E30 M3 Sport Evolution (cc.2.5L)

10 sets special edition

A limited edition of 10 sets carefully packed in special wooden boxes.

BMW owners are familiar with BMW Motorsport’s “M”. This time we would like to introduce the O/H with a MAHLE piston by 27MotorSports, which is set up to the E30 M3 power unit.

BMW E30 M3 and Sport Evolution

The E30 was being produced between the years 1983 and 1994. M3 was being produced from 1985 to 1990.
At first it was produced with cc.2.3L. After Evolution and Evolution II, Sport Evolution’s (2.5L) production was limited to 600 cars in 2 years (between 1989 and 1990).
The rumor said that 200 cars were imported to Japan, but we don’t know the actual number.

Sport Evolution (hereby SE ; 2.5L) was produced to homologate the M3 for touring car racing. It is a special one out of the special ones.

Special MAHLE piston

27MotorSports is Mahle MotorSports’ Japanese agent.
This time we got to the customized piston for E30 M3 SE just because we wanted to revive the good old MAHLE piston.

Let’s take a look at the SE genuine piston

The material is cast. On the backside of the pin the so called anchor is set up and it is a heavy construction.
The weight is 480g and the BMW genuine price is surprisingly high.
The SE was originally developed for racing – it is light, made of high quality material.

The characteristics of MAHLE’s piston

The compression ratio of the original piston for touring cars is over 12:1.
However, this time’s special piston by 27MotorSports has almost the same dimension as the genuine one with the purpose of keeping the original condition.

Bore diameter 95.50mm (genuine 94.80mm) Recess position same as in the case of the genuine one Valve genuine + 1mm Recess depth genuine + 1mm Weight 376g (genuine 480g) Pin 22mm (the same as in the case of the genuine one) with DLC coating Ring width 1st 1.2mm, 2nd 1.2mm Oil 2.8mm Compression ratio 10.5:1 (genuine 10.2:1) Piston volume -13cc

The bore has been set to the most suitable level for basic OH.
The recess can respond to the 1mm OS valve diameter and the 1mm OS high lift cam.
The recess is a bit bigger, but the compression ratio almost doesn’t change. It can be safely used with stock ECU control or with a genuine ROM.
A thick 1.2mm・1.2mm・2.8mm ring is being used and the slipper skirt has a special shape. Furthermore, to the skirt graphal coating is applied, which lowers the friction and the slap sound very much. In this way we can get great efficiency.

MAHLE piston

The original M3 SE is a MAHLE product too. This time’s newly designed piston is based on the M3 SE genuine one. For this reason its reliability and efficiency are very good.

DLC coating

In the case of E30 M3 Sport Evolution piston pin DLC coating is carried out.
The meaning of DLC is DIAMOND LIKE CARBON which indicates that the carbon film’s hardness is diamond-like.
It is an extremely hard carbon which lowers the sliding friction.
The thickness is on a nano-level and for this reason it doesn’t affect the clearance at all.
In the industry DLC coating has been tried on many items of the engine parts, however, we at Maruha use it on the tip of E30 M3 Sport Evolution.

Removal and re-installation of the engine

To the removal and re-installation we use a strong engine stand table that is specially designed for engine work. In this way we can work on it safely.

Then the engine and transmission ASSSY follows. We can say that our way is just the opposite to the maker’s way of assembling the engine.

The inside during the disassembly

The car is over 20 years old, so the inside parts are in different condition, which is understandable. We suppose that the user has exchanged oil from times to times. However, in reality there is sludge and some break too.

On the piston top land we can see damage that looks like a burrow. We can suppose that the reason for this damage might have been a blow or the fuel ratio was not appropriate.

M3-SE is pure bred and it can be enjoyed on circuits too. However, in these cases we have to be prepared for damages.

The characteristics of Sport Evolution

Compared to the M3 2.3L engine, there are a few changes.
The setup of the camshaft, valve, piston, crankshaft, metal bearing, oil pan etc. is completely different.

  1. Camshaft
    On the IN/EX sides of the special Evolution camshaft there is a notch with the mark A1.

    Before we disassemble the exhaust side, we carry out valve timing check.

