[Boostedphil698]

Hi everyone,

This being my first BMW and my first turbo car, I wanted to know what is the best way to keep my turbo and rod bearings from premature wear? I was told oil changes every 5000-7000 miles and wait till oil is at operating temperature before going over 3k RPMs. How durable are the rod bearings on the 435i N55? My engine has 34000 miles on it.

[F32Fleet]

Just wait until the oil temp gauge starts to move.

The N55 is solid in STOCK FORM. Once you start tuning then obviously all bets are off.

[Boostedphil698]

I've seen N55's handle up to 700whp, not sure how long they lasted. With that said, I will tune at some point after my factory warranty is up, but I don't think I'll ever upgrade the turbo.

[jh_f30]

The things you noted in your first post are spot on, IMO. Frequent OCIs, and keeping the revs down when cold will go a long way to protect your engine, and that's the case with just about any engine, not just the N55. I almost always keep it in Comfort (or even EcoPro) until the engine's had a chance to come up to temp. If I do pop it into Sport/Sport+ for any reason, I'll short shift at about 2500 RPM with the paddles.

Rod bearings aren't a common issue for the N55. At least not from what I've seen here on the forums. I'd also say pushing 700+whp is stretching it. N55s in the F3x don't have forged internals like the N54 did (afaik, the N55 in the first M2 did have forged internals before they went to the S55 in the M2 Comp). Personally, I don't think that's a safe target without building up the bottom end. Besides, it's not like anyone can really use that kind of power in the real world on public roads.

[IraHayes]

Originally Posted by 435i_Phil

Hi everyone,

This being my first BMW and my first turbo car, I wanted to know what is the best way to keep my turbo and rod bearings from premature wear? I was told oil changes every 5000-7000 miles and wait till oil is at operating temperature before going over 3k RPMs.

This is exactly the protocol I follow, not just for my bimmer, but for every car I’ve owned. My last car had 260k miles on it when I sold it and was still going strong.

I also let my car idle for at least a minute before driving off on a cold start, like first thing in the morning, just to give the oil a chance to circulate through the engine, and especially the turbo bearings before I put the engine under load. I also always let the car idle for 30 seconds to a minute after driving to let the turbo impeller/turbine spool down. I'll let the car idle two or three minutes before shut down if I was driving the car hard, or doing a lot of uphill driving; basically driving in a way that made the turbo work harder than usual.

[Boostedphil698]

Originally Posted by jh_f30

The things you noted in your first post are spot on, IMO. Frequent OCIs, and keeping the revs down when cold will go a long way to protect your engine, and that's the case with just about any engine, not just the N55. I almost always keep it in Comfort (or even EcoPro) until the engine's had a chance to come up to temp. If I do pop it into Sport/Sport+ for any reason, I'll short shift at about 2500 RPM with the paddles.

Rod bearings aren't a common issue for the N55. At least not from what I've seen here on the forums. I'd also say pushing 700+whp is stretching it. N55s in the F3x don't have forged internals like the N54 did (afaik, the N55 in the first M2 did have forged internals before they went to the S55 in the M2 Comp). Personally, I don't think that's a safe target without building up the bottom end. Besides, it's not like anyone can really use that kind of power in the real world on public roads.

Do you know why RealOem shows a set of connecting rods in the S55 and N55 as the same? I've seen some threads where people argue that the rods are the same.

[jh_f30]

Originally Posted by 435i_Phil

Do you know why RealOem shows a set of connecting rods in the S55 and N55 as the same? I've seen some threads where people argue that the rods are the same.

Hmm, I wasn't aware of that. Pistons and crankshaft have gotta be different.

[Boostedphil698]

Originally Posted by jh_f30

Hmm, I wasn't aware of that. Pistons and crankshaft have gotta be different.

That's what I'm thinking too. I know for a fact that rod bearings are the same, and my one friend said to me "gonna have to do those rod bearings at some point." I'm just like "they're the same as the S55 lol."

[jh_f30]

Originally Posted by 435i_Phil

That's what I'm thinking too. I know for a fact that rod bearings are the same, and my one friend said to me "gonna have to do those rod bearings at some point." I'm just like "they're the same as the S55 lol."

I'm not too familiar, but does the S55 have rod bearing issues like the S65 did? I'm wondering if BMW mostly solved the issue with the N55/S55 design.

[Boostedphil698]

Originally Posted by jh_f30

I'm not too familiar, but does the S55 have rod bearing issues like the S65 did? I'm wondering if BMW mostly solved the issue with the N55/S55 design.

S55 has solid rod bearings unless someone proves me wrong. The crank hub was the Achilles heel on the S55.

[thejeremyman9]

Originally Posted by F32Fleet

Just wait until the oil temp gauge starts to move.

The N55 is solid in STOCK FORM. Once you start tuning then obviously all bets are off.

I would wait a little longer before driving hard. The bottom of the gauge is only 160F. You really want around 210F before doing any hard driving so that the oil has reached the proper weight and any water/moisture can evaporate.

Another consideration is trans temp. From my monitoring/logging, coolant reaches temp in a few minutes, oil takes about 5 miles or 15 mins (on my commute), and my trans takes the longest. For example if i leave my house with trans at 65F and drive 15 minutes to work, trans might only be at 120F or so. Now trans doesnt have the same considerations at oil, but it does take quite a while to warm up. This is for 8AT.

[jh_f30]

Originally Posted by thejeremyman9

I would wait a little longer before driving hard. The bottom of the gauge is only 160F. You really want around 210F before doing any hard driving so that the oil has reached the proper weight and any water/moisture can evaporate.

Another consideration is trans temp. From my monitoring/logging, coolant reaches temp in a few minutes, oil takes about 5 miles or 15 mins (on my commute), and my trans takes the longest. For example if i leave my house with trans at 65F and drive 15 minutes to work, trans might only be at 120F or so. Now trans doesnt have the same considerations at oil, but it does take quite a while to warm up. This is for 8AT.

What do you see as normal operating temps on your trans oil during extended or spirited driving?

[thejeremyman9]

Originally Posted by jh_f30

What do you see as normal operating temps on your trans oil during extended or spirited driving?

Just confirmed in some of my logs, 180-185 seems to be normal steady state operating temp. A pull or two doesn't really affect this at all.

I'm not 100% sure after extended hard driving since i haven't been to the canyons in a while, but from what I remember, I never saw the trans getting "heat soaked" or struggling to keep the temps down. For example i dont think i ever saw 200F at any point, even in sport+, manual mode, hard driving.

Note: This is without any tune's active/enhanced cooling enabled. I ran MHD's increased cooling (slider in the middle, not full "track" setting), and that decreased my steady state oil temp from about 240 to 215 or so, and also decreased steady state trans temp a little. I only ran that briefly though and went back to stock for everyday driving.