Question about motor Break-in
Re: (deviousKA)
WOOT WOOT!! i have 3 month till i am legal..... You and I will have to hit some of the local bars.
-
deviousKA
- Posts: 1355
- Joined: Tue Aug 12, 2003 5:04 pm
- Car: 90 240sx NA /72 Datsun 510 NA /86 corolla GTS NA
- Contact:
Re: (wild_maxx)
Friendly gesture? or shameless plan to obtain "secret when sober" KA24 information? Haha.
Im gonna have a *legal* head start, but im down for a round any time.
Im gonna have a *legal* head start, but im down for a round any time.
Re: (deviousKA)
sounds good bud. /threadjack!
Re: (wild_maxx)
man i did the drive it to the dyno thats 20 miles away then do 4 pulls (330whp/330tq at 13lbs) beating the hell out of it then taking it home change the oil, take a 400 mile trip then change the oil again synthetic this time and now im happily boosting 18lbs! iono i never really babied it that much and it seems to be doing fine but it seems that everyone has their own method.
-
Craving4Boost
- Posts: 1495
- Joined: Sun Dec 19, 2004 10:44 am
- Car: 91 240sx fastback
Re: (ka24detsx)
you drove it 20 miles in what way?? is this freeway? doesnt that mean you were cruising at the same rpm for a long time? thats bad right? unless otherwise?
Re: Question about motor Break-in (s14det)
Breaking in an engine is all about 'seating' the rings, which in simple terms is allowing them to conform to exact the diameter of the machined cylinder wall. You want this to happen as quickly as possible without any adverse results.
All this nonsense about metal shavings is BS, as long as it's properly assembled and cleaned. There should be absolutely no rubbing between metal parts, i.e, bearings, etc., due to the clearance and oil film and no crap from sand blasting in the oil.
Rings and cylinder walls by nature have to make contact in order to conform to each other and seal that space for optimum performance. This is why the honing process of the cylinder wall is so important. It has to be rough enough to gently 'file' the rings to conformity while retaining enough oil to prevent 'microseizure' and corresponding hard spots due to localized overheating. Any ring manufacturer worth his name will specify the correct grit # of the stone and the angle of the crosshatch pattern for their installation.
Once starting the engine, you should never let it idle for prolonged periods of time as there is basically only ring tension tying to smooth out all those grooves and valleys caused by the honing process. They will smooth down very quickly due to the difference in metal properties between the ring and cylinder without allowing the ring to conform to the cylinder wall as the rings don't exert enough pressure by themselves, rotate around the cylinder or expand, basicaly, they're just going up and down. This can cause 'glazing' or smoothing the cylinder wall so that no additional filing action happens on the ring. It used to be that the rings were softer than the cylinder wall so that during a rebuild all you had to do was hone the cylinder and put in a new set of rings. Now, rings can be and often are, harder than the cylinder wall material so once you glaze the cylinder there's no more abrasive properties to file the ring and make it confirm to the circumference. Hence, leakage.
That being said, you also have to worry about applying too much load to the ring as it can overheat. Sort of like putting a blowtorch on on a spring - it will just lose it's tension and never conform to the bore diameter. Remember, the ring is a thin piece of metal, whereas the piston and block are huge chunks, if the ring sees this heat, which it will, it will expand quicker than the other two. If it overheats too much it can lose tension resulting in a 'collapsed' ring and if the ring gaps aren't correct it could expand enough to seize in the bore.
This extra load (force of the ring face to the cylinder wall) comes from increased cylinder pressures, i.e, lugging, full boost and WOT, anything that creates excessive bmep. The cylinder pressure escapes passed the ring groove and fills in the area above and behind the ring, creating more force on the piston ring contact area at the cylinder wall.
This is what you have to balance on a new build. There's nothing written in stone about this, especially turbo engines, but in the end it comes down to nature. Have you ever seen anything explode from birth to full maturity in a fraction of a second?
That said, I would make sure everything is ready to go with you new build; no leaks, timing set correctly, start it and drive it immediately. First run, I'd just take it out for about five miles driving fairly gently and making sure everything works correctly and it gets up to normal operating temp. Then park it and let it cool down completely so that the head and block can conform to each other with the new head gasket. Next run is to apply pressure to the rings. Start at a low speed in, say third or fourth gear at 30 mph and accelerate full throttle with as little boost (difficult with a small turbo) as possible to around 60 and coast down to 30 again. Repeat this for about 6 - 10 times and then drive it normally, i.e, very little boost, no full throttle openings and varying the speed and load of the engine for the next five hundred miles, increasing boost and throttle opening through out this period. No sustained high speed driving and no lugging while varying the speed.
