[Vwdiesel] Fwd: Altitude compensation (James Hansen)

Libbybapa@wmconnect.com Libbybapa at wmconnect.com
Sun Sep 4 18:33:58 EDT 2005


In a message dated 9/4/05 3:33:07 PM US Mountain Standard Time, Libbybapa 
writes:


> In a message dated 9/4/05 1:51:05 PM US Mountain Standard Time, 
> cjb at midrivers.com writes:
> 
> 
> >> "I don't know, but I doubt very much there are high enough compression
>> engines on the consumer market that REQUIRE high octane rated fuel."
>> 
> 
> IMO it would depend on the stock timing setting and the range of retard that 
> the knock sensor ignition could perform.  Regardless, the compression ratio 
> is certainly not the only factor.  Ignition timing setting is as much of a 
> factor.  When a vehicle utilizes a knock sensor, usually it is timed within the 
> range where the engine will start knocking.  The knock sensor retards the 
> timing to just before that point.  You can get an air-cooled engine with a 7:1 
> compression ratio to knock easy enough, just advance the timing far enough.  
> My point still makes sense to me.  An engine running on a lower octane fuel 
> will knock less at higher altitudes.  Therefore the knock sensor will retard 
> the timing less and the injection will enrich less.  My point:  A knock sensor 
> controlled engine will run on lower grades of fuel at higher altitudes with 
> less of an effect on mileage and performance.  Sorry for the in depth 
> non-diesel topic.
> 
> 




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