The engine was strengthened on the premise of a turbo conversion.



The turbo started as an RHC6 with 300ps. In search if more power, upgrades led to a K27, K27.2, K27MOJ and finally a K27-3476HHB which is more or less a full racing spec turbo. Boost at 1.4kg is 600ps but practical balance was pursued running regularly at a boost pressure of 1.2kg at 500ps.



Additional injectors in the intake manifold tell of the power this car has. The capacity is 350cc x 6 for the main, 350cc x 6 for additional and one for 550cc. A PFC F-CON manages base fuel control. The exhaust manifold is extended from each bank. The engine room is fully packed.



The hood duct is a necessary modification because the engine is packed with high power parts. The air which flows in from the front bumper inlet is forcibly extracted.



Since there are no suspension parts for the Diamante, GTO genuine brake parts were used. Front strut casings are from a Silvia.



The rear is equipped with a TRD suspension. Tires are 235 size Potenza RE711 front and rear.



Factory seats keep the image of a luxury sedan. The transmission only came in automatic with the 3.0L engine and cannot handle over 500ps. Therefore, it was replaced with the 5-speed manual from the 2.5L model. At one time, the seats were removed for weight reduction but on the bumpy metropolitan expressway, ride was rough so they were reinstalled.



There were no reinforced parts so the engine tune has reached its limit. Replacement parts like drive shafts, LSD and clutches are not available. This Diamante has been slowly tuned further and further by JUN. The owner, greedy for more speed insisted that the limits be pushed further.


●Special Thanks:JUN Auto Mechanic 102-1  Sayamagahara Matsubara, Iruma, Saitama  Prefecture TEL:04-2934-5335 


【Related Links】

JUN Auto Mechanic