What is "good" flow on a 3.2 injector

[Tom F2]

The car in question, an 87 Carrera with just 13,000 miles from new (!!), had sat almost continuously for four years, and would not run. After a few tests on other components, we felt that the injectors should be checked, so we removed them, and sent them to a "rebuilding" service.

Marren Fuel Injection reports 4 of 6 in a set had poor spray pattern, all had flows of approximately 73 cc/min. They were all "dirty" on the "reverse cycle." (What does "reverse cycle" mean.) Marren returned them "clean" with good spray patterns and 82 cc/min.

Will this fix the car? I can't know until later this week, when I get time to re-install them. Does anyone here understand the significance of these numbers?

[UK Carrera]

I very recently had my injectors cleaned. Car has 54k miles.

After cleaning they were all matched at:
103cc per 30 sec at static 2 bar
53cc per 30 sec at 50% duty cycle 2 bar
68cc per 30 sec at 50% duty cycle 3 bar.

A little more info on the test conditions relating to your figures might help the comparison.

[ChrisBennet]

I had some 3.2 injectors cleaned by Marren a few years ago. They sat on the shelf a few months before I assembled the engine. One went bad sitting on the shelf. I ended up buying 6 new ones.
I just talked to a shop owner yesterday and he had the exact same thing happen to him this spring (3.2 injector + Marren = bad injector). Injectors are expensive but I'm not sold on "rebuilt" injectors.
-Chris

[GeorgeM]

I had sketchy performance from my car a couple of years ago when I was still in Stuttgart. It just wasn't as peppy as it once was. I feared the worse, although I was just looking for an excuse to do a 3.6 swap.

I took it to Ruf and they recommended new injectors. They say new injectors every 130,000km or so. At 130,000 miles, I was abviously past that. I took their recommendation (got them online from our host vice paying 180 Euro each locally... ouch) and they made a significant difference. The compression and leakdown numbers ended up being great.

The new injectors were worth every penny.

[Tom F2]

Originally posted by UK Carrera
I very recently had my injectors cleaned. Car has 54k miles.

After cleaning they were all matched at:
103cc per 30 sec at static 2 bar
53cc per 30 sec at 50% duty cycle 2 bar
68cc per 30 sec at 50% duty cycle 3 bar.

A little more info on the test conditions relating to your figures might help the comparison.

They didn't express it in terms of duty cycle, they expressed the other conditions in terms of fuel pressure (43 psi, or 2.9 bar) and test cycle (6 ms, which I take to be an operating frequency of 17 Hz). I have no idea what this means in terms of the shape of the 17-times-a-second electric pulse to the injector. I see oscilloscope patterns in the shop manual, but I haven't tried to deduce the corresponding frequencies, yet. Can you explain what is meant by "50% duty cycle?"