gas mileage?
#51
02-19-2006, 01:12 PM
RE: gas mileage?
ORIGINAL: HankL
rayk3,
if you think any of those tips to improve MPG in 4 Wheeling magazine
say to increase the numerical gear ratio - you need to go back and
read that article again.
In the 50 tips I count 3 of them that correctly advise reducing rpms.
One of the tips:
"A vehicle that is either overgeared or undergeared will lose MPG"
gets right to the heart of the matter.
An engine is numerically overgeared if it is not cruising at about 60-75% open throttle.
An engine is numerically undergeared if it is trying to cruise in the 'Power Enrichment' zone
above about 80% throtttle where the PCM computer greatly enriches the air to fuel ratio.
For the same reason anyone who presses the accelerator down all the way near the floor
whether they are driving in the city, highway, climbing a hill, or pulling a trailer
is going to get about 25% worse MPG
than someone who presses right up to about 70% throttle but never goes over it.
This is why the old advice to install a vacuum gauge
can certainly help MPG
if the driver watches it out of the corner of his eye.
When the vacuum gauge reads below about 6 inches of mercury
you are in the fuel guzzling 'Power Enrichment' zone
but when the vacuum gauge is showing about 8
your engine is converting fuel into horsepower at its most efficient level.
Each engine goes into Power Enrichment at a slightly different MAP sensor level
but if you listen closely to the engine sound you can hear it happen
as the engine gets a bit smoother with the very rich mixture.
rayk3,
if you think any of those tips to improve MPG in 4 Wheeling magazine
say to increase the numerical gear ratio - you need to go back and
read that article again.
In the 50 tips I count 3 of them that correctly advise reducing rpms.
One of the tips:
"A vehicle that is either overgeared or undergeared will lose MPG"
gets right to the heart of the matter.
An engine is numerically overgeared if it is not cruising at about 60-75% open throttle.
An engine is numerically undergeared if it is trying to cruise in the 'Power Enrichment' zone
above about 80% throtttle where the PCM computer greatly enriches the air to fuel ratio.
For the same reason anyone who presses the accelerator down all the way near the floor
whether they are driving in the city, highway, climbing a hill, or pulling a trailer
is going to get about 25% worse MPG
than someone who presses right up to about 70% throttle but never goes over it.
This is why the old advice to install a vacuum gauge
can certainly help MPG
if the driver watches it out of the corner of his eye.
When the vacuum gauge reads below about 6 inches of mercury
you are in the fuel guzzling 'Power Enrichment' zone
but when the vacuum gauge is showing about 8
your engine is converting fuel into horsepower at its most efficient level.
Each engine goes into Power Enrichment at a slightly different MAP sensor level
but if you listen closely to the engine sound you can hear it happen
as the engine gets a bit smoother with the very rich mixture.
So by your theory you clearly state that 4.56's would not be overgearing.... I agree!
SPEED SAFE, AIR RAM
#52
02-19-2006, 01:45 PM
RE: gas mileage?
Well I just got back from my ride paying extra attention to the throttle % opening and RPM/SPEED... And it appears the info Hank has been sharing with us just does not apply to our OVERDRIVE vehicles... His info is DATED.
The FACT is at 65MPH on flat ground with 4.56's & (SHORT) 29.75” Tall tires my throttle opening is 13.5%@2631RPMs and at 70MPH it was 15%@2744RPM's ....No where close to Hanks suggested 60-70%... Ill have pictures up soon of the SAFC-II readings. Now I don’t doubt that if I had Overdrive off that I would have been WELL over those throttle % openings... So I can only assume his information is accurate for NON-overdrive vehicles.
SPEED SAFE, AIR RAM
The FACT is at 65MPH on flat ground with 4.56's & (SHORT) 29.75” Tall tires my throttle opening is 13.5%@2631RPMs and at 70MPH it was 15%@2744RPM's ....No where close to Hanks suggested 60-70%... Ill have pictures up soon of the SAFC-II readings. Now I don’t doubt that if I had Overdrive off that I would have been WELL over those throttle % openings... So I can only assume his information is accurate for NON-overdrive vehicles.
SPEED SAFE, AIR RAM
#53
02-20-2006, 02:09 AM
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#54
02-20-2006, 04:20 AM
RE: gas mileage?
ORIGINAL: tamuccmike
anyway...after rereading all these nifty posts on this matter...looks like I WIN!!! i am the greatest champion of all time!!! im the king-ding-a-ling of the gas posts...just admit it...
anyway...after rereading all these nifty posts on this matter...looks like I WIN!!! i am the greatest champion of all time!!! im the king-ding-a-ling of the gas posts...just admit it...
Now some people may not care to save a few gallons of gas... others may think it’s not even possible in such a HUGE truck.... but the fact is with the right mods and driving habits you can improve your fuel economy 4-5 MPG without a doubt. It’s about the combination of mods and driving style that make it possible...
SPEED SAFE, AIR RAM
