Maruha oil pan baffle

The oil pump is driven by the turns (revolution) of the crankshaft.
Once driven, the oil pump sucks up the oil from the bottom of the oil pan.
The oil is then filtered and supplied to all the sections of the engine.
This is the basic lubricating route.
However, under hard driving conditions, the oil level around the strainer in the pan becomes very uncontrollable.

The oil pan of Roadster(Miata)is comparatively a very well made structure.

Manufactured with aluminum it is rigid and light weight.
In addition cooling fin is provided at the outer side base for the heat emission.
The partition helps with controlling the oil level stability.
We think the stock type is enough if it is only meant for normal drive.

However, when the engine is modified for high performance it is very important to pay attention to the management of oil flow and supply.
For example:

  • Assure high speed of engine by inserting the high spec camshafts.
  • Increase the oil flow quantity by using NB8 oil pump for VVT system.
  • Increase the return spring rate of the relief valve and increase suction of the oil pump.
  • Driving hard - circuit attack and solo racing. Oil supply shortage under these working conditions leads to serious engine damage and substantially short life.
    Therefore,@Maruha devised the baffle plate, to stabilize the supply of oil.

    The characteristic of Maruha Oil Pan Baffle

    A space is established at the lower side of the partition wall and Pan Bottom so that it doesn't become an obstacle for the oil flow. An outlet is provided for the oil to flow to the lower part of the baffle plate as well.

    There is space for the oil to flow to the lower part of the baffle plate.
    A rubber valve is set up in order to prevent outflow of oil due to rolling.

    It is concomitantly used with a stock baffle that's specially designed for easy return of oil to the pan bottom.


    The fixing of the oil pan is a very easy process.
    Remove the stock plate by loosening the bolt.
    Place Maruha's baffle inside.
    Replace the stock plate over Maruha's baffle and retighten the bolt.

    The concern of the partition wall conversion

    Let us explain the above characteristic a little more in detail.
    The partition stops the oil from splashing out due to the rolling and in addition prevents the existence of oil around the strainer continually.
    It divides the bottom of the oil pan into 3 divisions by establishing the wall in the baffle.

    Areas of 3 divisions

    The three parts are the outside left (marked in blue), the outside right (marked in green) and the center (marked in red).
    A space is provided respectively to the lower parts so as not to obstruct oil flow.

    The structure is designed against gravity, especially to keep the flow of oil in 3 divisions, escape of oil is difficult from the respective sides.

    Structure that causes easy return of oil

    The most esteemed point is the oil return mechanism.
    The general plate on the tuning parts market puts emphasis on vibration and acts as a cover.

    The cover structure in G prevents the spill of oil a little bit due to rolling.
    However, after oil is pumped in with the strainer continually and is sent to the engine parts, the leftover oil must return to the oil pan.

    Once the oil returns to the oil pan bottom, it is prevented from returning to the strainer periphery.
    It is an easy oil return structure.
    The stock plate is jointly used with the wall and is effective in stabilizing the oil level.

    It is the sole invention of Maruha Motors.

    Using of the rubber valve

    Furthermore, oil return is facilitated by the rubber valve.
    The rubber valve opens in one direction to the length wall and hence allows easy oil return to the center area.

    It is the method that was adopted by other race engine manufacturers.
    Maruha has tested it in the N2 engine on Japan's famous Fuji speed way (FISCO) and could confirmed the good results.

    It is a structure to facilitate easy oil return by one way opening of the rubber valve.
    By using the steel plate of 1.6mm, toughness is added to the performance and in addition it also prevents from rust.

    Installation of the oil pan for NB8 C (latter model) to NA8C and NB8C (ealy model)

    The oil pan for NB8C (later model) adds the engine block strength.
    Especially even a stock crank baffle can be changed from the NB8C(later model).It raises the block stiffness substantially.

    On BP engine of NA8C and NB8C (early model), we strongly recommend the 3 parts set of Maruha's oil pan baffle, a stock oil baffle (the crank side) of NB8 (later model) and a stock oil pan of NB8 (later model).


    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