History and Information

The Daihatsu Charade GTti & GTxx was produced in Osaka, Japan from 1987 to 1993. It was the 3rd generation of Charade and the model series is known as the G100.

 

The GTti for export markets have engine code CB80. Japanese Domestic Market (JDM) versions have the same engine, But the engine code is called CB70. Also In Japan, The GTxx version was available. Essentially it is identical mechanically to GTti but came with power steering and air-con (and a few other extras).

 

CB70's all came fitted with exhaust catalyst.

CB80's had catalyst for some export markets,

 

But UK cars never came with catalyst.  

 

Both the GTti and GTxx were only made as a 3 door hatchback.

 

The CB70/80 engine is 993cc, 3 cylinder, Twin cam, 12 valves, Turbocharged, Intercooled and has electronic fuel injection.

 

Power is 99bhp at 6500rpm and 96 ftlb torque at 3500rpm.

 

This may not sound like much compared to today's standards!

But remember the GTti is a lightweight car, And the gear ratios are also quite low.  

 

Acceleration through the gears is impressive and these days you would need a car with nearly double the BHP to get the same thrill !

 

0-60mph is quoted as being between 7.7 - 8.0 seconds from various magazine road tests at time of production.

 

Top speed about 115mph.

 

Standing quarter mile 16.4 seconds

 

Design and development of the engine dates back to 1984/85. Daihatsu designed a 926cc, 3 cylinder, Twin cam 12 valve turbo engine to be used in Group 'B' Rally competition in a special mid-engine RWD DeTomaso version of the previous G11 generation of Charade (called the 926R). However, The project never saw proper production and was eventually abandoned because Group B Rally cars were banned after the 1986 season. A few prototype cars were built, And one was presented for display at the 1985 Motor Show in Tokyo.

 

So Daihatsu had the engine design already "on the shelf" that was later to become the 993cc CB70/80 and it was decided to put it into production and fit into the new 3rd generation Charade.

 

When launched in March 1987 (And until only quite recently), The GTti was the fastest 1.0 production car in the world. It was also the first <1000cc piston production engine to produce 100bhp per litre. 

 

The engine block is made of cast iron, With aluminium alloy cylinder head.

 

The crankshaft is noted as being particularly substantial, And the conrods are strong vanadium steel. The pistons are semi-forged (high pressure cast) with a thick flat-top crown. The bottom end also incorporates a oil spray bar, and a balancer shaft. 

 

Cylinder Bore is 76.00mm,

Stroke 73.00mm

Compression Ratio is 7.8:1

 

The turbocharger was sourced from IHI, And is the RHB5. Earlier cars had a oil only cooled turbo (RHB5 VQ10). During 1989 the cars then came with a revised version of turbo which had a water-cooled bearing housing (RHB5 VQ17). The turbos are otherwise identical and perform same. 

 

Standard Boost pressure is 10.5 psi

 

The 3x Denso fuel Injectors work in batch firing, and are the high impedance type. They flow approx 320cc if measured at the industry standard 3 bar of fuel pressure. However the GTti is a little unusual in that fuel pressure is set at 2.5 bar, So in effect the injectors are flowing a maximum of approx 300cc at the standard fuel rail pressure. 

 

The ECU is also made by Denso, And inside contains soldered Read-Only-Memory (ROM) chips. So unfortunately, The ECU is not "mappable" or able to accept a new chip. The rev limiter is set at 7600rpm.  The ECU allows a maximum boost pressure of approx 12-13psi. Anymore and it will automatically shut down the fuel and ignition as a safety measure (commonly called fuel cut).

 

This boost limit can be defeated easily enough by fitting a FCD (fuel cut defender), And boost pressure can then be raised. But 15psi (1bar) boost is about the limit to stay reliable using standard ECU without further modifications. Get carried away with too much boost and the fuelling will become too lean, and ignition timing too advanced which causes damaging engine detonation, blown head gaskets or cracked cylinder heads.

 

Having said that, A GTti with a FCD fitted to be able to use 1 bar boost, With standard turbocharger and a free flowing exhaust system will produce about 130bhp. Quite a bit quicker than standard !

 

Engines that are to be further tuned for larger power increases will really need a new aftermarket programmable ECU fitted (or a piggyback controller such a Greddy emanage) to properly setup the fuelling and ignition timing.

 

And to make serious power (180-250bhp) and have a acceptable level of reliability requires extensive mechanical modifications such as: custom made exhaust manifold, a larger turbocharger and intercooler, bigger fuel injectors, larger throttle body, custom made clutch and even stronger gearbox gears.

 

The engine will also have to be in fresh condition to start with.

 

However. With all the trick parts and proper tuning, The CB70/80 has been known to handle 2+ bar of boost, on race tracks and rally...on the standard engine internals !

 

The gearbox is a conventional 5 speed manual. Automatic was never a option.

The clutch is cable operated and the diameter of the friction disc is 180mm.

The Flywheel weighs 6.4kg and can easily be lightened down to around 4kg.

 

If you do plan on increasing power substanstially then be aware the gearbox is not particulary strong. Once you exceed 150 lbft torque the chance of breaking gears is greatly increased. 

 

The standard clutch is also a limiting factor. Perfectly OK for mildly modified cars but the clutch will start to slip if producing over 120lbft torque.

 

 

Front brakes are 234mm diameter, 18mm thick ventilated discs, Rears are a solid disc with built-in hub that holds the wheel bearings.

The brakes if in proper working order are good. But are sometimes regarded as poor by owners, with complaints of premature fade. Often this is due to aftermarket brake pads designed for the lesser Charade models which are not up to the job for a performance car. The original GTti genuine brake pads were a higher specification than the other G100 models.  

 

Suspension is independant with MacPherson struts.  

Anti-roll bars at front and rear.

 

Standard wheel size is 5J x 14", offset ET45.

Stud pattern 4x100.

Centre bore 56.1mm

 

Factory fitted tyre size was 175/60/14 - H speed rated (one of the first cars to use this tyre size). 

 

Many owners fit the more common and cheaper 185/60/14 size. Which is permissible. However this tyre size does tend to bulge out on the sidewall due to the narrow 5" wheel, And can make the handling feel a little sloppy.

 

And of course, Many cars have by now been fitted with aftermarket wheels of various sizes.

 

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© Nathan Munns