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Discussion Starter #1
Hello everyone.

Got a K24a2/K20a2 I recently put together. While apart I had the cylinders honed and installed some new Mahle pistons rings. Top ring is carbon steel with a chrome facing, oil rings are stainless steel with a chrome facing. Engine has about 250 miles on it so far. Lots of blowby and burns oil after coasting to a stop then taking off again (at least that's the only time I see smoke). Oil consumption is around a quart every 200 miles at the moment. I've run conventional 10W-30 oil, changed it after ~60 miles. After initial startup I burped the coolant system while fluctuating the throttle. Once warmed up I went for a drive and did some 3rd gear pulls then let it coast back down.

First time replacing rings but I have no doubts I installed them correctly. I regret not researching ring material more beforehand. I've read chrome rings can take upwards of 1,500 miles to fully seat, anyone have any first-hand experience with this?
 

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Arouse the DAMPFHAMMER!
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...First time replacing rings but I have no doubts I installed them correctly. I regret not researching ring material more beforehand. I've read chrome rings can take upwards of 1,500 miles to fully seat, anyone have any first-hand experience with this?
Yeah, this is pretty much what you likely see with hardened ring surfaces. The break in approach to get them sealed is the key to shorten the phase to get acceptable leakdown values. At the former company I was (industrial engine company) we experimented with different coatings and hardening approaches. One could clearly see the effect of the longer duration versus the duration to a sealed piston ring-liner system. It was good to adapt the break in approach to the ring properties. But there were also ring systems, which couldn't adapted to break in process, they were just to resistant for a healthy break in wear.

E.g. if you use chromated rings for NA purpose, I would say, as long as you won't to run it more then 200 kmiles it is overrated to have a chromated ring surface. The break in process, even it is very hard can't challenge the necessary wear of the surface to shape the ring as needed. I wouldn't use chromated rings for an NA application, the radial force to break them in is low and therefore the break in takes long and make the sealing not as good as with an fast break in.

:twocents:
 

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Really wish I would have researched more on the rings before buying. These were significantly cheaper than Honda rings and I only read good things about Mahle so I went with them.

Does 1,500 miles seem about right to finally seat? Anything I should be doing to help the process? Should I be avoiding idling and constant RPM highway driving?

Appreciate the input.
 

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Arouse the DAMPFHAMMER!
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Does 1,500 miles seem about right to finally seat? Anything I should be doing to help the process? Should I be avoiding idling and constant RPM highway driving?
I am not sure how long it will take to get them seated, this is completely depended on the wear partners, the forces, temperatur, cycles, ... . What you can do is to run mineral oil which has no friction reducers added and run the engine hard. Hard means a lot and long WOT section. It would help to let run the engine against the brakes to calm the vehicle speed. E.g. run it on the highway at 60 mph while having it in 3rd gear at WOT and control vehicle speed by the brake pedal. This put stress to all parts not only to the rings, but to wear the rings more fast it is the easiest way. If you cycle the engine load and engine speed the break in would be better. But this makes driving on the highway more risky for you and others, which I don't recommend to you.
 

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Thanks Lotus. I've heard about running non-detergent oil which I believe is equivalent to mineral oil. I'll see if I can find some locally.

What I've been doing is going for a ~45 mile drive every day. During this drive I am doing lots of 4th gear pulls up to 6-7k rpms then coasting back down. Trying to keep a lot of pressure on the rings to help them seat. Hopefully in the next couple hundred miles I start seeing some improvement.
 

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Arouse the DAMPFHAMMER!
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...I've heard about running non-detergent oil which I believe is equivalent to mineral oil...
I am not sure if the detergents affects the wear rate much. The property, which is important, comming with mineral oil, is the lack of friction modifiers like molybdenum or nano-particle based stuff etc.. Keep an eye on that.

...What I've been doing is going for a ~45 mile drive every day. During this drive I am doing lots of 4th gear pulls up to 6-7k rpms then coasting back down...
That is a very good approach. If you play with the car brake to keep WOT while driving within the speed limits, you will see much more duration in higher pressure condition (= higher wear of rings and liners). Just keep an eye on the backside followers of your car, not if they think what is this guy doing here...and call the race control guys :wink:.
 

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1,500 miles of very hard driving later and I haven't seen any improvement in oil consumption. The engine is coming back out and Honda genuine piston rings are going back in.

If I was driving the car hard I was seeing a quart of oil burnt every 100 miles.
 

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While its apart, check the bore with a bore gauge for out of round and taper.
Shars sells them. You will need a mic to set the gauge tho.
You could take the bare block to a machine shop and have them check it.
Maybe not the one you paid. They may not be truthful.
You said it was your first time...you did gap them correctly?
And clock them?
Maybe there were steps on the rings to face upward, etc.
Pretty rewarding to take it back apart and autopsy.
You may see something that makes you say "Wow, I can't believe I did that"
 

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Dropping the block back off at the machine shop today. There are a few vertical lines in the cylinder wall, nothing I can catch with my fingernail. Other than that the hone looks good still. They did check for out of round and taper last time they had it. They haven't given me a reason to not trust them yet so the block is going back to them. The machine shop is the only one nearby, I've taken multiple cylinder heads and blocks to them to be flattened. Haven't had any issues with those.

Rings were gapped and clocked correctly, I can't remember the what the gap was but it was within spec according to the service manual. I installed per the manufacturers specs. There is an 'M' or something on one side of the ring, that's the side that went up.

I don't see anything obviously wrong. At this point all I can think is the rings were just a junk set. Or maybe they just needed more time to seat, I don't know. OEM rings on the way, but it's going to take a good month. We'll find out then.
 
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