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Coating Air cooled pistons

General engine tech -- Drag Racing to Circle Track

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MadBill
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Re: Coating Air cooled pistons

Post by MadBill » Thu Oct 03, 2019 7:28 pm

So in addition to rented artwork, a Vintage Porsche in the driveway is part of the 'staging' process for high-dollar home sales?
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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Re: Coating Air cooled pistons

Post by JodyB » Fri Oct 04, 2019 1:00 am

Saw the idea years ago. A corvair land speed racer was injecting water into the cooling fan to help keep head temps under control. Why isn't this captain obvious idea more widespread with aircooled guys?

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Re: Coating Air cooled pistons

Post by hoffman900 » Fri Oct 04, 2019 6:58 am

JodyB wrote:
Fri Oct 04, 2019 1:00 am
Saw the idea years ago. A corvair land speed racer was injecting water into the cooling fan to help keep head temps under control. Why isn't this captain obvious idea more widespread with aircooled guys?
Road racing sanctioning bodies would have a fit over spraying the engine with water. Plus, a 40 minute road race session would need quite a bit of water.

Remember, Porsche’s have been successful from the onset in endurance racing, even in turbo trim (think 24hrs of Daytona and 24hrs of Le Mans, 12hrs of Sebring, etc). In vintage series today, they can be making 100hp/L + and gold together in 2hr endurance classes.
-Bob

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Re: Coating Air cooled pistons

Post by RCJ » Fri Oct 04, 2019 8:06 am

Besides coating, how are other ways to pull the heat out of pistons.

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Re: Coating Air cooled pistons

Post by hoffman900 » Fri Oct 04, 2019 8:41 am

RCJ wrote:
Fri Oct 04, 2019 8:06 am
Besides coating, how are other ways to pull the heat out of pistons.
Piston oil squirters. Porsche adopted them in the early 1970s. They’re pretty much a requirement on any high output engine that has to live for more than a quarter mile at a time.
-Bob

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Re: Coating Air cooled pistons

Post by JodyB » Sun Oct 06, 2019 12:20 am


Kevin Johnson
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Re: Coating Air cooled pistons

Post by Kevin Johnson » Sun Oct 06, 2019 2:13 am

hoffman900 wrote:
Fri Oct 04, 2019 8:41 am
RCJ wrote:
Fri Oct 04, 2019 8:06 am
Besides coating, how are other ways to pull the heat out of pistons.
Piston oil squirters. Porsche adopted them in the early 1970s. They’re pretty much a requirement on any high output engine that has to live for more than a quarter mile at a time.
Aside:

Proper windage control is needed to remove the oil droplets from the cloud at high rpm. The impacts with the rotating assembly heat the oil and are a parasitic drag as well as adding volume to trapped pooled oil under sustained lateral acceleration which could then be churned by the rotating assembly; i.e. the collected oil could not drain back to the sump proper. The areas where the oil temporarily collected became defacto sumps. Porsche had to withdraw the use of oil squirters in the 928 because of this. Other manufacturers designed pumping systems to transport oil away from these collection areas in the style of scavenge stages for dry sumps. Often something like this that works is illegal to retrofit in various racing classes.

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Re: Coating Air cooled pistons

Post by HiPer Express » 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.

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Re: Coating Air cooled pistons

Post by maxc » Sun Oct 06, 2019 7:11 am


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Re: Coating Air cooled pistons

Post by Truckedup » 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?
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire

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Re: Coating Air cooled pistons

Post by HDBD » Sun Oct 06, 2019 12:22 pm

Coatings, mainly skirt have become very popular on HD pistons. I use many that have the line2line coating on them. The motors run very quiet.

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Re: Coating Air cooled pistons

Post by JodyB » 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.

