WORSE fuel mileage with Gibson!
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Senior Member
Joined: Jan 1999
Posts: 164
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From: Calgary, AB, Canada
WORSE fuel mileage with Gibson!
Ok, guys, here's one for you!
I did a trip out for a few days, and decided to do a very accurate fuel calculation, because I had big plans for the truck. Namely, the Gibson Swept side, Velocity tube ( I have had this for a while, but my trip was actually to Calgary, AB, so I wanted WMS racing themselves to put it on properly, because of their original poor fit), Helix TB Spacer, and I figured hey, what the heck, I'll throw my Superchip back in and just run the truck on regular like I've been doing for a while now ( I ripped the thing out when the premium gas prices skyrocketed here in Canada).
Anyways, the fuel mileage was 15.8 mpg u.s. gallons, that was at an average of about 67-68 mph, fairly flat highway the whole trip. I was expecting great things with all the mods done. Well, Guess what? A trip back home a couple of weeks later, doing almost the same miles and average speed, my mileage went down to an abysmal 14.6 mpg!!! I had an extra 5 or 600 lbs of stuff on, and had a small headwind for part of the way, but the mods should have more than compensated!! I did a rough street driving calculation before the mods and after, and it showed a slight decrease in mpg as well.
So what do you guys think is the problem? Running the chip on regular? Probably not. I think that the Gibson dealer in Calgary may have put the exhaust on the wrong way! I cannot tell for sure, as there is no labelling on the exhaust. I think this may be the case, because the truck is so quiet, hardly louder than stock when idling to WOT. I know the Gibson SS is very quiet, but that much? Also, there did not seem to be any noticeable power gain. As a matter of fact, the truck seemed like it needed to downshift more.
I read an old post that I can no longer find that said you can tell by looking inside the holes and seeing which way the baffles go. Does any one of you know which way they should look on the inlet side? I may not be going back to Calgary with the truck soon, and I think I'll have to take it off myself to see (a big job-groan!)
This is the only thing I can think of, unless any of you can offer advice. Any help, please?!
By the way, the TB spacer seems to give no noticeable change (definately no improvement in mpg!), and just whistles under certain throttle positions/truck under pull.) Sounds something between a vacuum leak, loose belt, and a slightly open window. I read the posts, I read the comments regarding this thing, yet I still got it! Duh...
I did a trip out for a few days, and decided to do a very accurate fuel calculation, because I had big plans for the truck. Namely, the Gibson Swept side, Velocity tube ( I have had this for a while, but my trip was actually to Calgary, AB, so I wanted WMS racing themselves to put it on properly, because of their original poor fit), Helix TB Spacer, and I figured hey, what the heck, I'll throw my Superchip back in and just run the truck on regular like I've been doing for a while now ( I ripped the thing out when the premium gas prices skyrocketed here in Canada).
Anyways, the fuel mileage was 15.8 mpg u.s. gallons, that was at an average of about 67-68 mph, fairly flat highway the whole trip. I was expecting great things with all the mods done. Well, Guess what? A trip back home a couple of weeks later, doing almost the same miles and average speed, my mileage went down to an abysmal 14.6 mpg!!! I had an extra 5 or 600 lbs of stuff on, and had a small headwind for part of the way, but the mods should have more than compensated!! I did a rough street driving calculation before the mods and after, and it showed a slight decrease in mpg as well.
So what do you guys think is the problem? Running the chip on regular? Probably not. I think that the Gibson dealer in Calgary may have put the exhaust on the wrong way! I cannot tell for sure, as there is no labelling on the exhaust. I think this may be the case, because the truck is so quiet, hardly louder than stock when idling to WOT. I know the Gibson SS is very quiet, but that much? Also, there did not seem to be any noticeable power gain. As a matter of fact, the truck seemed like it needed to downshift more.
I read an old post that I can no longer find that said you can tell by looking inside the holes and seeing which way the baffles go. Does any one of you know which way they should look on the inlet side? I may not be going back to Calgary with the truck soon, and I think I'll have to take it off myself to see (a big job-groan!)
This is the only thing I can think of, unless any of you can offer advice. Any help, please?!
By the way, the TB spacer seems to give no noticeable change (definately no improvement in mpg!), and just whistles under certain throttle positions/truck under pull.) Sounds something between a vacuum leak, loose belt, and a slightly open window. I read the posts, I read the comments regarding this thing, yet I still got it! Duh...
Sorry I can't help you with your mileage. I have a question though. Do you have stock wheels? I noticed you have the same size tires as i do. Whoever owned the truck before I did changed the wheels.
