granada sol

Usually engine builds are synonymous with horsepower and torque numbers. I guess it's a sign of the times, but I was curious about fuel economy. Gas prices are on the rise and there seems no stop anytime soon.

So here's my question...

Has anyone built a motor based on fuel economy?

I'd like to build with fuel consumtion in mind but i would still like to have a decent ammount of power to go along with it. I mean what is the point of getting 70 miles to the gallon if you cant enjoy driving a little bit?

What characteristics are better for fuel economy?
SOHC or DOHC?
High / Low Compression?
Exhaust Backpressure?
Cam overlap?
Lightened valvetrain, drivetrain, overall curb weight?
VTEC?

quicksilver1689

d16y5 ftw!

granada sol

What about the D16Y5 makes it fuel efficient? Care to elaborate a bit?

LostBoy04

DOHC is more efficient.
I would also assume that a higher compression would be more efficient.

Aluminum wheels, lightened chassis.

Here's an interesting site about fuel economy. http://www.gassavers.org/

TunerN00b

Building and tuning, will improve mileage. Any part that is more efficient than stock, and most race parts are for power, can result in an increase in mileage, assuming you don't dump more fuel as a result of the mod.

My 1979 Triumph Spitfire came form the factory rated at 63hp, and 32mpg. No clue on power now, but with higher compression pistons, a more aggressive cam, a ported and polished head, Holley carb, equal length 4-1 header, Mallory dual point dizzy, and a free flowing exhaust, it easily manages 55mpg highway. My best tank was 62mpg.

Of course, since the carb is soo damn big, if you have a heavy foot on surface streets, it also has no trouble getting all the way down to 14mpg. Though, I usually manage 35mpg city without worrying about my fuel consumption.

However, most power mods cause the driver to enjoy the car more, and accordingly, to use more fuel driving it.

ickyhonda

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LostBoy04 &raquo;</TD></TR><TR><TD CLASS="quote">DOHC is more efficient.</TD></TR></TABLE>

Correct, a dohc is more efficient at pumping air. This does not translate into better fuel economy though. The more air you pump the more fuel you have to add into the cylender, so it actually hurts fuel economy. What you want to do is make the combustion efficient. I would say go with higher compression and get it tuned on a standalone system by a tunner that uses a load type dyno. Then learn how to control your foot (or put a block upder your gas pedal to limit how far you can press the gas).

TunerN00b

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

Correct, a dohc is more efficient at pumping air. This does not translate into better fuel economy though. The more air you pump the more fuel you have to add into the cylender, so it actually hurts fuel economy. What you want to do is make the combustion efficient. I would say go with higher compression and get it tuned on a standalone system by a tunner that uses a load type dyno. Then learn how to control your foot (or put a block upder your gas pedal to limit how far you can press the gas).</TD></TR></TABLE>

Or buy a new R18 Civic engine. The drive by wire controlled throttle body, and dynamic cam control, allows the engine to pump some air back out of the cylinder before closing the intake valves (piston already moving up) to create an essentially variable displacement engine. Less air in cylinder, less fuel needed.

Direct injection engines can also run insanely lean during cruise, if the combustion chamber was designed accordingly. Spray fuel into a rich pocket by spark plug, fire, and let the flame burn itself out before all the air is consumed.

I agree on the tuning part. Most cars run slightly rich from the factory, as its significantly safer than risking running lean. Free up the exhaust and intake, to improve efficiency, and get it tuned as lean under partial throttle as your tuner is comfortable.

Aquafina

iTrader: (3)

Not worth it. It would take a few years just to make back the money it cost to build it.

Edit: The Civic GX was 12.5:1 and ran on natural gas. This was Hondas fleet car for economy. D16B5 was the engine code.

quicksilver1689

d16y5 gets awesome mileage, VTEC-E has superior swirl characteristics in the combustion chamber allowing it to run alot leaner that most hondas. Look it up

1989rexsi

also go with a low fianl drive gear box what do you have or what are you looking at getting year of car

Aquafina

iTrader: (3)

I got better mileage with my EX trans w/ 4.714 FD than I did with my stock EX or stock Y7 trans.

1989rexsi

with a hydro 3.25 form 92-95 cx/vx
and a 5th gear ratio of .702---&gt; 80mph=2616 rpm's

with a hydro 4.25 from all si's and hydro ex
and a fith gear ratio of .702---&gt; 80mph=3421 rpm's

with a custom final drive of 4.714
and a 5th gear ratio of .702---&gt; 80 mph=3790 rpm's

the cx/vx trans wins with better fuel. ie:low rpm's at freeway speeds

Aquafina

iTrader: (3)

Not true.

Stock DX trans (.702 5, 3.722 FD) I got 43mpg.

