Date: Sat, 4 May 2002 08:45:01 -0400
Reply-To: Robert Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Donalds <bostneng@FCL-US.NET>
Subject: Fw: Advancing timing for more power, was: Boston Bob's web site
Content-Type: text/plain; charset="iso-8859-1"
Sent: Saturday, May 04, 2002 8:39 AM
Subject: Re: Advancing timing for more power, was: Boston Bob's web site
Let me start by telling you that my gas article on my web page was directed towards air-cooled engines. The air-cooled engine is very different than the water-cooled engine due to the temp ranges of the combustion chambers. Water-cooled engines have a very narrow operating range and the gas that is made today is designed to run within that narrow range. Air-cooled engines on the other hand have a wide range of combustion chamber temps due to the design of the cooling system. The stock air-cooled engines run at reasonable head temp range for the most part around town with a light load. the time the engine takes to warm up in this light load condition is determined by the ambient air temp, fan intake temp, the design of the stock camshaft, timing (lets call it state of tune) ,and the amount of time the engine is run.
When the air-cooled engine is driven under higher loads it runs hotter and it takes less time to warm up again depending on the list of variables I mentioned above. The air-cooled engines need for higher octane comes into play at the higher loads and head temps. The head temps will climb without LIMIT if the load exceeds the ability of the engine to cool itself and this is not that hard to do. Reasons for this could be a long hill climb after driving down the highway for a length of time or an oil cooler that is blocked of with crud missing tin work or when the air and cooling fan intake temps are over 70 F this decreases the cooling capability dramatically.
The higher octane fuel is needed and unfortunately the new designer fuels can let us down because they are not made to handle the higher combustion temps of the Air-cooled engine. the dyno testing I have done with higher octane fuels on an air cooled engine with higher and lower compression ratios showed that the higher octane fuels stopped the ping but the engine ran just as hot when placed under the same load short term. The reason I say short term is that the abnormal combustion does increase the engine head and piston temp if allowed to continue. the leaded racing fuel I blend with the pump gas MADE LESS power when compared to the pump gas by itself this was the new oxygenated fuels I am talking about.
I have found in my testing that the extra timing can be added to type 1 engines with a hemi cut head but the engine does get warmer sooner. the timing discussion of the past few months was directed exclusively at the 1.9 water-cooled engine I saw an increase of 10 % in power when the timing was changed to 5 before from 5 after in my big valve 21 engine in my 84 water-cooled vanagon with the stock 84 injection system I did test this extra timing on a chassis dyno.
There is no way I would add extra timing to an air-cooled vanagon unless I had some real time heat sensors installed and did some long term testing in high load conditions . The air-cooled engines do have problems with the pump gas when the engine is in severe duty condition like in a van on the highway in the summer at speed. The air-cooled engines do have limits and those limits drop as the air temp and the load increase.
with the radio on going faster miles an hour I remain
Bob Donalds
http://wwwbostonengine.com
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