Maruha alternator Type-R for Mazda Miata NA6CE

There are two types of Maruha alternators: one for NA6CE and one for NA8C.

The difference between them is the pulley.

The NA6CE crank pulley is made for the V-belt.

The alternator for NA6CE has a V-shaped pulley, the alternator for NA8C has a rib-shaped pulley
The V-type pulley’s cross section uses a trapezoid belt. Both sides of the belt come in contact with the pulley in order to gain friction.
Even if we apply adequate tension the belt sticks easily to the pulley’s center and it stretches in a short period of time. This is its weak point.
If the belt tension is not appropriate the pulley slips easily and it produces a strange noise at the engine’s start.
After a short period of time the sound ceases but the slip might cause an increase in the belt’s temperature.

In the case of high revolutions like that of races the belt starts flapping and there might be cases when it slips off the pulley.

Just like you can see on the right picture the V-belt penetrates the pulley and the belt becomes loose.

The rib shaped belt can fit the pulley’s unevenness and it makes slipping difficult.
Even if we put pressure on the rib belt it won’t penetrate the pulley and it is also better from the viewpoint of elasticity.

This time’s Type-R uses a rib-shaped pulley with the NA6CE alternator.
It makes a set with the rib-shaped crank pulley and the water pump’s pulley.

Even though the crank pulley is not a part that has to be exchanged periodically, in the case of NA6CE we recommend its exchange after 10 years.
It is also very effective for the tuning of a B6 engine.

Our advice

If you are exchanging the alternator with street drive on your mind the general type (V belt) is enough.
Please note that the crankshaft and crank pulley’s shape are different in the case of NA6CE’s early models and therefore cannot be adapted.
A rib-type belt has to be used with Type-R.
The alternator’s function is the same as the conventional ones’.
It is possible to use an NA8C alternator in B6 but because the wiring terminals are different, it is necessary to carry out wire processing.
There are aluminum rib-type pulleys by other makers too, however, we haven’t confirmed their compatibility with our alternator. For this reason we cannot recommend their simultaneous usage.


Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312