Proper engine break-in technique
05-27-2010, 11:53 AM
#21
Also, I disagree that things don't continue to break in after the first like 5min. Although, I would rather use the term "wear in". Sure your motor will continue to loosen up, but the initial ring seal is achieved mostly during initial warm up, then you get it on the road and beat it (with a good tune) with high rpm/very high vacuum to get maximum seal.
). The point I try to get across though is that after that initial warmup and seating period, its either going to work or it isn't.
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05-27-2010, 11:54 AM
#23
I'm not kidding at all, the rings will not flex more at first start than they will during the duration of their lifetime. The purpose of getting high RPM soon and quickly is because the principle that ring seal works on is applying gas pressure to the top and back of the ring through load. The more load the more pressure.
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05-27-2010, 11:56 AM
#24
EDIT: A few other posts were made while writing...I definitely don't recommend just sitting on the highway at 5K rpm for an hour. That would be the stupidest possible way to break-in a motor. But if you seriously thing that engine speed doesn't have a negative impact on part wear you my friend are the one using the crack. There is absolutely no reason to "rev it up" from the get go. Yes, vary rpm, yes, increase rpm, yes, you need to be using the whole rev range in less than 100 miles, but have you done any real research on just how many revolutions it takes to seat the rings? I've seen UOAs from 250mile break ins that were still showing cylinder wall material removal.
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05-27-2010, 12:07 PM
#26
Right, and that's it...and it varies maybe 5% across the rpm band we're discussing. Therefore you still have sufficient BMEP to do the job. You kept stating load load load. I agree. Full load is available at any rpm.
Now consider how engine speed does affect the rings as they glide (or are dragged) across the cylinder walls. How does the friction vary? Wouldn't you want to condition the rings, and smooth the ridges for every range of engine speed. And my arguement for starting at normal speed ranges is that this is where the motor will spend most of it's life unless it's a race motor.
Now consider harmonics and how much they will play into proper piston ring seating. Where do the uglier vibrations come out? Do we even know? We can safely assume they're higher up the rev range.
Now consider lubrication. When new, the grooves are still deep, and the rings aren't yet functioning in their "hydroplaning" fashion, but skipping across the tops of the ridges. Yes, you want it to wear, but without work hardening. If you do work harden the tops of those ridges you will actually work against the wear you desire, and likely damage the rings.
Again, all speculation, and you've apparently had success (and not puked any rings). But it's something to consider, and I don't see a downside to prudence in this case.
Now consider how engine speed does affect the rings as they glide (or are dragged) across the cylinder walls. How does the friction vary? Wouldn't you want to condition the rings, and smooth the ridges for every range of engine speed. And my arguement for starting at normal speed ranges is that this is where the motor will spend most of it's life unless it's a race motor.
Now consider harmonics and how much they will play into proper piston ring seating. Where do the uglier vibrations come out? Do we even know? We can safely assume they're higher up the rev range.
Now consider lubrication. When new, the grooves are still deep, and the rings aren't yet functioning in their "hydroplaning" fashion, but skipping across the tops of the ridges. Yes, you want it to wear, but without work hardening. If you do work harden the tops of those ridges you will actually work against the wear you desire, and likely damage the rings.
Again, all speculation, and you've apparently had success (and not puked any rings). But it's something to consider, and I don't see a downside to prudence in this case.
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05-27-2010, 12:13 PM
#30
I have found a continuing theme where new "performance oriented" rings (material used) seem to seat very rapidly. Some suggest that the rings are practically seat before the first start simply from rotating the engine to align the crank and cams. Others say 5 min and some say up to 50 miles of driving. The real debate seams to arise with level of load that should be place don the motor. I would agree with high load with no turbo i.e. keep out of boost with a turbo engine.
Maybe a better question is: How much pressure does it take to seat a ring for a given initial gap. At some point a threshold will be crossed where you are just creating more wear on the rings and cylinder walls. This is why a turbo engines running high boost are not expected to last as long as an NA version of the same engine.
Maybe a better question is: How much pressure does it take to seat a ring for a given initial gap. At some point a threshold will be crossed where you are just creating more wear on the rings and cylinder walls. This is why a turbo engines running high boost are not expected to last as long as an NA version of the same engine.
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05-27-2010, 12:20 PM
#32
I'm simply saying don't go straight to redline.
And djp:
The guideline for wear I've always heard is 50-100 miles for the rings to finish seating, although they continue the process for another 1000 miles or so to some extent.
The most important part of this all is to vary load, to both extremes, cover the rpm range withing that period, and then drive it as you intend.
