This picks up in the middle of the ‘problem on the dyno’ thread.
I started a new thread to avoid jacking the other one…
Nice to see a knowledgeable guy pointing to this link. I read Motoman’s break-in procedure some time ago and it made a lot of sense from an engineering point of view.
I posted the link on another board and had a couple of guys poking fun - asking who would YOU trust, Motoman or [insert major automaker name here]. I told them to evaluate Motoman’s advice based on the things they actually know. (No reply… Hmmm)
Anyhow, I’m interested to hear from anyone who’s done a relatively fast, but controlled, break-in.
That definatley makes some good points that seem to make a lot of sense. Like he has said though, it is a very controversial subject and there really is no “proof” for either side. I would be interested to see the other side of the argument from someone who also has a lot of real knowledge on the subject and advocates a very “light” engine break in.
At this point, I think when i rebuild my motor ill be running it “semi-hard” and for sure i will be changing the oil asap. I also will be only firing it up once im ready to break it in, and i wont be using synthetic oil (ive heard of that before).
As far as driving the car overly hard, im not really sure i can justify that without real proof and more knowledge on the subject.
I do know however that piston aircraft engine overhaulers and manufacturers say that you should not even start the motor up until you are ready to break it in and take off. They completely recomend against running it on the ground for any length of time, and they want you to take off at 75% throttle, and then cycle the rpms every 5 minutes while your flying for the first hour. So they too recomend that you have the engine under at least some load under the breakin time. They also recomend that you never use a synthetic oil at all, i guess if your changing your oil often enough it doesnt matter (the mineral oil is supposedly better at “cleaning” the engine).
And this is coming from the people who have designed the engines. Peoples lives depend on these engines working properly.
^^ I talked to the head mechanic up here and says that using a high grade synthetic oil will lubricate too well to break in the motor. The piston rings won’t seal up properly to the cylinder walls. Using a lower grade (non-synthetic) will allow everything to wear in and seal everything up. He said for diesels they’d run it with a “break in oil” for the first 250 hours. If it burned oil, they’d run it again for another 250. Usually by the first oil change it wouldn’t burn anything.
He never mentioned anything about how hard to run it tho … .
this is about motorcycle engines but a lot applies to car engines. . .
That lines up the idea that a good ring seal depends on a good ‘fit’. Getting that fit is the trick.
Here’s my current understanding. This is based mainly on thinking and experience in other fields, not engine building. DO NOT take this as truth - just my thoughts. If I’m off base on something, please let me know!
I think there are two wear modes. One when new rings are running in freshly honed cylinders. Initially the ‘rough’ peaks in the cylinder finish are getting knocked down by the rings and the rings are conforming to the cylinders. Contact area is relatively small, contact stress is high, and wear is relatively fast. Once contact area grows enough to drop contact stress below a ‘magic’ number and/or surface conditions change, wear rate drops off and you’ve got more or less the fit you’re going to live with. Lubrication is a key variable relating contact stress and wear.
Initially, you want pretty decent wear rates to achieve a good fit, so you avoid super good lube. Later, after fit is achieved, you want to minimize wear, so you run a great oil.
So why doesn’t wear continue until a good fit is achieved independent of rpms, load, etc? I think it’s related to the different friction, lubrication, and wear response to sliding contact of freshly machined parts vs ‘worn-in’ parts. Freshly machined parts are relatively soft and wear quickly. ‘Cold working’ steel hardens it, and I can imagine a surface layer being developed as a result of repeated sliding contact, let’s call it burnishing. (The link above calls it ‘glazing’)
If the load is ramped up really slowly you cold work and burnish the contact surfaces with relatively little wear resulting in higher contact stress, more ‘leakage’ of combustion gases and oil past the seal, and a higher steady state wear rate.
Starting with modest loads, but ramping them up relatively quickly maintains the high initial wear rate and chews off all the high spots BEFORE they get work hardened and burnished. Ideally, this results in larger contact area, lower leakage, and lower steady state wear - a tighter, more durable engine.
you want to run what they call a non-detergent oil, and additive that contains zinc. Obviously the first few minutes of the initial start up is to break the cam in, change the oil, and filter. The diesels are different than a gas engine, diesels piston rings are a spring type ring, where as a gas is not, gas engines require the compression to seat the rings against the cylinder wall. When i ran my car, i was easy for the first 10 km, then i started going semi harder in second to third, never use first. After 500km the engine was almost fully broken in.
This is kind of an old thread, but I want to add something that I learned in school. One of the main things about engine break in has to do with what type of rings get used. The two types of compression rings that are commonly used are the simple cast iron rings, or molybdenum (sp?). The cast rings are of softer material and are basically broke in after initial start-up. This would apply to the “rough” break-in method described above. The other type (molybdenum) or “chrome” are of a much harder material, these rings take a substantially longer time to break in, somwhere in the area of up to 5k km’s of no more than 50-75% engine load. After that though once they have seated properly you have an engine that is good for a much longer period of time. Moly rings are good for 200,000+ KM where cast are usually around half before they start to wear out.
I recently rebuilt the engine in my winter truck (94 Ford F-150 5L engine) for a project at school. (I was going to rebuild the CA in my car buy my budget wouldn’t permit) The engine in the truck had only 150,000km’s but was using 3-4L of oil between oil changes since about the 90,000-100,000km mark. The truck was never driven hard until 140,000km (thats when I got it) And it recieved the “easy break-in” being as it was only driven by two people before me and both of them are over 50. So now that the truck is complete and back on the road I am trying this rough break-in to see if it works.
So far for break-in what I have done is ran conventional oil in it for start-up and about 5km’s of driving, drained oil, replaced filter, new conventional oil. I am now running it with this oil for 500km then I will change it again with more conventional 5W-30. Then in 5k km I will run synthetic. Then I will see how that works. The instructor at school recommended this procedure and I trust his judgement.
I went with the standard cast iron rings. I was considering moly, but I had to order special because of the .020 overbore. It was going to take too long to get them.
If I understand correctly, if you’ve got very hard, strong rings and you push it hard at the beginning you don’t wear the rings in any faster because they’re pushing on the softer cylinder walls and you’ll probably just wear the walls more than you need to until the rings get ‘smooth’. The wear mode on the Moly rings isn’t accellerated significantly by harder loading.
I broke the engine in on my car kind of “by the book”. I did not do any hard revs (ie: shifts were no higher than 3K) and did my first oil change at 2400kms. The engine used about 1/2 litre of oil (which is normal). I will do another oil change at 7400kms. The engine has used another 1/2 litre of oil in the following 2000kms (again, normal).
I installed a magnetic drain plug and a “Filter-Mag” after the first oil change. I am curious to see what the plug will “catch” at the next change. I have rev’ed the engine hard since the first oil change. It is performing wonderfully. The dyno test was done at 20kms. I was kind of worried about rev’ing the engine hard for the test. Six gear-shifts at 7000 rpm was kind of disconcerting for a new engine. But the good folks at Steve Millen Racing assured me that there would be no problem. And there hasn’t been.
