BMW M30 Tuning

"All you need to know about tuning and performance parts on the BMW M30 engine!"

Our aim here is to provide a guide to M30 tuning and point out the ultimate modifications. BMW M30 are popular engines and with a few sensible performance enhancements like remapping or aftermarket ECUs, head work, turbo upgrades and camshafts you will really increase your driving fun.

From 1985 onwards the engine becomes much better and has more power and is a better base to work on.

Bear in mind this engine has had a very long production run and there were significant changes over the years. Because most of our readers have later models we are going to assume one of these more recent engines, but we encourage you to chat with others in our forums and online to determine the best mods for your M30.

The M30 is very durable and solid, early models were crying out for more power. We are not surprised they have such a good following and are well supported with upgrade parts and tuning options.

History, Power & Specs of the Engine

The M30 is a SOHC straight-six petrol engine which was produced from 1968 to 1995 and production ran for 27 years

  • M30B25V
    110 kW (148 bhp)  at 6,000rpm   211Nm (156 lbft) @3,700 rpm
  • M30B25
    110 kW (148 bhp) @6,000rpm 215Nm (159 lbft) @3,700 rpm
  • M30B28V
    125 kW (168 bhp) @6,000rpm 235Nm (173 lbft) @3,700
  • M30B28
    135 kW (181 bhp) @5,800rpm 240Nm (177 lbft) @4,200 rpm
  • M30B30V
    132 kW (177 bhp)  at 6,000rpm 255Nm (188 lbft) @3,700 rpm
  • M30B30
    149 kW (200 bhp) @5,500rpm 272Nm (201 lbft) @4,300 rpm
  • M30B32
    147 kW (197 bhp) @5,500rpm 285Nm (210 lbft) @4,300 rpm
  • M30B33V
    139 kW (186 bhp) @5,500rpm 289Nm (213 lbft) @3,500 rpm
  • M30B34
    160 kW (215 bhp) @5,800rpm 310Nm (229 lbft) @4,200 rpm
  • M30B35
    155 kW (208 bhp) @5,700rpm 305Nm (225 lbft) @4,000rpm

Applications for the M30 engine over the years.

 

M30B25V

The first 2,494 cc M30 in the 1968 E3 2500. This version uses dual Solex Zenith 35/40 INAT carbs, and produces 110 kW (148 bhp) in most applications.

The M30B25 has previously been called the M06 and M68, prior to BMW retroactively renaming it the M30B25V

  • 1968–1977 E3 2500
  • 1974–1975 E9 2.5 CS
  • 1973–1976 E12 525 107 kW (143 bhp), Solex 4A1 carb
  • 1976–1981 E12 525
  • 1977–1979 E23 725

M30B25

In 1981, Bosch L-Jetronic electronic fuel injection was added to the 2,494 cc (152.2 cu in) version. Peak power  110 kW (148 bhp), 215Nm (159 lbft).

  • 1981-1987 E28 525i
  • 1981-1986 E23 725i

M30B28V

The M30B28V version produces up to 125 kW (168 bhp) and 235Nm (173 lbft) depending on the model year, carb and region. It has a compression ratio of 9.0:1 and initially used dual Zenith 35/40 INAT carbs.

This version has also been known as the M06 and M68, prior to BMW renaming it the M30B28V.

  • 1968-1977 E3 2800 / 2.8L - 125 kW (168 bhp)
  • 1968-1971 E9 2800 CS
  • 1971-1971 E3 Bavaria - US only
  • 1974-1976 E12 528 - 121 kW (162 bhp), dual Zenith INAT carbs
  • 1976-1978 E12 528 - 125 kW (168 bhp), Solex 4A1 carb
  • 1977-1979 E23 728 - 125 kW (168 bhp), Solex 4A1 carb

M30B28

In 1977, Bosch L-Jetronic electronic fuel injection was added to the 2,788 cc (170.1 cu in) version. Power increased to 135 kW (181 bhp) and torque increased to 240Nm (177 lbft).

