Timing, Towing, and Altitude - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 6 (permalink) Old 08-29-2006, 02:44 PM Thread Starter
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Timing, Towing, and Altitude

Casually looking over the tables of the stock tune, vs other tunes, using EFI,

I notice only low altitude timing maps (C) are addressed, when added performance is downloaded, say from a predator. They add boost to the high altitude maps, fuel is added, but timing remains unchanged. This appears to be a common oversight.

This means somewhere around 4000-5000 ft, it appears the D-max takes a real performance hit. It gets more air, more fuel duration, but the start of fuel injection is not moved back. The result should be that more of the power stroke, is occuring well past TDC, depending on fuel quality and other factors. More heat, less power.

Opinions?

Michael
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post #2 of 6 (permalink) Old 08-30-2006, 03:31 AM
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i never noticed that. eveyone allways said to chang the the C table so i never looked at the other ones.

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post #3 of 6 (permalink) Old 08-30-2006, 04:29 PM Thread Starter
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Re the stock maps, I notice that, as a rule, with increased altitude (decreased baro):

-Timing is advanced
-Mass Air flow is reduced

Turbo compression is nearly constant (after compensating for reduced barometric pressure as we climb, so mass air flow is constantly declining with changing altitude)

-The same pulse duration is used, I find no pulse duration compensation for baro.

The question i have, is why is timing advanced with increased altitude, in the stock timing maps?

Michael
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post #4 of 6 (permalink) Old 08-31-2006, 01:48 PM Thread Starter
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Kathy and Pat? You guys ever do runs in Denver, or other low baro locations?

Michael
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post #5 of 6 (permalink) Old 10-01-2006, 01:33 AM
 
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KB,
I am at 5500ft elevation and if I run any tune over 80hp whether it be BU,predator,or Edge I get very loud valve train noise from timing. It is hard for me to run a tune over 80hp knowing what what is doing to the engine. Maybe EFI live is the cure for that at my elevation.
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post #6 of 6 (permalink) Old 10-01-2006, 04:10 AM Thread Starter
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You are at the elevation where most tuners ignore.

Michael
Vehicle Systems Engineer/Professional Tuner
04.5 GMC 2500HD SRW LLY

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