Thread: What mod point will fuel mileage start suffering

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  1. #1 What mod point will fuel mileage start suffering 
    GTX Level Member Elite6's Avatar
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    This relates to driving the car normally (commuting). I drive about 170km's per day at the car is getting about 8.7L/100km. I would like the car faster but not sure at what modding point the cruising gas mileage starts to suffer? Any thoughts on this? I am thinking the following wouldn't hurt things:

    1. headers
    2. intake
    3. intercooler
    4. ported supercharger

    Really have no idea. This car might end up coming off the road soon & getting built over time but for now my goal would be low 13's but still great cruising mileage at 65-75mph
    2005 E55 - stock
    1999 GTP 2dr - 9" HAI | Headers | 1.84's | 3.4 | Ported SC|
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  2. #2 Re: What mod point will fuel mileage start suffering 
    GTX Level Member real diehl's Avatar
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    Quote Originally Posted by Elite6 View Post
    getting about 8.7L/100km
    Wat.
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  3. #3 Re: What mod point will fuel mileage start suffering 
    GXP Level Member ctracer's Avatar
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    your foot is the biggest factor for gas mileage with these cars. headers and intake will probably increase your gas mileage. another thing you can do is mod it pretty well but you can tune it conservatively for better gas mileage. ive heard of people getting insanely high gas mileage with mods like a cam.
    07 Black GXP.
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  4. #4 Re: What mod point will fuel mileage start suffering 
    I live here. MoarkatsINmuhtrailer's Avatar
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    all in the tune and your foot. use the cruise as much as you can....remember, 55mph or about 90kph is max fuel economy. anything higher is depleting that number.
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  5. #5 Re: What mod point will fuel mileage start suffering 
    GTX Level Member real diehl's Avatar
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    Pretty sure some of the KC/GBP guys were getting upwards of 27mpg with cams....among other things.
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  6. #6 Re: What mod point will fuel mileage start suffering 
    I live here. MoarkatsINmuhtrailer's Avatar
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    hense,..

    cam
    intake
    headers
    rockers
    = flow mods....better flow= better mileage
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  7. #7 Re: What mod point will fuel mileage start suffering 
    GTX Level Member real diehl's Avatar
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    Sure.

    More air is going in and out, which is stupid without more fuel as well. You still want stoich, and to take advantage of what you've invested.

    OP just do bolt ons with a good tune...headers/pulley/intake/port/rockers will net you high 13's. With traction and a good driver, it could give you mid-low 13s. You'll likely still be able to get 27+ on the highway. Love life.
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  8. #8 Re: What mod point will fuel mileage start suffering 
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    Not so much about air because more air usually means more fuel. What timing you are running and at what AFR is important. That's why you might lose some mileage before an intercooler but you will gain some back after.

    Obviously a leaner AFR with more timing is going to net better MPGs.
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  9. #9 Re: What mod point will fuel mileage start suffering 
    The Blue One blueguy's Avatar
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    30+ in the blue car.

    Ported Heads/Blower/LS1 TB/LIM/Thrasher Cam/42.5lb Injectors, Custom Tuned.

    3.29 gearing as well.

    I got 28-29 being an asshat all the way to the Iowa meet and back last May.
    Sold WBody's: '03 Blue GTP/'98 Green GTP/'98 Silver GT/'05 GXP
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  10. #10 Re: What mod point will fuel mileage start suffering 
    Moderator dsmuts's Avatar
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    I get better gas mileage now then i did when i was stock. If i baby it i get 32 ish highway
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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  11. #11 Re: What mod point will fuel mileage start suffering 
    GTX Level Member Elite6's Avatar
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    Quote Originally Posted by real diehl View Post
    Wat.
    Huh.

    27.1mpg using a US gallon
    2005 E55 - stock
    1999 GTP 2dr - 9" HAI | Headers | 1.84's | 3.4 | Ported SC|
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  12. #12 Re: What mod point will fuel mileage start suffering 
    Moderator dsmuts's Avatar
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    Dang canucks and the metric system lol
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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  13. #13 Re: What mod point will fuel mileage start suffering 
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    Quote Originally Posted by dsmuts View Post
    Dang canucks and the metric system lol
    its us Americans that need to join the rest of the world, we must think were special
    03 GTP - 13.8 @ 100 2.160ft
    99 GTP - DD
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  14. #14 Re: What mod point will fuel mileage start suffering 
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    Worst mod I did to kill MPGs was puttin on 20 inch rims... So far only gettin 20 mpgs when last summer it was 24ish... we'll see when the weather warms up though.
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  15. #15 Re: What mod point will fuel mileage start suffering 
    GTX Level Member Elite6's Avatar
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    As much as I don't like the looks, that is partly why I kept the Limited Edition Torq Stars. Think i remember reading they are the lightest of the GP rims??
    2005 E55 - stock
    1999 GTP 2dr - 9" HAI | Headers | 1.84's | 3.4 | Ported SC|
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  16. #16 Re: What mod point will fuel mileage start suffering 
    I live here. stealthee's Avatar
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    With more air flow it takes less throttle to acheive points of acceleration. For instance it may take 50% throttle when stock to acheive a certain desired accerlaration, but add the flow mods and that same acceleration may be reached with 35% throttle. If you continue to use the 50% throttle, though, then your mileage will suffer because you will be using more fuel.

    Over stock I'd say my gains in fuel mileage are minimal in my GP, but I only have an open cone and catted 3" downpipe. On my Stealth I got 19-20 mpg when stock. When I parked it I was getting 26 mpg on daily driving, 28+ on trips.


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    1991 Mitsubishi 3000GT - Many mods to come
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  17. #17 Re: What mod point will fuel mileage start suffering 
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    A decently larger cam will Hurt mileage along with a steeper gear change.

    Anything else with a good tune will improve fuel economy.
    98-XP e85 SSAC HPT AGX Bullets Every BRM piece home built trans
    99-HPT ssic headers ported blower
    94z28 with a cam that chops so hard it hurts def peopels ears.
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