Blue vs Yellow injectors

Volker, maybe you can answer a question that has puzzled me for some time.

The Euro 350SLs use the yellow Bosch injector.
North America 4.5L engines use the Blue Bosch injectors.
The Blue injectors have higher capacity than the yellow ones.
The Euro engine has smaller displacement but it puts out approx same or more power than the lower compression 4.5L NA model. Yet it is provided with lower capacity injectors.

Presumably the ECU is designed to provide sufficient fuel to the engine in either case. But why the difference? Injector capacity is usually chosen to match power output.

Hi Graham,

yes the variating flow of both injectors is compensated by injector opening times as determined by ECU. Highest flow rates of blue inejctors (neglecting the never released whit ones) are also used by many 4- or 6-calinder engines like Citroen DS, BMW 3.0, Opel 2.8 . So it has nothing to do with engine volume. And finally don't forget that the MB 450SL also has a higher compression, power and torque version in Europe. It makes a real difference and fortunately MB uses the same injectors and throttle switches on both versions of the 450 engine. Even the lowest compression version NV for Middle East uses those.

And finally be happy that you can still buy the blue injectors. Yellow and green ones became very rare.

Although there are probably still some Bosch blue injectors in stock at various vendors, most are now saying NLA (No Longer Available) A year or two ago, one US vendor was selling them for a low price ($58) each. Now those that have them want $200-$300! I have read that production has stopped. There are other makes available and some injector shops are offering a modified modern injector that will work with D-Jets. Several sizes available.

One other question - Do the Euro 350SL/450SL have the same MPS as the North American models? If so, is the compensation (injector pulse length) done with a different ECU design, or just by adjusting MPS to provide correct exhaust %CO?