Good discussion about prolonging race motors
Aug 26, 2011, 10:31 PM
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Good discussion about prolonging race motors
okay guys, i am well known to the fact that built motors will not last as long as oem cast pistons simply of the fact that piston rings get worn down faster and you will have to be rebuilding the motor when needed.
my question is. what if you had forged pistons with forged sleeves?? you can have very close piston-wall clearance and both should expand at the same rate. which should mean that your motor should last longer with a built motor?
thanks for your input..
my question is. what if you had forged pistons with forged sleeves?? you can have very close piston-wall clearance and both should expand at the same rate. which should mean that your motor should last longer with a built motor?
thanks for your input..
Aug 27, 2011, 02:13 AM
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Forged aluminum pistons and forged iron sleeves still won't have anywhere near the same thermal expansion. If you're trying to use forged aluminum sleeves, then you're defeating the purpose of a sleeve, and it still won't expand the same because the sleeve has water jackets to cool it, while the piston has only oil, which is not nearly as good at carrying away heat. It's necessary for a racing engine to be put together more loosely because its going to see more rapid and more drastic swings in temperature.compared with the stock engine. Additionally, if you have a racing engine together long enough to be worrying about piston wear, then you're very lucky anyway.
Aug 27, 2011, 09:26 AM
#3
My engine was built very loose which burned a hell of alot of oil. But in the end it just kept making more and more power and I had 3 years of running hard and it took and destroyed every Turbo we slapped on. I'm extreme and I was very shocked it lasted that long.
Aug 27, 2011, 03:01 PM
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^^^ thanks for the info.: ]
it just kind of boggles me that no one can build a forged piston car to handle power while lasting long.
from what i have gathered is that cold starts hurt built motors alot. some people even run block heaters so that the pistons expand .
it just kind of boggles me that no one can build a forged piston car to handle power while lasting long.
from what i have gathered is that cold starts hurt built motors alot. some people even run block heaters so that the pistons expand .
Aug 28, 2011, 02:59 AM
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Big ring gaps, piston to wall clearance, bearing clearance... Basically all the things you check when building an engine need to be bigger when you're building an engine to make big power.
If the ring gap is too small, the rings heat up and expand and close the gap, which forces them into the cylinder wall, the downside to this is it burns a lot of oil.
Ditto for piston to cylinder wall clearance, with the added bonus of piston slap when cold-this kills engines with super strong pistons, as high-end pistons use a softer, but tougher aluminum alloy, which will take way more abuse, but necessarily wears quicker because of it.
Larger bearing clearances place more oil between the cranks and the block/ rods to take the added shock load of higher power. This doesn't necessarily burn more oil, but if the engine has a relatively small oil pump (the Evo pump is much smaller relative to oil demand when compared with a chevy V8 for example) , it will force you to run a heavier oil. Also, race bearings generally use a softer bearing surface metal to help stop bearing from spinning in case there is a lack of lubrication. This also makes the engine not last as long.
When looking at a race engine, it's important not to look at oil consumption as a surefire sign of a failing engine, As Sharkbite pointed out, race engines will use some oil, sometimes a lot of it. Low oil pressure at idle can definitely mean bearing wear is beginning to be an issue. Low compression too.
If the ring gap is too small, the rings heat up and expand and close the gap, which forces them into the cylinder wall, the downside to this is it burns a lot of oil.
Ditto for piston to cylinder wall clearance, with the added bonus of piston slap when cold-this kills engines with super strong pistons, as high-end pistons use a softer, but tougher aluminum alloy, which will take way more abuse, but necessarily wears quicker because of it.
Larger bearing clearances place more oil between the cranks and the block/ rods to take the added shock load of higher power. This doesn't necessarily burn more oil, but if the engine has a relatively small oil pump (the Evo pump is much smaller relative to oil demand when compared with a chevy V8 for example) , it will force you to run a heavier oil. Also, race bearings generally use a softer bearing surface metal to help stop bearing from spinning in case there is a lack of lubrication. This also makes the engine not last as long.
