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      12-29-2010, 03:25 AM   #129
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Quote:
Originally Posted by jaybird124 View Post
Tony,

As you've stated piston swelling due to heat under high load has been the primary cause of the scoring.
Do you see any evidence with your tear down that supports the concerns people have about fuel dilution caused by DI?
Doesn't seem to be any fuel dilution evident, although it is hard to say for sure after the tear down...

Quote:
Originally Posted by AstonMartin View Post
Aside from those deep scores, sidewalls seem like they experienced some serious wall wash.

What tune have you been running?
The original tune was from a company in the UK called DMS. Was very good at the time, but after developing and modifying the car more their tuning capabilities didn't seem as comprehensive and rock solid as I was hoping. Changed to a custom map from a great race shop in Germany and would keep using them had it not been for the need to see how Procede would work with a fully upgraded engine.

Currently using Procede...


Quote:
Originally Posted by voltron1011 View Post
Wow, I'm really starting to rethink whether or not I want to order a E92 335i.
I'm a regular 'Ring Runner' myself and I think I might be better off springing the extra 10 grand for an M3. It's neither FI nor DI.

Honestly, I wouldn't order a 335i for use on the 'Ring if you are a dedicated 'Ringer and know how to drive properly there. It depends how many laps you will be doing, and how fast you'll be driving. The N54 engine needs so much modification to make it reliable and suitable for the track. You're better off springing the extra 10k for an M3 if 'Ringing is your main aim for the car.

Having said that, Marcel (Alpina_B3_Lux) has a fully modified 335i (everything except engine internals) with an all-aluminium radiator as well and he does maybe 50 laps of the 'Ring a year and his car seems fine so far.


Quote:
Originally Posted by myke354 View Post
tony i know u dont know me but i would love to add some of my .02 cents..

first off a good way a way to stop that carbon from building up would be to run a aftermarket coil per cylinder. this would allow you to burn fuel better there for less carbon would build you would gain a few mpg's and make a few more horses..

second: why not go to a flat face valve to add back some of the compression??

i have to admit i am so glad someone has had the balls to tear down this motor so on the u have my respect .. i know i have been waiting for it to blow before i tore mine down.

to be honest i would have went a different way with the rebuild and i would have had the block sleeved and i would have ran with a 10.1 piston and and i would of liked to see a piston that would give better flame travel..

did u have the piston coated with teflon and ceramic??
i dont know if u looked into it but i know for a fact that having the combustion chamber , valves and piston top ceramic coated has shown to make more power last longer and on turbo cars spool turbos faster cause u push more hot air out to the turbo and have less heat soak..
and have you looked into having the rods, skirts and bearings WPC treated???

i wish you the best of luck with ur rebuild

When you say aftermarket coil, do you mean an extra injector? Have looked into adding extra injectors, but I would then have to change the BMW ECU and use a KMS or Motec system if I wanted it to run properly.

I have to decide ultimately what this car is going to be used for. My 335i is a road car first and foremost, although it has done maybe 500 laps of the 'Ring! If I keep it as a road car, then I won't go to the extreme of a KMS or Motec ECU. If I wanted it as a dedicated 'Ring car, then yes I'd make the N54 race-ready with changes to the fuelling system, the ECU, fabricate a dry sump system for the engine, and then I'd strip out the car completely.

The fact I'm in the process of building another dedicated 'Ring car (with an E46 M3 race engine in a 1 series hatchback body) means that I'm less inclined to go the whole way and make the N54 engine race-ready.


My rebuild spec of the N54 engine is designed so it's more reliable under boost than the standard engine. I want a lower-compression (9.5:1) rather than an almost-normal 10.1:1 as you suggest. I am sure the block is strong enough not to require sleeving, and with the new piston design I don't think I will suffer from piston over-growth.

And yes, the pistons are teflon and ceramic coated

Quote:
Originally Posted by m6pwr View Post
I'm coming in to this thread a bit late, but I do have an interest (I've got an N54 in an '09 Z4). And I have a couple of thoughts that might be of interest re oil and the N54.

