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  #11  
Old 02-06-2015, 09:16 PM
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RV10inOz RV10inOz is offline
 
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Hi Kevin,

Quick correction you might like to make to your opening post.
Quote:
more resilient to the fuel is to knock (pre-ignition).
That is detonation you are referring to not pre-igntion.

Nice piston work

What is the design ICP you are working to and spark timing on the mogas? PM if you want to keep that confidential.

Cheers,
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  #12  
Old 02-07-2015, 05:43 AM
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Designed squish clearance dimension? If small, is there a procedure to check it during assembly?
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  #13  
Old 02-07-2015, 06:07 AM
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Quote:
Originally Posted by DanH View Post
Designed squish clearance dimension? If small, is there a procedure to check it during assembly?
Good Question - and how long does it take for the lead build up to create a mechanical knock by filling that space with material?


That was one of the issues in cars with close piston-to-head clearance when leaded gasoline was in vogue. I sounded like a bad rod bearing at idle. The shade tree method of repair was an 8oz Coke bottle of water dribbled in the carb to break loose the lead/carbon deposits while reving the engine (mostly to keep if from dying with the water ingestion). I treated many an engine this way.

The factory method was head removal and scrape off the deposits.
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  #14  
Old 02-08-2015, 05:22 PM
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Default Injection

You can automatically run lean of peak today with the EFII system.
Direct injection is a completely different animal from any of the engine parts, or engine management parts that small aircraft are working with today.
It would cost a LOT of money for small gains to even play with direct injection.
Ever increasing emissions standards are the main incentive for car manufacturers to keep finding ways to reduce their fleet emission averages.
Fortunately, we don't have to deal with the cost and complexity that auto makers are stuck with.

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  #15  
Old 02-09-2015, 09:00 AM
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Quote:
Originally Posted by DanH View Post
Designed squish clearance dimension? If small, is there a procedure to check it during assembly?
Absolutely, in early testing just such check was not completed by the engine builder of my 720 and the result destruction of the engine resulted. The clearances for a new case must be reserved or possible shimming can restore the clearance for the chamber.
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  #16  
Old 02-09-2015, 09:06 AM
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Quote:
Originally Posted by BillL View Post
Good Question - and how long does it take for the lead build up to create a mechanical knock by filling that space with material?
The design is such that the squish zone promote a violent action that pushes the mixed gases into the center of the piston.
The standard "Lycoming type engine" piston arrangement do not do this
and deposits build quickly to the edges of the piston.



Another solution, switch to unleaded fuel
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  #17  
Old 02-09-2015, 09:53 AM
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Quote:
Originally Posted by Relentless View Post
The design is such that the squish zone promote a violent action that pushes the mixed gases into the center of the piston.
Yep. Pretty sure Bill and I know how squish works We're curious about the actual squish dimension.

Here's an example, one of my old experiments from the Wayback Machine. Pentroof 4-valve Honda with the squish area in the combustion chamber welded in, then milled flush with the gasket surface. Squish clearance was set by adding or removing plies from the Honda OEM multi-layer metal head gasket. Measurement was by trial; assemble with a crushable media on top of the piston's squish area (a strip of 0.040" rosin core solder worked well), pull through TDC once, then disassemble and measure the media thickness. I ran this setup very close (crush measurement 0.035"), so the squish areas were nearly in contact at 10,000 RPM...so close that they would not build carbon in the squish areas, at least not within the overhaul time frames of a racebike. Ran on race gas, but it would accept 93 pump gas without detonation if I didn't lug it.



BTW, piston on right was modified to improved overlap flow, and unshroud the areas off the end of the hump. It made more power.
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  #18  
Old 02-09-2015, 10:02 AM
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Quote:
Originally Posted by DanH View Post
Yep. Pretty sure Bill and I know how squish works We're curious about the actual squish dimension.
I was not actually trying enlighten you Dan, I am sure what you have forgotten is more than I will ever know about this. My responds was for the Vans audience to share the effort we are putting into moving these engines forward.

Our squish dimension is proprietary. As you have proven by your post this is not an easy thing to get right. Although, computers have certainly made the process more efficient.
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  #19  
Old 02-09-2015, 10:13 PM
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1) I presume this piston / cylinder configuration could have an ideal ignition timing curve requiring less advance at full power low RPM (think fixed pitch prop take off @ sea level). Could this be provided so it can be programmed into any of the electronic injection systems?
2) Can you make the cylinders for 'Narrow Deck' engines?
I know there are not many of them left, but I have one...
3) My small group of RV & PITTS flyers all fly O-360 & O-320 fixed pitch. We have good engines that would likely be top overhauled before the next major overhaul.
Are these cylinder assemblies going to work for this segment of the market?
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  #20  
Old 02-10-2015, 07:43 AM
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Kevin & Dan, not trying to be a dicc here but do setups like this have any FOD tolerance at all?.
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