An interesting way in which I improved Fuel Economy.
 

Hey all,
If you read any of my past posts you'd have seen that I've been
pretty dissapointed with my gas mileage. My car has 2300 miles on it
and I was consistently getting 12-13 mpg.
My driving consisted of about 65% highway/35% city in cold
temperatures. 30 degrees and lower. My shifting habit included the
majority of my gear changes around 4000 RPM on average and I rarely
ever ran the car hard.

After reading a post by Maurice (canzoomer) that stated that the
second intake port opens up at 3750 RPM I decided to try an
experiment.

I drove an entire tank of gas shifting under 3000 RPM (around 2700).
The results where phenomenal in proportion to the MPG that I was used
to getting. This last tank gave me a whopping 18.7 MPG with outside
temps in the 30's and 65% highway/35% city driving.
I was shocked to see such a difference by shifting at a slightly
lower RPM.
The opening of the second intake must dump quite a bit of gas in the
motor.

I'm glad to see that it is possible to improve the fuel economy but
at the same time...IT WAS THE MOST BORING 243 MILES I'VE EVER
DRIVEN!!!!!!!!! People in econoboxes were passing me by like I was
standing still and giving me dirty looks. (perhaps my imagination).

Although I found a way to increase gas economy I feel like I'd rather
be in an automatic if I have to drive to slow. Not to mention that it
was nerve racking trying to keep the revs so low as to not disrupt my
experiment.

I'm still discouraged that it has to be this way but at least I know
it can be done.

BTW- I read that gas prices might hit $3.00 a gallon by summer.
Yeah!!!!!!

Gary

if it hits $3 this summer my Miata will see a lot more duty! I've been averaging 21MPG; hit 4-5K regularly, except on the first shifts of the day - I hit the highway .1 mile from my house - so I take it easy the first 5 miles. That includes some rather aggressive driving and I try to hit 9K at least once/day.

21 MPG?
In cold Maryland?
87 octane hasn't been a problem?
The $3.00 article was on netscape but I can't find it now.

GT

Canzoomer data.....
 

Very similar to an experiment I tried back in October....

'Zoomer was heavy into the details of the fuel maps, and mentioned that the curve got quite LEAN above 5000 revs.....
O.K.....I can handle that - so I used a tankful, NEVER letting the revs drop BELOW 5k!

MAN, that was fun! and actually harder than it sounds! however gas mileage sucked even worse.

I thought it might take plastic surgery to get the silly grin off my face!

S

Why the huge dump at 3750 then??????????

I posted a while back of a 30.22 MPG I got on my way back from Reno. I did this over a 100 mile stretch. I got flamed and called BS. I did this under 3000 RPM, about 57 MPH on cruise control.

If I drive 3500 RPM on the same trip back I get 25-26 MPG.

I just did my own mini mileage experiment.

My highest mpg was 19.2mpg on my second tank during careful break-in regimen. No shift over 3500, no driving over 65, varying rpms constantly.

Subsequently, all tanks have been in the 17's and 18's. My weekly schedule is always the same. M-F is light stop and go, short trips under 4-5 miles. My weekend has two highway runs of 65 miles at 75+mph.

All tanks are 93 octane, various premium brands - mostly BP/Amoco.

This past weekend, I had to fill up just before getting on the highway. There weren't more than 3-4 traffic lights before getting on the highway then a straight run for 65 miles. I do mean straight run - this is FL - no hills, no headwind, temp about 58 degrees. Kept the cruise between 73 and 75 (just under 4k rpms). Got off the highway and sure enough, 17.64mpg.

The prior tank was 17.92 and that included plenty of short hop stop and go.

My conclusion, in my car's current state of tune/ECU mapping, it doesn't matter how you drive it, you can't baby it to get better mileage.

I have noticed that there is a misfire at idle lately (cold or warm) and I will have the dealer check it soon, but I'd be surprised if that alone could be responsible for the mileage.

I just got 18.3 MPG in a 170 mile fill up, that was gentle driving (getting passed by econboxes as well) and I only broke 3500 RPM a few times. About 100 of those were urban miles, 40 were expressway, and the last 30 split between city and rural. The dominant drive has been 7 miles to and from work, in cold weather.

