Honda City Turbo

[Randy]

The Models

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City Turbo, or better known as the City or Jazz is a small commuter car.

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City Turbo I from 81-83, City Turbo II -1987 Both motors were based on a 1237cc CVCC Honda engine. Compression ratio was 7.5:1 with boost up to 12psi. The Turbo II had a compression ratio of 7.6:1 now with an intercooler.

Honda has only manufactured two models of turbocharged car (other than F1). One was a 2.5 litre V6 Legend needing a bit more go, the other, a tiny commuter car known as the City or Jazz. It’s ironic that the car they choose to release as a special edition turbo was the least sports-car 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’s company Mugen had already proven it’s worth making performance parts for motorcycles and some cars but was largely unheard of out of racing circles. Hirotoshi Honda took Honda’s ugliest, most ungainly vehicle and turned it into an aggressive performer that was well ahead of its time (as with most Honda’s) and Honda released a production version of it.

Honda City Turbo2Honda City Turbos were manufactured in three guises. The City Turbo, basically a standard looking City with a turbo motor and a hood hump. In Japan, the second model City Turbo is affectionately known as the “Bulldog”. This model had aggressively flared guards, spoilers and was adorned with wild graphics straight from the factory designating it a HYPER 11. Very few city turbos were also released as a cabriolet model (most cabriolets are not turbo charged but still have the flared guard body kit typical of the turbo 11).

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The City Turbo 1 was manufactured from 1981-83, the Turbo 11 was manufactured until 1987. 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. Both models were powered by an all alloy 1237cc motor with CVCC (we’ll get to that), IHI RHB51 turbocharger, multipoint fuel injection and a magnesium rocker cover. Compression ratio was down to 7.5:1 and the boost was wound up to 12psi, fairly high for a factory turbo car. The Turbo 11’s were inter-cooled, had a revised intake plenum, slightly larger throttle body, modified inlet manifold, higher AR turbo compressor and exhaust housings as well as a slightly raised (7.6:1) compression ratio. Both motors have the same sort of power potential.

CVCC

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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 3 barrel downdraft carby. One barrel has a very small port size and actually houses a single injector. This port leads to a separate set of intake runners which provide fuel to each of the CVCC valves located within a combustion prechamber.
The combustion pechamber is actually separated from the main combustion chamber by a perforated collar. A rich mixture of fuel and air are added to the combustion prechamber which also houses the spark plug. This is ignited and creates a single flame front out of the prechamber. While this goes on the main combustion chamber is fed fuel via sequential multipoint injectors in the same manner as most modern EFI cars.
The only difference is that in City turbo motor this is a relatively lean mixture, not easily ignited by a spark plug alone. The flame front from the prechamber is used to ignite this lean mixture. Apart from decreased emissions and increased fuel economy this stratified charge helps to ward off the killer of many turbo engines, DETONATION. Detonation occurs when two flame fronts (or shock-waves) collide in a standard combustion chamber. One is caused by the spark plug, the other is caused by the high pressures, friction and shock-waves on the other side of the cylinder igniting an easily combustible mixture. Detonation can also be caused by superheated carbon particles or sharp edges in the combustion chamber that can operate like a glow plug in a diesel engine. Stratified combustion such as the CVCC system makes this 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). When you do get them going with a few modifications you will soon find the digital speedo maxes out at 180 while the revs continue to climb. The braking system is very capable for such a small car. Honda raided the parts bin and the front brakes are the vented disks and calipers straight of the Prelude from the same era, rear brakes are stock city items.

CITY TURBO RACING

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Mugen and Honda ran a single make racing series using the city turbos. The cars were based on the production vehicles as were the motors. The motors had larger exhaust, injectors, production type turbo (with 22psi), production type inter-cooler, and a modified camshaft. These cars did the standing 1/4 mile in 13.5 seconds (which isn’t bad for a front wheel drive car set up for circuit racing).
They ran very fat tires (9” front and 7” rear). The official mugen figure for power output is 138+hp @ 5500rpm but the torque is around 22kgm @ 3500rpm (standard twin camshaft VTEC 1600 has 16kgm, NSX V6 has about 28kgm). It takes little work to produce these power figure in a street motor. The cars from the one make racing series were bought by an Australian entrepreneur with the view to continuing the series in Australia. Unfortunately all the vehicles were in a warehouse in Osaka waiting to be shipped when an earthquake struck and buried the lot.

Year/Model Motor CC Bore


Stroke HP Torque Compression
81-87 City ER 1231 66 90 67 @ 5.5k 72 @ 3.5k 10.0:1
City Turbo I ER 1231 66 90 100 @ 5.5k 108 @ 3k 7.5:1
City Turbo II ER 1231 66 90 110 @ 5.5k 118 @ 3k 7.6:1

Credits

RaceCraft thoughts on motor swaps
Racecrafts thoughts on City Turbo
www.cityturbo.com

[Randy]

Conversion for First Gen Civic.

https://www.cityturbo.com/forums/viewtopic.php?t=5