ESE's works engine tuner

**TZ350** · 16th February 2009, 19:09

Originally Posted by F5 Dave

yes it's not hugely specific, the squish area is in the chamber. nice to see pic

These are homemade copper cylinder head inserts for an Aprilia.

This is what I would call " a copper cylinder head insert to conduct combustion heat away faster "as apposed to a detonation insert which is more of a ring around the squish band area.

I have not been able to find a Honda or Aprilia RS125 head thats been ceramic coated.

Would like to confirm if the Yamaha ones actualy exist, and a pic would be nice.

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**F5 Dave** · 17th February 2009, 08:46

That will be probably a vhm head with replaceable inserts & perhaps as you say they have made own inserts. Not sure why you would bother on a water cooled bike, you can over-cool them quite easily.

**bucketracer** · 17th February 2009, 09:00

Originally Posted by F5 Dave

That will be probably a vhm head with replaceable inserts & perhaps as you say they have made own inserts. Not sure why you would bother on a water cooled bike, you can over-cool them quite easily.

Over-Cool them quite easily, good point when you think about it.

I think a combustion chamber cut into a slug of copper and then pressed into an alloy muff may have possibilities for an air cooled motor.

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**F5 Dave** · 17th February 2009, 09:06

Yeah [thinks] you still have that thermal barrier that the heat has to pass into the ally cooling fins, even as 'cast over it' like the japs do their barrels over steel liners, not sure you would be better off. as 'pressed in' you may well be quite a bit worse off. Be hard to measure if it was working better or worse. Hmmm...

**bucketracer** · 17th February 2009, 11:26

Originally Posted by F5 Dave

Yeah [thinks] you still have that thermal barrier that the heat has to pass into the ally cooling fins, even as 'cast over it' like the japs do their barrels over steel liners, not sure you would be better off. as 'pressed in' you may well be quite a bit worse off. Be hard to measure if it was working better or worse. Hmmm...

My thinking on my own GP100 was to use a copper insert to quickly remove thermal energy from the smallish surface of the combustion chamber (copper does this faster than aluminum) which the copper transmits quickly (twice as fast as alloy) to the larger outside surface area of the copper plug to be transmitted by conduction across the copper/alloy interface and onto the alloy fins.

I was hoping because of its much greater surface area the conduction across the copper/alloy interface would happen quicker than the thermal uptake at the relatively smaller combustion chamber surface.

My thinking is if this happens then the combustion chamber surface should run cooler with the copper insert than it would have with the ordanary alloy combustion chamber.

Its a fine thery but measuring/proving it, thats a bit harder.
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**Sully60** · 17th February 2009, 14:37

This thread needs a musical interlude...

**TZ350** · 17th February 2009, 15:39

Originally Posted by F5 Dave

not sure that cellar dweller articles have been written for many years, suspect the article is say 10 yrs old, but no mind.

Does reiterate the bit about wrapping pipes & appears the belief that head inserts (that people had been using since the late 80s, but probably before) were actually helping rather than just reducing the damage from detonation. Would be proof i suppose if set up with a det counter & fitted same head with a ring insert & see if det count reduces or stops. (tricky electronic racing setups mean you can jet your RS or whatever so that it is just on borderline of detonating where it produces most power, but not go too far. Shorter sparkplugs are fitted with a piezoelectric det counter underneath).

F5 your right, I emailed the source, that article was writen in the 90's by Kevin Cameron an engine tuner, I had not heard of him before. I Googled him and he has written several books and many articles. He's worth a Google. I am trying to find a contact so I can ask about the TZ copper inserted heads.

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**F5 Dave** · 17th February 2009, 16:07

He wrote for Cycle which merged with Cycle world, he took over as technical writer from Gorden Jennings. Has been very prolific. Seek out a copy of his Sport bike performance handbook, is very worthwhile.

**TZ350** · 18th February 2009, 21:29

Going to Tech Books Saturday to see what I can find.

**TZ350** · 18th February 2009, 21:29

An Abstract from a Uni paper that looked into combustion chamber temperature. Although this was done using a 4-stroke it makes interesting reading and gives some insight into the combustion heat processes in a 2-stroke.

Combustion Chamber Temperature and Instantaneous Local Heat Flux Measurements in a Spark Ignition Engine

Document Number: 930217
Date Published: March 1993

Abstract:
Cylinder head combustion chamber and piston temperatures and heat fluxes were measured in a 2.2 L 4 cylinder spark ignition engine. Measurements for the combustion chamber were made at wide open throttle conditions, 1400 rpm to 5000 rpm at 600 rpm increments, additional measurements were made on the combustion chamber at part throttle conditions at 3200 rpm. Piston temperature and heat flux measurements were made at WOT conditions from 1400 to 3200 rpm in 600 rpm increments. Average combustion chamber surface temperatures ranged from 130 degrees C to 248 degrees C, while peak combustion chamber surface temperatures ranged from 142 degrees C to 258 degrees C for WOT conditions. Peak heat flux at the surface for WOT conditions in the combustion chamber ranged from 1.2 MW/m\u2 to 5.0 MW/m\u2. Central region heat fluxes were 2.3 to 2.8 times greater than those in the end gas regions of the combustion chamber. Piston temperatures were 10 to 25 degrees centigrade hotter than corresponding combustion chamber surfaces at WOT conditions. Peak heat flux values in the end gas region of the piston were 2 to 4 times greater than corresponding locations on the combustion chamber at WOT conditions. The Woschni heat transfer model correlated well with the experimental instantaneous local heat flux data. Long term heat flux data indicates that deposit formation greatly modifies surface heat transfer.

I found it interesting that:-

Average combustion chamber surface temperatures ranged from 130 degrees C to 248 degrees C and peak combustion chamber surface temperatures ranged from 142 degrees C to 258 degrees C.

Central region heat fluxes were 2.3 to 2.8 times greater than those in the end gas regions (squish area) of the combustion chamber.

Piston temperatures were 10 to 25 degrees Centigrade hotter than the corresponding combustion chamber surface.

Peak heat flux values in the end gas region (squish area) of the piston were 2 to 4 times greater than corresponding locations on the combustion chamber (squish area).

As the heat load goes up and drives the combustion chamber surface temperature up you can see how the thermal conductivity through the combustion chamber wall becomes important in avoiding localized overheating.
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