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Coating Air cooled pistons

General engine tech -- Drag Racing to Circle Track

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ptuomov
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Re: Coating Air cooled pistons

Post by ptuomov » Mon Oct 07, 2019 11:10 am

Kevin Johnson wrote:
Mon Oct 07, 2019 10:36 am
If you have not already done so, the factory GKN sinter-forged rods can be modified with slots to direct ejected oil from the rod bearings towards the pistons. This will not increase the demand on the oil pump.
We've though about that, especially since modern pistons will require different length rods anyway. The issue is that it's difficult to get a narrow enough spray pattern from that sort of slot. The engine has too much oil on the bore walls anyway, so anything that has a wide spray cone is not ideal. Because of this, the jets from the main are likely to best piston cooling solution.

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Re: Coating Air cooled pistons

Post by Truckedup » Mon Oct 07, 2019 1:48 pm

JodyB wrote:
Sun Oct 06, 2019 6:31 pm
Back to the original poster's GS1100. Being air cooled, piston to bore clearance at your average riding or racing conditions/temp will be #1 priority for making hp and having the mill live. Magic coatings, oil squirters, water injection are distant 2nds if you have sufficient octane.
Stock piston to wall clearance on these engines is .002", fairly tight for an air cooled engine, likely cast pistons...These engines do have a repuation for reliability even when abused...An increase in power of let's say 30% may require no special treatment
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Re: Coating Air cooled pistons

Post by ptuomov » Mon Oct 07, 2019 4:05 pm

lewy-d wrote:
Wed Oct 02, 2019 1:45 pm
I've got a bit of analysis paralysis on this one. The engine is a 1980's Suzuki GS1100, mild performance build. Will hard anodizing, coating piston tops and or skirts reduce the effective heat transfer from piston to block to air? Will it matter?
thanks, Lewy
Here's a question/comment. For air cooled application like that, would there be any downside from thermal barrier coating the exhaust port and the back of the exhaust valve? It seems to me that insulating those components should reduce cylinder head temperatures and shouldn't increase detonation tendencies. Any thoughts?

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Re: Coating Air cooled pistons

Post by Kevin Johnson » Mon Oct 07, 2019 4:45 pm

lewy-d wrote:
Wed Oct 02, 2019 1:45 pm
I've got a bit of analysis paralysis on this one. The engine is a 1980's Suzuki GS1100, mild performance build. Will hard anodizing, coating piston tops and or skirts reduce the effective heat transfer from piston to block to air? Will it matter?
thanks,
Lewy
I rode a GS back and forth to school for several years. Got tired of arriving drenched and bought a Metro.

You ARE already using an oil cooler, correct? Reject the mild performance build heat from the oil, i.e, the interior of the pistons and bores. Tons of aftermarket kits.

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Re: Coating Air cooled pistons

Post by David Redszus » Mon Oct 07, 2019 5:19 pm

lewy-d wrote:
Wed Oct 02, 2019 1:45 pm
I've got a bit of analysis paralysis on this one. The engine is a 1980's Suzuki GS1100, mild performance build. Will hard anodizing, coating piston tops and or skirts reduce the effective heat transfer from piston to block to air? Will it matter?
thanks, Lewy
Hard coat anodizing is, de facto, a ceramic coating called alumina. It has a thermal conductivity one tenth that of aluminum. It will reduce the heat transfer from the surface to the interior of the metal surface, leaving the surface in a higher temperature state.

An examination of the thermal transfer path and the insulation properties of each layer will provide an insight to the issue of heat transfer.

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Re: Coating Air cooled pistons

Post by JodyB » Fri Oct 11, 2019 12:15 am

To the original poster: What approximate wheel hp range are you shooting for with the air cooled suzuki?

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Re: Coating Air cooled pistons

Post by Truckedup » Fri Oct 11, 2019 7:02 am

JodyB wrote:
Fri Oct 11, 2019 12:15 am
To the original poster: What approximate wheel hp range are you shooting for with the air cooled suzuki?
What is the stock RWHP? Maybe about 80?
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Re: Coating Air cooled pistons

Post by lewy-d » Fri Oct 11, 2019 8:49 am

thank you for all the help.
I'm not sure about the original HP. 80 sounds right. Vance and Hines sold a video about degreeing cams on the 16valve GS (I bought it can't find it now!) and they showed 149 at the sprocket. Same size engine but I don't know the rest of the specs.
Diamondyze is the anodizing I'm thinking of using. It's interesting to me that the coater will anodize pistons then coat the tops and skirts. I've had some parts WPC processed lately and I like it. so maybe anodize the piston and coat the top and WPC the skirts and pins.
I hadn't thought about doing the exhaust ports but they're short and it might not be a bad idea.
I agree the clearance is important I had the block bored and honed by a shop I trust but I will check. Other than Wiseco's recommendation I'm not sure what I should do. Any help here is appreciated.

