Too much time on my hands, so I have been thinking about what mods I might do on my head before I bolt it on.
My goals would be to improve the ability to run on pump gas (91 octane) without trying to wring out more power.
This would be a modification to the air cooled head.
I have come to the conclusion that I want to:
i) Correct the squish band so it can do its thing, 0.040” ~ 0.045” clearance at the outside edge.
ii) Modify the head volume / deck height to restore the compression ratio.
iii) Reshape the head dome to reduce the heat transfer from the air fuel / combustion gases to the head.
The main goal of these mods is to reduce the occurrence of detonation.
So, how did I come to these conclusions?
Too much reading.
I have been looking for good technical information on line.
Most of what I am finding is stuff like “My Banshee has 2000 psi compression and never knocks using Mexican pump gas”, yea right.
A lot of this information is unusable even if it is true.
I need tech information that I can translate to my Odyssey.
I finally found a site that had a list of books and some information on what type of information was in them.
http://www.briansolex.com/books-tuning.htmlFrom this list I have Jennings and Bell.
Jennings has a lot of description about what you want but there is a lack of ‘numbers’ you could use to transfer his findings to your Engine.
To use this information you would have to do a lot of experimentation, I just have one
Engine and I would like to rebuild it just once.
Bell has some hard information that can be used to predict how a particular Engine will behave.
Below I have a graph made from Bells information that predicts the limits of compression ratio vs fuel octane.
From the list above, I found a copy of Blair.
This is the type of book I was looking for.
His basic theory for detonation is to keep the compressed air / fuel below a cut off temperature during the compression stroke.
His methodology is rather complex and involves a computer program (also available for a price).
I find it entertaining that I had read about Blair on McDizzys web site.
This is just what I was looking for.
More to come.