  • 1977-1978 E12 528i - North America only, 129 kW (173 bhp), 9.0:1 compression ratio
  • 1978-1981 E12 528i
  • 1979-1986 E23 728i
  • 1979-1987 E24 628CSi
  • 1981-1987 E28 528i

M30B30V

Based on the M30B28V version with a 3 mm (0.12 in) larger bore, the M30B30V produces 132 kW (177 bhp) and 255Nm (188 lbft),uses dual Zenith 35/40 INAT carbs

  • 1971-1975 E9 3.0 CS
  • 1971-1972 E9 3.0 CSL
  • 1971-1974 E3 3.0 S / 3.0 L / Bavaria
  • 1976-1979 E24 630 CS - 136 kW (182 bhp), Pierburg 4A1 carb
  • 1977-1979 E23 730 - 135 kW (181 bhp), Solex 4 A 1 carb

M30B30

The fuel injected version of the 2,986 cc (182.2 cu in) M30 debuted in 1971 in the E9 3.0 CSi and initially used the Bosch D-Jetronic mechanical fuel injection system. In 1976, the injection system was upgraded to Bosch L-Jetronic

  • 1971-1975 E9 3.0 CSi - 149 kW (200 bhp)
  • 1972-1973 E9 3.0 CSL - 149 kW (200 bhp)
  • 1972-1975 E3 3.0 Si - 147 kW (197 bhp)
  • 1975-1978 E12 530i - North America only, 131 kW (176 bhp)
  • 1976-1976 E12 530 MLE - South Africa only, 147 kW (197 bhp)
  • 1977-1978 E24 630CSi - North America only, 129 kW (173 bhp)
  • 1986-1995 E32 730i - 138 kW (185 bhp)
  • 1988-1990 E34 530i - 138 kW (185 bhp)

M30B32

Despite having a capacity of 3,210 cc (195.9 cu in) In the E24 633CSi coupe, the M30B32 uses Bosch L-Jetronic electronic fuel injection. The US version used L-Jetronic from 1978 until mid-1981, changing over to Motronic electronic fuel injection in June of that year. The 1979 732i is BMW's first use of Bosch's Motronic injection.

  • 1973-1975 E9 3.0 CSL - 152 kW (204 bhp), 3,153 cc (192.4 cu in)
  • 1976-1984 E24 633CSi - 145–147 kW (194–197 bhp) in Euro spec, 128–130 kW (172–174 bhp) in USA spec
  • 1976-1979 E3 3.3 Li - 147 kW (197 bhp)[34]
  • 1977-1984 E23 733i - 147 kW (197 bhp) in Euro spec, 130–145 kW (174–194 bhp) in USA spec
  • 1979-1981 E12 533i - North America only, 135 kW (181 bhp)
  • 1979-1986 E23 732i - 144 kW (193 bhp)
  • 1982-1984 E28 533i - North America only, 135 kW (181 bhp)
  • 1984-1986 E30 333i - South Africa only, 145 kW (194 bhp)

M30B33V

The carb fed M30B33 produces 139 kW (186 bhp) and 289Nm (213 lbft)

  • 1973-1975 E3 3.3 L

M30B34

The M30B34 engines sold in Europe and most other markets used a 10.0:1 compression ratio and produced 160 kW (215 bhp). In North America and Japan, the M30B34  136 kW (182 bhp). In all markets, the Bosch Motronic digital fuel injection system was used.

  • 1982-1987 E23 735i / L7
  • 1982-1987 E24 635CSi / L6 - 163 kW (219 bhp) in Euro spec
  • 1985-1988 E28 535i / 535is / M535i

M30B35

This engine has a capacity of 3,430 cc (209.3 cu in), despite the "B35" model code. It produces 155 kW (208 bhp) and 305Nm (225 lbft)

  • 1988-1989 E24 635CSi
  • 1986-1992 E32 735i
  • 1987-1992 E34 535i
  • 1988-1989 Rayton Fissore Magnum 3.5

Tuning the BMW M30 and best M30 performance parts.

Best M30 tuning parts

When talking about the best modifications for your M30 engine, we are going to focus on the ones that give the best value for money.

