Question about 7.3 MPG, EGT's, and Boost

[Pigman]

Hey guys, I've got questions related to my MPG, boost and EGT's so I figured I'd address all 3 in one thread.

Boost - When I first entered the diesel world a year and a half ago, gauges were the first thing I did...Autometer Cobalt boost and pyro to be exact. I was kind of hesitant to install them myself so I had a shop in Katy install them for me and I'm curious if they installed them properly. At 62 MPH and 1750 RPMs the boost reads 5 PSI and WOT with the All Out tune from Gearhead I can get it up to about 26 max on flat ground. Does this seem about right?

EGTs - Similar to the boost gauge, I'm not quite sure the pyro is installed in the correct place. They tapped into the exhaust downpipe right before it bends to connect to the rest of the exhaust. At 62 MPH and 1750 RPMs in Gearhead's economy tune the EGT's read 600 degrees. Any idea if this seems right?

Note: I have no reason to believe that my gauges are reading incorrectly, I'm just trying to figure out whether they seem correct or incorrect out of curiosity.

MPG - Unlike the gauges, I DO believe that my MPG is not quite as high as it should be. During the summer of 2013, with a stock truck other than 4" exhaust and DP-Tuner's 80e tune, I got 16 city and almost 20 highway. Over the past year or so I've noticed the city MPG fall to about 14, and after installing a 4" lift, 20x12's and 35's this past July it proceeded to fall to 11.5. I finally got an S&B intake and a Hydra chip with tunes from Gearhead a few weeks ago and witnessed an even further decrease. I've filled up 3 times since the new chip and intake and the MPG has been 7.75, 10.4, and 9.5. I filled up today and got 9.5 MPG after doing 30 mins of city driving per day for a week and then making a 1.5 hour highway trip yesterday. I'll admit, first two full ups were in the Street tune which I found out last week from Lars is NOT an economy tune lol. I've been driving in Economy now since last Wednesday and apparently it didn't help much. I know I probably need to get my speedometer and odometer recalibrated due to the larger tires but I feel like I should still be seeing higher numbers than this. Here in the next few months to a year, I plan on addressing the HPOP, turbo, injectors, fuel system, and up pipes, all of which are the originals after 285k miles so it's very possible my issue lies somewhere in there. I'm going to email Lars this weekend to see if there is ANY way to squeeze a little more fuel mileage out of the Economy tune.

 

[Powerstroker7.3]

When I installed my gauges I put my egt sensor in the manifold. I thought this would give me a better reading


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[bruce]

600 degrees that far down the exhaust leads me to believe pre turbo they are high as hell. Sounds like you have a boost or exhaust leak. You can also clean the exhaust back pressure sensor and tube. Those wide, heavy wheels and tires sure ain't doin you any favors either, plus you might be on winter blend fuel already.

 

[Zaairman]

I think his boost and egt numbers are about normal, especially when you consider he has some big azzzz heavy wheels on the truck that he is having to turn.

OP, has the speedo been corrected for the larger tires? Are you accounting for them in your MPG math?

 

[Arisley]

I think his boost and egt numbers are about normal, especially when you consider he has some big azzzz heavy wheels on the truck that he is having to turn.

OP, has the speedo been corrected for the larger tires? Are you accounting for them in your MPG math?

That's my thoughts also. It will make a huge difference in your math.

I would move that EGT probe to pre turbo instead of post turbo. Put it in the driver side exhaust manifold. Boost is about right for stock turbo and injectors.

 

[Jomax]

35s are heavy sobs. Try lifting a stock rim with 31s, I can lift it one handed easily into the bed. A 35s required two hands and it's a job..

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[Pigman]

Thanks for the input everyone! The speedometer and odometer have not been corrected since the tires. I was driving down the highway with a friend last week and apparently when we were going 80 MPH my speedo was reading 72 MPH. Hopefully that is my problem. Anybody know how to get them recalibrated? I'm also curious why the MPG would decrease after adding an S&B intake and Gearhead tunes. Do y'all think it's a tuner related issue? Don't get me wrong, I'm not expecting to get great fuel mileage after adding a lift and heavy ass tires and wheels, I just think I can do a little better.

I've taken out the EBPS and tube a couple times in the past year. I got the tube pretty clean with brake cleaner but I probably need to get a new sensor. I tried cleaning it out with a Q-tip and a toothpick but it's pretty clogged up. What exactly does a clogged or bad EBPS affect?

So y'all think my EGT's are reading lower than they really are? If I were to relocate the probe for the pyro what would I do about the hole I would then have in my downpipe? I've also been looking at the tapped AIH delete plug from Riffraff. Would this give me a pretty accurate boost reading? And again, if I relocated the boost gauge how would I fix the hole I'd have in my turbo?

 

[Moejoe]

Boost.....is about rigth. Somewhere between 25 - 30 is fine, I think.
EGT.....is also fine. If egt-sensor is about 6-8 inches from turbo...you kan add 150 degrees to your reading.

MPG.....difference between stock tires and 35's are 11%. So you have to multiply miles with 1,11 to have right distance.


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