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05-27-2010, 12:21 PM
#33
I have found a continuing theme where new "performance oriented" rings (material used) seem to seat very rapidly. Some suggest that the rings are practically seat before the first start simply from rotating the engine to align the crank and cams. Others say 5 min and some say up to 50 miles of driving. The real debate seams to arise with level of load that should be place don the motor. I would agree with high load with no turbo i.e. keep out of boost with a turbo engine.
Maybe a better question is: How much pressure does it take to seat a ring for a given initial gap. At some point a threshold will be crossed where you are just creating more wear on the rings and cylinder walls. This is why a turbo engines running high boost are not expected to last as long as an NA version of the same engine.
Maybe a better question is: How much pressure does it take to seat a ring for a given initial gap. At some point a threshold will be crossed where you are just creating more wear on the rings and cylinder walls. This is why a turbo engines running high boost are not expected to last as long as an NA version of the same engine.
It looks like I might end up putting together 2 engines this summer. If that happens, I'll have to break them in differently. One will be my low comp high-boost monster, which I'm planning on breaking in around 5psi and 6k-1k overrun. The other will probably be a ~9:1 1.8l block. If I can, I'll try to break that one in using your method and then compare results.
edit: Although this won't necessarily be apples to apples, I can compare the resulting compression #s against the factory spec, which will tell how well the rings seated in.
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05-28-2010, 02:51 PM
#35
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Since some of my background is in piston engined aircraft, I knew that manufacturers were specific about the need for high load and varying engine speeds to be applied to an engine during break-in (run-in). So, I did some digging. The specific procedures were a bit dry, but this overview from Lycoming is insightful. http://www.factoryengines.com/docs/H...20Break-In.pdf
One of the specifics that was common to both Continental and Lycoming's break-in procedures was the bold print insistence that the engines not be run in a high vacuum condition during initial break-in. It was stated that high vacuum conditions promoted ring flutter which stressed the rings and could cause failure. I knew you were supposed to descend gradually without cutting power much after a break-in flight, but have not heard of ring flutter being the reason until now.
One of the specifics that was common to both Continental and Lycoming's break-in procedures was the bold print insistence that the engines not be run in a high vacuum condition during initial break-in. It was stated that high vacuum conditions promoted ring flutter which stressed the rings and could cause failure. I knew you were supposed to descend gradually without cutting power much after a break-in flight, but have not heard of ring flutter being the reason until now.
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06-02-2010, 11:17 AM
#39
Two major considerations for break in.
Cylinders- Cylinder prep and ring pack choice need to be considered. Using high precision rings with well prep'd straight cylinders should be "broke in" by the time the motor is fully assembled. Going back a few decades. Cast rings adn cylinders you could sharp[en your fingernails on took a bit of low load "break-in" to wear in the ring to the cylinder.
Camshafts - Since most here likely use precision rings, the break-in would most likely be about the camshafts. This will vary with the cam type. If not roller cams they most certainly need to wear in before they are exposed to high RPM. (Many a bike cam was severely damaged due to this). V8 cams need the 20 minute run then a 24 cool down to work harden the cam. They run 2k on those for proper oiling during the run. Sometimes a light spring is ran for breakin then heavier springs that belong in the motor. Point is with proper cylinder prep rings really dont need a breakin. Other parts can though.
Cylinders- Cylinder prep and ring pack choice need to be considered. Using high precision rings with well prep'd straight cylinders should be "broke in" by the time the motor is fully assembled. Going back a few decades. Cast rings adn cylinders you could sharp[en your fingernails on took a bit of low load "break-in" to wear in the ring to the cylinder.
Camshafts - Since most here likely use precision rings, the break-in would most likely be about the camshafts. This will vary with the cam type. If not roller cams they most certainly need to wear in before they are exposed to high RPM. (Many a bike cam was severely damaged due to this). V8 cams need the 20 minute run then a 24 cool down to work harden the cam. They run 2k on those for proper oiling during the run. Sometimes a light spring is ran for breakin then heavier springs that belong in the motor. Point is with proper cylinder prep rings really dont need a breakin. Other parts can though.
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06-02-2010, 11:40 AM
#40
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My builder told me that he burnished the cylinder walls and there was no real break-in other than pulling some vaccum with some RPM. He told me to drive it to the dyno, tune it and change the oil, then race it the next day...and after a few days at the track it will make about 20% more on the dyno than the first time you tuned it.
They guy has a pretty solid record with FI engines in general, everyone around here uses him.
They guy has a pretty solid record with FI engines in general, everyone around here uses him.
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