    The lift is 1mm, duration is 248°and the central angle is 100°.
  2. Valve guide
    BMW doesn’t supply only valve guide.
    If there is too much clearance at the guide, the makers suggest an exchange with cylinder head ASSY.
    This time we exchanged with our original one only the guide on the EX side.

    The guide’s abrasion on the exhaust side was in progress.
    The material is phosphor bronze and the guide’s external dimensions are completely the same as in the case of the genuine one.
    Generally the external dimensions are made a little bit bigger than those of the genuine one for stopping too much clearance. But our method of exchanging guides is different. We don’t use hammer, but remove it by heat shrinking, so at assembling it fits perfectly.
  3. Reface and seat-cut
    The genuine valve is a high quality product with Natrium inside and for cost saving it is recommendable to reuse it.
    Of course, the deformed valve must be removed, but if we somehow manage to restore the guide’s condition, then we can secure the efficiency.

    The problem is the seat-cut. After removing the guide’s core, we carry out seat-cut.

    As a result, we can’t avoid the shim’s exchange, but we can get some change in the size. This means that we can cover the genuine shim’s size.
    Many users might be deceived by the nicely polished, glittering combustion chamber and the port’s surrounding. However, let us mention that for the guide and valve’s higher precision it is more important to carry out precise seat fitting.
  4. Valve spring

    It becomes a double construction, with the ability to respond to high rotation.
    Its perpendicularity is not destroyed and it can be reused.
    It is understandable, that with a heavy genuine valve a double spring is being used.
  5. Shim plate
    It seems that in BMW the shim is set to a size of 3.65mm to 3.75mm, but if we carry out seat cut etc. thicker shims become necessary.
    The genuine shim range is from 3.35mm but it is hard to get it in Japan quickly and many customers have to order from overseas. For this reason we decided to regrind the genuine shims.

    The new shim is very beautiful and we can expect reliable processing management.
    This is the base for a good engine.

    On the lifter side too we lowered the friction by polishing.
  6. Port grinding

    We particularly don’t grind the combustion chamber and the port for basic O/H work.

    This work must be expensive, but it is not easy to get power.
    This time our purpose was a basic O/H, because even if we grind the genuine parts, we don’t expect the efficiency to change too much.
    The grinded polished port looks beautiful, but only from the looks the engine’s performance won’t get better easily.
  7. Cylinder head surface grinding
    If a timing chain is being used, it means that the head’s surface grinding is difficult.
    On the cylinder head bolt’s surrounding we can see some deformation. It looks as if the area of deformation would have been generated on purpose.
    Minimum modification has been carried out.

    Left: before the surface grinding
    Right: after the surface grinding
  8. Head bolt
    We use 10 pieces of M10×P1.75 head bolts.
    However, there is a problem. The bolt’s allowance is not being fully used. In other words, the stress concentrates near the block’s surface, its peak is around the bolt and leads to cracks or other troubles.
    In our case we chose to use a special strengthened bolt.

    The stud can use the bolt’s stress from the core of the block.
    With this the block’s damage can be prevented.

    Just like even in the case of the 2.3L engine, we highly recommend the usage of the studbolt too.
    Altogether there are 10 head bolts.
  9. Connecting rod, crankshaft

    We reused the genuine rod. The genuine rod is very heavy.
    Luckily we found that the cap bolt can be reused.
    But if one has more budget, one might want to use a lighter type.

    The BMW stock crank’s design is very beautiful.
    We were aiming for a precision under 1/100mm, so we had to check carefully at each part and bending with our allowance range.
    We can say that the crank is like a person’s backbone. And just as in a human’s case, even the engine needs to have a nice straight backbone.
    Even the tale’s pilot bearing is simultaneously exchanged.

    In the case of the early model there is a shatterproof felt. If you try to purchase it from BMW, you will get a recent type.
    Even if the felt is not necessary anymore, we set it up just like it is said in the manual.
  10. Metal bearing
    The metal bearing is a very important point when we talk about engine building.
    In the cases of the 2.5L engine and the 2.3L one, the size is the same, but the construction is completely different.