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1997 XLT Teal 4.6L Flareside 4x4 ORP. Automatic, Reg. cab, 3.55LS, tinted windows, bug deflector, Dual exhaust, K&N Generation 2 air filter, BullDog keyless entry/remote start(installed myself), Modern 16" wheels, bedliner, Covercraft tonneau cover, White faced gauges, electronic shift on the fly, Clarion ADX5655z Double Din Cassette & CD, 2 Pioneer TS-A6865 speakers and superchip. Going to add headers.
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1997 XLT Teal 4.6L Flareside 4x4 ORP. Automatic, Reg. cab, 3.55LS, tinted windows, bug deflector, Dual exhaust, K&N Generation 2 air filter, BullDog keyless entry/remote start(installed myself), Modern 16" wheels, bedliner, Covercraft tonneau cover, White faced gauges, electronic shift on the fly, Clarion ADX5655z Double Din Cassette & CD, 2 Pioneer TS-A6865 speakers and superchip. Going to add headers.
Thread Starter
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Senior Member
Joined: Jan 1999
Posts: 164
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From: Calgary, AB, Canada
Yes, they are 16x7 rims. A 265 tire should fit on any rim size from 7 inch wide up to 8.5 inches. I am thinking of going to a 16x8 rim, when I can afford it again. Nice looking rig!
Senior Member
Joined: Nov 2000
Posts: 2,444
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From: DFW, Texas
I'd have to vote for the Throttle Body Spacer. I've seen ather posts claiming that the spacer/paper weight did degrade MPG.
As for the Gibson, I believe the inlet side of the muffler is marked as such. I installed mine about 2 months ago but I think it is. As for the sound, yes, it is quiet. According to Gbson only 2-3 dB over stock. WOT I don't notice much sound at all, as a matter of fact, the FIPK makes enough noise to compete with the exhaust. It "rumbles" though at easy cruising speeds at about 1500-1800 RPM. I like it.
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2000 EDDIE BAUER EXPEDITION 4x2
-->Come share my Addiction<--
As for the Gibson, I believe the inlet side of the muffler is marked as such. I installed mine about 2 months ago but I think it is. As for the sound, yes, it is quiet. According to Gbson only 2-3 dB over stock. WOT I don't notice much sound at all, as a matter of fact, the FIPK makes enough noise to compete with the exhaust. It "rumbles" though at easy cruising speeds at about 1500-1800 RPM. I like it.
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2000 EDDIE BAUER EXPEDITION 4x2
- Estate Green
- 5.4 ltr
- 3:55 LS rear
- Superchip!
- Airaid FIPK
- Gibson S/S Swept Side Cat Back Exhaust
- Hellwig Rear Anti-Sway Bar
- Xenon Super White Headlights
- Tow Package
- Rear Load Leveling
- Moonroof
- Century Child Seat!
- Front Polyurethane Anti-Sway Bar Bushings ordered
-->Come share my Addiction<--
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Senior Member
Joined: Jan 1999
Posts: 164
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From: Calgary, AB, Canada
Familyride:
Thanks for the post. I would certainly hope that a Gibosn dealer who does these installs all the time should know the right way to put one on! However, I have seen stranger things. Nothing surprises me, particularily coming from supposed "professional" mechanics and such.
As for the TB spacer, I wouldn't be surprised, either. I saw the posts on the paperweight, though not the ones claiming reduced fuel mileage. I guess the only way to find out is to take the sucker out and do another calculation. I am sick to think I may have spent all that money including install on the stupid thing, and all it does is cost me more money! I could have got the bush bar like I'd originally planned!
Thanks for the post. I would certainly hope that a Gibosn dealer who does these installs all the time should know the right way to put one on! However, I have seen stranger things. Nothing surprises me, particularily coming from supposed "professional" mechanics and such.
As for the TB spacer, I wouldn't be surprised, either. I saw the posts on the paperweight, though not the ones claiming reduced fuel mileage. I guess the only way to find out is to take the sucker out and do another calculation. I am sick to think I may have spent all that money including install on the stupid thing, and all it does is cost me more money! I could have got the bush bar like I'd originally planned!
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Joined: Nov 1999
Posts: 1,177
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From: Carolina, Puerto Rico, USA
I would suggest to get a more representative sample. Say three or four gas tanks (something over 1000 miles) and then compare again.
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My Ride: 1998 F150 4x4 Lariat Supercab Flareside 5.4L in Oxford White/gold, ORP, Tow Package, 3.55 Gears.