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Re: Coating Air cooled pistons

Post by HiPer Express » Fri Oct 18, 2019 5:35 am

Truckedup wrote:
Sun Oct 06, 2019 7:59 am
HiPer Express wrote:
Sun Oct 06, 2019 5:44 am
Truckedup wrote:
Thu Oct 03, 2019 9:16 am
Smokey Yunick claimed that on the dyno,a SBC continued to make more power up to about 230F if detonation was under control...
It was Grumpy , guy who actually knew something.
It was Yunick in the 80's Power Secrets book.Mybe he stole it Jenkins... Not that everything Yunick claimed was true...Did Jenkins run his drag engines at hight tempoeratures?
Jenkins said in his book that engines made the most power just beforel they boiled.

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Re: Coating Air cooled pistons

Post by RCJ » Fri Oct 18, 2019 6:18 am

Grump and Smokey knew what they were doing, but some of the stuff they were doing was because of 1960s technology .Getting the oil hot might of helped more than anything.After we get the best power out of a motor, sometimes we make a "Hero" pull.Dump the water out and refill with cold water as fast as possible and pull. Usually good for 5 to 10hp.

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Re: Coating Air cooled pistons

Post by Kevin Johnson » Mon Nov 25, 2019 9:45 am

Specific information on a GS1100:
https://www.speed-talk.com/forum/viewtopic.php?f=15&p=836997#p836997 wrote:
Re: Thermal Barrier Coatings - Is it good? Where to get it in Northern California?
Unread post by Arttu » Mon Nov 25, 2019 9:17 am

Well, I can only provide one anecdotal experience on the topic. I had the piston tops coated on my air cooled turbo engine (Suz GS1100). The coating was made by Cerakote. The pistons were in use for several years and about 20 000km until I had to replace them due to detonation damage.

What I can say for sure is that the coating was holding up pretty well. When removing the pistons from the engine the coating was still there except the points where detonation was eaten also metal away. Since I don't have any proper comparison point I can't tell if the coating helped to prevent detonation or promoted it. But I would guess the effect was neutral at worst since the engine was able to handle quite high boost considering the compression ratio and other factors. I never found out the reason for detonation damage for sure but I assume it was just too high ignition timing on partial throttle since the damage was clearly accumulated over longer time.

On negative side I noticed that carbon build-up was sticking really firmly on the coating. And that's one of the reasons that make me doubt how beneficial this kind coating really is on street driven engine. I would guess that the coating doesn't make any difference anymore once there is a carbon layer on top of it.

So, as conclusion I can't say if the coating did any good in my case but at least it didn't do anything bad either.

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Re: Coating Air cooled pistons

Post by NewbVetteGuy » Tue Nov 26, 2019 4:58 pm

Seems weird to see thermal barrier coatings and oil squirters discussed as being "equivalents" in this discussion; aren't they effectively "opposites"?

-Coating will increase combustion temps and makes "Effective compression" higher and "effective octane" lower while
-Oil squirters decrease combustion temps through removal and transport of heat in the oil and makes "Effective compression" lower and "effective octane" higher?

Both just seem like a compression / octane "hack" to me, but ones working in opposite directions, no?

With turbo engines doesn't colder air at higher pressures == more power with a given octane fuel? Is this not also the case with N/A engines?

Earlier comment that you make more power with higher temps if octane isn't a limiting factor seems reasonable, but at the same time in the more common scenario where octane IS a limiting factor, lower temps = more power with lower recurring costs at the pump. More heat also means decreased longevity, right?

Piston top coatings seem to be the only time "more heat = more better" any more and it just stands out as strange to me. Feels like a solution looking for a problem or a sales person looking for a story.


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Re: Coating Air cooled pistons

Post by ptuomov » Tue Nov 26, 2019 5:13 pm

The one way in which TBC on the piston crown and piston oil squirters can be thought of as substitutes is limiting otherwise excessive piston temperatures.

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