Supertech p/wall clearance
09-26-2010, 11:21 PM
#23
I guess you're done asking questions and now you're telling us what you're doing? How much more reliable and stronger will your motor be than Savington's, thesnowboarder's, and mine? I guess this machinist knows something most don't since he insists on cutting the manufacturer's spec in half. What does he plan on checking with the bore scope? Lol @ oldschool break-in.
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09-26-2010, 11:25 PM
#25
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After working around a lot of older guys in the industry and guys who have "lived a little" so to speak, I take everything that ANYONE says with a grain of salt. Keep an open mind. Don't listen to someone who is an "expert" just because they say so. Now on that note, if tons of guys are running with .004 (myself included) and havn't had any problems, (and honestly, no way in hell would I run a track car at half that spec either), I'd go with the known good, and not some spec that a so called expert pulled out of his ***. I work with "experts" and roll my eyes at **** that they do a lot of the time. Just think about what would happen if you ran a piston that is SUPPOSED to be run with .004, and you run it with half that, and it expands.
The "experts" at my job told me that my ES bushings would "make my car pull/cause play in my steering/control arms/was the cause for clunks when I step on the brake"
Thats my 2 cents.
The "experts" at my job told me that my ES bushings would "make my car pull/cause play in my steering/control arms/was the cause for clunks when I step on the brake"
Thats my 2 cents.
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09-26-2010, 11:30 PM
#26
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Then delete this thread.
We know; I thought you didn't care about what others did?
Wow, lots of anomolies on this forum alone. I guess my days are numbered on this motor.
That makes two of us.
Then why did you make this thread again?
They do, and we all run a loose bore. I don't understand his logic of running a turbo track car "tight". Does he run cars that make less than say 175hp/L at .001"? Ironically, my machinist showed me 3-motors lying around where customers did a "tight bore" and letter added forced induction, and those same motors were in line for a bore and hone so they could try again. That convinced me to go loose as he suggested.
Is this guy going to warranty the labor, pistons, rods, valves, weld the head, and replace turbo if something goes south? Is he going to blame it on detonation? Is he going to insist that you didn't follow his absurd break-in?
They do, and we all run a loose bore. I don't understand his logic of running a turbo track car "tight". Does he run cars that make less than say 175hp/L at .001"? Ironically, my machinist showed me 3-motors lying around where customers did a "tight bore" and letter added forced induction, and those same motors were in line for a bore and hone so they could try again. That convinced me to go loose as he suggested.
Is this guy going to warranty the labor, pistons, rods, valves, weld the head, and replace turbo if something goes south? Is he going to blame it on detonation? Is he going to insist that you didn't follow his absurd break-in?
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09-26-2010, 11:36 PM
#27
Then delete this thread.
We know; I thought you didn't care about what others did?
Wow, lots of anomolies on this forum alone. I guess my days are numbered on this motor.
That makes two of us.
Then why did you make this thread again?
They do, and we all run a loose bore. I don't understand his logic of running a turbo track car "tight". Does he run cars that make less than say 230hp/L at .001"? Ironically, my machinist showed me 3-motors lying around where customers did a "tight bore" and letter added forced induction, and those same motors were in line for a bore and hone so they could try again. That convinced me to go loose as he suggested.
We know; I thought you didn't care about what others did?
Wow, lots of anomolies on this forum alone. I guess my days are numbered on this motor.
That makes two of us.
Then why did you make this thread again?
They do, and we all run a loose bore. I don't understand his logic of running a turbo track car "tight". Does he run cars that make less than say 230hp/L at .001"? Ironically, my machinist showed me 3-motors lying around where customers did a "tight bore" and letter added forced induction, and those same motors were in line for a bore and hone so they could try again. That convinced me to go loose as he suggested.
And it's not going to be turbo'd, it's going to be rotrex'd with water injection. Slightly less AIT than a turbo, and the WI will assist with keeping the motor cool as well. Also higher comp with lower boost... (10-12PSI).
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09-26-2010, 11:43 PM
#28
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Those are all vaild points. If the engine ***** the bed I'll eat my words, but for now we'll see how it goes.
And it's not going to be turbo'd, it's going to be rotrex'd with water injection. Slightly less AIT than a turbo, and the WI will assist with keeping the motor cool as well. Also higher comp with lower boost... (10-12PSI).
And it's not going to be turbo'd, it's going to be rotrex'd with water injection. Slightly less AIT than a turbo, and the WI will assist with keeping the motor cool as well. Also higher comp with lower boost... (10-12PSI).
