Is break-in or run-in really required?
10-09-2013, 01:46 AM
#62
Pro
Good questions. Most people seem to assume that there just has to be metal to metal contact occurring, to some degree or other, more or less all the time. Under that assumption they come to the obvious conclusion that more throttle and higher revs just naturally equals more "wear and tear."
But what actually happens is hydraulic forces (aka, lubrication) prevents this contact. "Wear and tear", in the sense most people think of it, happens not when you floor it but when you first start it up. Those few moments after starting and before oil pressure comes up account for virtually all the "wear and tear" over an engines lifetime.
But what about high RPM? Still no contact, therefore no "wear and tear". But, lots more physical stresses on all the parts. Its the repetition of these high stress cycles that can cause parts to fail. Its obvious when parts break. But they don't always break. Stress cycles can also result in parts merely going out of spec- and out of spec parts can result in contact, and wear and tear, eventually failure.
And so: when is it safest to use max output and RPM's? When the engine is fully in spec. And when is an engine most likely to be fully in spec? When its brand new.
But what actually happens is hydraulic forces (aka, lubrication) prevents this contact. "Wear and tear", in the sense most people think of it, happens not when you floor it but when you first start it up. Those few moments after starting and before oil pressure comes up account for virtually all the "wear and tear" over an engines lifetime.
But what about high RPM? Still no contact, therefore no "wear and tear". But, lots more physical stresses on all the parts. Its the repetition of these high stress cycles that can cause parts to fail. Its obvious when parts break. But they don't always break. Stress cycles can also result in parts merely going out of spec- and out of spec parts can result in contact, and wear and tear, eventually failure.
And so: when is it safest to use max output and RPM's? When the engine is fully in spec. And when is an engine most likely to be fully in spec? When its brand new.
10-09-2013, 07:49 AM
#64
Three Wheelin'
Back on topic:
I'm breaking in my engine, full stop. I don't know enough about the subject to contradict Porsche's recommendation. Plus I don't want to give them a proverbial stick when something goes bang in my car.
10-09-2013, 04:12 PM
#65
Rennlist Member
Suzy is a levelheaded, grown up lady. She is not going to be offended by an ANALOGY ! Neither should anyone else for that matter !
Back on topic:
I'm breaking in my engine, full stop. I don't know enough about the subject to contradict Porsche's recommendation. Plus I don't want to give them a proverbial stick when something goes bang in my car.
Back on topic:
I'm breaking in my engine, full stop. I don't know enough about the subject to contradict Porsche's recommendation. Plus I don't want to give them a proverbial stick when something goes bang in my car.
10-21-2013, 06:58 PM
#66
Drifting
Interesting PCA article on the subject of engine break-in.
http://yel.pca.org/porsche-engine-break-in/
The article covers Porsche new engine testing at the factory and contains quotes from a factory engineer on the subject. I apologize in advance if this is a repost.
http://yel.pca.org/porsche-engine-break-in/
The article covers Porsche new engine testing at the factory and contains quotes from a factory engineer on the subject. I apologize in advance if this is a repost.
10-21-2013, 08:09 PM
#68
These threads are always a hornets nest, although like chuckbdc, I always wonder why someone would take anyone but a Porsche Engineer's opinion.
(No, please don't answer that, seriously
)
I do however, have a question...
Can someone define what "varying the revs" strictly in the context of engine break in mean? Does it mean varying the revs often under the ~4K RPM ceiling or does it mean varying throughout the rev range on occasion but keeping it under 4K for most of the driving?
I kept mine at or under ~4K for the first 900 miles or so. After that I varied the RPMS throughout the rev range for just a bit every time I drove after the engine was up to temp keeping it at or under 4K most of the time until I hit 2K on the odometer. Hope I did it right for a car I plan to keep for the long haul.
(No, please don't answer that, seriously
)I do however, have a question...
Can someone define what "varying the revs" strictly in the context of engine break in mean? Does it mean varying the revs often under the ~4K RPM ceiling or does it mean varying throughout the rev range on occasion but keeping it under 4K for most of the driving?
I kept mine at or under ~4K for the first 900 miles or so. After that I varied the RPMS throughout the rev range for just a bit every time I drove after the engine was up to temp keeping it at or under 4K most of the time until I hit 2K on the odometer. Hope I did it right for a car I plan to keep for the long haul.
10-22-2013, 04:54 AM
#69
These threads are always a hornets nest, although like chuckbdc, I always wonder why someone would take anyone but a Porsche Engineer's opinion.
