better gas mileage
07-07-2013, 08:45 AM
#1
Launching!
Thread Starter
better gas mileage I have a 2001 4.8 with a stock cam and a edelbrock 600 I put it in a 1974 mgb the car weighs 2200 and I have a turbo 350 with 3.90s in the rear I am getting about 16-17 maybe I think I can do better any suggestions were to start would be great
07-07-2013, 10:04 AM
#2
Get the carb tuned in on a dyno using a wideband...maybe look into getting a 700r4 trans bc that overdrive really helps at highway speeds or swap the rear gears to a more gas friendly ratio like 3.23/3.08...and most of all keep your gas pedal off the floor lol
07-07-2013, 11:52 AM
#5
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Gear, gear, gear. Oh, and an OD transmission. Or both!
Our 96 Impala SS with bolt-ons and a 3.73 gets about that, while our 95 Impala SS with exhaust and ram air with stock 3.08's gets upper 20's.
Our 96 Impala SS with bolt-ons and a 3.73 gets about that, while our 95 Impala SS with exhaust and ram air with stock 3.08's gets upper 20's.
07-07-2013, 12:17 PM
#6
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My carbed 6.0 in my gmc s15 got 23 mpg on the highway still cruising at a rich 11.7 afr turning 33-3400 at 65. Tuned carb and a map sensor adding lots of timing will help a lot.
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07-08-2013, 05:11 AM
#8
That almost seems like you have a fuel leak. My 2500# Datsun 240z pulls down 25 mpg. It has a stock LS2 cam 6.0L with a 750 carb, but a 5 speed manual with a 3.5 rear gear and 25" tall tire.
The difference has to be in the gearing with mileage that bad.
Have you posted pics? Sounds like a fun car.
The difference has to be in the gearing with mileage that bad.
Have you posted pics? Sounds like a fun car.
07-08-2013, 05:06 PM
#9
Launching!
Thread Starter
mgb That almost seems like you have a fuel leak. My 2500# Datsun 240z pulls down 25 mpg. It has a stock LS2 cam 6.0L with a 750 carb, but a 5 speed manual with a 3.5 rear gear and 25" tall tire.
The difference has to be in the gearing with mileage that bad.
Have you posted pics? Sounds like a fun car.
The difference has to be in the gearing with mileage that bad.
Have you posted pics? Sounds like a fun car.
07-08-2013, 07:30 PM
#10
5th gear on my car is a 0.64:1 overdrive. I turn something like 2200 RPM at 70mph. I sometimes wish I had another gear, the car would cruise even better with the motor down under 2000 RPM at 70 mph.
If I drop down to 4th gear, a 1:1 gear that I think matches the top gear in a turbo 350, it is spinning something like 3400 RPM. That makes a huge difference in both fuel use and noise.
What RPM are you spinning on the highway? I think if you really want good mileage you need to go to an OD trans. I don't think you will get there through rear gears alone.
As far as car tuning invest in or at least borrow a wideband. A wideband will let you get the cruise jetting right in an afternoon. That should be the majority of your MPG tuning. Then if you are like me it will take you a year or two to get all the throttle transitions just right. LOL
If I drop down to 4th gear, a 1:1 gear that I think matches the top gear in a turbo 350, it is spinning something like 3400 RPM. That makes a huge difference in both fuel use and noise.
What RPM are you spinning on the highway? I think if you really want good mileage you need to go to an OD trans. I don't think you will get there through rear gears alone.
As far as car tuning invest in or at least borrow a wideband. A wideband will let you get the cruise jetting right in an afternoon. That should be the majority of your MPG tuning. Then if you are like me it will take you a year or two to get all the throttle transitions just right. LOL
07-08-2013, 11:23 PM
#12
Launching!
Thread Starter
wideband 5th gear on my car is a 0.64:1 overdrive. I turn something like 2200 RPM at 70mph. I sometimes wish I had another gear, the car would cruise even better with the motor down under 2000 RPM at 70 mph.
If I drop down to 4th gear, a 1:1 gear that I think matches the top gear in a turbo 350, it is spinning something like 3400 RPM. That makes a huge difference in both fuel use and noise.
What RPM are you spinning on the highway? I think if you really want good mileage you need to go to an OD trans. I don't think you will get there through rear gears alone.
As far as car tuning invest in or at least borrow a wideband. A wideband will let you get the cruise jetting right in an afternoon. That should be the majority of your MPG tuning. Then if you are like me it will take you a year or two to get all the throttle transitions just right. LOL
If I drop down to 4th gear, a 1:1 gear that I think matches the top gear in a turbo 350, it is spinning something like 3400 RPM. That makes a huge difference in both fuel use and noise.
What RPM are you spinning on the highway? I think if you really want good mileage you need to go to an OD trans. I don't think you will get there through rear gears alone.
As far as car tuning invest in or at least borrow a wideband. A wideband will let you get the cruise jetting right in an afternoon. That should be the majority of your MPG tuning. Then if you are like me it will take you a year or two to get all the throttle transitions just right. LOL
Last edited by billymgb1000; 07-08-2013 at 11:25 PM. Reason: forgot something
07-09-2013, 05:11 AM
#13
3400 RPM is definitely affecting the mileage. I guess just get the tune right first.
Wideband O2 sensor read the air fuel ratio from the exhaust. Widebands do this more accurately than the standard narrow bands in most cars. Innovate makes a nice but expensive one. Here is a link to their website.
http://www.innovatemotorsports.com/r...rb-central.php
Look at the CHP article first.
http://www.innovatemotorsports.com/r...FI_mileage.php
Wideband O2 sensor read the air fuel ratio from the exhaust. Widebands do this more accurately than the standard narrow bands in most cars. Innovate makes a nice but expensive one. Here is a link to their website.
http://www.innovatemotorsports.com/r...rb-central.php
Look at the CHP article first.
http://www.innovatemotorsports.com/r...FI_mileage.php
