Maruha motors

MAHLE 85.5mm piston for Miata MX5 BP


Minor change for MAHLE BP piston has been made.

ロードスターBP用 85.5mm MAHLE(マーレー)製 パワーピストン
Mahle Custom made PistonFor BP engine 85.5mm
Mahle パワーピストン MAHLE SPECIAL 85.5mm
code:mar16032600 For BP

With reconsidering valve recess, it can be responded to variable valve timing system used after NB8C (Sr-2).
The old model has also a recess position responding to the same system, but in case that MARUHA variable camshaft is used with a grinded head, it might have a chance to touch a grinded head slightly, so the recess position has been changed since this version.

ロードスターBP用 85.5mm MAHLE(マーレー)製 パワーピストン
ロードスターBP用 85.5mm MAHLE(マーレー)製 パワーピストン
ロードスターBP用 85.5mm MAHLE(マーレー)製 パワーピストン

Additionally, due to the impact of higher cost price, the price has also been changed.


For BP

  1. Outer diameter 85.5mm (1928cc)
  2. Pin diameter 20mm (compatible with genuine connecting rods)
  3. Pin height 31mm
  4. Valve recess available / For camshaft lift 12mm (in case of no VVT)
  5. Ring 1st 1.2mm, 2nd 1.2mm Oil 2.8mm
  6. Top volume 9cc
  7. Compression ratio 11.0:1 (MARUHA 86mmx0.8mm gasket)
  8. Weight 300g
  9. For variable valve timing system after NB8 (Sr-2)

About variable valve timing system (VVT) after NB8 (Sr-2):


VVT is inside of variable valve timing system equipped with BP (BP-VE) engine (Only for NB8/Sr-2)
Using oil pressure occurred from engine drive, the system can control camshaft pulley position appropriately by ECU program.

The pulley is locked with the extruded pin by spring when engine is not running, but the locked pin is pushed back by oil pressure when the engine is started, and the pulley is under variable condition.
The retarded and the advanced angle chambers are oil-pressured by ECU program, and the system can control valve timing.
So, in case of installing MARUHA/MAHLE piston in BR VE, the pulley at inside has to always be broken down, and temporarily assembled after taking out the locked pin. Please make sure the recess clearance between valve and piston top of retarded and advanced angles.

1 The imaged pulley with variable system should be broken down and the lock pin is taken out.
2 The valve clearance for the maximum of retarded / advanced angles should be checked out.
3 In case of the turned up engine, the above-mentioned 1 and 2 are recommended.
  1. Even if the VVT system comes with the pulley, in case that the combination of MARUHA F camshaft (lifting amount 10.8mm), grinded head surface (0.8mm), head gasket (0.8mm), there is no contacting among them at all.
  2. The confirmation of valve contacting occurred by surging during high-speed rotation is not covered.
  3. The confirmation of using outside valve, changing seat ring on cylinder head and so on is not applicable.

The MAHLE piston project has started since 2004. A lot of communication with MAHLE engineers was made with repeating of basic designs, trial productions, and testing in order to complete the sophisticated forged piston.

Features about MAHLE forged pistons:

1. The products are processed by the exclusive machining machines in the integrated manufacturing factory.
The machines used for machining were developed for MAHLE exclusively, not for other company’s products.

2. The forged pistons are produced by the exclusive molds. Its feature is the sophisticated shape which cannot be achieved by universal general molds.
If you have a chance to check out around piston pin, thickness on backside of skirt, backside of piston top (ceiling) and so on, you will find its sophisticated design obviously.

3. MAHLE piston is very lightweight and compact design.
The outstanding feature of outside appearance is slipper skirt typed design.
The slipper skirt was firstly adopted by MAHLE, and it is very contributed for lightweight.
The technique of extending the skirt to certain length for smooth piston action seems to be already an old idea.
The short skirts are getting more opportunities to be used for the domestic and the genuine pistons with the high-performance engines.
The current piston designing summarizes MAHLE technology utilizes the appropriated profile, the exact machining accuracy, the certain material for tiny clearance, and the custom coating.


4. The coating is very effective features of the originality.
The coating in deep black all over is called “PHOSPHATE”.
Generally, it might be misunderstood as thermal barrier, but correctly it is coating for improving the early stage of break in between rings and pins.
The skirt part is processed with GRAFAL for playing a role in reducing the piston sliding resistance greatly.


5. The 4032 Aluminum is used. Thermal expansion is low because it contains a lot of silicon. (Some other MALHE is by 2618 material.)
So, smaller piston clearance can be taken comparing with standard aluminum forged piston. (Designation for Miata: 50/1000mm)
Quiet because of no tapping sound, and controlling oil and fuel consumption by keeping clearance properly and the perfect engine can be built up.

6. The weight of each piston is controlled with accuracy, and not only the piston body and pins are lightweighted, but the weight difference is also very small amount.The pin stopper (circlip) looks like a simple shape, but the round-lock typed F-1 style is equipped as standard.
Everything including the rings are made by MAHLE. Especially the rings are thinner for reducing friction.


Important point of when attaching:


The designing of MAHLE piston is the original slipper skirt typed.
The skirt rib structure for forming the skirt part is interfered with the oil jet for cooling equipped on engine block for designing reasons.
So, when it is equipped, the tip of oil jet is needed to be bent slightly after building the piston up previously.
If this process proceeded wrongly, the serious damage with engine blow might be occurred.
The modified oil jet is also able to provide by MARUHA. The highly recommend to use this modified oil jet together, because possible to minimize bending the jet nozzle linking your easy and safety work.

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