The problems associated with direct injection engines (not just the N54 but apparently all di engines) are fairly well known by now. There have been SAE papers on the subject and research is underway by at least one piston ring manufacturer to try to address these problems. And on the BITOG (Bob Is The Oil Guy) forum, a lubricants engineer who regularly attends the 24 Hrs of the Nurburgring race, and meets with race and lubricants engineers there, recently posted rather cryptically that the topic of the hour at the last race was the problems associated with direct injection (which is becoming pretty much the standard in engine design). When I sent him a pm to ask for more information all he would say is that the problems would have to be solved by the engine mfrs, not the lube mfrs. Nice.

The problem is fuel dilution. DI engines operate on much, much higher injection pressures than the "old" port injection engines. In the N54, fuel is injected at 1200-1700 psi, compared to about 45-75 psi in a port injected engine! Pretty amazing. That means higher blow by of fuel past the rings and more "wash down" of the oil film on cylinder walls. The fuel dilution in turn causes two major problems with the oil: viscosity loss (shear back) and significant lowering of the flash point of the oil (more oil vapors form to be sucked up by the CCV system and possibly form deposits in the intake track and valves). The extra heat generated by turbo charging can exacerbate these problems. There is one study I have read about that indicates if the fuel dilution gets bad enough, it can dissolve the tribological film laid down by the anti wear additive ZDDP. Sounds like Doomsday. You have to wonder why aren't BMWs with the N54 disintegrating all over the place. Must be good metallurgy in those motors.

As owners we can't do much about the design of the N54 but we can focus on the oil. I'm not going to recommend any specific oil, but I can say if your concerned like me you probably ought to change the engine oil frequently and do used oil analysis (UOA) at a good lab (flash point measured under ASTM 93/closed cup, and % fuel dilution measured by gas chromatograph) to figure out the oil change interval (OCI). There are no absolute standards or pass/fail marks for these indicators. Each lab seems to have their own standards and I sometimes wonder if some labs have any pass/fail limits at all. I have seen N54 UOAs posted on BITOG where the oil (the BMW 5w30 factory fill) has sheared back to a 20 wt (in as little as 1500 miles OCI) and no warning or negative comment given by the lab at all. In my opinion an oil should never shear back out of grade; and I'd start to be concerned if % fuel dilution exceeds 2%, and flash point goes much below 375 degrees F. I am frankly wary of BMW's 5w30 oil, and the factory OCI of approx 15000 miles is absurd in a motor like the N54. I would use the best grade synthetic (PAO or ester base stock) I could find and afford, preferably one that meets BMW's LL-01 standard and is in the viscosity range recommended for the N54: 5w30, 5w40, 0w30, or 0w40. And I would do regular UOAs until I could figure out how the oil is performing in my particular style of driving. If your N54 is out of warranty, or you don't care about warranty questions, you can go farther afield. Some folks in the lubricants industry think that part of the answer to di is vegetable-based motor oils, or bio-syns, which appear to stand up to fuel dilution better than conventional synthetics. Others mock these lubes as Mazzola/Canola oils. I do know that Fuchs (a leader in synthetic oils since the 1930s) has recently come out with a bio-syn series of synthetics. Unfortunately, I can't remember the name (Fuchs motor oils aren't available in the U.S.).

Tony, when you get your new rat motor finished you might want to try to communicate with John Rowland, the head chemist with Fuchs, through your Fuchs distributor. He is an avid racer and can be quite forthcoming with advice for individuals using his oils. He may be able to give you some ideas on the best oil for your application.

Sorry for taking so much band width. Hope I didn't go over stuff you already know. By the way, I think the N54 is a dynamite motor and I knew all about the di problems (and the HPFP) before I bought the Z4.


Thanks for the great info above. This will help a lot of people on the forum

I have already been in contact with John at Fuchs as I know them well from Nurburgring races. I have been using the Fuchs ProS 5W-40 ester-based synthetic oil for the last 40,000 miles. I personally don't subscribe to BMWs insistence that the Castrol 0W-30 or 5W-30 is suitable in the N54 engine with oil changes potentially only every 18,000 miles. The viscosity loss suffered by the Castrol Edge oil is well known in the racing fraternity here and given the N54 runs hot anyway, it staggers me that not more people have switched to a more performance-oriented oil.

Despite all the problems, I also think the N54 is a dynamite engine but not if you're subjecting it to the high-stresses and operating temperatures that a race track induces.
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