[Ruster82]

I am going to replace injector number 6 and I see various posts about not mixing index's per bank. Some say you have to religiously change at least the 3 on the faulty bank, some say you have to change all 6 and some say just the 1 that's faulty is fine.

So what is the right answer? and why would you need to replace all 3 or 6 if only 1 was faulty? What's the logic behind it?

Also feel like a noob asking but but if you don't ask you don't learn. If I replace stock turbos with upgraded turbos would I need to remap the car to handle them?

[Emilime75]

For a long time it was thought that they could not be mixed within a bank. Recently it's been mentioned that they could. The reasoning for replacing 3/6 when only 1 or 2 were bad was because the engine management is divided into 2 banks of 3, with a turbo, downpipe and dedicated O2 sensors per bank. If you've got 2 older and out of spec, but working, injectors mixed with a new, in spec, injector, the DME will alter fuel trims to all injectors based on the O2 readings. While this may not pose any codes or noticeable driviability issues, it isn't ideal.

[alpnwss]

Kinda like having a dog sled team with 10 different dog breeds.
You're giving them all the same command, asking them to complete the same task. Some are going to do well and some are gonna suck at it, and overall the team will suffer.
Why not just get a bunch of Huskies?

[BSM n54iS]

Stick with convention, at least 3.

[Torgus]

My vote is buy six v12s the from FCP with a lifetime warranty and then just replace all 6 every time one goes bad.

You pay once to do it right and then they are free to replace. Swapping injectors and coding takes 30m.

[Ruster82]

Thank you all for the info on the injector query, seems unless I care about absolute min/maxing performance then replacing just the one will be fine.
(I am in the UK and FCP don't ship here atm due to GDPR privacy laws)

[Torgus]

Originally Posted by Ruster82

Thank you all for the info on the injector query, seems unless I care about absolute min/maxing performance then replacing just the one will be fine.
(I am in the UK and FCP don't ship here atm due to GDPR privacy laws)

I have 12-18 used injectors. 6 were perfect I removed them(I forget the rev and which ones they were).

Want to buy them

[BSM n54iS]

Originally Posted by Ruster82

Thank you all for the info on the injector query, seems unless I care about absolute min/maxing performance then replacing just the one will be fine.
(I am in the UK and FCP don't ship here atm due to GDPR privacy laws)

No, it won't.. but go ahead if you want.

[Smgs1992]

Do what you want but shit like this is why these cars get the reputation for being unreliable. People want to cut corners and penny pinch instead of properly fixing their cars. Then come on here again in 2 weeks wanting to know why their car runs like shit. Or they sell them for dirt for the next guy to fix and brag about how cheap he got his for.

[stewbets]

Originally Posted by Ruster82

Thank you all for the info on the injector query, seems unless I care about absolute min/maxing performance then replacing just the one will be fine.
(I am in the UK and FCP don't ship here atm due to GDPR privacy laws)

Those who paid $1400 on 6 new index 12's certainly want to justify their purchase. Don't let them scare you too much. Your plan is fine.

[Torgus]

Originally Posted by stewbets

Those who paid $1400 on 6 new index 12's certainly want to justify their purchase. Don't let them scare you too much. Your plan is fine.

This sucker paid:

BMW Fuel Injector Kit (Set of 6 for N54
Genuine bmw- SKU: KIT-13538616079KT
In Stock
$797.99

132.99 each.

Lifetime warranty


But seriously someone buy all my used injectors. There at least 6-10 that were not leaking when removed. Just not rev 12s. Someone buy the lot and I will make a deal. Again, I think have 18 in total. Various vintages.

[Smgs1992]

Originally Posted by stewbets

Those who paid $1400 on 6 new index 12's certainly want to justify their purchase. Don't let them scare you too much. Your plan is fine.

Lmao i’m running index 11s that arent leaking so who’s trying to justify $1400 index 12s?
Just saying fix the car right and be done with it. If atleast one is leaking then the rest are soon to follow

[alpnwss]

Additionally, if you're running super rich on some cylinders you'll get blowby and thin out your oil, and then you're really playing with fire.
I think the general opinion went from do whatever Daddy Deutsche says, to 'Stick it to the corporations don't play the game' back to 'If BMW had done a better job explaining 'why' a long time ago I would have done this.'
Just know that what you save now you might pay later in rod bearings.

[iqraceworks]

Just chiming in here.....I have index 4 injectors in one bank, and 7's in the other. That's how I bought the car. One of the 7's had a slight leak.... So I replaced it with a new index 12 and coded it in. So that bank now has a 12 and two 7's.

Been running it like that for 6+ months, not a single issue. The car makes great power (running stage 2+ V5 e40 tune) and it runs great!! Flow rates are flow rates......not really sure why the index type makes a difference. AFR's on both banks are very similar when looking at logs. No signs of anything funky going on. As long as you code them in....you will be fine.

I've even pulled all the spark plugs and checked them after a long pull....they all look the same, no dark (rich) spark plugs in the index 12 cylinder. All is good.



....just my experience.

[stewbets]

Originally Posted by Torgus

This sucker paid:

BMW Fuel Injector Kit (Set of 6 for N54
Genuine bmw- SKU: KIT-13538616079KT
In Stock
$797.99

132.99 each.

