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7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

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Old 12-23-2007, 05:00 PM   #1 (permalink)
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Compression ratios

Ok, i know im reading way into this truck but i like to know as much as possible, but ive said that before.

What is the compression ratio on a 89 7.3 idi n/a motor, what is the compression ratio on a 93 7.3 idi turbo motor.

Im willing to bet theyre different.

Will
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Old 12-23-2007, 06:22 PM   #2 (permalink)
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Re: Compression ratios

i belive there both 17:1 compression

the least amount of compression for a diesel is aproximatly 16:1
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Old 12-23-2007, 06:31 PM   #3 (permalink)
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Re: Compression ratios

17:1 is for a powerstroke.

I am 90% certain the older one is 21.5 to 1 as well for the 93......at idle that is. With the turbo, you could possibly get 30:1 I think probably more.


They are essentially the same engine if its a pre-powerstroke.
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Old 12-23-2007, 06:48 PM   #4 (permalink)
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Re: Compression ratios

Both N/A IDI and Turbo IDI share the same compession ratio 21.5:1
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Old 12-23-2007, 07:04 PM   #5 (permalink)
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Re: Compression ratios

yes 21.5 to 1
the psd is less and a turbo will increase it only when the engine is pulling load
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Old 12-23-2007, 07:12 PM   #6 (permalink)
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Re: Compression ratios

PSD is less, turbo does not change compression ratio. It increase cylinder pressure on compression stroke. More air in same space.
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Old 12-23-2007, 08:54 PM   #7 (permalink)
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Re: Compression ratios

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: J_Wagner</div><div class="ubbcode-body">PSD is less, turbo does not change compression ratio. It increase cylinder pressure on compression stroke. More air in same space. </div></div>

HAHA! you are right!! i dont know what i was thinking. the valves are closed when it compresses so it doesnt make a difference.

My bad lol
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Old 12-23-2007, 10:11 PM   #8 (permalink)
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Re: Compression ratios

Thanks for the help. I was just figuring the later model turbo trucks might have lower compression due to the factory turbo.

Thanks again

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Old 12-24-2007, 03:17 PM   #9 (permalink)
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Re: Compression ratios

oops my bad i read the artical wrong

sorry for the false info
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Old 12-24-2007, 04:59 PM   #10 (permalink)
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Re: Compression ratios

No worries man, i appreciate any and all info i get.

Will
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