When looking at a race engine, it's important not to look at oil consumption as a surefire sign of a failing engine, As Sharkbite pointed out, race engines will use some oil, sometimes a lot of it. Low oil pressure at idle can definitely mean bearing wear is beginning to be an issue. Low compression too.
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Aug 28, 2011, 10:51 AM
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then IMO the only reason that you should go for aftermarket bearings (and even make the clearances larger) is because you will be reving the car to a higher rpm.
for subaru's it seems the case for them with built motors is that they usually just wear down the rings faster then the bearings. but for evo's i hear a lot of people wear down the bearings faster then the rings...
maybe because people are revving there evo's more then they should making the bearings wear down faster.this is an assumption though.
for subaru's it seems the case for them with built motors is that they usually just wear down the rings faster then the bearings. but for evo's i hear a lot of people wear down the bearings faster then the rings...
maybe because people are revving there evo's more then they should making the bearings wear down faster.this is an assumption though.
Aug 28, 2011, 02:28 PM
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The downward force on the bearings increases doubly in a race engine also. Both from increased RPM (the inertia of the piston and rod changing direction) and increased torque pushing the rod down harder (inward in a subaru) The increased short term durability is necessary in a lot of applications just to finish a drag racing pass. An engine isn't going to last 50,000 miles if it doesn't make it down the 1/4 mile.
The piston rings themselves are not what generally wear out in any engine. They're specifically made to be harder than the block. Generally using either nitride coatings or standard chrome. The bock will eventually have it's crosshatch from the honing procedure wear away, limiting the amount of oil the cylinder walls can retain and reducing lubrication to the piston skirts. When the piston skirts wear, piston slap occurs, as well as excessive oil consumption.
Two things should be made clear, though, the first is that built engines generally don't fail from wearing out. but rather from something going catastrophically wrong. Honestly, shakbite's engine going three seasons with the way it was treated comes down to some very talented people never messing up as much as it does to the engine being physically durable. At that power level, one second of fuel pressure drop, or a missed shift is all it can take to send even the best engine ever made straight to hell.
The second is that the longevity of high performance engines is dramatically better than the same engine built 10 years ago. An engine built now with modern technology can make 250 crank HP per cylinder and last THREE YEARS. Ten years ago, that power level was miraculous for a season. Twenty years ago it was basically impossible.
New techniques are becoming available to make engines more durable in the long and short terms, but they cost money and take time to create and implement. Special hard coatings on piston skirts make pistons last longer. Special block treatments can increase the life of the block. Low friction bearing coatings take the stress off the locating tangs, decreasing the risk of spinning a bearing. In fact, the factory Evo engine makes use of a nitrided crank and hard coated piston skirts to make an engine that makes ~140 HP/liter something that can carry a 100K mile manufacturer's warranty.
Of course, all these same ideas can also be applied to your conventional grocery getter and make it last half a million miles which makes 50K out of an 800 HP race engine look pretty wimpy.. In the end, anything that's highly stressed is not going to last as long as the same thing that isn't as highly stressed. It's up to the engine builder to decide which piston, bearing material, block treatment, oil, and build techniques are best suited to the application. Most guys tend to err as far to the overkill side as possible because engines are expensive and nasty surprises are no fun.
The piston rings themselves are not what generally wear out in any engine. They're specifically made to be harder than the block. Generally using either nitride coatings or standard chrome. The bock will eventually have it's crosshatch from the honing procedure wear away, limiting the amount of oil the cylinder walls can retain and reducing lubrication to the piston skirts. When the piston skirts wear, piston slap occurs, as well as excessive oil consumption.
Two things should be made clear, though, the first is that built engines generally don't fail from wearing out. but rather from something going catastrophically wrong. Honestly, shakbite's engine going three seasons with the way it was treated comes down to some very talented people never messing up as much as it does to the engine being physically durable. At that power level, one second of fuel pressure drop, or a missed shift is all it can take to send even the best engine ever made straight to hell.
The second is that the longevity of high performance engines is dramatically better than the same engine built 10 years ago. An engine built now with modern technology can make 250 crank HP per cylinder and last THREE YEARS. Ten years ago, that power level was miraculous for a season. Twenty years ago it was basically impossible.
