HONDA CITY TURBOS AND MUGEN MOTORSPORTS.
By Charles Hatcher
Honda has only manufactured one model of turbocharged car (other than F1). It's ironic that the car they choose to turbo was the least sportscar like vehicle in the Honda range. The Honda City Turbo was the brainchild of Hirotoshi Honda. Hirotoshi is the son of Honda's Founder. Hirotoshi wanted to prove his ability as a performance specialist for Honda. To prove his point he took Honda's ugliest, most ungainly vehicle and turned it into an aggressive performer that was well ahead of its time (as with most Hondas). It doesn’t come as a surprise that he was the founder of Mugen Motorsports.
There is in fact another turbocharged model that Honda has manufactured, again in the mid-1980s. This is a special turbo'ed version of the Honda Legend. For some details about this other model, refer to TOVA's H-Topics section - WongKN
Honda City Turbos were manufactured in two guises. The City Turbo, basically a standard looking City with a turbo motor and a bonnet hump. The Second City Turbo is affectionately known to the Japanese as the "Bulldog". This model had aggressively flared guards, spoilers and often adorned with wild graphics designating it an INTERCOOLED TURBO 11.
The City Turbo was manufactured from 1982-84, the Turbo 11 was manufactured until 1986. Both models featured a digital speedo surrounded by a Tacho so that all relative information could be taken at a glance. The last run of Turbo 11s had a normal speedo/tacho assembly. The motors in both models were essentially the same. An all alloy, 1237cc, CVCC (we'll get to that), turbocharged, multipoint fuel injected motor with a magnesium rocker cover and 8.5:1 compression ratio powered the beast. The Turbo 11's were intercooled, had a revised plenum, throttle body and inlet manifold, a larger turbo compressor housing and a slightly raised (8.6:1) compression ratio.
CVCC is a system used by honda to reduce emissions by stratifying the combustion charge. In the City turbo the throttle body appears much like a carby. However fuel is only applied through one barrel via a single injector (the throttle body has three barrels). A separate set of intake runners provides fuel to each of the CVCC valves located with a combustion prechamber. A rich mixture of fuel and air are added to the combustion prechamber which houses the spark plug. This is ignited and creates a flame front out of the prechamber. The flame front is used to ignite a lean mixture (normally hard to ignite using a spark plug) fed to the main combustion chamber via individual injectors. Apart from decreased emissions and increased fuel economy the stratified charge helps to ward off the killer of many turbo engines, DETONATION. Detonation occurs when two flame fronts collide in a standard combustion chamber. One is caused by the spark plug, the other is caused by the high pressures, friction and shockwaves on the other side of the cylinder igniting an easily combustible mixture. Stratified combustion such as the CVCC system makes the second front less likely to occur as the lean mixtures in the main combustion chambers are hard to ignite.
Performance of Honda City Turbos is really up to the individual owners. The standard Turbo 1 produces 100hp and has a top speed of 179km/hr, the Turbo 11 produces 110hp and has a top speed of 175km/hr (lower top speed due to spoilers and body flares). The braking system is very capable for such a small car. The front brakes are the vented disks and callipers straight of the 84 model Prelude, rear brakes are stock city items.
Modifications. Honda city Turbos can be easily modified for some good results. The filter can be replaced with a high flow item and cold air ducting is already present behind the passenger panel. The filter box can be removed completely and a high flow item put in it's place. A 2 1/2 inch exhaust straight off the turbo will liberate boost and provide a large increase in power. Honda cities have MAP sensed airflow so you don't need to muck about with high flow airflow meters. By the way the City turbo has twin map sensors, one for boost and one for vacuum (Map sensors did not appear in cars available in Australia until 1990). City Turbos have a boost cut at about 16psi boost. This must be disabled if you want to run high boost levels.
Raising boost. Because the City motor has a long stroke and small diameter bore there is a small surface area within the combustion chamber. This combined with the CVCC system and the factory flat top pistons and the inherent bottom end strength of Honda motors allow for large increases in power through boost increase. Sources within Honda say tuned correctly Honda motors will run double the factory output without self destructing. That's a big call. Just imagine a series 11 Turbo with a fresh motor, bigger turbo and high boost with 220hp on tap. That's more than a stock WRX with approximately half the weight. That being said these motors will take high boost levels.
Information provided by some members of the Honda City Club in Japan on stock vs the class 2E Race production city turbos.
Normal 110ps.(110ps/5,000rpm 16.3kg-m/3,000rpm)
Change camshaft and boost-increase(0.85 -> 1.63kg/cm2)
Up to 138ps.(138ps/5,000rpm 22kg-m/3,000rpm)
0 -> 400m in 13.5sec
I don't know about you but I think a 13.5 second 1/4 is pretty good, especially for a car designed for the track. I cannot guarantee the accuracy of the performance figures.
Any objections, queries and part enquires can be directed to Charles.Hatcher@jcu.edu.au
If anyone has any parts or cars for sale I will drop it onto my database and might be able to help. Anyone requiring new honda city turbo factory parts can also contact me.