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Hello all!

I just recently picked up a brand new limited auto BRZ and I'm loving this car just as much as the rest of you are loving yours. I got this car exactly a week ago from today and on a few different occasions I have drove the car above the 4K mark. Well come to find out after reading online today, and as most of you already know, the car has to be broken in properly before doing anything crazy. Unfortunately I did not know at the time and now I am a little scared I might of hurt my car a bit. Now, I have been good to the car otherwise and will continue to do so from here on out. No cruise control, sudden stopping or aggressive accelerating.

However, what I need to know is can someone tell me what damage I may have done to the vehicle by revving to the 5K-6K range 3-4 times during the cars first 400 miles?


Thanks.
 

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Oh, you're screwed. Go over 4k once before 1000 miles and she will fall apart. You've no doubt completely ruined the engine at this point.
 

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Ignore Ragnar - If you read the owner's manual carefully, you will note that the statements about not exceeding 4k rpm and avoiding constant engine speeds are qualified by the phrase, "...except in an emergency". I certainly did, and I am sure most of our brethren on this forum also did encounter several emergencies during the break-in period.

Just don't make a habit of it.
 

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It's not like you drove 75 in second gear for an hour, so don't worry about it. A few times over 4K - in my case it was accidental ;) - is not going to hurt anything. So relax and enjoy.
 

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Agreed. The specified break in requirements are intended to prevent you from overheating the rings. Subaru is just advising you not to run the engine too hard except briefly during the first 1,000 miles or so.

You can actually feel the engine loosen up as it breaks in.

This is a strong engine constructed to run at 7,000 rpm for as long as you like, after initial break in, so 5,000 rpm for a few seconds isn't going to affect the break in.
 

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Where does that come from?
Any engine builder knows this. The piston speed and ring loading need to be limited but at the same time the rings need to grind themselves into perfect conformity with the cylinder walls. All breaking in procedures are designed to optimize these two conflicting requirements.

If engine longevity isn't an issue so excessive ring and bore wear are not a concern then a hard break in works fine. On the other hand, if you want the engine to seal well and retain that seal for very high mileages you would be wise to break in the engine as per Subaru's recommendations.

Do you have sources that say otherwise?
 

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Any engine builder knows this. The piston speed and ring loading need to be limited but at the same time the rings need to grind themselves into perfect conformity with the cylinder walls. All breaking in procedures are designed to optimize these two conflicting requirements.

If engine longevity isn't an issue so excessive ring and bore wear are not a concern then a hard break in works fine. On the other hand, if you want the engine to seal well and retain that seal for very high mileages you would be wise to break in the engine as per Subaru's recommendations.

Do you have sources that say otherwise?
No, I do not have sources. I note that you don't either.
 

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No, I do not have sources. I note that you don't either.
I do actually. The Subaru handbook is one.
Here's another although racing engines are run in quickly for other reasons, longevity isn't a factor.

http://www.ret-monitor.com/articles/wp-content/uploads/pdf/rings.pdf

If you understand how piston rings work the reason for break in requirements is easy to understand.

Of the two conflicting requirements piston speed is the one to avoid.

The rings need load to bed in. So there is no real reason to avoid wide throttle openings as long as the engine is not lugged or revved too high, or for too long at high rpm.

Full load at low rpm can cause excessive blow by and full load at high rpm can cause excessive ring temperature. The uppermost compression ring gets very hot, adding friction heat from the bedding process can lead to ring failure due to heat.

The reason new engines use oil is the same reason they need to be run in carefully. Oil gets burned wherever the piston ring pressure is lower, I e. The "low spots" in the ring/cylinder wall contact points. This oil prevents the ring from wearing at that point. At the high points ring pressure is higher and ring wear is higher. Eventually all the high spots wear down and ring pressure is even all around.

Piston rings only seal very lightly by inherent internal spring pressure. The real seal results from combustion gas pressure leaking behind the ring into the ring groove. Rings are L shaped in profile for this reason. Piston rings seal by gas pressure in much the same way as O rings work.

For combustion pressure to leak behind the ring face the initial light spring pressure must be preserved or combustion pressure will simply blow by.

Revving too high or too low can disturb this initial spring pressure seal. Running at too light throttle can reduce the ring pressure produced by combustion pressure. The worst situation is to run high load and high rpm. Low load and high rpm are nearly as bad, especially on overrun when oil is literally sucked past the rings. Best technique is mid range piston speed and fairly high engine load, just as Subaru recommends.

Rpm needs to be varied to ensure the piston travel steadily increases its range up and down the bore to ensure the no wear ridge at the top of the piston travel really is at the top when the engine is revved to maximum. That's the reason to really drive the engine as hard as possible once initial break in has occurred. Every engine will be different unless run in on a test bed so running in requirements are conservative. Too long running in is worse than too quickly.
 

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Thanks so much for that detailed explanation, Subie! I now realize I've not been running it hard enough since I passed the 1,000 mile mark (I've got about 1,200 on it now, and have only been revving to about 5Gs.)

Starting tomorrow I'll be going to 6G and 7G often.

I'm not mechanical minded, so didn't understand the need for revving it so hard. So thanks for the explanation.

Buzz.
 

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Subieman,

I have a question for you. As I was revving up to 7Gs today in first (before shifting into second and revving again, etc.,) I wondered if by "driving it hard" you meant for me to keep it at or near 7Gs for a sustained amount of time (actually driving it in first or second gear at 7Gs for a sustained period,) or did you mean just rev it to 7, then shift and rev it to 6-7 before shifting again and down into the 3-4G cruising range? I just want to make sure I understand the correct procedure and meaning of "driving it hard."

Today I revved it to 7 starting off in first, and then to 6-7Gs in second before shifting and driving the rest in the 3-5 range.

Is this right - or should I drive it "harder?"

Thanks for the advice.
 

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Just run it to red line, shift and repeat until you crash or get arrested!

Seriously, the only time you run an engine for a continuous period at redline is on a track down the fast straights where your speed is rev limited.

Use full throttle often and do redline shifts. Rings benefit from combustion gas pressure. The whole engine is designed to do redline shifts all day every day. No need to actually run it at the redline for any length of time though.
 

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Just run it to red line, shift and repeat until you crash or get arrested!

Seriously, the only time you run an engine for a continuous period at redline is on a track down the fast straights where your speed is rev limited.

Use full throttle often and do redline shifts. Rings benefit from combustion gas pressure. The whole engine is designed to do redline shifts all day every day. No need to actually run it at the redline for any length of time though.
Okay. That's what I wanted to be sure about. Thanks!
 
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