Tuning the BMW M70

"Comprehensive guide to performance parts and tuning the BMW M70 engine!"

Let us examine M70 tuning and summarise the ultimate modifications. BMW M70 are good project engines and with the ultimate tuning upgrades like a remap, turbo kits and camshafts you will positively improve your driving fun.

The greatest M70 tuning parts on an engine are usually the ones that give the best value for money.

We won't be swayed by popular M70 tuning parts, they need to be cost effective.

Significant gains on the M70 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road camshafts commonly raise the performance throughout the rpm range, you might lose a little bottom end torque but your high end rpm power will be lifted.

Competition camshafts, raise the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport and race camshaft will just annoy you whilst in heavy traffic.

You should ideally match your power band to your usage of the car so for a typical daily driver stick with a mild fast road M70 camshaft

Each engine responds better to different cam durations than others.

The ECU mapping and injectors and fuel pump also will make differences on the torque gains you'll hit.

Altering valve durations can alter the torque 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.

Stage 1 mods: Fast road camshaft, Panel air filters, Drilled & smoothed airbox, Remaps/piggy back ECU, Intake headers, Sports exhaust manifold.

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

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

 

The M70 units respond well to upgrades and we see that there is a growing number of modifications and tuning parts around.

 

A remap allows a tuner to fully realize the full potential of all the upgrades you've done to your M70.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output will depend much on the upgrades you've carried out and the condition of your engine.

Pulling air into the M70 engine is the aim to any tuning project.

Intake headers carry the air from the air cleaner and allow it to be drawn into the engine and mixed with fuel.

Structure and rate of flow of the Plenum can make a substantial improvement to fuel atomisation on the M70.

We often see air intake manifolds are needing an upgrade, although some car makers provide reasonably good air intake manifolds.

Increasing the M70 valve size, doing a bit of port matching and head flowing will also lift power, & more importantly will afford you raising the power increase on other tuning mods.

Turbo upgrades

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 M70

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 your car is turbo charged mods are relatively easy and we find turbocharged engines will have better components.

However every engines will have power limits

We recommend you find these restrictions and upgrade to better pistons and crank to cope with the power.

It's not unheard of mechanics spending a lots of money on turbo upgrades on the M70 only to have the engine block go up in smoke just after it's been finished.

Large upgraded turbochargers tend to suffer low end lag, and small turbochargers spool up more quickly but do not have the peak end power band gains.

Thanks to progress the range of turbochargers is always developing and we commonly find variable vane turbochargers, allowing the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbochargers divert the exhaust gases into a couple of channels and flow these at differently angled vanes in the turbo charger. They also help the scavenging effect of the engine.

It is not unusual that there's a restriction in the air flow sensor AFM/MAF on the M70 when a lot more air is being fed into the engine.

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

Adding a supercharger or additional turbo will make large bhp and torque gains, although more challenging to configure. We have this article covering twinchargers if you want to read more.

Fuelling upgrades and mods

You will need to ensure that the engine is not starved of fuel so will have to pay attention to the fuelling when you start extending past 20% of a performance increase.We would recommend you to over specify your injector capacity.

 

The rule of thumb is to add another 20% when buying an injector, which takes into account injector deterioration and provides some spare capacity should the engine require 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.

Exhaust upgrades and mods

You should look to replace your exhaust if your exhaust is actually causing a restriction in flow.

On most factory exhausts you'll see the exhaust flow rate is ok 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 out of the engine but do not go too wide or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Typically exhaust restrictions can be traced to the catalyst and filters installed, so adding a better flowing high performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the M70

The M70 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M70, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M70 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M70 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.

We really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M70 guides and tips are kept up to date.

History of the Engine

The M70 is a SOHC V12 petrol engine, which was BMW's first production V12 in 1987 and production ended around 1996.

Each cylinder bank used a separate ECU and MAF sensors with drive by wire and hydraulic valve lifters.

M70B50

220 kW (295 hp)  at 5,200 rpm 450 N⋅m (332 lb⋅ft)  at 4,100 rpm 1987-1994

1987–1994 E32 750i/750iL
1989–1994 E31 850i/850Ci

S70B56

280 kW (375 hp)  at 5,300 rpm 550 N⋅m (406 lb⋅ft)  at 4,000 rpm 1992-1996

1992–1996 E31 850CSi

S70/2

461 kW (618 hp)  at 7,400 rpm 650 N⋅m (479 lb⋅ft)  at 6,700 rpm 1993-1998

1993–1998 McLaren F1

S70/3

427 kW (573 hp)  at 6,500 rpm 670 N⋅m (494 lb⋅ft)  at 4,500 rpm 1998-2000

1998–1999 BMW V12 LM racing car
1999–2000 BMW V12 LMR racing car
2000 BMW X5 LM racing car

Tuning the BMW M70 and best M70 performance parts.

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