Heat or Revolutions? - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 23 (permalink) Old 01-14-2009, 05:17 PM Thread Starter
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Heat or Revolutions?

So my question is fairly simple. Which one hurts mileage more EGT or RPM? I drive 37 miles one way to work and am able to cruis for 20ish miles at 50-60MPH. I have noticed that doing 55 in overdrive my egt's sneak up above 600 sometimes up around 900. I will be cruising at 1500 RPM. I can lock the OD out and my EGT's drop to ~450 but my RPMs jump to ~2300.

So which is better:

the low EGTs with higher RPMs

Low RPMs with Higher EGTs?

Sam
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post #2 of 23 (permalink) Old 01-14-2009, 05:36 PM
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Re: Heat or Revolutions?

I am curious about that myself...

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post #3 of 23 (permalink) Old 01-14-2009, 05:46 PM
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Re: Heat or Revolutions?

IMO if you're driving light, Rpms should make a bigger difference.
I base this on No scientific data, comparison or thought. Just an opinion.

Dan
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post #4 of 23 (permalink) Old 01-15-2009, 01:04 PM
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Re: Heat or Revolutions?

Yeah, personally, I'd feel that higher RPM's are going to hurt.

I feel that way for a couple of reasons. First, friction. Second, the aerodynamics of moving parts. I would think that those items increase exponentially as RPM's go up.

Dave
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post #5 of 23 (permalink) Old 01-16-2009, 10:55 PM
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Re: Heat or Revolutions?

Genie144:

Why don't you do a test and tell us?

A couple of tankfuls with low RPM/high EGT note the MPG.
A couple of tankfuls with high RPM/low EGT note the MPG.

Not a tough test to do. Enlighten the masses.

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post #6 of 23 (permalink) Old 01-16-2009, 11:02 PM
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Re: Heat or Revolutions?

sounds like a good idea to me.
But you need a baseline first...

Dan
96 Powerstroke: 6637, downpipe to dump exhaust, 140v IDM and a shift kit.

84 Honda Sabre V65 1100: pipes, jet kit and new tires. Faster than I think I'll ever need.
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post #7 of 23 (permalink) Old 01-17-2009, 05:42 PM
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Re: Heat or Revolutions?

Yup. Two weeks baseline. That also gives you a chance4 to standardize your driving.

Then two weeks one way (high RPM/low EGT)

Then two weeks the other way.

Don't sweat the fact it is winter. The percentage change is what you are looking for. Maybe repeat in mid-summer.

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post #8 of 23 (permalink) Old 01-18-2009, 05:48 AM
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Re: Heat or Revolutions?

as long as all the tests are done on winter fuel, it won't matter...

Dan
96 Powerstroke: 6637, downpipe to dump exhaust, 140v IDM and a shift kit.

84 Honda Sabre V65 1100: pipes, jet kit and new tires. Faster than I think I'll ever need.
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post #9 of 23 (permalink) Old 01-19-2009, 03:17 PM Thread Starter
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Re: Heat or Revolutions?

Dave

Normally I would do the testing and report. A single tank load each way (100 gallons). But I won't be able to perform the testing for a month or two. I have some things I am tweaking with my fuel system that would make it impossible to establish an accurate baseline. Not to mention the validity of any data would be suspect with the change of fuel pump and additional filtration in the middle of it.

I was curious if anyone had done the testing - I know you always say keep heat down and RPMs low. I can see an argument for each being more important.

As soon as I get the fuel system locked up I will do the testing.

Sam

On edit - not to mention that my fuel additive choice (SVO) makes my truck less than an ideal test bed for the masses
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post #10 of 23 (permalink) Old 01-21-2009, 09:45 PM
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Re: Heat or Revolutions?

If it's not hilly run in OD for the best mpg in this case.

EGTs are higher but that is a function of less boost, not more fuel being used as you might have suspected.

I'm officially...Stroke-less.
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