Farm Equipment - wd timing or gas tractor engine

wd timing or gas tractor engine

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Category: Allis Chalmers
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Topic: wd timing or gas tractor engine

Posted By: HudCo
Subject: wd timing or gas tractor engine
Date Posted: 28 Nov 2022 at 12:39pm

i never thought about this until the other day, so here at 5000ft. we all run our ignition timing about 4 degrees more on our non computer controlled cars and trucks , so what about our tractors ? or even diesel tractors ?

Replies:

Posted By: Ed (Ont)
Date Posted: 28 Nov 2022 at 2:04pm

Interesting. We put smaller jets in the carb on our race motors at higher altitudes but left the timing the same.

Posted By: DaveKamp
Date Posted: 29 Nov 2022 at 2:29am

Both adjustments are valid... and for the same reason.

At higher elevation, there's a less dense atmosphere, which means the concentration of oxygen in a given volume of displacement is naturally lower.

The density being lighter means that gross compression will be lower (because starting pressure is lower). Advancing the spark by four degrees puts the ignition event farther BEFORE TDC's peak compression point, so you're most likely to get a complete combustion pattern, thus a more complete burn and earlier full chamber pressure before reaching TDC.

Modern ECMs on fuel injection systems automatically compensate for whatever conditrions of altitude throw at us... mixture AND timing are necessary to optimize for power.

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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.

Posted By: DrAllis
Date Posted: 29 Nov 2022 at 6:48am

Maybe and maybe not. Some engines may benefit, others not so much. Take a WD tractor with 5.5 to 1 compression ratio at 100 psi which is timed at 30 degrees BTDC. I doubt that increasing the timing from 30 to 35 would yield much difference on a fairly low performance engine like that. Then, take a 175 gas tractor with 8.25 to 1 compression at 170 psi which needs to be timed at 22 degrees BTDC to keep detonation in check. There might be an advantage there, but the engine will never perform like it would at sea level timed at 22 degrees. Some of us older guys are wary of advancing timing on the higher compression gas engines because we have experienced the center main bearing "thump" that comes from too much ignition timing. The "thump" ain't a good thing. Direct injection diesels with turbochargers are much less affected by the altitude. Direct injection diesels that get the timing advanced are at risk of squirting the fuel over the top of the combustion chamber bowl and over time will burn the top of the piston. Again, some engines react differently than others depending on several things. In-direct inject diesels wouldn't be prone to piston burning, but they are lower performance anyway. So to end my thoughts.....maybe or maybe not.

Posted By: HudCo
Date Posted: 29 Nov 2022 at 9:34am

good answers. my buddy takes the pulling truck to washington and runns at 1000ft its like adding an extra engine . some of my snowmobiles will run about the same at 5000ft and 8000ft the higher performce engines have a much narrower window on clutching and jetting they are also 1 to 2 degrees more on the timing. i had just never thought about doing machinery and equipment any differant than stock specs.

Posted By: DaveKamp
Date Posted: 29 Nov 2022 at 11:36pm

Neither timing NOR mixture will ever bring a naturally-aspirated IC engine's power up to equate what it would get at significantly lower altitudes... they'll simply dial-in the details that best suit the context. Compression and mixture are both dynamic circumstances, and atmospheric density has a profound effect on BOTH.

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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.