I think the city driving, with time spent at stop lights, really degrades the MPG. We also have an Odyssey, and I have started taking that for stop and go city driving. I have also started considering taking longer routes that have less stop and go.

Does anyone know what the consequences or symptoms are driving a rotary in low RPMs? I purposely get it on the expressway once a week to get it some revs.

<Mar 18, 2004>
My last four tanks were 19.3 - 19.9 MPG for city+highway mix, including some high revs on every tank. I am getting good results from Regular and may have a different acceleration noise after two consecutive tanks of Reguar.

I am consistently getting 19.2(city)-20.4(highway) from my 8. It is Louisiana so I know that makes a difference for you Northern guys, but I drive it hard one day and easy the next with similar results. I have 6133.6 on my odometer and it has produced the same mileage straight out of the showroom. Maybe you should take a trip down here and see what the car does? Besides, you never know what you will find when you wake up here,whether it be rain, sun, hot, or cold. Always an adventure.

At 3750 rpm the secondary fuel injector comes on line

more rpms + more fuel (and air) is going to hit mpg.

I've averaged 19.6 mpg in my first two tanks. Mixed driving, cool-to-cold temperatures (MD), and shifts at around 3500-4000 rpm.

Beachdog, I've noticed a slight misfire at idle as well (cold or warm) -- it's nothing dramatic, and it stops as soon as I touch the gas pedal.

If you've seen my threads, you know about my 10-12 mpg/city complaints. I wonder how difficult it would be to reprogram (or make mechanical adjustments?) that would extend the the 2nd port opening from 3750 to say...4,500 or something? That way, you could cruise in 6th and not get run over!

Re: An interesting way in which I improved Fuel Economy.
 

LOL Gary

I thought I would try a similar experiment- I only made it about 2 miles down the road before I accidently started reving it up again :D I'm very impressed with your show of self restraint!

Will,
That would definitely be a good idea. I think Canzoomer's ECU mod is supposed to improve the air fuel map somewhat better than stock.

I know I'm going to get flamed for saying this but a shift light wouldn't be such a bad idea either. perhaps one that you can turn on or off.

:)
Gary

Silvercloud,
It wasn't easy!!!!!!!!!!

HEHE!

Gary

I have consistently averaged 19 mph since I got the car (2000 miles). It drops to under 17 when raced a lot, well over 20 on the highway under 70 mph. I usually shift at 4000-5000 in first and second, and accelerate moderately. I am very conscious of minimizing braking in traffic. I watch ahead and coast a lot. My daughter took it for a day and got under 15. She tends to scoot from traffic light to traffic light and brakes heavily.

so to say I should really keep my car above 3200 rpm when cruising on highway?... another excuse to cops. :p

It's been a while since I posted but I too did this "experiement" in September 03 and found the same results.

Rodster-
were you getting low mpg in sunny florida?

Gary

IT WAS THE MOST BORING 243 MILES I'VE EVER
DRIVEN!!!!!!!!! People in econoboxes were passing me by like I was
standing still and giving me dirty looks.


-At this point I acctually laughed so hard I farted. You da man for following through with the experiment.

LOL! Thanks! Could you bottle that gas and send it to me?

I tried the experiment once. Lasted until just after I turned the key. If I wanted mileage, I wouldn't have bought this car. God killed the dinos so we could drive fast, not so we could worry about MPG.

GuysI know you say this isthe best way to get highest MPG but Iam almost positive Ive donethis before and all it reallydid was frustrated the hell out ofme. I do 100% city driving so maybe that is why I got nothing out of drivingthis car like an old lady.

Had a chat with a friend today, and he told me his interesting way of getting more miles out from his drive.

Well, he never pump a full tank of petrol, imagine, 58-60liters when full, that's alot of extra weight to run around with! So for those who can excess to petrol station easily might wanna try this. Just go with half tank, don't fill up anything more than you need. Basically is a weight theory.

cheers

Keeping the tank mostly empty all the time is not good for the tank in the long run if it's metal. Do we have plastic tanks? I never looked...

Those of you who have the stamina to shift these cars under 3K for 200 miles or more amaze me. This car is no fun under 4K! Might as well be a diesel under 3K.