(No, please don't answer that, seriously )
I do however, have a question...
Can someone define what "varying the revs" strictly in the context of engine break in mean? Does it mean varying the revs often under the ~4K RPM ceiling or does it mean varying throughout the rev range on occasion but keeping it under 4K for most of the driving?
I kept mine at or under ~4K for the first 900 miles or so. After that I varied the RPMS throughout the rev range for just a bit every time I drove after the engine was up to temp keeping it at or under 4K most of the time until I hit 2K on the odometer. Hope I did it right for a car I plan to keep for the long haul.
(No, please don't answer that, seriously
)I do however, have a question...
Can someone define what "varying the revs" strictly in the context of engine break in mean? Does it mean varying the revs often under the ~4K RPM ceiling or does it mean varying throughout the rev range on occasion but keeping it under 4K for most of the driving?
I kept mine at or under ~4K for the first 900 miles or so. After that I varied the RPMS throughout the rev range for just a bit every time I drove after the engine was up to temp keeping it at or under 4K most of the time until I hit 2K on the odometer. Hope I did it right for a car I plan to keep for the long haul.
Anyone?
Does anyone find it the least bit odd that these Porsche engineers, so technically well trained they could cite the spec and stress parameters of every part to the micrometer and millistrain http://www.ni.com/white-paper/3642/en/ suddenly lapse into the most vague language of ease and bedding whenever talking about "break-in"?
Anyone?
(rpilot asked not to answer so instead of answering I'm asking
Oh, I know- and what is the engineering reason for specifying rpm and not throttle or load?
(Yes, please do answer that- seriously.)
10-22-2013, 05:32 AM
#70
Drifting
The average driver/operator can easily monitor the engine RPMs simply by looking at the tach. OTOH, accurately monitoring throttle application and/or load is far less precise and very hard to monitor with any accuracy.
Disclaimer: My right foot is not precisely calibrated(otherwise I'd be a pro racer) but YMMV.
10-22-2013, 07:37 AM
#71
Instructor
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Chuck,
don't spoil a perfectly good conspiracy theory and discussion topic with logic and common sense. Porsche laid down the law. Does not have to make sense. Does not have to be right either. That's why more lawyers than engineers can afford to buy 911's.
I'll bet my life's pension that the rules where not made by a Porsche engineer. They where made by management (stocked with lawyers) after consulting the guy that sweeps the factory floor. No really - the guy that sweeps the floor knows everything. It's a big floor and he gets to see more of the factory than anybody else. And he sweeps it every day. Really !
Rainier
don't spoil a perfectly good conspiracy theory and discussion topic with logic and common sense. Porsche laid down the law. Does not have to make sense. Does not have to be right either. That's why more lawyers than engineers can afford to buy 911's.
I'll bet my life's pension that the rules where not made by a Porsche engineer. They where made by management (stocked with lawyers) after consulting the guy that sweeps the factory floor. No really - the guy that sweeps the floor knows everything. It's a big floor and he gets to see more of the factory than anybody else. And he sweeps it every day. Really !
Rainier
Can anyone quote any engineer (bonus points for Porsche but I'll accept any) giving any specific engineering reason why exceeding 4k rpm will cause damage before 2k miles but is fine after 2001 miles?
Anyone?
Does anyone find it the least bit odd that these Porsche engineers, so technically well trained they could cite the spec and stress parameters of every part to the micrometer and millistrain http://www.ni.com/white-paper/3642/en/ suddenly lapse into the most vague language of ease and bedding whenever talking about "break-in"?
Anyone?
(rpilot asked not to answer so instead of answering I'm asking
Oh, I know- and what is the engineering reason for specifying rpm and not throttle or load?
(Yes, please do answer that- seriously.)
Anyone?
Does anyone find it the least bit odd that these Porsche engineers, so technically well trained they could cite the spec and stress parameters of every part to the micrometer and millistrain http://www.ni.com/white-paper/3642/en/ suddenly lapse into the most vague language of ease and bedding whenever talking about "break-in"?
Anyone?
(rpilot asked not to answer so instead of answering I'm asking
Oh, I know- and what is the engineering reason for specifying rpm and not throttle or load?
(Yes, please do answer that- seriously.)
