EJ1 RaceBound

I have had a 1994 civic DX in hand for quite some time now. The stock motor finally gave out one day and i used some spare D-series parts to and other parts i had to put an engine together for it because i use this car as a daily commuter car. The engine ended up being just a make **** mini-me really. D15b7 block and crank. Honda VX rods. 76MM vitara pistons. Y8 head with B7 cam gear. P28 ECU with the timing advanced 2 degrees. I calculated my MPG out and it read 63mpg....My first thought is i messed up my calculations. But no i did not. I recorded mileage in this realm several times. Is this normal? Has anyone received mpg this high or maybe even higher? Also this was highway miles at a steady 62mph. City mileage was around 50's. According to this http://www.fueleconomy.gov/feg/topten.jsp not too many cars can top that...

dem0nk1d

what tranny are you using...

EJ1 RaceBound

Stock DX tranny

fleabag

Running lean? 63mpg seems very high and the only way I'd imagine being able to pull that off is if the fuel station you're using is underfilling and over reporting and or you're filling up with a hot gas tank causing the fuel cutoff to happen too soon. I'm finding these fuel economy numbers to be very hard to believe without using a transmission with VX gearing and or the car running lean.

If the car is running lean, I think I can believe it.. Is this p28 programmed or something to get a little better fuel economy than usual?

dem0nk1d

63MPH is pretty low.... That should keep the RPMS down in 5th gear even on a DX trans. I would also think there is some reprogramming going on to get the leanest and somewhat safe burn.

fleabag

Let me just say this... It is my observation that in order to achieve the highway fuel economy numbers one sees on the EPA's CAFE fuel economy cycle (the one developed in the 1970s and is still used today, though is heavily revised downward), you have to be driving about 55mph to get their numbers. The 1992-1995 Civics with the D15B7 engine do NOT achieve fuel economy numbers that high, but instead in the high 40s to low 50s. That's why I don't believe this is 'normal'. On a properly tuned up car, driving at 55mph, on a flat grade, I have never gotten more than 1-3% above or below that CAFE highway fuel economy rating. OP would have to be driving in top gear but at like 30mph to get those kind of numbers... Again, that's my observation and I've done a LOT of testing on various cars. The RPMs are simply not low enough on that DX transmission at 63mph which is why I know that fuel economy to be impossible save for a car running lean or something of the sort.

On my Civic LX with the D16Y7 engine, driving at 55mph, scangauge reports no higher than about 55mpg, though that is going DOWN a slight grade, and about 45mpg going UP a slight grade (opposite directions on that road) so that average is about 50mpg, and the car is rated at 48mpg on the CAFE mpg highway test cycle.

NotAJDMFanBoy

with such low compression (zeal auto works calculates it to 8.35:1) you could probably get away with running leaner, but who knows how long it will last.

Linked

i guess on the right conditions, theres some percentage that high 50s could be had

my girlfriends 97 3.0l taurus is rated at 18 mpg city/ 24 highway.

on our 5 hour trip she drove directly behind me at about 75mph the entire way there, and she netted a 36mpg on half a tank

so if your were trailing an 18wheeler, had NOTHING but yourself in the car. and everything top-notch, i see you having a good chance of hitting the 50s

(trailing a huge car makes a big difference cause you'll have 0 wind resistance

EsotericImage

iTrader: (8)

^^

and shift like grandma

fleabag

The 1997 Ford Taurus with the 3L engine is rated at 36mpg on the CAFE cycle. Again, I have to emphasize that if you fill your gas tank on a hot day and or after a hot drive, the fuel filler at the gas pump will click off sooner and therefore give the appearance of better fuel economy than you actually had. Best way to calculate fuel economy is to do it on a cold day with a cold engine. Those factors would easily be enough to explain the Taurus getting 36mpg on that road trip.

EJ1 RaceBound

I my self could not believe this. And fleabag, i know what you are talking about. I kept putting fuel in the tank until i could see the fuel just below where the cap sits JUST to make sure it was all the way topped off. I am not to sure if the car is running abnormally lean i will have to check into that this week. But i am honestly astonished and the fuel mileage i am receiving with this car. I have checked and checked and rechecked my calculations. I even recorded the miles i drove based off of mile markers on the freeway just in case my odometer was off. But its all spot on..The car is lowered about 3 inches off the ground tops. I know this will improve the mileage slightly. But not a significant amount. I called my father to report this too him and he was utterly surprised. He wants to Patton the engine and sell it to the government LOL

EJ1 RaceBound

And as far as the ECU. I bought it from a guy off craigslist. Its a P28 and he said it was chipped on chrome and the timing was advanced 2 degrees. That is all i know about it

95b18c1egcoupe

i mean i believe it my gsr with a gsr tranny gets 40 mpg on a stock p72 so i would think a d series with a lotlonger tranny could get near 60 on a good day

DumpdEJ6

When calculating MPG's, its imperative that instead of just filling it up and using the gas tank size as a factor, to instead trip the odometer after filling, then at the NEXT fill up, note the amount of gallons used to fill it completely. Then divide the number of miles on the odometer by the amount of gas used to fill it.