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Re: Coating Air cooled pistons

Post by MadBill » Sun Oct 06, 2019 6:56 pm

Abradable coatings like Line2Line's self-clearance to the tightest piston-bore conditions the engine encounters, rather than machining the latter to accommodate the tightest contemplated. The difference provides more safety factor and less piston rock.
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Re: Coating Air cooled pistons

Post by ptuomov » Mon Oct 07, 2019 9:44 am

Kevin Johnson wrote:
Sun Oct 06, 2019 2:13 am
Proper windage control is needed to remove the oil droplets from the cloud at high rpm. The impacts with the rotating assembly heat the oil and are a parasitic drag as well as adding volume to trapped pooled oil under sustained lateral acceleration which could then be churned by the rotating assembly; i.e. the collected oil could not drain back to the sump proper. The areas where the oil temporarily collected became defacto sumps. Porsche had to withdraw the use of oil squirters in the 928 because of this. Other manufacturers designed pumping systems to transport oil away from these collection areas in the style of scavenge stages for dry sumps. Often something like this that works is illegal to retrofit in various racing classes.
Having now run 928 S4 engines both with piston oil cooling jets and without them, I would dispute both the fact about what they do and don't do inside the engine and also the reason for their discontinuation by the factory. I believe that the most likely reason why the piston oil cooling jets were removed from the 928 S4 was that a multi-car track testing program showed very low piston temperatures and that they were therefore unnecessary. Expensive and unnecessary things are not added to car engines by car factories. The existing blocks with piston oil cooling jets were used, though. The crankcase breathing and oiling behavior of engines with and without the piston oil cooling jets appear close to identical in our use.

If you have evidence on either (the piston oil cooling jets actually causing problems or the factory discontinuing their use for any other reason other than cost), I'd like to hear it. I recall Porsche communication on the discontinuation being: "Bores for piston crown cooling have been omitted in the upper crankcase section since January of 1987 because of positive endurance testing results."

This has been of interest to us recently, because in order to run higher rpms, we need lighter pistons and thinner piston rings which will by our calculations require piston oil cooling jets.

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Re: Coating Air cooled pistons

Post by Kevin Johnson » Mon Oct 07, 2019 10:36 am

ptuomov wrote:
Mon Oct 07, 2019 9:44 am
Kevin Johnson wrote:
Sun Oct 06, 2019 2:13 am
Proper windage control is needed to remove the oil droplets from the cloud at high rpm. The impacts with the rotating assembly heat the oil and are a parasitic drag as well as adding volume to trapped pooled oil under sustained lateral acceleration which could then be churned by the rotating assembly; i.e. the collected oil could not drain back to the sump proper. The areas where the oil temporarily collected became defacto sumps. Porsche had to withdraw the use of oil squirters in the 928 because of this. Other manufacturers designed pumping systems to transport oil away from these collection areas in the style of scavenge stages for dry sumps. Often something like this that works is illegal to retrofit in various racing classes.
Having now run 928 S4 engines both with piston oil cooling jets and without them, I would dispute both the fact about what they do and don't do inside the engine and also the reason for their discontinuation by the factory. I believe that the most likely reason why the piston oil cooling jets were removed from the 928 S4 was that a multi-car track testing program showed very low piston temperatures and that they were therefore unnecessary. Expensive and unnecessary things are not added to car engines by car factories. The existing blocks with piston oil cooling jets were used, though. The crankcase breathing and oiling behavior of engines with and without the piston oil cooling jets appear close to identical in our use.

If you have evidence on either (the piston oil cooling jets actually causing problems or the factory discontinuing their use for any other reason other than cost), I'd like to hear it. I recall Porsche communication on the discontinuation being: "Bores for piston crown cooling have been omitted in the upper crankcase section since January of 1987 because of positive endurance testing results."

This has been of interest to us recently, because in order to run higher rpms, we need lighter pistons and thinner piston rings which will by our calculations require piston oil cooling jets.
I don't have written evidence nor do I have written testimony from the Porsche shops who were threatened that their factory support for other vehicles would be withdrawn if they continued to try to campaign the 928 in North American racing. Porsche and Mercedes both had very carefully cultivated prestigious images in North America and Porsche's Racing Heritage was not furthered by engines regularly blowing up on the track.

Project 928 talked about the epic endurance testing of the engine -- on a fixed dyno -- for thousands of hours. Careful examination of the photos therein revealed that they found it necessary to greatly overdrive the already large oil pump. Nowhere in the text are the epic problems with rod bearing failure mentioned. I did note in one of my readings of the service manuals for a related engine that it was the first that I had ever read that went into great detail about how to remove the detritus from a failed bearing.

I am pleased that you have had success in getting the engine and transaxle to survive at much higher power levels. 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.

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