Poor fuel economy??? - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

 
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post #1 of 8 (permalink) Old 08-02-2019, 01:51 PM Thread Starter
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Poor fuel economy???

I installed a K&N filter along with a 4" exhaust with straight through muffler, new bellowed up pipes and deleted the back pressure valve. Didn't change anything else. My fuel economy dropped by about 2 MPG. Anybody have any ideas? Did I do something I shouldn't have? It seems that these mods should improve economy and performance but neither is better. The only thing I've noticed is a different exhaust tone and I can hear the turbo whistling a bit more.

2000 F350 XLT crewcab 4X4 longbed single rear wheels. 195,000 miles.
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post #2 of 8 (permalink) Old 08-02-2019, 03:50 PM
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What kind of K&N did you use? Most of us agree that they are not the greatest filters to use on our trucks. Is it the K&N direct stock replacement filter?Did you oil it? You may have restricted flow if you did, which would explain the drop in MPG. I recommend the ford AIS air filter setup if you really want a good filter. Take out the K&N and put the old filter back in and recheck your MPG. A new exhaust would not typically cause a drop in MPG but a exhaust or turbo/up pipe leak might. Check for leaks on the new up pipes. Did you loose any boost after the new work?

2002 F250 Super Duty Crew Cab 7.3L Lariat 2WD 131,000mi; 4in turbo back custom exhaust, Garrett GTP38R turbo, Riffraff intercooler boots, Dorman Up-Pipes, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, Scangauge II, ISSPRO EV2 Boost-EGT-Trans temp-Fuel pressure Gauges, DP T-5 Tuner (stock ,60HP tow, Decel, 60HP highway econo, 80HP city econo), Dieselsite coolant filtration, Max Air A/C mod, foglight mod, AIH delete, LED interior, back up camera, hid foglights.


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post #3 of 8 (permalink) Old 08-02-2019, 04:12 PM
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If mods improved mileage as much as they claim to they would put the oil refineries out of business.

So, how are you checking the mileage? Using math or the lie-o-meter? How many tanks of fuel have you ran through since doing these mods? Did you change your driving style?

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96 F250 PS XLT 4X4 long box, 5sp,4.10, manual hubs,pyro+boost guages, Dark Toumaline, add a leaf, Dale's TYMAR, and HX hose, downpipe, coolant filter, Luk clutch
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post #4 of 8 (permalink) Old 08-02-2019, 05:45 PM
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Check for boost leaks. That would be a sure source of decreased fuel economy. You can buy or build a leak tester.

2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM, Full Force Stage 1 injectors

IF MY BODY IS EVER FOUND ON A JOGGING TRAIL JUST KNOW THAT I WAS MURDERED SOMEWHERE ELSE AND DUMPED THERE
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post #5 of 8 (permalink) Old 08-03-2019, 07:53 AM
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I used to have problems with my back pressure sensor. It would malfunction and shut the truck down. Unplugged I could get going again. That said. The only difference I noticed with it unplugged was crappy fuel economy. Plug back in and all good again, once I replaced the sensor. So, Im guess its your missing back pressure sensor.

2002 F350 Super Duty, Crew Cab,Long box,4x4, 7.3 PSD, Complete rebuild .010 over by myself except balancing, 2000hp billet connecting rods, ARP main and head studs, ceramic coated pistons, Smith Bros Chrome Molly push rods, Comp Cams springs, shims and seals. Competion complete valve set and head grinding and vacuum tested, Adrenaline HPOP, DP Tuner Infinity DX programmer and full load of tunes modified for my new Stage 3 250 shot injectors, ceramic coated exhaust manifolds and up pipes and collector, BD Diesel triple clutch furnace brazed billet torque converter and BD pro engine brake and compressor set up, MBRP 4" stainless turbo back, Driven Diesel regulated fuel return system, AFE pro stage 2 cool air intake, riffraff billet Whicked Wheel 2 compressor wheel in a GTP38R turbo, riffraff blue cooler boot kit and coil clamps, International Double Ceramic Coated Bellowed Up Pipes
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post #6 of 8 (permalink) Old 08-10-2019, 12:29 PM
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Quote:
Originally Posted by jobaa View Post
I installed a K&N filter along with a 4" exhaust with straight through muffler, new bellowed up pipes and deleted the back pressure valve. Didn't change anything else. My fuel economy dropped by about 2 MPG. Anybody have any ideas? Did I do something I shouldn't have? It seems that these mods should improve economy and performance but neither is better. The only thing I've noticed is a different exhaust tone and I can hear the turbo whistling a bit more.
The exhaust should sound different, youíve removed the original set up..

Since youíve changed a few items, any single one may be the culprit. As mentioned above, I hope itís just data from only one fill up. You need a few fill ups/tanks of fuel before you want to compare data sets.

'00 F250 XLT 4x4 (born on 6/00), manual tranny & hubs, SPA Techniques EGT/Boost Gauge, Homemade Return Fuel Regulator, Toro Liner, 203* T-stat and Coolant Filter, LUK Clutch, flywheel & pressure plate, Amsoil Dual Bypass Filter
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post #7 of 8 (permalink) Old 08-17-2019, 11:52 AM
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Once again. Removing the back pressure sensor will directly effect your fuel economy. In fact, on a diesel that's all it helps the CPU with. It helps the CPU determine fuel mixture along with other sensors of course. So you removed one of its equations and it runs on default now. Which will be rich, which will drop your fuel economy. 2 mpg would be about right over a tank a bit rich. Put it back, and your CPU will then be able to calculate fuel economy with your new add ons, and fuel economy will be better than before most likely. If not the same. The CPU already recognizes your add ons, but has lost part of its information network without back pressure, and cant take advantage of your add ons because it must run rich on default information. Default will never run lean. Lean doesn't keep your truck running in a sensor loss situation. So all vehicles will either run rich on default, or de rate hp and run rich like a semi truck does with sensor loss.

2002 F350 Super Duty, Crew Cab,Long box,4x4, 7.3 PSD, Complete rebuild .010 over by myself except balancing, 2000hp billet connecting rods, ARP main and head studs, ceramic coated pistons, Smith Bros Chrome Molly push rods, Comp Cams springs, shims and seals. Competion complete valve set and head grinding and vacuum tested, Adrenaline HPOP, DP Tuner Infinity DX programmer and full load of tunes modified for my new Stage 3 250 shot injectors, ceramic coated exhaust manifolds and up pipes and collector, BD Diesel triple clutch furnace brazed billet torque converter and BD pro engine brake and compressor set up, MBRP 4" stainless turbo back, Driven Diesel regulated fuel return system, AFE pro stage 2 cool air intake, riffraff billet Whicked Wheel 2 compressor wheel in a GTP38R turbo, riffraff blue cooler boot kit and coil clamps, International Double Ceramic Coated Bellowed Up Pipes
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post #8 of 8 (permalink) Old 08-17-2019, 12:13 PM
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I missed where he said he removed the sensor. He did say he removed the exhaust back pressure valve, but that is a common delete and has no affect on the sensor.

2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM, Full Force Stage 1 injectors

IF MY BODY IS EVER FOUND ON A JOGGING TRAIL JUST KNOW THAT I WAS MURDERED SOMEWHERE ELSE AND DUMPED THERE
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