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Now, that said... As you can see all of this is hard work. At the end of the day the fuel injectors in the newest 996 are 15 years old. For more than half that period of time they have been exposed to crappy fuel. They are tired and should be replaced simply due to time in service.
From the perspective if the engine is out and apart anyway I totally agree here. Every motor I have built got new injectors regardless, but for cars still in service it may not be feasible from an economic/effort perspective to do this at let's say 100K miles. That being said I am all behind developing some kind of test to see if they should be replaced or investigated further that is relatively easy to do without pulling the motor. You have provided way more insight on this than I was hoping for so thank you for that again. I am going to ponder this a bit more and maybe let the community digest some of the thoughts floating around here. For sure I understand this way better than I did at the beginning of yesterday.
To add to Jake's point about replacing tired injectors as preventative maintenance, I have decided to replace the injectors on my 3.6 FSI engine, which was a 3.4L originally. I think that something that scares off a lot of MK1 owners from replacing injectors is how expensive the specific 3.4L injectors are.....somewhere around $1.5K to $1.8K for a set. This leads one to look for alternatives to replacing (i.e cleaning, refurbishment etc). However the MK2 (3.6L) injectors can be had new for less than $40 each and it is my understanding that they will work on the 3.4L engine with a minor mod to them. Jake tells me they will be fine on my 3.6 FSI engine so I am going to put on new as they are relatively affordable (although the labour is the same) and will give great peace of mind! I am looking at this as preventative maintenance just like water pump, AOS etc.
My car is starting to experience this and has destroyed my catalytic converters. On initial start I have to let it warm for a few minutes before I can drive it without backfiring. They aren’t clogged enough to cause any misfiring but I want to get this fixed asap. I’ll be replacing the fuel pump and all 6 injectors along with new coils packs, plugs, and oil change on my 99. My question is on the injectors. From searching I have noticed some places notating that the Bosch 0280156211 are an upgrade to the Bosch 0280150455 (what comes stock on the 99). It’s quite the price difference is the main reason I am asking if the ‘upgraded’ ones are useable. They flow roughly a pound more which shouldn’t be that much of an issue with a full bolt+ car.
To add to Jake's point about replacing tired injectors as preventative maintenance, I have decided to replace the injectors on my 3.6 FSI engine, which was a 3.4L originally. I think that something that scares off a lot of MK1 owners from replacing injectors is how expensive the specific 3.4L injectors are.....somewhere around $1.5K to $1.8K for a set. This leads one to look for alternatives to replacing (i.e cleaning, refurbishment etc). However the MK2 (3.6L) injectors can be had new for less than $40 each and it is my understanding that they will work on the 3.4L engine with a minor mod to them. Jake tells me they will be fine on my 3.6 FSI engine so I am going to put on new as they are relatively affordable (although the labour is the same) and will give great peace of mind! I am looking at this as preventative maintenance just like water pump, AOS etc.
Glad to see that you are doing these injectors. Back when your engine was built we were only having the injectors professionally cleaned during an engine build. We had yet to connect these dots concerning injectors, and of course, the injectors were 7 years newer at that time as well.
Concerning the injector mods, basically the groove that holds the retention clip is not deep enough in the replacement injectors to use the earlier rail/ retention clips. This groove can be made slightly deeper, and wider (when necessary) to accept the earlier clip.
I plan a Rennvision video for this as soon as we get the chance.
To add to Jake's point about replacing tired injectors as preventative maintenance, I have decided to replace the injectors on my 3.6 FSI engine, which was a 3.4L originally. I think that something that scares off a lot of MK1 owners from replacing injectors is how expensive the specific 3.4L injectors are.....somewhere around $1.5K to $1.8K for a set. This leads one to look for alternatives to replacing (i.e cleaning, refurbishment etc). However the MK2 (3.6L) injectors can be had new for less than $40 each and it is my understanding that they will work on the 3.4L engine with a minor mod to them. Jake tells me they will be fine on my 3.6 FSI engine so I am going to put on new as they are relatively affordable (although the labour is the same) and will give great peace of mind! I am looking at this as preventative maintenance just like water pump, AOS etc.
They aren't that much as I said earlier they are available in uk from design 911 for £75 each!!photo252.jpg
Just throwing in something here. Has anyone sent old/bad injectors to one of these specialist places that checks/cleans/measures them? Surely they would flag them as bad and they should have seen quite a lot of these by now?
Chris
If you scroll the photos there's one showing a picture of the injector, the one you pictures looks like the later model 3.6 it's different and that one looks aftermarket aswel, the ones I've quoted are Bosch oem and porsche
From a quick google of the 996-1 Vs 996-2 injectors it looks like there is an extra groove where a metal clip anti-rotation feature fits. (green and red arrows). I also noticed the distance between the inlet sealing O-ring and the main retention groove is longer on the newer injector; although this may not matter depending on what it fits into.
The .2 injector you are showing is not the oem Bosch number. That number is the one I referenced in question to slightly up on this page if it can work. The 996.2 Bosch number is 0280156053.
I have a recently acquired 3.8L FSI motor built by Jake (was originally a 2002 M96 3.6L). The torque this motor puts down is really impressive - LOVE IT DEARLY!!! Plan to keep it long term.
Time to change the AOS.
Motor has only run on DT40 since the build in 2013.
Last edited by UBER_MOTO; May 30, 2021 at 02:01 PM.
I reached out to Jake, he suggested injectors or AOS. So, I'll start there. I'll go with the OEM AOS.... I've swapped one out before on M96, not fun with engine in.
I’d suggest the UAOS.
What injector am I'm looking for? ....the stock 3.6 injector or something designed for the 3.8L??
Open a ticket with Jake and ask him.
I can guess, but he definitely knows.
You most likely will have to pay for his consulting time, but he will know all the answers.
It will almost certainly be worth the money spent.
Last edited by TexSquirrel; May 9, 2021 at 01:14 AM.
Different animals.. The Mezger, along with all aircooled engines use Nikisil plated cylinders. Nikisil will streak and consume oil when too much fuel is present, but they will not score. Often once the over- fueling issue is corrected, the issues go away. The only thing that will touch the surface of a Nikisil bore is a diamond, or a tungsten- carbide cutter. remember, Nikisil is a composition of Nickel, Silicon, and Carbide.
Hey Jake. Goes without saying, I always appreciate so much of the free information you have provided as a practitioner and contributions that you have made in the Porsche and VW community. Sorry for reviving a very old thread but I was wondering your thoughts on the following.
Talking water cooled engines only here: Isn't the reason the Mezger is immune to this because of the Nikasil, of course, but also because it's not direct-injected?
When you say "Nikisil will streak and consume oil when too much fuel is present, but they will not score" and "The only thing that will touch the surface of a Nikisil bore is a diamond" does that effectively mean that Nikasil (and SUMEbore) are completely invincible? For example, I have seen Charles state in the past "no cylinder solution is 100% impervious to damage when the engine is not operating properly, like with a leaky injector, or conditions like a vacuum leak that lead to over-fuelling." Trying to reconcile these statements.
Thank you for your time.
Last edited by silver_tt; Aug 15, 2021 at 06:34 AM.
Even Nikisil can be damaged from excess fuel. It takes a lot, and the Nikisil is very tough, but rings can glaze and cause issues.
Nothing can live through too much fuel.. SUMEBore appears to be even more resilient than Nikisil, and my testing to see just how much fuel SUMEBore can retain ring seal with is happening very soon.
The Nikisil is honed with a diamond... If you have too much fuel in the equation, and the oil is washed off the wear surfaces, you'll have problems..
