ring on injector tip - can someone tell me what this is ?

[Belgian1979]

I have a set of used injectors here that I intend to test for flow rating and hopefully make a set of flow matched ones out of them.

After removing the pintle cap, I found this :



What is this and what caused it ? Any problem for the injectors in question ?

[The Radius Kid]

I'm guessing it means nothing.
Does carb cleaner remove it?

[Belgian1979]

I'm guessing it means nothing.
Does carb cleaner remove it?

No it's imbedded in the tip. When going over it with you nail, you can feel a depression where it is.

[Kevin Johnson]

Well, it is off-center. If I had to make a WAG I would say that it is a stamp made by a remanufacturer or cleaner so that they can positively identify used injectors that they have worked on. What is the history of the set?

[Kevin Johnson]

Sorry about previous response -- here is a better thought. In this ad you can see that reworked injectors have a circular machine weld. That seems more likely. They might not be reworked -- the original might also use this same circular weld.

type3tip.jpg

http://stores.ebay.com/Osidetiger-Fuel- ... grade.html

[The Radius Kid]

I'm guessing it means nothing.
Does carb cleaner remove it?

No it's imbedded in the tip. When going over it with you nail, you can feel a depression where it is.

It's probably just a mark from a clamp that holds the disc in place as it's being swedged into a cup shape.

[Kevin Johnson]

I'm guessing it means nothing.
Does carb cleaner remove it?

No it's imbedded in the tip. When going over it with you nail, you can feel a depression where it is.

It's probably just a mark from a clamp that holds the disc in place as it's being swedged into a cup shape.

That's a good thought too. I think if Yves took a high res picture and then looked at it on his computer he could easily magnify it about 17x and examine that area more closely.

[dieselgeek]

If you're doing a flow bench test, talk to some of the more knowledgable EFI gurus out there. Matching flow is only marginally important (because airflow differences in your engine will be on teh order of 10-15% per cylinder), but if you have a chance to characterize them in detail - THAT is helpful info.

[Belgian1979]

I tested them and they are working fine so far. Guess it's not really something to loose sleep over. Just find it kind of strange.

Anyway, these turn out good. I managed to get the fuel flow difference to within 1% where before it was 4%.
Only issue is that flow differences still arise over the range of opening times they are tested, but so far they are within 1% over the entire range of opening times.

Additionally I got to characterise them pretty well.

As for airflow differences : an ITB had the advantage that the airflow into the cyls can be set individually and they should be very close with marginal difference.

[Belgian1979]

Sorry about previous response -- here is a better thought. In this ad you can see that reworked injectors have a circular machine weld. That seems more likely. They might not be reworked -- the original might also use this same circular weld.

type3tip.jpg

http://stores.ebay.com/Osidetiger-Fuel- ... grade.html

I got this comment on another forum as well. Seems like this is it.

[dieselgeek]

As for airflow differences : an ITB had the advantage that the airflow into the cyls can be set individually and they should be very close with marginal difference.

Heh, then don't run O2 per cylinder because it will break your heart. I've yet to run into any engine with less than 2 points AFR differeces between cylinders, ever. That includes CNC porting, lots of work on intake and exhaust. There will still be huge differences so make sure to keep it safely rich if only looking at average AFRs or bank averages.

[RednGold86Z]

As for airflow differences : an ITB had the advantage that the airflow into the cyls can be set individually and they should be very close with marginal difference.

Heh, then don't run O2 per cylinder because it will break your heart. I've yet to run into any engine with less than 2 points AFR differeces between cylinders, ever. That includes CNC porting, lots of work on intake and exhaust. There will still be huge differences so make sure to keep it safely rich if only looking at average AFRs or bank averages.

Just curious if you're meaning 0.2 difference or 2.0 difference? On OE 4 cylinders, I see pretty consistent AFRs, but 0.2+ difference at times. On a bank to bank compared V8, 1.5+ points I've often seen. That's one good reason for air injection on those old cats, and why they switched to bank / sequential.

Original post - that's a welded ring, as stated. Laser welded. I've been to an injector factory - the holes are laser "drilled" too.

[dieselgeek]

Just curious if you're meaning 0.2 difference or 2.0 difference? On OE 4 cylinders, I see pretty consistent AFRs, but 0.2+ difference at times. On a bank to bank compared V8, 1.5+ points I've often seen. That's one good reason for air injection on those old cats, and why they switched to bank / sequential.

Bone stock LS engines will be lucky to keep 1.5 - 2.0 FULL POINTS OF AFR between all 8 cylinders during a WOT pull. So, if you have one cylinder at 12:1, you'll easily have another showing 14:1.

These are common plenum v8 engines, and this is common. The EMC engines are even worse before individual cylinder trims. I'm sharing what I observed, I'm not the OEM designer so don't shoot the messenger. I usually get a lot of messages claiming I must be doing something wrong, but I've done it enough to think most of those theorists don't really understand what they thought they did? not sure, but that's how it goes. Clean it up, lean it out and you can make more power.

[Belgian1979]

I have only one wideband, so only measure one bank, however injectors are wired 1-4-6-7 and 2-3-5-8. Idle moves around quite a bit with my original set of injectors. Dead time varied between .66 and .51. This was still with 1.0 ms of dead time.
When doing experimenting with the dead time, it seemed to like the lower values and it got noticable more stable at idle. This was still with the old set.

The additional injectors gave me a set with a dead time of .51-.58. Getting a set to flow evenly at 3 different opening times is impossible. Probably a moot point.

It depends on how close you want them. I currently averaged the µl flowed at a certain opening time, and picked injectors that were within +.5/-.5%, next +1/-1%, then +2/-2%
When combining them in the best possible way, I was able to get averages between volume flowed from one bank to the other of within 1.5%. However individual injector high vs low is still higher, with a max of 4.5%.

Not sure what it does on WOT. I would think that individual throttles are different in that air flows into the engine at different point, instead of through one TB. I can see how on a plenum the cyls on overlap will cause filling differences. This is not possible on an ITB unless via the airboxes I use and then I would think influence of overlap would be reduced. I haven't noticed any adverse effects of the airbox at idle for instance.
A throttle can be set so that the cyl flows an even amount of air. Only drawback on my setup is that throttle plates are paired, so I can only set a pair and I'm still left with some differences but they are not big. Setting them even has a noticable effect on idle quality.