zeroptzero

engine wear isn't really related to break-in, but piston ring sealing is related to how you break-in your engine. Good ring sealing affects power/compression, oil consumption etc... The majority of break-in occurs within the first 100 miles, and it is pretty much all done by 600 miles. After 600 miles the rings are done sealing their fullest, it's not really about wear , but ring sealing. Driving WOT gives you maximum engine sealing potential during the break-in process, but you need to think about it as soon as you drive off the dealer lot.

Engine wear after that is all based on how you drive and maintain the car, # of cold start-ups, stop and go vs. highway, high rpms vs. low rpms, maintenance etc.. . Engine wear isn't always linear, it's affected by a lot of different factors too complicated to discuss in one post. For example once you are driving your car down the highway in cruise conditions with low load and fully hot oil and coolant, the engine is experiencing almost zero wear and that could go one for hundreds of miles. The wear would be very different compared to driving hundreds of miles in stop and go city traffic.

starchland

Ok so how is it done let's say after 600 miles? The surfaces in the engine are going through the same movements, so what changes?

zeroptzero

not exactly sure what you are asking, but the shape of the rings and the shape of the cylinders are not perfect as soon as they are introduced to eachother. The surfaces mate up due to wear that occurs between them within the first 100 miles (estimate), they continue to mate up at a slower rate after that. By 600 miles (estimate) the two parts are as good as they are going to get for the most part. If you put enough pressure on the rings at first start the rings will mate at an angle that is more square to the cylinder as the rings are pushed into the cylinder through pressure. Without maximum pressure they wear into eachother at different angles, very slight differences but enough to make a difference in terms of compression and power. After 600 miles engine wear is pretty much the same either way but the shape of the piston ring at the cylinder mating surface is what can be different, at very minute levels. Hope I'm making sense

SgtB

The piston walls and the rings have microscopic hills and valleys when they are assembled. The initial break-in is with those rough edges filing into each other. The idea is to hone them against each other until the have smooth parallel surfaces to mate against. If you don't push the car hard enough, the cylinder pressure will not be high enough to smooth them completely as the rings pressure against the cylinder wall is driven by that cylinder pressure. As they wear, they smooth out, and as they smooth, they cut less and less until they are in their broken-in state. That's the simple version at least.

steven975

I've recently had the startup stumble, too. My starter was diagnosed as failing...only pulls 70A. If I blip the throttle right when it starts to catch, no stumble. I'll need a clutch soon, so I'll probably just put in a new/rebuilt starter at that time. I can live with it for now.

zeroptzero

That's exactly what mine was doing too , if I gave it throttle it would come alive. I've always thought that my car turns over a bit on the slow side but then I thought they must all be like that. Im going to see a Friend tomorrow so I might see if his car turns over similarly.

I dont think it's related to the starter though because it improves with throttle added, and it has been totally gone after doing some lapping at the track, it has not happened since going to the track. Hmmm mm.

deepbluejh

The initial post was about "blowing out the carbon" on an older car, not about break-in. I'm wondering about that myself as well. Would driving an older car really hard (redline) occasionally help keep power up to snuff? I've got a 2000 Celica GTS that I don't drive very hard at all. Power seems way down from what it was when I got it 8 years ago. I don't know whether this is some sort of particulate buildup in the engine, or just the engine losing compression. I'm scared to redline the motor too much with 188k miles.

zeroptzero

Blowing out the carbon is just a generic phrase used for years going back when autos were built very differently than todays modern engines. What I think happens when running hard is that the plugs get cleaned up a bit of deposits, injectors may clean up from full flow and pressure, and perhaps better engine cleaning from hotter oil flowing through at higher pressure, maybe the PCM adjusts things as well as it is always making changes. I think you should give it good hard run once and a while, not abuse it. It seems to have helped my issue so far.

starchland

I think after a decent run the cat would run hotter and possibly flow better after forcing more ar through it?

rrounds

We have done it this way for years
http://www.mototuneusa.com/break_in_secrets.htm

If you want a totally clean engine(inside), while the engine is running squirt a little water in the intake(think water injection). That will get rid of all the carbon on the pistons, valves and combustion chamber. Don't go out and turn on the garden hose, I use a battery operated squirt gun to clean my engine. I do this about every 10k miles and I do this if I'm going to be taking apart a engine, it cleans the inside spotless so I don't have to much cleaning to do after I take it apart.

ROD