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09-27-2010, 12:09 AM
#30
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Last thing I have to say on this thread is I have also NEVER heard of an engine builder offering a warranty. Maybe for rare situations they might redo some work but in general, NO. You really think he will buy you new parts?
What the **** is wrong with you? You are just being taken by this guy. I predict catastrophe and tragedy. And holy ****, WI should not be your failsafe against your pistons expanding and seizing in the bore. **** man, ****.
What the **** is wrong with you? You are just being taken by this guy. I predict catastrophe and tragedy. And holy ****, WI should not be your failsafe against your pistons expanding and seizing in the bore. **** man, ****.
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09-27-2010, 03:43 AM
#33
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Supertech recommends .0028" wall clearance for their pistons, and that's considered extremely tight for a forged piston. Weisco recommends .004" or .005" for "heavy blower/nitrous use". .0025" is really, really tight, but hey, if your builder thinks he knows better than the folks that design pistons for a living, knock yourself out.
I might be able to get on board with tight wall clearances if the builder has had good luck with it using a certain piston or a certain motor, but once he recommends a 500km break-in my opinion quickly declines. Motor break-in is done and over with by the 50 mile mark - modern bearings need no break-in and if the rings haven't seated by the 50 mile mark they aren't going to seat at all. (I'm giving you the benefit of the doubt by assuming you meant 500km - if your builder wants a 5000km break-in period you should run screaming from his shop.)
I might be able to get on board with tight wall clearances if the builder has had good luck with it using a certain piston or a certain motor, but once he recommends a 500km break-in my opinion quickly declines. Motor break-in is done and over with by the 50 mile mark - modern bearings need no break-in and if the rings haven't seated by the 50 mile mark they aren't going to seat at all. (I'm giving you the benefit of the doubt by assuming you meant 500km - if your builder wants a 5000km break-in period you should run screaming from his shop.)
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09-27-2010, 11:05 AM
#34
This guy's website is horrible but his logic is exactly what i've heard over and over again from every expert i've ever had a "break-in" conversation with.
http://www.mototuneusa.com/break_in_secrets.htm
In short, you need to wear down the imperfections of the brand new rings to get a good seal against the cylinder bore. This is what that cross-hatch is for. If you do an easy break-in, you wear down the cross-hatch and not the rings which will screw you big time in the long run.
My engine break in procedure:
1. Start engine, warm it up while watching for leaks.
2. As long as there are no oil leaks and no MAJOR coolant leaks, take it for a ripper around the neighborhood. Second gear works great for me. All the way to redline, then overrun all the way down to idle a few times. Some say to stay out of boost. I personally use boost to my advantage. The more combustion pushing the rings into the bore the better in my opinion. Lots of vacuum as well which is why you let it overrun from redline back to idle.
3. Go home and check for leaks again. Put all the **** back on that you never put on for the first drive (under-tray, etc.)
We should meet up and have a chat again sometime soon. I know i'm not an alleged "expert" and you probably aren't interested in any of my suggestions, but i've had 100% success on every engine i've built. If there was ever a problem with an engine i've put in a car, it wasn't anything related to my engine building. Unless you count not checking pistons/rings in my last motor that ended up having broken ring-lands before I even got my hands on it.
http://www.mototuneusa.com/break_in_secrets.htm
In short, you need to wear down the imperfections of the brand new rings to get a good seal against the cylinder bore. This is what that cross-hatch is for. If you do an easy break-in, you wear down the cross-hatch and not the rings which will screw you big time in the long run.
My engine break in procedure:
1. Start engine, warm it up while watching for leaks.
2. As long as there are no oil leaks and no MAJOR coolant leaks, take it for a ripper around the neighborhood. Second gear works great for me. All the way to redline, then overrun all the way down to idle a few times. Some say to stay out of boost. I personally use boost to my advantage. The more combustion pushing the rings into the bore the better in my opinion. Lots of vacuum as well which is why you let it overrun from redline back to idle.
3. Go home and check for leaks again. Put all the **** back on that you never put on for the first drive (under-tray, etc.)
We should meet up and have a chat again sometime soon. I know i'm not an alleged "expert" and you probably aren't interested in any of my suggestions, but i've had 100% success on every engine i've built. If there was ever a problem with an engine i've put in a car, it wasn't anything related to my engine building. Unless you count not checking pistons/rings in my last motor that ended up having broken ring-lands before I even got my hands on it.
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09-27-2010, 11:21 AM
#35
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Wayne, your "that is what cross-hatch is for" statement doesn't make sense to me.
Why would lower cylinder pressures and less vacuum cause the rings OR the cross hatch to wear at a different rate than high pressure/vacuum? The only variable I can think of is that high pressure/vacuum generates more heat which um makes the rings more maleable????