New techniques are becoming available to make engines more durable in the long and short terms, but they cost money and take time to create and implement. Special hard coatings on piston skirts make pistons last longer. Special block treatments can increase the life of the block. Low friction bearing coatings take the stress off the locating tangs, decreasing the risk of spinning a bearing. In fact, the factory Evo engine makes use of a nitrided crank and hard coated piston skirts to make an engine that makes ~140 HP/liter something that can carry a 100K mile manufacturer's warranty.
Of course, all these same ideas can also be applied to your conventional grocery getter and make it last half a million miles which makes 50K out of an 800 HP race engine look pretty wimpy.. In the end, anything that's highly stressed is not going to last as long as the same thing that isn't as highly stressed. It's up to the engine builder to decide which piston, bearing material, block treatment, oil, and build techniques are best suited to the application. Most guys tend to err as far to the overkill side as possible because engines are expensive and nasty surprises are no fun.
Sep 20, 2011, 04:46 PM
#11
The downward force on the bearings increases doubly in a race engine also. Both from increased RPM (the inertia of the piston and rod changing direction) and increased torque pushing the rod down harder (inward in a subaru) The increased short term durability is necessary in a lot of applications just to finish a drag racing pass. An engine isn't going to last 50,000 miles if it doesn't make it down the 1/4 mile.
The piston rings themselves are not what generally wear out in any engine. They're specifically made to be harder than the block. Generally using either nitride coatings or standard chrome. The bock will eventually have it's crosshatch from the honing procedure wear away, limiting the amount of oil the cylinder walls can retain and reducing lubrication to the piston skirts. When the piston skirts wear, piston slap occurs, as well as excessive oil consumption.
Two things should be made clear, though, the first is that built engines generally don't fail from wearing out. but rather from something going catastrophically wrong. Honestly, shakbite's engine going three seasons with the way it was treated comes down to some very talented people never messing up as much as it does to the engine being physically durable. At that power level, one second of fuel pressure drop, or a missed shift is all it can take to send even the best engine ever made straight to hell.
The second is that the longevity of high performance engines is dramatically better than the same engine built 10 years ago. An engine built now with modern technology can make 250 crank HP per cylinder and last THREE YEARS. Ten years ago, that power level was miraculous for a season. Twenty years ago it was basically impossible.
New techniques are becoming available to make engines more durable in the long and short terms, but they cost money and take time to create and implement. Special hard coatings on piston skirts make pistons last longer. Special block treatments can increase the life of the block. Low friction bearing coatings take the stress off the locating tangs, decreasing the risk of spinning a bearing. In fact, the factory Evo engine makes use of a nitrided crank and hard coated piston skirts to make an engine that makes ~140 HP/liter something that can carry a 100K mile manufacturer's warranty.
Of course, all these same ideas can also be applied to your conventional grocery getter and make it last half a million miles which makes 50K out of an 800 HP race engine look pretty wimpy.. In the end, anything that's highly stressed is not going to last as long as the same thing that isn't as highly stressed. It's up to the engine builder to decide which piston, bearing material, block treatment, oil, and build techniques are best suited to the application. Most guys tend to err as far to the overkill side as possible because engines are expensive and nasty surprises are no fun.
The piston rings themselves are not what generally wear out in any engine. They're specifically made to be harder than the block. Generally using either nitride coatings or standard chrome. The bock will eventually have it's crosshatch from the honing procedure wear away, limiting the amount of oil the cylinder walls can retain and reducing lubrication to the piston skirts. When the piston skirts wear, piston slap occurs, as well as excessive oil consumption.
Two things should be made clear, though, the first is that built engines generally don't fail from wearing out. but rather from something going catastrophically wrong. Honestly, shakbite's engine going three seasons with the way it was treated comes down to some very talented people never messing up as much as it does to the engine being physically durable. At that power level, one second of fuel pressure drop, or a missed shift is all it can take to send even the best engine ever made straight to hell.
