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Old 02-26-2013, 11:23 AM   #1
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Intake air temperature

Ok I have been reading a thread where some people are debating intake air temps and the range they should be.

On my 5.9 ISB my intake air temps are just around 115* when it is 70* outside. So technically I can say my intake air is 45* warmer than ambient air.

Someone posted this:
Quote:
Maximun allowable air temperature rise over ambient at intake manifold 16.7 C
(30 F )
Intake Manifold Air Temperature Warning Limit 74 C (165 F)
Intake Manifold Air Temperature Shutdown limit 76.7 C (170 F)
Diesel engines are best suited for air temperatures between 60 and 90 F ( 15 and 32 C)
Engines can withstand temperatures below or above this range, but their efficiency drops.
Intake Air That Is Too Hot
Engine horsepower fails about 1% for each 10 degrees of intake air temperature rise above 90 F (32C )

An engine rated at 250 horsepower will develop only 240 horsepower when the
intake air temperature is 130 F (54C) with the same fuel delivery.
Two things here:
1) 16.7*c is not 30*f but 62*f
2) are these statements correct?

I keep reading that intake air should not be more than 30* over ambient air but even when it is cool outside mine is always higher than that.
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Old 02-26-2013, 11:40 AM   #2
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Somewhere in the rest of the thread near the last it explains it, and yes it is correct.
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Old 03-01-2013, 05:15 PM   #3
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I think the ISB may run a little warmer. My 05 ISL 400 runs between 26 - 29 degrees warmer than outside air. I can pretty much tell the outside temp within a few degrees.
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Old 03-01-2013, 05:37 PM   #4
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In most cases when one see's intake air temp at or above 30 plus degrees above
outside air it indicates either a dirty CAC or restricted air flow thru it.
One can also see a increase if the turbo compressor is at or near max output caused
by damage or exceeding the turbo design.
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Old 03-01-2013, 06:12 PM   #5
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Quote:
Originally Posted by Zoafan View Post
.........................
Two things here:
1) 16.7*c is not 30*f but 62*f
2) are these statements correct?
...................
I got schooled on the 16.7*C issue. So based on my schooling in another thread the literal statement of "1) 16.7*c is not 30*f but 62*f" is true. That is to say that when you read the temperature at 16.7*C that does equate to 62*F. But, the problem is that in the context that you are talking about the 16.7*C is a differential temperature. In other words; If ambient temp is say 15*C the intake temp (for best performance) should be no more than 15*C (ambient) plus 16.7*C (differential) or 31.7*C intake air temp. If you prefer to speak in F then just multiply 16.7*C X 1.8 which will equal 30*F (the differential temp).
Hope you guys that schooled me read this.
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Old 03-01-2013, 06:40 PM   #6
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Kix,
We are
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Old 03-01-2013, 06:45 PM   #7
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On my ISM500, the intake temp normally is about max 20 deg above ambient, The setup uses the CAC style cooling in front of radiator, must work as it will maintain that general difference even when pulling 34 psi boost. Also no heating issues at all, water temp max has been 202 going up, and with the retarder, have seen 220 going down mountains, quickly cools when hit the level areas.
No such thing as too much HP
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Old 03-01-2013, 07:07 PM   #8
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Quote:
Originally Posted by KIX View Post
I got schooled on the 16.7*C issue. So based on my schooling in another thread the literal statement of "1) 16.7*c is not 30*f but 62*f" is true. That is to say that when you read the temperature at 16.7*C that does equate to 62*F. But, the problem is that in the context that you are talking about the 16.7*C is a differential temperature. In other words; If ambient temp is say 15*C the intake temp (for best performance) should be no more than 15*C (ambient) plus 16.7*C (differential) or 31.7*C intake air temp. If you prefer to speak in F then just multiply 16.7*C X 1.8 which will equal 30*F (the differential temp).
Hope you guys that schooled me read this.
Your formula for converting Celsius to Fahrenheit is incorrect. The proper formula is 16.7 * 1.8 +32= 62. The formula to go from F to C is (F - 32) * .55 = C
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Old 03-01-2013, 07:34 PM   #9
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Quote:
Originally Posted by BFlinn181 View Post
Your formula for converting Celsius to Fahrenheit is incorrect. The proper formula is 16.7 * 1.8 +32= 62. The formula to go from F to C is (F - 32) * .55 = C
We're talking a temperature differential and not an absolute temperature.
I am not converting temperature. When you do a little research you will find that a change in temperature of 1*C will equal a 1.8*F change in temperature.
Does this help?
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Old 03-01-2013, 07:35 PM   #10
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Here we go again the difference between ambient and differential
never mind Cummins thoughts on the matter.
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Old 03-01-2013, 07:41 PM   #11
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Quote:
Originally Posted by wb7auk View Post
Here we go again the difference between ambient and differential
never mind Cummins thoughts on the matter.
How am I doing, Art?
And where's Rusty?
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Old 03-01-2013, 07:41 PM   #12
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Kix,
Having been there and done that who better to explain it.
Will watch
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Old 03-01-2013, 07:46 PM   #13
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The first time I read that I also jumped to the bait but with a little more thought
on the matter seen the error of my thinking.
Maybe Rusty is still on the floor giggling .
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Old 03-01-2013, 07:46 PM   #14
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BFlinn, et al, Here is possibly a better explantion.
1*C is 1* above freezing on the C scale.
1*C is equal to 33.8* on the F scale.
Now, deduct the freeze temp from each and you will find that 1*C = 1.8*F......and that is differential temperature.
Believe me now?
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