OP may have actually been using this method, but I just thought I would point this out for people who don't know. I've seen waaaaay too many people saying that "x car gets x miles per tank!!!" without actually mentioning how many gallons they went through or even how much the tank holds.

My last fill up in my DOHC ZC CRX with minor bolt ons I got 40.3MPG mixed highway/city driving, with 2 full throttle hard pulls mixed in there somewhere. :-)

B20BP8R

iTrader: (1)

my stock 97 LX sedan gets 42 mpg on the highway, its got a lifter tick and 250K miles, so its realistic. Pretty cool stuff man, keep updating this if something changes.

EJ1 RaceBound

Just an update, i am getting ready to take the car for a long drive from Seattle to Portland and back in about a week to basically triple check the MPG. Ill post the results when i get back

98civdx

I just did 50mpg in my dx from tacoma to friday harbor.

EPA ratings don't have **** on these cars.

fleabag

see this post:

likwidchz

I think it would totally be fun to put some crazy *** tune on a stock engine and optimize it for mpg.

Run 15-16-17:1 AF ratios just enough fuel to prevent the engine from bucking at cruise, and run high ignition timing values during cruise.

It would also be cool to have the car suck in some HHO gas from electrolyte cells and power it off the alternator or even a 2nd alternator.


Would be an interesting experiment.

98civdx

I did it with a auto DX tranny, a full tank of gas is a full tank of gas.

Is the car runing lean? I don't know, I don't have a air/fuel guage, or any way to measure that.

I know I got 48-50mpg......... If you don't belive me, that is fine. I am NOT the only person, nor is the OP to see this mpg from these cars.

Texas4door

Dumb question, but how did you calculate your mpg?
Did you use the odometer?
If so, my next question is: what size tires are you using?
If you use a tire/wheel with a smaller than stock circumference, your tire will have to turn more times to move the same distance than a stock tire would.
But your odometer, a mechanical one on these older Hondas, is calibrated to stock tire size, ergo, it will seem like you're going further on your odometer than what you really are when using smaller tires, sometimes as much as 10% or more!
(to test it yourself, use a tire size calculator to figure out the circumference difference... or be lazy and use a GPS and compare it to your odometer XD;

BUT, if you ARE using stock tire size, then I say take care of dat Honda and enjoy the great gas mileage!

98civdx

No, I read your post. In fact I read it twice.

fleabag

Let me try this again. The only way I'd imagine YOU (not op) being able to explain your numbers is if the fuel station you're at is underfilling and or you filled up with a hot gas tank causing the fuel cutoff to happen too soon.


For example, this means that when you go to fill up your gas tank, you can only add 9 gallons instead of 10 gallons worth of gasoline. The fuel pump's auto shut off is dependent on the pressure inside of the tank. Hot fuel out gasses more than cold fuel. So, accounting for the fact that you likely filled your tank right after a long drive, which means you have heated fuel in your gas tank which means the pump will stop sooner due to the build up in pressure in the gas tank, your calculated fuel economy will appear higher than it actually was. Getting 45mpg in your car is not unheard of at all and does not call into question the validity of the EPA's fuel economy calculation because the way the EPA tests is vehicles is very different and there is more to it than cruising at a set speed.

92lxsleeper

i believe you. my 92 would constantly hit 52mpg doing only highway driving with a d15b7 with timing advanced 4 degrees

98civdx

Actually, I filled up in the morning, literaly 10 minutes AFTER I started my car in the morning.

I did approximently, 44MPG on the way up there. (it's not exact, I filled the tank the next day, and it took 4.5ish gallons to fill the tank.)

Driving home, and driving on the tank for 1.5 or 2 weeks, I got like 490 something, miles on the tank.( think it was like 498) YES, I did restart the trip meter after filling up.

When I filled up, I put just about 10 gallons in the car, I think it was 9.8 or so to be exact.

If MY type of car can do 45, why isn't it possible to do 50?

Wether it's hard for you to belive or not, is totaly fine. I didn't belive it at first either. But, when I did the math 3 times, and my dad did as well, we reaslised I was dead on.

All I have is a SRI, and some cheap *** dunlops on 15's lowered 2.5'' I am sure the intake played some sort of a roll in this.