    Especially in the case of the main bearing at the block side grooving is being carried out and it allows the oil to flow out from the metal’s back.
    In the metal’s center there are holes (oil hole) from which the oil can flow evenly to the journal. In the case of the 2.5L engine there are more oil holes on the metal.

    The main journal is being supplied by oil – oil enters into the main journal’s orifice – the metal on the conrod’s tip gets supplied by oil.
  11. The M3 SE oil pump is no longer available at BMW and that’s why it causes a big problem.
    Even though the construction allows us to use an oil pump for 2.3L, BMW doesn’t recommend it.
    In this case we chose not to do an ASSY exchange, but to dismantle and overhaul it with our technique.

    We didn’t exchange the inner parts, but carried out microshot, which is a very advanced method and limited the gear’s abrasion trace and got higher lubrication.
    Even when turning it manually you can feel its smoothness.
    While providing oil lubrication, the oil pump has to operate under severe conditions.

    These kinds of friction marks can be seen when because of the fretting and the change in high revolution, the metal parts rub against each other.
    We are aiming for reduced friction and an improved oil retention.
    At the time of installation we don’t only apply oil, but use an assembly paste too, which acts like a lubricant and protects the engine at starting.

    The M3 oil pan consists of 2 pieces. A baffle is inserted in the inside (partition) and it prevents oil offset.
    Its capacity is full, but we have to be aware, that when mounting the engine in an oblique position, from the engine gasket’s joint oil might leak.
  12. Oil pump relief valve
    With growing revolution the oil pressure also grows. So that the oil pressure doesn’t go over a limit, a relief valve is being used.

    The tip of the relief valve is taper-shaped, but even though it can be moved into an oblique position, its top might hit the surface. There used to be cases of E30 when the relief valve seat hit its margins, the oil pressure didn’t rise and it caused engine blow.
    Generally, in the case of a pump made in Japan a gallery is being set up to the pump itself and a valve in the shape of a piston is responsible for the stroke.
    However, in the case of BMW the valve is not protected by a tube and it might happen that it gets out of position and oil might leak.

    The relief valve’s top is repaired while being polished by a #2000 grit paper.
  13. Torque management
    As we all know, when assembling the engine, all the bolts and nuts are being controlled by the torque. Here we have to mention a few points though.
    One of them is the torque wrench. The tool with the preset type doesn’t fit the engine’s construction.
    If we try to set the torque manually we cannot set it properly. A better way is to use a gage indicating type friction pointer. If we start setting the torque and check the indicator, we can see the bolt’s efficiency, in other words we have to listen to the “bolt screaming”.
    Even though the maker suggests 10kgmf, we cannot get more torque with 8kgm indeed.
    We cannot put on more torque than the bolt would permit. If it exceeds the limit, the head and the block would get deformed.
    Even if it is written in BMW’s manual, it is good to think and decide by ourselves and not to do impossible things. Let’s take a look at the cracks on the head and block.

    Even though it is cast iron, it gets damaged. The water jacket is quite near to the head bolt’s surrounding.
    There are 3 jackets altogether. If we use a strong bolt, it might lead to a crack.
    At the jacket’s brim we use a leutor for shaping it. This kind of work might prevent cracking.
    It’s not only about confirming that there is deformation, but about considering which part is deformed and why it happened. This is how the maintenance generally should be and the maker’s manual should be merely a reference book to it.
  14. Engine impression
    The engine that started up silently, can continue a stable idling.
    This time we set a little bit narrow valve clearance.
  15. The ECU control is one of the most important points. Even in the case of this car a tuning ROM used to be installed. After we checked the Air/Fuel ratio, we found that it is lean and it can be dangerous . You can see lean burn scar marks on the piston and the valve.
    It is very dangerous to drive the car with a ROM that doesn’t match and it might damage the engine.

Delivery to overseas

We are looking for partners who could become dealers of our special BMW Pistons. Please feel free to contact us if you are interested or have any questions.


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