Altering your M30 camshaft will make a dramatic difference to the engine bhp, and other than forced induction upgrades is generally one of the biggest power gainers. Choosing a higher performance camshaft profile raises the bhp accordingly through the rev range, but especially at the middle to top end.

There are a few suppliers that offer offer a cam duration of around 275, with common choices being the Piper 270/285 & Shrick 284/280 degrees which when combined with a remap will yield a decent power figure. Depending on where you live there will be other sources of decent cams, that will help raise your top end power.

A vernier pulley wheel will allow fine tuning of the cam durations and timing.

On most of the early M30 engines you'll need to change con rods over 250bhp for the 745i engine, as these don't rev to 6500rpm, when Alpina tuned this they fitted new spec rods which avoided the stretch issue.

We have been informed that later conrods are much stronger, so do your research carefully. The Alpina ones show the potential here.

A ported head on the basic M30's along with headers will give you around 230bhp and a cam will bring that up to around 240bhp. This engine has had many revisions and improvements over the years, so it's really hard to cover all the bases here especially since the first units date back to the 60's.

Generally speaking later heads E32/E34 flow really well so there is no need to port or polish them.

If you have experience with your M30, please drop some tips in the comments below so we can pass these on to others, there is a shortage of good information out there about this lovely engine.

The M88 M5 engine is a good engine swap candidate for the M30

Alpina used a medium cam of around 275-280 degrees to achieve 260bhp. We certainly wouldn't recommend a more aggressive duration than this or you'll end up with most of the power at the top end of the rev range, and a lumpy tickover, but it depends on your plans for the car and what you are prepared to live with.

The M30 is not a high rpm engine, and you'll get oil delivery issues at around 7750rpm at the camshaft.

If you have the time and budget there was an interesting M30 tuning project where the bottom end was revised and it had custom hi-compression pistons and was bored out to around 3.7 liters.

In a typical daily driver should ideally to match your power band to your cars usage.

Different M30 engines respond better to more aggressive cam durations so view each engine as unique.

The map and fuel pump and injectors also have a large bearing on the power gains you'll hit.

remap allows you to get the full potential from all the tuning parts you've done to your M30.

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the end result usually varies depending on the tuning parts you've fitted and the condition of your engine.

Remaps on the M30 are popular and net quite impressive power gains, but to hit the max you need to go with an aftermarket ECU such as the Emerald, it depends on the other mods you've done.

For modest tuning with a few stage 1 parts an ECU remap is all you need, but to release more power the aftermarket ECU is a better option.

Extending exhaust or intake durations can alter the power band and on most engines, the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Typical stage 1 mods often include: Intake headers, Panel air filters, drilled & smoothed airbox, Remaps/piggy back ECU, Sports exhaust manifold, Fast road camshaft.

Typical stage 2 mods often include: Fast road cam, high flow fuel injectors, fuel pump upgrades, Sports catalyst & performance exhaust, induction kit, Ported and polished head.

Typical stage 3 mods often include: Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting, Twin charging conversions.

Early heads actually flow really well so gains can be had by shortening the inlet valve guides to increase volume. But there are gains to be had with enlarging the intake ports on most M30 setups and increasing the valve size.

Big valves and a 3 or 5 angle valve seat job will help you achieve higher power figures, we've seen claims of around 12% more power, and 25% when combined with the camshaft and aftermarket ECU.

The M30 engines respond well to mods and thankfully there is a growing number of parts and tuning parts out there.
  • M30B25V 1968
  • M30B25 1981
  • M30B28V 1968
  • M30B28 1977
  • M30B30V 1971
  • M30B30 1971
  • M30B32 1976
  • M30B33V 1973
  • M30B34 1982
  • M30B35 1988

Feeding fuel and air into the M30 engine is the whole point to any engine upgrade job.

Air Intake manifolds take the air from the air cleaner and allow it to be drawn into the engine and mixed with fuel.

The structure and flow rate of the Intake can make a noticeable improvement to fuel atomization and engine efficiency on the M30.