Modifications:
Optima Red Top Battery
Split Fire Spark Plugs
K&N FIPK
Gibson Supertruck Exhaust System
Stepshield door sill protectors
Performance Accesories 3" Body Lift
Performance Accesories Lift Lips by Mountain Enterprises
Superlift 3" lift blocks
Gabriel Gas Ryder LT VST Shocks
Daystar Front Anti-sway Bar Polyurethane Bushings
Heckethorn Steering Stabilizer
35x12.5R16.5LT BFG All Terrain KO's
16.5x9.75 American Eagle 589's.
McGard Premium Wheel Locks
Photos at: http://www.communicomgroup.com/jmtruck
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My Ride: 1998 F150 4x4 Lariat Supercab Flareside 5.4L in Oxford White/gold, ORP, Tow Package, 3.55 Gears.
Modifications:
Optima Red Top Battery
Split Fire Spark Plugs
K&N FIPK
Gibson Supertruck Exhaust System
Stepshield door sill protectors
Performance Accesories 3" Body Lift
Performance Accesories Lift Lips by Mountain Enterprises
Superlift 3" lift blocks
Gabriel Gas Ryder LT VST Shocks
Daystar Front Anti-sway Bar Polyurethane Bushings
Heckethorn Steering Stabilizer
35x12.5R16.5LT BFG All Terrain KO's
16.5x9.75 American Eagle 589's.
McGard Premium Wheel Locks
Photos at: http://www.communicomgroup.com/jmtruck
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Joined: Feb 2001
Posts: 75
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From: Orlando, FL
Jim W, in response to the T/B spacer...I called Airaid about the "poweraid" I bought and they openly admitted that it whistles! I wish I had know that before I ordered it. I was pulling my hair out trying to figure out where the noise was coming from. Was very glad to find out it was not the FIPK but was the spacer. I pulled it out yesterday and no more noise and truckperformance.com said they would take it back. (refund of 80$) I guess this will pay for my clear corners.. 
I feel for you on the price of gas up there, I could never afford to run my truck if I still lived in Canada!
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My Ride:
2000 Flareside EC/SB 4.6 4X2 (Harvest Gold)
Airaid FIPK/w K&N filter
Gibson Split back dual/w tips
Factory bedliner
Westin nerf bars-PowderBlk
Lund vent shades, bug shield
V-Tech tail light covers (painted to match)
Tinted Windows
Factory street flares (painted to match)
(added and chg'd mudflaps)
Factory grill w/honeycomb insert
(swapped out plain chrome one)
Tow Package-Class III
Future Mods:
Fabtech 3 1/2 lift with
Eagle 589's/tires to match
Clear Corners/w bulbs
View my Ride: http://www.f150world.com/trippn/
I feel for you on the price of gas up there, I could never afford to run my truck if I still lived in Canada! ------------------
My Ride:
2000 Flareside EC/SB 4.6 4X2 (Harvest Gold)
Airaid FIPK/w K&N filter
Gibson Split back dual/w tips
Factory bedliner
Westin nerf bars-PowderBlk
Lund vent shades, bug shield
V-Tech tail light covers (painted to match)
Tinted Windows
Factory street flares (painted to match)
(added and chg'd mudflaps)
Factory grill w/honeycomb insert
(swapped out plain chrome one)
Tow Package-Class III
Future Mods:
Fabtech 3 1/2 lift with
Eagle 589's/tires to match
Clear Corners/w bulbs
View my Ride: http://www.f150world.com/trippn/
Thread Starter
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Senior Member
Joined: Jan 1999
Posts: 164
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From: Calgary, AB, Canada
Trippn:
Yes, I realized that it would whistle under various combinations of throttle and acceleration. The dealer said that, and I read all the posts. I just wonder if it actually does anything for the performance. It is a cheap enough mod, and I can live with the whistling, even if it gave a small performance gain. But I'm not sure it does. Some say yes, others no. I haven't really driven with it much to notice either way. If it gives worse fuel economy, then the thing is outta my truck. As for the fuel, the cost of what I pay for regular is
2.53 per u.s. gallon! Premium is usually 40 cents more per. What is it on Orlando? Incidentally, my wife and I were there for vacation a while back, it was the best vacation we've ever had. I absolutely loved the whole area.
Yes, I realized that it would whistle under various combinations of throttle and acceleration. The dealer said that, and I read all the posts. I just wonder if it actually does anything for the performance. It is a cheap enough mod, and I can live with the whistling, even if it gave a small performance gain. But I'm not sure it does. Some say yes, others no. I haven't really driven with it much to notice either way. If it gives worse fuel economy, then the thing is outta my truck. As for the fuel, the cost of what I pay for regular is
2.53 per u.s. gallon! Premium is usually 40 cents more per. What is it on Orlando? Incidentally, my wife and I were there for vacation a while back, it was the best vacation we've ever had. I absolutely loved the whole area.