So I ususally average about 33-35 mpg with my stock 4.40 with a healthy mix of highway and backroads. 12 mile roundtrip to work on all back roads, so I don't exactly drink down gas.

On my first tank with the 4.7 I got 38.4mpg. That is better than any tank that I ever recorded with the 4.4. My best with the 4.4 was about 37.4mpg and that was about 90% highways/constant driving.


So from my results, 4.7 didn't negatively impact my gas milage. Probably helped more than anything on the backroads.

 

Did it involve more frequesnt gear changes?

How does the 4.7 compare in acceleration compared to the 4.40 FD?

I'm very VERY close to buying a 4.7 FD.

 

Your gearing will be 8.75% shorter... potentially more shifting depending on where you look at.

I'm assuming you are partial throttle tuned? I don't think I've every gotten anything close to 38mpg... probably something like 29mpg with my 4.4FD on the way to expo4 was my best.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DC2fanboy &raquo;</TD></TR><TR><TD CLASS="quote">Your gearing will be 8.75% shorter... potentially more shifting depending on where you look at.

I'm assuming you are partial throttle tuned? I don't think I've every gotten anything close to 38mpg... probably something like 29mpg with my 4.4FD on the way to expo4 was my best.</TD></TR></TABLE>

I'm not tuned at all. Just running off of whatever map I got from phearable.net. Car is a CRX so I have less weight to pull around, BUT I'd imagine the reults would have been similar had my car wieghed a couple hundred pounds more. The tank I got 38.4 mpg involved 1/2 tank of everyday back street driving to and from work and around town. The other half was to the track (1.5 hours of highway driving in NJ ) and then 4 passes down the track and then to the gas station.

My best guess is easier acceleration cancels out the shorter gears for around town driving giving me better milage compared to the 4.4 for shorter drives.

I do drive considerably slower on the highway (~70 MPH) due to the gears now, but I don't think that will have any positive effect.

People would always have negative comments about how HORRIBLE your milage will be with a shorter FD, but I'm just posting this to show that my results contradict that statement/myth.

 

I tend to agree with you. I think most of the people that had bad results from it was because the gearing caused them to be in vtec more since they didn't want to adjust they're driving habits.


You seem more responsible and drive reasonable, than the others. Not all, but the type that install a intake and go ripping all over just to hear the sound.

So I fully believe that your gas mileage increased.

It all has to do with throttle position and you already stated that you adjusted your highways speeds to reflect the new FD change.

Good stuff

 

yep..... ive heard this also just because it is less overall stress/ load on the engine to pull your car around town, therefore increasing gas milage

 

If u change to a larger FD, your local driving mileage would be better. Because of the larger FD, your engine need less torque to start moving the car.

 

With my stock Y7 trans (.702/3.722) I got about 38mpg. With an EX trans and 4.71 FD (.702 still) I get around 43mpg (before my header which gets me around 115 KM's 4.5 gallons of gas).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 88 rex &raquo;</TD></TR><TR><TD CLASS="quote">I do drive considerably slower on the highway (~70 MPH) due to the gears now, but I don't think that will have any positive effect. </TD></TR></TABLE>

Oh really?
That was the FIRST thing I thought of upon reading your initial post!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zygspeed &raquo;</TD></TR><TR><TD CLASS="quote">

Oh really?
That was the FIRST thing I thought of upon reading your initial post!</TD></TR></TABLE>

Do you think that has a lot to do with it? I think I gained a lot for around town driving. But on the highway I tend to drive slower but RPM's are still the same. I just figured it kind of equaled itself out, although it doesn't take as much throttle to maneuver around other cars, so maybe there is some gain there.

 

what fuel pump are you running?

 

Stock

 

well, that may also contribute to your extraordinary gas milage. Your fuel pump delivers less fuel than DOHC B-series pumps.