This has worked well for me, but I'm an o' timer. Newer materials and different machining methods may prove me old fashioned or even wrong but I still believe patience is best for a long lasting, driven daily, street machine.
There are many posts on this list about flogging the sh*t out of it right after a rebuild and it seems to work for them 'as they say', but if I'd invested a lot of time and money in a rebuild, I surely wouldn't be happy with 170 psi compression readings or worse yet a smoke screen behind me.
Of special note to the KA engine is to be sure you have no air pockets in the cooling system that can cause localized overheating before starting it. This is not as easy as it appears and a complete topic altogether.
YMMV, just go with what feels right to you. If it blows up on your first run by flooring it, you'll blame yourself. If it blows up 500 miles latter when you floor it - it will still be just as bad but you can rule out impatience.
All this nonsense about metal shavings is BS, as long as it's properly assembled and cleaned. There should be absolutely no rubbing between metal parts, i.e, bearings, etc., due to the clearance and oil film and no crap from sand blasting in the oil.
Rings and cylinder walls by nature have to make contact in order to conform to each other and seal that space for optimum performance. This is why the honing process of the cylinder wall is so important. It has to be rough enough to gently 'file' the rings to conformity while retaining enough oil to prevent 'microseizure' and corresponding hard spots due to localized overheating. Any ring manufacturer worth his name will specify the correct grit # of the stone and the angle of the crosshatch pattern for their installation.
Once starting the engine, you should never let it idle for prolonged periods of time as there is basically only ring tension tying to smooth out all those grooves and valleys caused by the honing process. They will smooth down very quickly due to the difference in metal properties between the ring and cylinder without allowing the ring to conform to the cylinder wall as the rings don't exert enough pressure by themselves, rotate around the cylinder or expand, basicaly, they're just going up and down. This can cause 'glazing' or smoothing the cylinder wall so that no additional filing action happens on the ring. It used to be that the rings were softer than the cylinder wall so that during a rebuild all you had to do was hone the cylinder and put in a new set of rings. Now, rings can be and often are, harder than the cylinder wall material so once you glaze the cylinder there's no more abrasive properties to file the ring and make it confirm to the circumference. Hence, leakage.
That being said, you also have to worry about applying too much load to the ring as it can overheat. Sort of like putting a blowtorch on on a spring - it will just lose it's tension and never conform to the bore diameter. Remember, the ring is a thin piece of metal, whereas the piston and block are huge chunks, if the ring sees this heat, which it will, it will expand quicker than the other two. If it overheats too much it can lose tension resulting in a 'collapsed' ring and if the ring gaps aren't correct it could expand enough to seize in the bore.
This extra load (force of the ring face to the cylinder wall) comes from increased cylinder pressures, i.e, lugging, full boost and WOT, anything that creates excessive bmep. The cylinder pressure escapes passed the ring groove and fills in the area above and behind the ring, creating more force on the piston ring contact area at the cylinder wall.
This is what you have to balance on a new build. There's nothing written in stone about this, especially turbo engines, but in the end it comes down to nature. Have you ever seen anything explode from birth to full maturity in a fraction of a second?
That said, I would make sure everything is ready to go with you new build; no leaks, timing set correctly, start it and drive it immediately. First run, I'd just take it out for about five miles driving fairly gently and making sure everything works correctly and it gets up to normal operating temp. Then park it and let it cool down completely so that the head and block can conform to each other with the new head gasket. Next run is to apply pressure to the rings. Start at a low speed in, say third or fourth gear at 30 mph and accelerate full throttle with as little boost (difficult with a small turbo) as possible to around 60 and coast down to 30 again. Repeat this for about 6 - 10 times and then drive it normally, i.e, very little boost, no full throttle openings and varying the speed and load of the engine for the next five hundred miles, increasing boost and throttle opening through out this period. No sustained high speed driving and no lugging while varying the speed.
This has worked well for me, but I'm an o' timer. Newer materials and different machining methods may prove me old fashioned or even wrong but I still believe patience is best for a long lasting, driven daily, street machine.
There are many posts on this list about flogging the sh*t out of it right after a rebuild and it seems to work for them 'as they say', but if I'd invested a lot of time and money in a rebuild, I surely wouldn't be happy with 170 psi compression readings or worse yet a smoke screen behind me.
Of special note to the KA engine is to be sure you have no air pockets in the cooling system that can cause localized overheating before starting it. This is not as easy as it appears and a complete topic altogether.
YMMV, just go with what feels right to you. If it blows up on your first run by flooring it, you'll blame yourself. If it blows up 500 miles latter when you floor it - it will still be just as bad but you can rule out impatience.