The second is that the longevity of high performance engines is dramatically better than the same engine built 10 years ago. An engine built now with modern technology can make 250 crank HP per cylinder and last THREE YEARS. Ten years ago, that power level was miraculous for a season. Twenty years ago it was basically impossible.
New techniques are becoming available to make engines more durable in the long and short terms, but they cost money and take time to create and implement. Special hard coatings on piston skirts make pistons last longer. Special block treatments can increase the life of the block. Low friction bearing coatings take the stress off the locating tangs, decreasing the risk of spinning a bearing. In fact, the factory Evo engine makes use of a nitrided crank and hard coated piston skirts to make an engine that makes ~140 HP/liter something that can carry a 100K mile manufacturer's warranty.
Of course, all these same ideas can also be applied to your conventional grocery getter and make it last half a million miles which makes 50K out of an 800 HP race engine look pretty wimpy.. In the end, anything that's highly stressed is not going to last as long as the same thing that isn't as highly stressed. It's up to the engine builder to decide which piston, bearing material, block treatment, oil, and build techniques are best suited to the application. Most guys tend to err as far to the overkill side as possible because engines are expensive and nasty surprises are no fun.
Sep 21, 2011, 08:15 AM
#14
Depending on what power level you are after, you may not really need "race pistons" which is the primary issue on a built motor.
My last 2G DSM was rebuilt before I owned it and I didn't know that when I bought it. I had an oil cooler split and mix my coolant and oil together which lead to light rod knock. I tore it apart to find that it had already been rebuilt and one cylinder was bored out 0.0025". I decided to bore/hone the other 3 cylinders out to loosen the piston-to-wall clearances to 0.003". I replaced the rings bearings with OEM parts. I filed the ring end gaps out to rather large clearances. I polished the crank journals and resized the rods (ARP rod bolts too) to provide 0.002" bearing clearances on the mains and 0.0015" on the rods.
That motor saw a sever amount of abuse after that at the 500+ HP level and 8000 RPM. Even on the stock rods, it took a serious beating for a long time without an issue. Didn’t burn oil and was dead quiet on cold starts.
The EVO parts are even stronger. If all you want is 500-600 WHP but want something stronger then the OEM motor that can last, I’d consider using the OEM pistons/rings/bearings with aftermarket rods and open up the clearances on everything.
Just a thought anyway.
My last 2G DSM was rebuilt before I owned it and I didn't know that when I bought it. I had an oil cooler split and mix my coolant and oil together which lead to light rod knock. I tore it apart to find that it had already been rebuilt and one cylinder was bored out 0.0025". I decided to bore/hone the other 3 cylinders out to loosen the piston-to-wall clearances to 0.003". I replaced the rings bearings with OEM parts. I filed the ring end gaps out to rather large clearances. I polished the crank journals and resized the rods (ARP rod bolts too) to provide 0.002" bearing clearances on the mains and 0.0015" on the rods.
That motor saw a sever amount of abuse after that at the 500+ HP level and 8000 RPM. Even on the stock rods, it took a serious beating for a long time without an issue. Didn’t burn oil and was dead quiet on cold starts.
The EVO parts are even stronger. If all you want is 500-600 WHP but want something stronger then the OEM motor that can last, I’d consider using the OEM pistons/rings/bearings with aftermarket rods and open up the clearances on everything.
Just a thought anyway.
Sep 23, 2011, 05:33 AM
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I think that's a very good discussion topic and a good look at why engine build techniques are so important. I would be very surprised if an engine at OEM clearances and ring gaps would be able to take that power. Given that it used the stock parts, most of the longevity would be kept, though potentially a slight drop thanks to the opened up piston wall clearance. wider ring gaps would definitely keep things running ok when things got hot. However, I've been hearing recently that the Evo rods are only good for roughly 400 Ft/Lbs of torque, so the 500 HP you made was (I assume) at pretty high RPM.
Personally I have an irrational fear of connecting rod failure, so I'll spend way more on my rods than necessary for the peace of mind.
Personally I have an irrational fear of connecting rod failure, so I'll spend way more on my rods than necessary for the peace of mind.