Compression ratios - Diesel Forum - TheDieselStop.com
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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post #1 of 10 (permalink) Old 12-23-2007, 05:00 PM Thread Starter
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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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post #2 of 10 (permalink) Old 12-23-2007, 06:22 PM
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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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2002 ford F-350 powerstroke cc sb zf-6
1987 ford F-350 6.9L idi flat bed
1989 ford F-350 7.3L idi pick up

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post #3 of 10 (permalink) Old 12-23-2007, 06:31 PM
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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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post #4 of 10 (permalink) Old 12-23-2007, 06:48 PM
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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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post #5 of 10 (permalink) Old 12-23-2007, 07:04 PM
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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

88 f250 96 bed 95 front clip western mirrors and big ole bumper.

7.3 idi t70, 3g, g31,

other mods, oba, warn winch, big steel goodies including a headache rack etc.

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post #6 of 10 (permalink) Old 12-23-2007, 07:12 PM
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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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post #7 of 10 (permalink) Old 12-23-2007, 08:54 PM
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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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post #8 of 10 (permalink) Old 12-23-2007, 10:11 PM Thread Starter
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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

Will
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post #9 of 10 (permalink) Old 12-24-2007, 03:17 PM
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Re: Compression ratios

oops my bad i read the artical wrong

sorry for the false info

company trucks
2002 ford F-350 powerstroke cc sb zf-6
1987 ford F-350 6.9L idi flat bed
1989 ford F-350 7.3L idi pick up

CURRENT PROJECTS
1978 ford F-350 custom
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post #10 of 10 (permalink) Old 12-24-2007, 04:59 PM Thread Starter
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Re: Compression ratios

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

Will
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