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Old 03-02-2012, 10:51 AM   #61
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I'm more skeptical of coatings in general than Kojima. Ceramic crowns may reduce piston temp but the heat that doesn't go into the piston is in the chamber on the next intake stroke. Similar "adiabatic" engines always have shitty VE as a result.
Couldn't you then, raise the expansion ratio, aka compression ratio and bring the temps down to that of the coatingless piston, and raise your efficiency and output as a result?
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Old 03-02-2012, 10:53 AM   #62
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Hmm, so you mean it goes into the valves and the um, valve dome? Wouldn't some of that heat also be pushed out when the valves open?
Most of the heat in the chamber goes out through the head and through the piston (via contact with the cylinder walls). Although I'll be the first to admit I'm not well studied on the effects of keeping that heat in the residual of the chamber. In turbo engines there is a large amount of residual combustion components because cylinder pressure is never going to drop below turbine inlet pressure before the intake valves open. So you end up with PV/RT=N (Where V is the volume of the chamber at which the exhaust valves have closed) at a high temperature left in the chamber. I believe the argument is, if you don't extract the heat out of this charge then it preheats the next intake cycle which can cause pre-ignition combustion.

If that's really the case, then this alone could explain why water injection is so good for turbo engines and not as effective for NA engines. (Charge cooling is important even after combustion!)

As far as oiling grooves. I only know what I know from experience. As far as I can tell its all blackart!
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Old 03-02-2012, 11:23 AM   #63
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You're kidding, right? If that bothers you...
It doesn't bother me that they are believers. It bothers me because they put it there to make an overt statement.

I once had a company send me my order with a pamphlet about jesus and christianity attached. I was pissed and wrote to them. I am not giving them my money so they can preach to me.

Also would you want to shop somewhere that claims to do lots of data gathering scientific testing to prove their product's worthiness but then actively promotes the opposite?

Quote:
Originally Posted by JKav View Post
I'm more skeptical of coatings in general than Kojima. Ceramic crowns may reduce piston temp but the heat that doesn't go into the piston is in the chamber on the next intake stroke. Similar "adiabatic" engines always have shitty VE as a result.

That said, I do like dlc coating esp on valve buckets. Nice on wrist pins too, since you can then delete the bushing and save some more rod mass. Spendy, though.
One thing they mention in the article was "spreading out the heat" in the crown. I read that and thought of my fancy clad cookware. It doesn't stop heat transfer so much as it evens it out so that the heat is evenly distributed in the pan. I don't know if there's an "All-Clad" type coating that's like that but it'd be an interesting way to address your concern.
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Old 03-04-2012, 11:53 AM   #64
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They vary significantly from block to block, so you really need to measure yours.
Thanks, after I get the block measured, what thickness after boring do you recommend be left?
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Old 03-05-2012, 05:01 PM   #65
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Thanks, after I get the block measured, what thickness after boring do you recommend be left?
That's a discussion you should have with your machine shop or engine builder.
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Old 03-05-2012, 05:07 PM   #66
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One thing they mention in the article was "spreading out the heat" in the crown. I read that and thought of my fancy clad cookware. It doesn't stop heat transfer so much as it evens it out so that the heat is evenly distributed in the pan. I don't know if there's an "All-Clad" type coating that's like that but it'd be an interesting way to address your concern.
Also, it continues the discussion on piston coatings or it gets the hose again.
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Old 03-05-2012, 07:03 PM   #67
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Also, it continues the discussion on piston coatings or it gets the hose again.
Savington:

Quote:
Originally Posted by y8s View Post
I read that and thought of my fancy clad cookware. It doesn't stop heat transfer so much as it evens it out so that the heat is evenly distributed in the pan. I don't know if there's an "All-Clad" type coating that's like that but it'd be an interesting way to address your concern.
Subtle "I have baller cook-ware" post.

I would buy all-clad pistons.
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Old 05-24-2012, 05:39 PM   #68
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Lord knows is hate to bump this, but has there been any updates to this project?
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Old 05-25-2012, 06:13 PM   #69
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Old 05-25-2012, 07:55 PM   #70
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^yes.

It's coming along gradually. Steady progress, but progress nonetheless.
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Old 09-04-2012, 07:06 PM   #71
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Many, many delays later...

Things are coming together! Yes, Keegan is quite detail-oriented. Here's a look at some of the work that goes into one of his short blocks:

1997 Mazda MX-5 Miata: Assembly By Keegan Engineering, Pt. II
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Old 09-04-2012, 07:33 PM   #72
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So, yeah, you could say Mike Keegan is thorough when it comes to his craft.
Understatement of the year, so far.
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Old 09-04-2012, 11:05 PM   #73
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Since this has been bumped.

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Originally Posted by Savington View Post
Also, it continues the discussion on piston coatings or it gets the hose again.
What do we think about ceramic coating everything, piston dome, combo chamber, valves, exhaust port. You end up with more heat into the exhaust/turbo and less heat wasted into the coolant.

Personally I think you'd cook head gaskets.
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Old 09-04-2012, 11:47 PM   #74
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Doesn't carbon on the piston do a pretty good job of not absorbing heat?
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Old 09-05-2012, 05:07 AM   #75
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Doesn't carbon on the piston do a pretty good job of not absorbing heat?
I dunno but carbon buildup is typically not even. Hotspots on piston = premature combustion
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Old 09-05-2012, 05:13 AM   #76
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Originally Posted by Savington View Post
Also, it continues the discussion on piston coatings or it gets the hose again.
Coat it in supasikultrahawtwinnangbbqheadermaniturbinespraypa int1200degreewinning.com or no deal.

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Old 09-05-2012, 09:40 AM   #77
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Nice article & informative. Now is the time to weld on a turbo oil drain onto the oil pan.
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Old 09-05-2012, 10:07 AM   #78
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Great write-up on the build. I like actually seeing explanations of his reasoning instead of the usual "this is the way it's done" that is often pronounced as common logic when talking about building engines.
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Old 09-05-2012, 09:07 PM   #79
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TurboTim, very true, if you look closely at the lead pic you will see just such a bunghole.

Keegan's the real deal. It's no wonder his shop is quickly becoming a very very busy place.
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Old 09-05-2012, 10:09 PM   #80
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needs more teepee for the bunghole
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