Piston surface treatment

About double treatment

Model: genuine piston for NB8C (Sr-2)
Left: with double treatment Right: without surface treatment

The best way to get better piston efficiency is the double treatment.
The double surface treatment consists of:
1. Micro shot peening and
2. Molybdenum shot
Even if one uses a genuine piston, with surface treatment one can get a very good effect.

Model: genuine piston for NB8C (Sr-2)
Left: with double treatment Right: without surface treatment

1. Micro shot peening

Micro shot peening has been used in racing and automotive industry for many years. Ultra fine particles are being fired to the piston’s surface changing it. In this way the piston is being strengthened and the friction is being reduced.

With the micro shots fired at high speed the material’s structure changes, in other words it has a heat-treatment effect. During the treatment smooth minute unevenness with strong structure is generated.

In the case of pistons without treatment when we start using them, the friction surface becomes plane, the resistance grows and the oil film breaks.

If treatment is carried out, on the surface many refined dimples are formed.
The oil stays between the dimples and the sliding friction becomes lower.

It is a frequently used technique in the motorsports world. In F1, Le Mans, GT etc. it is used on parts like the engine, mission, differential etc.

2. Molybdenum shot

A technique, where particles of molybdenum are being shot by compressed air to the piston’s surface.
The technique used earlier was to apply molybdenum coating on the surface by using a binder. However, after the treatment because of the film’s thickness there was a change in the dimensions and because of the abrasion the long-term efficiency couldn’t be preserved.

In the case of molybdenum blast binder is not used at all and there is no change in size caused by the film’s thickness.
Furthermore, there is no abrasion between the piston and the cylinder. Which means, that low sliding friction can be maintained for a long period of time.

We highly recommend the piston’s double treatment. It eases the break-in of the product and allows us to use it for long time with good efficiency.


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
E-mail: info@maruhamotors.co.jp