Maruha 2.1L Stroker Kit for Mazda MX-5 NA NB 1.8

£5,055.78 inc. VAT

Maruha 2.1L Stroker Base Kit

£4,736.78 inc. VAT

Maruha Power Metal Rod Bearings

£99.70 inc. VAT

Maruha Power Metal Main Bearings

£145.00 inc. VAT

Maruha Oil Jet Squirter for Mazda MX-5 NA NB × 4

£18.58 inc. VAT each

Maruha 2.1L Stroker Kit for Mazda MX-5 NA NB 1.8

Maruha’s custom stroker kit uses oversize pistons and a stroked crankshaft to achieve an insane 2.1L displacement from any 1.8 BP engine. This kit comes from one of the most respected Japanese manufacturers of Mazda MX-5 parts, Maruha. There are two ways of increasing displacement in an engine, you can increase the piston diameter, or you can increase the piston stroke. Maruha’s stroker kit increases both of these things, taking the pistons to a huge 85.5 (the biggest you can reliably fit in a BP block) and increasing the stroke to 89mm. The stroke is how far down the piston goes on the downward stroke and how far up the piston comes on its upward stroke.

Crankshaft

The billet crankshaft is beautifully machined from 43040 Chromoly Steel and has a whole host of features not seen in the stock crankshaft. Firstly, Maruha have added 3mm to the crankpin diameter which increases the surface area between crankpin and journal bearing, further increasing durability. The crankshaft features two chamfered oiling holes and, when used with Maruhas upgraded main and rod bearings, ensures a consistent and healthy flow of oil into the crankpin. Maruha has also taken the time to improve on the crank nose of the engine. They’ve achieved this by enlarging the crank nose to increase the durability of the pulley boss, preventing accelerated wear in extreme driving conditions. On top of all this, the crankshaft is finely balanced at the final stage of manufacturing to ensure the most seamless install possible.

The main event, however, is the massive 89mm stroke that the crankshaft is designed around. This increases the distance of the rod bearings from the crankshaft centre and allows the piston to travel both further up and further down in the chamber, increasing displacement to 2.1L.

Connecting Rods

Maruha have used their own forged connecting rods which have been specifically designed for use in the stroker kit. The H-beam rod weighs in at only 460g and is 80g lighter than stock Mazda MX-5 rods. For use in the stroker kit, the rod has been shortened by 2mm to ensure the piston doesn’t travel too far upwards and hit the head. The big end on Maruha’s rod has been enlarged by 3mm to reduce loads on the crankpin journal. Alongside this, oversize ARP bolts have been used to secure the cap to the rod for all the high revving goodness you can throw at them.

Pistons

To complement the custom crank and rods, Maruha has commissioned a custom piston spec for their stoker kit from Mahle, a well-known manufacturer of Formula 1 pistons. These pistons feature a unique piston skirt shape which allows for the use of Maruha modified oil squirters to enhance oiling and piston cooling. Measuring at 85.5mm, they are the biggest pistons you can realistically fit in a BP block and use a unique GRAFAL coating to reduce drag, friction and piston noise.

Compression ratio: 11.6:1 with standard height head.

Rod and Main Bearings

Designed specifically for the stroker kit, Maruha’s own rod and main bearings allow for more oil flow to the crankpin journal increasing overall durability.

Maruha Modified Oil Squirters

Due to the unique design of the MAHLE piston, there is a chance of running into interference issues with the stock oil squirter. Maruha have solved this by creating a modified version of the OEM oil squirter that clears the large MAHLE pistons.

Kit includes

  • 89mm stroker crank
  • 2mm shorter Maruha connecting rods
  • Main bearings
  • Connecting rod bearings
  • 85.5mm high comp Mahle custom forged pistons
  • 4x Maruha oil squirters

Additional information

Brand

Maruha

Model

Mk1 (89-98), Mk2 (98-05)

Maruha 2.1L Stroker Base Kit

Weight 25 kg
Dimensions 98 × 48 × 48 cm
Brand

Maruha

Model

Mk1 (89-98), Mk2 (98-05)

Maruha Power Metal Rod Bearings

Weight 0.2 kg
Dimensions 10 × 10 × 10 cm
Brand

Maruha

Model

Mk1 (89-98), Mk2 (98-05)

Maruha Power Metal Main Bearings

Weight 0.2 kg
Dimensions 10 × 10 × 10 cm
Brand

Maruha

Model

Mk1 (89-98), Mk2 (98-05)

Maruha Oil Jet Squirter for Mazda MX-5 NA NB

Weight 0.02 kg
Dimensions 5 × 4 × 2 cm
Brand

Maruha

Model

Mk1 (89-98), Mk2 (98-05)

Warranty information

Warranties cover defects in materials and workmanship only. Warranty is for replacement of a similar product, repair of the original product or refund of the purchase value only and excludes all labour and incurred charges including towing, fitting, inconvenience, and purchases of other manufacturer's products. The warranty is good for the period stated in the additional info tab from the date of purchase. Mileage warranties are for road use only and proof of mileage is required. Products must be installed by an independent experienced professional mechanic and the suspected defect must be present at the outset. The warranty does not cover damage caused by incorrect installation, failure to comply with the maintenance requirements of the vehicle, processing or otherwise changing the product, ordinary wear and tear, or any other external influences. Warranties are invalid if the product is used for racing, rallying, drifting, track days or any other form of motorsport or competition. Please refer to the manufacturer's own warranty documentation for more information.

Making a warranty claim

Proof of purchase receipt showing the date of purchase, proof of mileage at installation, proof of current mileage and invoice of the work undertaken by an independent experienced professional mechanic must be supplied along with the returned products for a warranty claim to be considered. If your vehicle needs to be used whilst your warranty claim is considered replacement parts from the same manufacturer should be purchased through BOFI Racing. In the event of a successful warranty claim, we will refund the card that was originally used to purchase the replacement parts, in full or in part depending on the nature of the claim. BOFI Racing reserves the right to make full or partial compensation at its sole discretion depending on the condition and mileage use of the returned suspect parts. For example, if you have used the part for several thousand miles before a defect is noticed, only partial compensation may be offered.

Make Model Year
Mazda MX-5 I (NA) 1993 - 1998
Mazda MX-5 II (NB) 1998 - 2005

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