Lower EGTs and mileage - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 5 (permalink) Old 11-12-2007, 03:27 PM Thread Starter
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Lower EGTs and mileage

So I have always tried to drive with the numbers, <2000RPM <70MPH <600deg EGT. With my new 4" magnaflow exhaust I notice my highway cruising EGTs dropped. It's pretty easy to keep it below 600 now. This got me thinking, if a change like exhaust lowers the EGTs are you really going to see an increase in mileage. How does the higher heat relate to higher mileage. Obviously more heat comes from more fuel being burned, but at the same cruising speed with a larger exhaust does the truck use less fuel? Just thinking.

2001 F350 CC LB 4X4
TN, AIS, DP 80hp, ITP boost elim, Magnaflow 4".
Tows the big white hauler.

When life gives you Lemons, throw them at the stupid people.
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post #2 of 5 (permalink) Old 11-12-2007, 03:56 PM
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Re: Lower EGTs and mileage

i dont think its using more or less fuel, its just that the exhaust is flowing more freely through the system. by keeping the hot gasses moving, it keeps your egt's down. basically, theres not as much "trapped" gasses in the exhaust system anymore

2005 F350 prairie tan/black crew cab FX4 innovative tunes, exhaust

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post #3 of 5 (permalink) Old 11-12-2007, 11:10 PM
 
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Re: Lower EGTs and mileage



I've thought about this before. I think the 600&#186; rule is for a stockish truck. Obviously if you added no more fuel, and had a free flowing exhaust, open intake, big intercooler, and say a BB turbo your EGT's would drop at the same cruising speed (amount of work) but you are still burning the same amount of fuel to do the same amount of work, so mileage would remain the same.

The caveat is the increas in efficiency you have gained by the mods. The IC, and turbo and intake all contribute to the temperature and therefore density of the air that enters the engine. With the same amount of fuel, and more air you have now increased the efficiency of the engine, and it should be able to do the same amount of work as before on less fuel.

So I guess the answer to your question is "yes and no".

The egt's dropped because the exhaust is not as restrictive, however IF the exhaust makes the engine more efficient, it is now doing the same amount of work as before with less effort.
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post #4 of 5 (permalink) Old 11-14-2007, 03:36 AM
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Re: Lower EGTs and mileage

Exhaust heat wont really help or hurt MPG but allowing the truck to breathe easier will. The truck works less with the same amount of fuel. Now if you install a 203* thermostat, the extra heat the coolant and oil have will help promote better combustion and that has been said to increase MPG a little. When I change coolant next spring in my 2 strokers, I will install the hotter stat.

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1996 PSD F-350 crew cab 4x4, 5 speed,AB CODE CALI TRUCK- Tuned by DI

2013 F250 4x4 CCLB Platinum Edition
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post #5 of 5 (permalink) Old 11-14-2007, 09:10 AM
 
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Re: Lower EGTs and mileage

Actually an exhaust reduces back pressure as well, so it may help, just probably not anything perceptible without exacting calculations.

I picked up a solid, hand-calculated 1.5mpg when I put on the DIY intake, and walker BTM. Wonder how much the muffler had to do with that

Maybe it was all a plugged stock air filter
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