Why would lower cylinder pressures and less vacuum cause the rings OR the cross hatch to wear at a different rate than high pressure/vacuum? The only variable I can think of is that high pressure/vacuum generates more heat which um makes the rings more maleable????
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09-27-2010, 12:04 PM
#36
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This is true, I did a bunch of reading before I bought my pistons. Supertechs are 4032 alloy whereas most Wisecos, JE, CP and a bunch of others are 2618. The silicon content is much higher in 4032, so it doesn't expand as much as 2618. You can therefore run a bit tighter bore and get less piston slap on cold startup with 4032 so many people use that alloy for street cars. 2618 expands more and is a little softer so it can take a bit more abuse before it fails outright.
I went with Supertechs (4032) because there are several Miatas boosting around race tracks with them who haven't had any problems. I'm not going to be throwing such a shitload of boost at it and running at the ragged edge where 2618 becomes necessary. It's also a street car and I don't want to have to run .005"+ clearance on a motor that will see a bunch more cold starts than a dedicated track car does.
It also doesn't matter so much which forced induction method you use. Lower IATs from a more thermally efficient compressor, water injection, etc. allow you to safely make more power without knocking, but anything resembling a temperature low enough to keep your pistons from expanding is history once you light off the charge. You can't make power without making heat. It takes a specific amount of fuel to make a certain amount of power, and burning that specific amount of fuel creates a specific amount of heat in the combustion chamber. There's really no way around it. If we're both running around a track, you've got a rotrex and WI and I've got a conventional turbo with just an IC, if we're making the same power our pistons will be seeing all but identical temps. Significant expansion will occur, and if you run less than the piston manufacturer's minimum clearance spec you're a ******* moron.
Your used up Bubble-Yum sphincter notwithstanding, I've seen a specific number out of Savington (.004") but not from you. Are you running the same? If you don't know off the top of your head, look it up from the spec sheet you got from your machinist plsthxbai.
I went with Supertechs (4032) because there are several Miatas boosting around race tracks with them who haven't had any problems. I'm not going to be throwing such a shitload of boost at it and running at the ragged edge where 2618 becomes necessary. It's also a street car and I don't want to have to run .005"+ clearance on a motor that will see a bunch more cold starts than a dedicated track car does.
It also doesn't matter so much which forced induction method you use. Lower IATs from a more thermally efficient compressor, water injection, etc. allow you to safely make more power without knocking, but anything resembling a temperature low enough to keep your pistons from expanding is history once you light off the charge. You can't make power without making heat. It takes a specific amount of fuel to make a certain amount of power, and burning that specific amount of fuel creates a specific amount of heat in the combustion chamber. There's really no way around it. If we're both running around a track, you've got a rotrex and WI and I've got a conventional turbo with just an IC, if we're making the same power our pistons will be seeing all but identical temps. Significant expansion will occur, and if you run less than the piston manufacturer's minimum clearance spec you're a ******* moron.
Your used up Bubble-Yum sphincter notwithstanding, I've seen a specific number out of Savington (.004") but not from you. Are you running the same? If you don't know off the top of your head, look it up from the spec sheet you got from your machinist plsthxbai.
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09-27-2010, 03:51 PM
#37
Wayne, your "that is what cross-hatch is for" statement doesn't make sense to me.
Why would lower cylinder pressures and less vacuum cause the rings OR the cross hatch to wear at a different rate than high pressure/vacuum? The only variable I can think of is that high pressure/vacuum generates more heat which um makes the rings more maleable????
Why would lower cylinder pressures and less vacuum cause the rings OR the cross hatch to wear at a different rate than high pressure/vacuum? The only variable I can think of is that high pressure/vacuum generates more heat which um makes the rings more maleable????
This is how I understand it anyway. Someone smarter than me will likely correct me. I'm no injuneer. But using this logic, it makes sense that breaking it in like a man will get those rings in shape rather quickly. I like to think of this as setting the pace for the type of life the engine will be living. I also have piece of mind in knowing that if anything horrible is going to go wrong, it'll go wrong in that first 20 miles of absolute abuse.
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09-27-2010, 04:01 PM
#38
I think there is a bit of misunderstanding as to how I will break the engine in. I'm not going to baby the hell out of it for that long. I've broken in a few engines before as well as motorcycles, I know that you need a lot of engine braking/compression braking and accelerations through the gears, not staying int he same gear/RPM for long periods of time etc.. All I said was there will be an RPM limit for a predetermined time... that's it. And no boost until he gives me the go ahead. Which is fine considering he is the one building and tuning the engine.
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