EX trans (.705 5, 4.714 FD) I got 47mpg. No other changes.

ef nightkids

What about turbos?some people say u can get up to 35 or 40 mpg with the right turbo set up.I'm running a sohc zc 65 shot and I'm trying to get the best milage and I'm going to boost it this summer only if I get that kind milage .any one know about what kind of tuning to do for turbos and good milage.

Aquafina

iTrader: (3)

Boost is not for economy.

TunerN00b

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aquafina &raquo;</TD></TR><TR><TD CLASS="quote">Boost is not for economy. </TD></TR></TABLE>

Perhaps not if someone is using boost for more power on an engine that otherwise was capable for the car.

However, since the full potential of the engine isn't needed during cruise, a smaller turbo engine can make better mileage, by virtue of being a smaller engine.

Imagine a 1 liter turbo. It might only make enough power under boost to keep up with a more typical NA 2 liter, but under cruise and idling at lights, its much less wasted engine. Similar to how the Honda hybrid systems use the electric engine as a power bump when needed, in order to run too small of an engine the rest of the time.

cetcivic

get an LS swap(w/ everything)drop it in and save cash and get some added pep

ef nightkids

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cetcivic &raquo;</TD></TR><TR><TD CLASS="quote">get an LS swap(w/ everything)drop it in and save cash and get some added pep</TD></TR></TABLE> I'm getting hooked up on a 14b turbo so I rather use that .so do u thing that is a good turbo for the fuel side of things ,and I heard running real lean will get some good milage but will that hurt the motor at all?

Aquafina

iTrader: (3)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TunerN00b &raquo;</TD></TR><TR><TD CLASS="quote">

Perhaps not if someone is using boost for more power on an engine that otherwise was capable for the car.

However, since the full potential of the engine isn't needed during cruise, a smaller turbo engine can make better mileage, by virtue of being a smaller engine.

Imagine a 1 liter turbo. It might only make enough power under boost to keep up with a more typical NA 2 liter, but under cruise and idling at lights, its much less wasted engine. Similar to how the Honda hybrid systems use the electric engine as a power bump when needed, in order to run too small of an engine the rest of the time.</TD></TR></TABLE>

That argument is out the window. An N/A engine will get better mileage than it would if it was boosted. We're talking about building a Honda engine for the best possible economy. Not doing a custom destroked to hell build to get the same economy while making more power and spending a lot more money.

quicksilver1689

yeah for best mileage, n/a wins. Light chassis, the right gearing, a small displacement motor, maybe a custom chipped ecu tuned for mileage. maybe a turbonator for good measure

cachehx

the best i EVER got with my d16y5 was 35 mpg and that was TRYING to get the best mileage i could possibly get... just to see what it would do.

their not all their cracked up to be... (to me anyway)

Aquafina

iTrader: (3)

Put a shorter 5th in one and it would be alright.

StorminMatt

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aquafina &raquo;</TD></TR><TR><TD CLASS="quote">Not true.

Stock DX trans (.702 5, 3.722 FD) I got 43mpg.

EX trans (.705 5, 4.714 FD) I got 47mpg. No other changes.</TD></TR></TABLE>

It is true that taller gears can DECREASE mileage. This is particularly true if the motor you are using was not designed for tall gears. Remember that, in MANY instances, lower revs mean that you are dumping more gas straight out the exhaust. So in order for a taller transmission to help fue ecoomy, you MUST use an engine that was designed to go along with it.

With this said, probably one of the BEST engines Honda has made for fuel economy is the D15Z1. People routinely get 50+MPG from the Civic VXs that this motor came in. And with gas getting ever more expensive, more and more people are swapping this motor into other Civic models. Probably one of the best combintions for mileage would be a 1988-1989 CRX HF with a D15Z1 swap. These cars are light and have GREAT aerodynamics. They also have a tall geared transmission that works REALLY well with the D15Z1 (which is also designed for a tall transmission). This combination should DEFINITELY be good for 50+MPG - even without trying.

One more thing. As far as compression, this generally improves fuel economy. BUT, it does so at the expsne of requiring higher octane gas. The need for more expensive gas can EASILY wipe out any gas savings when it comes to actual operating costs. SO consider this carefully. It might also not be the best choice for a motor with a lean burn cycle, like the D15Z1.

ef nightkids

How much power is the d15z1 maken?I would like have some kind of horses under the hood(130,145) but keep the gas cost on the low low.would u guys use a apexi afc air/fuel controller to run your car lean or is that unsafe

ickyhonda

I feel sorry for anyone that puts an afc hack on a car. If I were to give a list of all the reasons as to why they are the worst things to happen to automobiles, this thread would be 10 pages long. I will leave it at that.