Bense

In reference to my d16y5 project: https://honda-tech.com/zerothread?id=1414454

I have heard different theories as far as which is better for gas mileage. As stated in my d16y5 thread, I am building a motor to be as efficient as I possibly can. I am at the point where I am about to be building my d16a6 block and I don't know what pistons to order. Regardless of what I do, I want (what everyone else wants) my car to be dual purpose: to be able to use as little fuel as possible when crusing and as much as possible when accelerating.

In doing this, I realize that d16s aren't the real "power houses" of honda motors. In fact, before my turbo GSR swap was stolen the idea of me ever building a NA d16 would have seemed foolish, funny how perspectives shift. I don't know why I'm rambling and telling you all this bullshit when I really just have one question

Which is more efficient (better for gas mileage)?
High compression NA?
or
BOOST?

If boost is more efficient, then supercharger or turbo?

#####################################
In posting this in the All Motor forum I realize that this really isn't the place for questions on boost, etc. However, you guys are the ones that know the most about engine building and optimizing. Whereas the FI guys are seeing how much boost they can throw in their b18c1.

drdisco69

A turbo will be more efficent than a supercharger, and more compression will be more efficient than less, for a given motor.

Rocket

on what gas?

You can do 16 CR on alcohol.

Bense

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

You can do 16 CR on alcohol.</TD></TR></TABLE>

I was planning on 93octane. However I'd love to be able to run that stuff that the FFV vehicles use. Granted I'd have to get all new fuel lines, fuel tank, etc. But still.

Bense

bump for more insight

xEnderx

Boost is WITHOUT A DOUBT more effecient when it comes to a combination of power and mileage when you are talkign about pump gas.....or even race gas for that matter. Boost increases the VE of a motor beyond `00%....which if tuned properly will result in more power with increased gas mileage.

Bear in mind that there are other concerns when building a motor though.

Bense

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xEnderx &raquo;</TD></TR><TR><TD CLASS="quote">Boost is WITHOUT A DOUBT more effecient when it comes to a combination of power and mileage when you are talkign about pump gas.....or even race gas for that matter. Boost increases the VE of a motor beyond `00%....which if tuned properly will result in more power with increased gas mileage.

Bear in mind that there are other concerns when building a motor though.</TD></TR></TABLE>

i realize that. However my main goal in this project is to completely **** on the toyota prius. Whereas most people in civics wanna be able to look at *insert domestic v8* and say "i'm better than you in almost every single way" I wanna do that to the prius. I want the most mpg on paper and I want a lot of power. If high cr is something that will yield in better mpg on a flat cruise for 50miles at 60mph then I want to do that. If not then I might look at other alternatives

digitalcongo

you can tune NA for efficency...
then add boost for power...
its probably the only way to get the best of both worlds...
once you start raising the c/r the temps rise and you start adding in the fuel to fend off detonation...
the colder the intake charge air...the higher c/r you can run on a constant basis...
and naturally...once you throw the switch for boost mode...you can kiss the mileage goodbye on that tank...
but hey...there's plenty of room using crome/uber etc to get this done...

xEnderx

That is an idiotic goal. You are NEVER going to acheive a mix of power and gas mileage that will beat a hybrid vehicle. Now if you go with a TDI motor then you MIGHT get close, but the way that a benzine motor works will never be able to get more than 40 MPG.

rjay8604

I would have to vote for a small motor with light boost as the most efficient and power producing. Note: s2000's get unusually poor mileage for their engine size and vehicle weight. The turbo can provide boost when needed and the motor when off boost will have near stoich air/fuel ratios as in cruising and low load and low rpm usage. Small motor/light boost for the win.

Bense

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xEnderx &raquo;</TD></TR><TR><TD CLASS="quote">That is an idiotic goal. You are NEVER going to acheive a mix of power and gas mileage that will beat a hybrid vehicle. Now if you go with a TDI motor then you MIGHT get close, but the way that a benzine motor works will never be able to get more than 40 MPG. </TD></TR></TABLE>

why don't you go sit with the guys that said that civic could never be fast

Tony the Tiger

There are ways to squeeze efficiency out of our engines, but most factory cars simply cannot go to that extent because of emissions laws and still be able to use regular unleaded gas. Really high compression isn't really environmental friendly.
Premium gas and fuel economy (saving $$$) simply do not belong in the same sentence either, but if you are strictly trying to get big MPG numbers, than that would work I guess. You can also dial in the cam timing to bias more low-end to improve fuel economy. You also want a really good ignition system. You'd probably end up ditching the stock distributor and go with individual coil packs with much longer spark dwell time to promote a consistent and complete burn. Might as well go with smaller injectors and slightly increase the fuel pressure for better atomization while still having enough fuel for the engine. All the above mods would increase economy and increase performance at the same time.