It's not uncommon that intake are begging for aftermarket parts, although a few makers provide well optimized intake.

M30 Turbo upgrades

Most NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your M30 (some of the later M30's are pretty strong, and we've seen decent turbo conversions on stock internals.)

The later Highline post 87 version has lower compression therefore would be better suited to adding forced induction.

Depending on your compression ratio we would suggest that most of the M30's can run 1 bar of boost quite happily, but you get more power if you are prepared to more engine work.

Without going forced induction on most of these engines, especially the early ones, you'll have to stick with power figures around 265bhp, but adding forced induction can see around 330bhp on the right setup. (Obviously the sky is the limit if you are prepared to do some internal work and strengthen the engine and alter the compression ratio.)

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes impressive power gains.

When an engine is fitted with a turbo upgrades are giving better power gains and most turbocharged engines are made with uprated components.

There are common areas of failure for every engine, with some being over specified and some only able to handle stock power

Research these restrictions and install better quality components to survive the power.

Larger upgraded turbo chargers tend to experience low end lag, and smaller turbo chargers spool up really quickly but do not have the peak rpm power band gains.

In the last 10 years the choice of turbo chargers is always moving on and we are seeing variable vane turbo chargers, permitting the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbo chargers divert the exhaust gases into two channels and feed these at differently designed vanes in the turbocharger. They also boost the scavenging effect of the engine.

It is not unusual that there's a restriction in the air flow sensor MAF/MAP on the M30 when considerably more air is being pulled into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp and torque at a much lower level.

Adding a supercharger or additional turbo will make large power gains, although harder to configure. We have this in depth look at twinchargers if you want to read more.

Fuelling

You will need to ensure that the engine is not starved of fuel so must increase the fuelling when you start exceeding 20% of a torque increase.We would recommend you to be generous with your injectors flow rate.

 

The accepted safe increase is to add another 20% when fitting an injector, which takes into account injector deterioration and allows some spare capacity should the engine need more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Adding fuel injection to the older Carb versions seems like a sensible upgrade for a decent power hike and more control over power delivery.

Later engines used various fuel systems with some performing better than others, but even the early systems have proven reliable with similar systems in use on the M20 blocks.

  • E8 E9 type - D Jetronic
  • E12 & E34 type -Bosch L Jetronic
  • E12 type - 3453cc, 218bhp, K jetronic injection .
  • E23 E24 & E28 type - 3430cc, 218bhp, motronic injection.
  • E34 type - 3430cc, 211bhp, revised cylinder head, lower comp pistons, revised motronic.

We do see people swapping out later ECU's and fuel systems to early engines for a simple power hike.

M30 Exhaust upgrades

You should look to upgrade your exhaust if the existing exhaust is actually creating a restriction.

In most M30's the exhaust is sucking a little potential power, replacing the manifold and downpipe will gain around 6bhp in most cases.

On most factory exhausts you'll see your flow rate is good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts will certainly help air flow from the engine but avoid an exhaust that is too wide or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to around 2.5 inches to maximise flow rates, and this should take into account the amount of air your engine is moving.

Common exhaust restrictions can be located the catalyst installed, so adding a faster flowing performance catalyst removes the restriction. We note that performance cats perform similarly to decats and have the added benefit of keeping your car street legal, as decats or catalyst removal is illegal in most territories for road going cars.

Weak spots, Issues & problem areas on the M30

The M30 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Using the wrong coolant can cause hot running problems as the aluminum oxide deposits in the head coolant channels.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

The early M30 (1977-80) suffered from a horrible EGR design that claimed many heads but most of these have been replaced by now.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to the design of this engine, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the M30, especially when tuned and will help extend the life and reliability of the engine.

One essential piece of maintenance that needs to be done every 20000 miles at most, is adjusting the valves.

There are issues with hot starting on the M30, particularly the M30B35 and this is generally down to a split vacuum line or worn injectors that leak.

If you would like to know more, or just get some friendly advice on Tuning your M30 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M30 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

Please help us improve these tips by sending us your feedback in the comments box below.

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