Cant Get Mpg or Boost Up?!?!?!? - Ford Powerstroke Diesel Forum
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Old 04-15-2013, 06:28 PM
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Question Cant Get Mpg or Boost Up?!?!?!?

Hi all! I've got the 7.3 in my sig, and the problem im having is that I can't seem to get my mileage to come up much at all.. it started out at about 10 mpg when I got it a few months ago.. and its slowly (very slowly) came up to about 12.5 to 13 mpg when I checked it last week.. I only have like 31-32 in tires, stock height, and i think i have 4:11 gears, but im not sure about that.. And I don't drive over 67-68 mph.. Im not sure what the problem could be??

I do have a tony wildman chip in it, and I think im on my highest setting but im not sure cause the tunes are not in the right order, but I didn't have time to send the chip back..

Also it seems that I can't get my boost to go over 20-21 psi? It seems like its spooling, ( you can sure here the turbo really loud) but it just doesn't seem like there's all the power that there should be.. I was pulling a car trailer with my camaro on it the other day and it was kinda having a hard time on our little rolling hills.. (more like big bumps. Ha!) I could only get like 10-12psi max, going 60-65 in 5th on any hills or even if I was just speeding back up.. I get a max of about 12 psi at 2000 rpm no matter what im pulling/not pulling..

I do think my back right tire is dragging alittle bit, but its not alot, anyone know how to loosen the brakes up a bit on these 350s?

Any ideas guys?

Last edited by Smokin_fast; 04-15-2013 at 06:37 PM.
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Old 04-15-2013, 06:45 PM
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You said 20PSI then only 12PSI max so huh?
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Old 04-15-2013, 07:25 PM
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The 20 psi is at 3000+ rpm.. normal highway driving with cruze on doesn't really go over 10 psi or so..
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Old 04-15-2013, 09:55 PM
Can you hear the derail??

 

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normal highway with cruise I rarely hit 10 bud, it sounds like your expecting 40 psi, but then it sounds like you have a boost leak, or an exhaust leak, maybe try to keep the rpm's under 2k, your full hwy speed sounds like the sweet spot, but I wanna say its all in your shifting
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Old 04-16-2013, 07:34 AM
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My normal highway driving just cruzing is like 2 psi.. the 10 psi is just on long hills. No im not expecting 40 psi, duh! But I would like to be able to hit 28-29 psi..
I don't have a boost leak.. I may have a leak before the turbo, the uppipes are not leaking, so it would be my manifolds if anything is leaking,, but I haven't been able to find a leak....
What would staying under 2xxx rpm do? I mean I haven't drove over 65-68 mph. (Which is it right under 2xxx rpm..)
Do have a clue what you mean about shifting..

My problem is I need to get better mpg, which I think is related to my low power..
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Old 04-16-2013, 11:17 AM
Hee Hee, he's doing it...
 

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Your cruising PSI is normal to me. So is the hill PSI. What are your EGTs when you push her? Stock turbo was only expected to go to 16-18 psi. Hitting 20-21 is a gift for 90cc injectors. Check your fuel pressure.

What he meant by staying under 2k was simply that the lower you keep the RPMs the less fuel you use down the road. We have autos but I'd question you 4.10 rear gearing. At 65 I am at near 2100 RPMs. Lift one back tire, make a mark straight down on the tire with chalk or the like and make a matching mark on the ground. Now make a mark on the driveline and pinion neck so those are in line. Put the trans in neutral and spin the tire one complete turn. How many times did the driveline rotate in the one tire rotation? Don't know why but I'm thinking that you have 3.73's. Can't shake it...
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Old 04-16-2013, 03:32 PM
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I think that you might have a combination of boost leaks and exhaust leaks.
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Old 04-16-2013, 07:32 PM
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I don't have an egt gauge... Umm im not sure where your turbo numbers are from, but with my chip I am suppose to get around 28 psi..
I realize that slower might net me slightly better, but I should be able to get good mpg at 65a -2000 rpm.. im not sure about the gears, although even if we have the same gears, I would have lower rpm 5 gear vs your 4 gear..

Jes-- I don't have a boost leak, I may have an exhaust leak, but I can't seem to find it..
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Old 04-17-2013, 03:34 AM
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Why do you say you're "supposed" to get 28PSI? If you're talking about the '95 with 287k miles on it, you won't. Unless you're HPOP is new, injectors are new, ICP, IPR, intake boots, and exhaust are all new, fuel pressure is up to spec, you will not. There are way too many things to take into account that are old to just say you're supposed to get 28PSI.
And also, for your truck, 15-16 MPG is probably the average.
And for your boost leak, have you pressure tested the system?
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Old 04-17-2013, 05:45 AM
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How would you pressure check the system? Send air back though the map line with an air compresser?

Oh BigFuel, I have 69 psi fuel pressure..

Last edited by Smokin_fast; 04-17-2013 at 05:48 AM.
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