Lifetime warranty


But seriously someone buy all my used injectors. There at least 6-10 that were not leaking when removed. Just not rev 12s. Someone buy the lot and I will make a deal. Again, I think have 18 in total. Various vintages.

Now you're just rubbing it in

[stewbets]

Originally Posted by Smgs1992

Lmao i’m running index 11s that arent leaking so who’s trying to justify $1400 index 12s?
Just saying fix the car right and be done with it. If atleast one is leaking then the rest are soon to follow

So fixing the car "right" means fixing it your way, which is to say he must replace all 6 since one is leaking. This does beg the question of how you know (like absolutely positively know) none of your index 11 injectors are leaking. I say you should fix your car right with the latest index so that you don't further tarnish the N54 name with another spun bearing.

I'm joking, of course. All in good fun.

[Ruster82]

Fit one new injector yesterday, decided with a split opinion to just go with what I thought myself.

Logic behind it being if the car is smart enough to know if each injector is programmed correctly per cylinder then it is smart enough to take the readings and adjust fuel per cylinder too.

At the end of the day replacing all 6 is the safer option to stop another injector failing in the future but it takes 20 mins to do and injector and it is a 14 year old car so not worth throwing £1500 at if only one injector is faulty at the time of testing.

Thank you all for the input, if it turns out I took the wrong option or in a few months everything is fine I will make sure to come back to this post so other trying to make the same choice have more info to go on.

[Emilime75]

Originally Posted by Ruster82

Logic behind it being if the car is smart enough to know if each injector is programmed correctly per cylinder then it is smart enough to take the readings and adjust fuel per cylinder too.

It isn't. The code on each injector is a calibration code, and the DME is "smart enough" to know what to do with those injectors when they are installed and coded/registered. But, that calibration is only valid when the injector is new, and as time/use progresses it falls out of spec - obviously this is mostly mild as cars keep running with old injectors. Beyond that, the DME can only monitor AFR by bank, not by cylinder, meaning that if you have 1 new injector spraying to spec, and 2 injectors that are out of spec, in the same bank, the AFRs will be adjusted globally across all 3 cylinders in that bank, not individually. Is this an issue, probably not, especially if you're stock or just a mild tune. Is it the "right/best" way, that depends.

There's 2 major polar opposites when it comes to maintenance/repair philosophies. On one side, you've got people who will only fix exactly what broke, when it broke and nothing more. On the flip side, there's people who'll go beyond the broken part and add the "while I'm in theres" and the "might as wells" before they brake. I'm of the latter. When 2 of my injectors were found to be bad, I replaced all 6. When one of my outer tie rods was seized, I replaced both sides, inner and outer. When 2 of my tires wore out, I replaced all 4...it's my money and my car, just as yours is yours. I just want the best out of it as I can get.

[Ruster82]

Exactly, everyone has a line to draw where they want.

For me if I was going to put an extra £1250 (1/4 of the value) into my car just because it might save me a problem months/years down the line I would rather use that money and the equity in my car to get an upgrade/newer car.

I do 100% see why you do it your way and I commend you for it. Anyone buying a car after you have owned it is in for a bargain

[Jeff@TopGearSolutions]

Regardless of what method you choose, it should be known many revisions of these injectors are failure prone. Index 5 7 and 9 are some of the worst.
Budgeting on injectors is an understandable thing, especially when the vehicle may operate fine.
However it's important to know these failure prone injectors can cause a CYL to run lean OR if they are leaking, Fuel Wash will dilute your oil, causing engine failure.

It's best practice to replace all 6.

If it's not worth the cost, then it's assumed you are OK with the cost of engine replacement.

Coding of the injectors is important for the performance of the injectors.

This is not really a place to just do it "good enough" but to each their own.

[iqraceworks]

Or...just use common sense. If your car stumbles at startup in the morning....find out why, it could be a leaky injector....don't ignore it.

Check your plugs every 6 months.....it's easy to tell if you have a rich or lean cylinder.

Run logs every once in a while ......make sure everything is working properly.

Send an oil sample to Blackstone labs every other oil change ($28)....they will tell you if you have higher than normal levels or oil, water, coolant, metal, etc..in your oil. Always a good idea.

Just.....replacing all 6 injectors any time one acts up may be ideal, but replacing just the bad one isn't a horrible idea.....as long as you do the things above, and just use common sense.

[BSM n54iS]

Originally Posted by iqraceworks

Or...just use common sense. If your car stumbles at startup in the morning....find out why, it could be a leaky injector....don't ignore it.

Check your plugs every 6 months.....it's easy to tell if you have a rich or lean cylinder.

Run logs every once in a while ......make sure everything is working properly.

Send an oil sample to Blackstone labs every other oil change ($28)....they will tell you if you have higher than normal levels or oil, water, coolant, metal, etc..in your oil. Always a good idea.

Just.....replacing all 6 injectors any time one acts up may be ideal, but replacing just the bad one isn't a horrible idea.....as long as you do the things above, and just use common sense.

Lol the common sense was already mentioned in the post above yours. There really isn't much more else to say on top.