Fuel Injectors (again)

Or you could go on ebay and buy new Bosch injectors. Bosch told us back in the early 80's they had intended those to be replaced like spark plugs.

 

I second that. Just replace with 8 new ones.


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Buy new Bosch ones! $20 each at MB online parts stores.

 

In my 90k miles QV, I still using the original steel injectors, and my 308 has been running like new car Although I have the original injectors, ultrasound, clean twice as I was told, the original steel injectors are better than the new brass ones, I don’t know how true that is as I’ve never tried new brass injectors and for 18 years of ownership, I always use the Chevron fuel that has techron injector cleaners in it.

 

Interesting! I wondered about that. Any suggestion for time (or mileage) interval. Thanks!

 

Pretty sure Donnie Callaway was one of them.

 

Its complete BS.

 

I had a convenient BOSCH service center nearby, and I brought a set of steel injectors in to be checked out. They had 40k miles on them. The technician had testing equipment for the Ferrari injectors. He connected them up right there and pumped a solvent through them into a clear container.

Of the eight, three had great spray properties (proper spray pattern, and immediate transition to spray at low flow). The other 5 had variations of either nonuniform streaming, intermittent spray to stream, etc. There's an active component in the injector that you hear oscillating when it makes the proper spray and hear it sticking or some variation when it doesn't. I can imagine that part is getting gummed up or worn. The solvent used for the spray test helped clean them. They started to behave a little better after running through the solvent, but the takeaway was to get a fresh set. With the new injectors (that were brass), I'd say it was a big improvement with many drivability properties notably improved.

To the OP's questions regarding mix-n-match: i.m.h.o. I'd spring for a new set. It's not too pricey, considering. Makes the car feel a lot newer.

 

Ultrasonic cleaning does nothing on a closed injector and there is no way to hold a CIS injector open. Electronic injectors are cleaned by having them hooked up electronically and cycling while in an ultrasonic bath. The Bosch cleaning/testing equipment just sprays a cleaning fluid through them. It helps, it fixes some but as I said, Bosch never intended for them to be a long life part. They are made far too cheaply for that.

 

Bosch CIS systems are personal hobby of mine and I can't help but chime in. Regarding the question of mixing brass and steel injectors I would highly recommend against it as the two injectors types have different operating characteristics that I believe would result in less favorable drivability issues if mixed in the same engine. In particular, the original steel injectors (Bosch 0437502010) that went out of production in 2011 have an average opening pressure of 3.5bar with a 35 degree spray pattern while the brass injectors (Bosch 0437502047) have an average opening pressure of 3.8bar with a 47 degree spray pattern. It's not entirely clear whether the different spray patterns have much of an effect on engine performance, however, the different opening pressures of the injectors will result in differential fuel flow rates that ultimately reach the cylinders which is less than ideal. With the correct equipment the fuel flow from the individual ports of the fuel distributor could be adjusted to compensate for the different injector opening pressures however in my opinion, the best course of action is to match a fuel distributor with equal port flows with a set of injectors with equal opening pressures.

One additional point, . . . with the utmost respect to Mr. Crall who knows more about these vehicles than the entire collective of this forum, I can confirm that there is a method to hold the pintle open on a CIS injector during ultrasonic cleaning that dramatically improves the success of correcting a leaking CIS injector. Prior to creating a method to hold the pintle open my success rate of correcting a leaking injector was around 50% via external ultrasonic cleaning and pushing cleaning fluid through the injector at high pressure. Ultrasonic cleaning with the pintle open increased the success rate to 80-90%.

 

The spray degree, can't see how that would really have much of any effect. CIS which stands for continuous injection system, is just that. If the fuel pressure exceeds the pintle spring rate, the fuel flows regardless of the valve timing.

As noted by Crall, they're replacement wear items. Nobody gives this a second thought in the Mercedes, VW's, Porsche etc ... That use the system too. Why fuss about it in this application?

 

Agree that the spray angle may not have much material impact. Discussions in the distant past on this forum that included my other favorite Ferrari "Professor" (Dave Helms) raised the question of whether the amount of fuel hitting the walls of the intake manifold with the different injector spray angles could have an impact on the character of the fuel entering the combustion chamber with appropriate atomization and emulsification. That stated, when looking at the anatomy of the intake manifold on the car that I'm most interested in (328) I'm not sure how much of a difference a 35 degree vs. 47 degree spray pattern would make:

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CIS does indeed stand for "continuous injection system" and fuel will flow uninterrupted once the operating pressure exceeds the force of the internal spring holding the injector pintle closed. That stated, if the opening pressures of the individual injectors are different the flow rates to the respective cylinders will be different as well (presuming the flow rates out of the individual fuel distributor ports are equal). In the situation of uneven flow rates due to disparate injector opening pressures the flow rates can be balanced by adjusting the flow at the individual fuel distributor ports. On my 328 and on other CIS cars I work on I prefer to dial in the fuel distributor port flows evenly and then match the distributor with a set of fuel injectors with equal opening pressures. I developed a CIS test bench that allows for flow rate analysis and distributor calibration with or without the injectors in place. In the photo below the distributor flows are being tested/calibrated without the injectors in place. I have a separate set up that allows for flows to be tested with the injectors in the individual circuits.

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I wonder if the difference in spray angle between the steel/brass injectors MIGHT also include a difference in atomization of the fuel. The more complete the atomization, the more efficient the fuel burn. Might have been some research that led them to change the angle...OR might have simply been easier to manufacture the "newer" angle. OR...they might have not even realized they were changing the angle!

 

Just something to noodle on... The angle assumes static. The atomized flow will follow some parabolic function related to air velocity. The difference is probably negligible or only seen on a dyno.

 

The injectors were universal. Bosch did not tailor them to specific port shapes. Either the originals or the current replacements. Ferrari used the same injectors in 308/2, 308/4, 400/412, BBi, TR, all with different head designs. Which head do you suppose those nozzles were designed for?
The injector is spraying full time. Out of a 720 degree cycle the intake valve is only open for about 240 degrees of that. Explain to me how fuel pooled on the back side of the intake valve has any understanding of spray pattern? The rush of incoming air and its associated turbulence when the valve opens creates the spray pattern.

Please, lets stick to reality and leave the fairy tales out of the discussion.

 

Fair enough.

The different opening pressures of the fuel injector types causing differential fuel flows is not a fairy tale, however, and I am hopeful there is agreement that it is ideal to have equal fuel flows to the cylinders for an engine to operate most efficiently.

 

No fairy tales here. Bosch makes changes for a reason.

 

I have the Swiss market Mondial 3.2 that uses unique spec injectors for its higher pressure KE3 injection system. They appear to still be avilable, albeit special order at much higher price than for other F cars, so I ordered them a couple of years ago anticipating eventual need. It appears Bosch is still the manufacturer, and I am surprised they would not do them in brass if that has turned out to be the preferred material.

 

As rare as your cars system is I strongly suspect the injectors you got were new old stock. For ours it is a very common part number and are probably under continuous production.

As far as the brass body is concerned, it is just a container for the functional parts, makes zero difference to the quality or function of the injector. Brass is just an easy material to work with.

 

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Click on attached link, simple tool to clean & test your injectors


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Sorry wasn’t able to attach link, but the photo contains the web page


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