10-22-2013, 10:14 AM
#72
Race Director
10-22-2013, 07:18 PM
#73
Was not for nothing I said that. Take the comment above attempting to answer my question "what is the ENGINEERING reason for specifying RPM instead of throttle" with a reply that answers the question "what is the BEHAVIORAL reason"? An engineering answer would take account of, for example, connecting rod stretch at high rpm, or maybe valve float, or something- anything- having to do with, you know, ENGINEERING factors: Mechanics. Hydraulics. Materials. Loads. That kind of thing. Instead we got something completely different, which basically boils down to "the engineer said RPM because he knows the average driver has no idea how much throttle he's using or how to control it."
One of the things I first noticed when I decided to make a serious effort at understanding this topic is, not just the utter lack of logic and reason but the outright disdain and disregard for it. Not just once but several times now people have literally said they really don't care about reasons, the Porsche engineers said so, and that's that.
So they place all their trust in the engineers. Okay. I get that. But then, who do the engineers place their trust in? Who tells them how things work? Is there no independently verifiable means of getting at the truth?
As a kid I was taught that modern man had developed this thing called the scientific method, a revolutionary process by which anyone, anywhere, and at any time is equally capable of solving and understanding a problem as well as anyone else.
But that's just me being me again, spoiling a perfectly good conspiracy theory with logic and common sense.
10-22-2013, 10:23 PM
#74
Drifting
Was not for nothing I said that. Take the comment above attempting to answer my question "what is the ENGINEERING reason for specifying RPM instead of throttle" with a reply that answers the question "what is the BEHAVIORAL reason"? An engineering answer would take account of, for example, connecting rod stretch at high rpm, or maybe valve float, or something- anything- having to do with, you know, ENGINEERING factors: Mechanics. Hydraulics. Materials. Loads. That kind of thing. Instead we got something completely different, which basically boils down to "the engineer said RPM because he knows the average driver has no idea how much throttle he's using or how to control it."
I clearly stated an answer to your question about throttle application during break-in. The engineers did not specify throttle application during break-in because there is NOT an easy way to monitor this. If there was an accurate way to monitor this, perhaps they would have. I don't know.
Are you an engineer? If so, I'd love to hear you refute the recommendations of the P engineers(at least the comment by the single engineer quoted in the above referenced article) with facts instead of pure hearsay.
10-22-2013, 11:03 PM
#75
The ENGINEERING reason for specifying limited RPM during break-in is answered in the article I cited. Now, whether or not you want to believe that is your choice.
I clearly stated an answer to your question about throttle application during break-in. The engineers did not specify throttle application during break-in because there is NOT an easy way to monitor this. If there was an accurate way to monitor this, perhaps they would have. I don't know.
Are you an engineer? If so, I'd love to hear you refute the recommendations of the P engineers(at least the comment by the single engineer quoted in the above referenced article) with facts instead of pure hearsay.
I clearly stated an answer to your question about throttle application during break-in. The engineers did not specify throttle application during break-in because there is NOT an easy way to monitor this. If there was an accurate way to monitor this, perhaps they would have. I don't know.
Are you an engineer? If so, I'd love to hear you refute the recommendations of the P engineers(at least the comment by the single engineer quoted in the above referenced article) with facts instead of pure hearsay.
http://yel.pca.org/porsche-engine-break-in/
The relevant passage is here:
"When we do our engine test, the metals inside the engine never reach the temperatures they would when driven on the street since the test session is fairly short. In other words, the bearings, pistons and cylinders never get a chance to thermally expand to their maximum. Therefore, there is little wear on the moving components. But when you drive a car on the street, the engine parts expand considerably more because of the heat being generated from the engine running for an extended period of time."
He clearly states the concern is temperature not RPM! I frankly have been trying to avoid this article, because its one of the worst examples of writing (or speaking, if the engineer is quoted accurately) on this subject I've ever seen. The so-called engineer continues:
"Porsche wants the engine to break-in slowly, which means it needs to maintain a lower operating temperature (below 4,000 RPM)"
So I have to ask: is operating temperature now measured in RPM? Is it okay to redline so long as we "maintain a lower operating temperature"? He sure seems to be saying that, because that is EXACTLY the 'reason' he gave for it being okay at the factory. But, if we follow his "reasoning" then how low of an operating temperature are we to maintain? "Below 4,000 RPM"!This is what passes for reasoning with the break-in crowd?
And please, don't even try and say I'm cherry picking or taking out of context. Later on down the writer summarizes:
"Porsche’s time frame for that to occur is calculated to be 2,000 miles, with the heat restriction being 4,000 RPM."
I think its pretty clear, either the 'engineer' or the 'writer' (or both!) think temperature is measured in RPMs.