Author Topic: How do I make my engine Better? Racing Engines 101 . . . . .  (Read 41637 times)

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Offline tauruck

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #30 on: January 11, 2016, 06:10:49 PM »
IntObs;

I was under the impression that a significant portion of the ceramic coating advantage was its reflecting of the radiant heat of combustion.

Regards, Neil  Tucson, AZ

These guys want to help me with coating. Check them out Neil.

 http://td.co.za/

Offline manta22

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #31 on: January 11, 2016, 07:05:35 PM »
Thanks, Mike- will do.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Interested Observer

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #32 on: January 11, 2016, 08:05:55 PM »
Mike:
From TD Coating website with regard to their ceramic/thermal materials:
“These coatings can take very high flash temperatures well over 1000°C. Due to the coatings thin nature (25 microns) it is not a solution for efficient sustained thermal insulation..”

Neil:
Some while back you raised the question of reflectivity contributing to possible reduction of heat transfer. I did not ignore your point as this was an aspect I had not considered, and since have done some reading and consulting of knowledgeable individuals.  The upshot of this is that yes, a portion of the incident thermal radiation may be reflected, depending on the reflectivity of the material, but practically, with gasses being essentially transparent to thermal radiation, it just gets reflected to the surrounding surfaces over and over until absorbed.   Net result is a minimal insulating effect.

Offline manta22

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #33 on: January 12, 2016, 12:11:18 PM »
Mike:
From TD Coating website with regard to their ceramic/thermal materials:
“These coatings can take very high flash temperatures well over 1000°C. Due to the coatings thin nature (25 microns) it is not a solution for efficient sustained thermal insulation..”

Neil:
Some while back you raised the question of reflectivity contributing to possible reduction of heat transfer. I did not ignore your point as this was an aspect I had not considered, and since have done some reading and consulting of knowledgeable individuals.  The upshot of this is that yes, a portion of the incident thermal radiation may be reflected, depending on the reflectivity of the material, but practically, with gasses being essentially transparent to thermal radiation, it just gets reflected to the surrounding surfaces over and over until absorbed.   Net result is a minimal insulating effect.


IO;

Yes, the heat of combustion is reflected off the coating on top of the piston and it is absorbed by the combustion chamber and valve faces. How much of that heat is absorbed is determined by the geometry and emissivity of those surfaces. True- some heat is reflected rather than absorbed but not much. What is reflected back to the piston crown is again reflected efficiently by the coating and the whole cycle repeats at a far lower level until it reaches equilibrium.

If its melting point were not so low, gold would be an ideal heat reflecting coating since its emissivity in the infrared is so low. That's why most spacecraft are wrapped in gold coated Mylar foil to reflect solar radiation.

The point is that the heat reflectance of the coating reduces the temperature of the piston crown compared to an uncoated piston.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline jacksoni

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #34 on: January 12, 2016, 02:26:11 PM »
In his 1976 book "The Chevrolet Racing engine", Bill Jenkins had this comment: "The last procedure (after bead blasting the dome- my addition) is an application of Sperex VHT white paint to the dome surface followed by a 8-10 hour heat bake with infrared lamps. This is, more or less, a shield to provide faster heat buildup when the car is leaving the line. On the dynamometer we haven't found any power increase from this technique after the heat has stabilized. We know that an engine which as been assembled with bright , shiny, new combustion chambers requires a different "tune up" setting until the chambers have become coated with a fine carbon layer. The VHT paint acts similar to a thin carbon layer and helps promote carbon build up. Without using the paint it takes 6-10 hard passes before we can get back to our race tune-up. By using the paint we can go straight from the shop to the strip with a brand new motor, fire the engine, and hit the first pass with our race tune-up. The carbon buildup , incidentally, is very important in a drag engine. It acts as a head dam or absorption layer inside the chamber and on the head of the piston. During operation it reaches glowing-hot temperatures and assists heat buildup in the chambers during initial full throttle application- quickening response in the first few , ultra-critical feet of the race. "

There is some more but the above covers the topic here.
Jack Iliff
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Offline tauruck

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #35 on: February 16, 2016, 11:11:01 AM »
Mike:
From TD Coating website with regard to their ceramic/thermal materials:
“These coatings can take very high flash temperatures well over 1000°C. Due to the coatings thin nature (25 microns) it is not a solution for efficient sustained thermal insulation..”

Neil:
Some while back you raised the question of reflectivity contributing to possible reduction of heat transfer. I did not ignore your point as this was an aspect I had not considered, and since have done some reading and consulting of knowledgeable individuals.  The upshot of this is that yes, a portion of the incident thermal radiation may be reflected, depending on the reflectivity of the material, but practically, with gasses being essentially transparent to thermal radiation, it just gets reflected to the surrounding surfaces over and over until absorbed.   Net result is a minimal insulating effect.


IO;

Yes, the heat of combustion is reflected off the coating on top of the piston and it is absorbed by the combustion chamber and valve faces. How much of that heat is absorbed is determined by the geometry and emissivity of those surfaces. True- some heat is reflected rather than absorbed but not much. What is reflected back to the piston crown is again reflected efficiently by the coating and the whole cycle repeats at a far lower level until it reaches equilibrium.

If its melting point were not so low, gold would be an ideal heat reflecting coating since its emissivity in the infrared is so low. That's why most spacecraft are wrapped in gold coated Mylar foil to reflect solar radiation.

The point is that the heat reflectance of the coating reduces the temperature of the piston crown compared to an uncoated piston.

Regards, Neil  Tucson, AZ
What's your take on the combustion chamber material ie cast iron vs Aluminum?. Thanks. :cheers:

Offline tauruck

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #36 on: February 17, 2016, 12:35:18 AM »
Thanks for your insight. I think I'll be OK. :cheers:

Offline Polyhead

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #37 on: February 18, 2016, 10:42:14 PM »
Should just add, aluminum carries away more heat so it can solve some detonation problems.  But usually engine builders respond to this with even more compression... so... you're back where you started.
Ben 'Polyhead' Smith
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Offline wobblywalrus

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #38 on: March 08, 2016, 10:50:35 PM »
Right now I figured out my piston demand at 28 inches per crank degree using PipeMax.  I know the cam lift per degree and have flows at 28 inches.  Now I am trying to figure out if the flow past the valves is equal to piston demand throughout the intake cycle.  Somehow I need to factor lag into these calks.  It is being done by hand and it is driving me nuts.  Paying $99 to get software to do this is a bargain.  Old Wobbles put in his order. 

Offline gearheadeh

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #39 on: March 11, 2016, 05:03:24 PM »
 :-D  Yeah, people,----- can't wait to start me learnin un stuff.....   :mrgreen:

Really hope there are another 48 thrifty people out there!
40 is the old age of Youth, 50 is the young age of the Senior years.

Offline wobblywalrus

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #40 on: March 16, 2016, 09:39:20 AM »
The head is being flow tested and the machinist is trying to get that last little bit of flow.  He give me charts of flows at 28 inches vs valve lift for the intake and exhaust.  It looks like I also need "throttle cfm @1.5 inches Hg" and "Reference Bore Diameter - inch" according to the Horsepower Chain book.  I do not have the program, yet.  Is there more info than these two added items that I need from the flow testing?

Offline wobblywalrus

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Re: How do I make my engine Better? Racing Engines 101 . . . . .
« Reply #41 on: March 17, 2016, 02:15:34 AM »
This weekend I will open the program and figure out exactly what they need.  The download came in on today's e-mails.