The moment you put a turbo on there, your fuel economy will suffer. During off-boost situations, the engine is working against exhaust back pressure and it hurts efficiency during cruising. During boost however, the engine is efficient with fuel vs power; however, by the time the engine is boosting ,it is probably pushing 160+ HP which in turn doesn't do so good with fuel economy

Bense

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">There are ways to squeeze efficiency out of our engines, but most factory cars simply cannot go to that extent because of emissions laws and still be able to use regular unleaded gas. Really high compression isn't really environmental friendly.
Premium gas and fuel economy (saving $$$) simply do not belong in the same sentence either, but if you are strictly trying to get big MPG numbers, than that would work I guess. You can also dial in the cam timing to bias more low-end to improve fuel economy. You also want a really good ignition system. You'd probably end up ditching the stock distributor and go with individual coil packs with much longer spark dwell time to promote a consistent and complete burn. Might as well go with smaller injectors and slightly increase the fuel pressure for better atomization while still having enough fuel for the engine. All the above mods would increase economy and increase performance at the same time.

The moment you put a turbo on there, your fuel economy will suffer. During off-boost situations, the engine is working against exhaust back pressure and it hurts efficiency during cruising. During boost however, the engine is efficient with fuel vs power; however, by the time the engine is boosting ,it is probably pushing 160+ HP which in turn doesn't do so good with fuel economy </TD></TR></TABLE>

excellent, that's exactly what I was asking for I realize that turbos are the easiest way to increase volumetric efficiency, however in trying to get a high mpg number (not necessarily to save money) then I should upgrade my spark system. So the engine working against the exhaust pressure is less efficient than turning a supercharger? I realize that a turbo makes more power, but which is more detremental to cruising?

slofu

c'mon, guys, let's be creative. you've seen e-cutouts and diverters, right? who says that you have to fight the turbo under low loads? just bypass it altogether. (it's far less complicated than vtec.)

i'm with rjay. a mildly boosted small engine is great for fuel efficiency at lower rpm under higher loads, e.g. hwy driving. and, using less premium fuel is cheaper and likely more environmentally friendly than using more lower-grade fuel. (topic for another discussion is that emissions are a spit in the ocean concerning the environmental impact of modern gas cars.) run ~10:1 static compression, ensure that you maximize quench and reduce surface area in the combustion chambers, get a mild cam which will work decently for NA and a few #s of boost on a fairly small turbo, and have a good tuner use a decent EMS to make it all work.

if you drive the car either primarily in the city or on the hwy, you could go one route or the other with better results, but if city/hwy use is about =, you have to make a compromise or the benefits of one setup in one application will be detriments in others. for primarily city driving, i'd say higher comp, NA all the way. but for mostly hwy use, FI should win.

xEnderx

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bense &raquo;</TD></TR><TR><TD CLASS="quote">why don't you go sit with the guys that said that civic could never be fast</TD></TR></TABLE>


Look dude, you are trying to make a car with alot of power that gets incredible gas mileage. ITS NOT GOIGN TO HAPPEN. Of course if you do manage to pull it off then by all means....sell it to every major car company. They've been wanting to make this miracle motor for....hmmmm....well the last 60 years really.


Power or gas mileage....choose one.

digitalcongo

you can have both...just not at the same time...
but you can have both in one car...
which is something that very few do...or have done...

be careful not to choose the answers you WANT to hear...
waiting around for replies that make your idea feel better are not going to actual make the project work in reality...
physics rule...and its fairly basic...
the more variables that you put into your calculations for a desired end...
the more accurate they will be...
so dont be sucker and trust what people say...just cuz it fits into what you WANT to hear...
it actually has to work

the moment you put a turbo on your car does not mean you are going to kill gas mileage...
a turbo consists of many components...that all work towards a desired goal by the designer...
particularly in this case...the wastegate...
if you use a tial small yellow spring on an external wastegate...your max boost is approx 3lbs...until you turn up the boost controller
running a light boost and/or zero vac increses efficiency as the engine no longer has to pull the air and the cylinders get a better charge...
but not so much that your a/f is compromised

a car will not run without backpressure...unless you are dumpoing fuel
backpressure is a train of unburnt fuel...
its called scavenge...and if you removed backpressure altogether you cannot accellerate...(with stock injector fuel supply)
an engine uses unburnt fuel on the next burn cycle
on an engine like the vx or hx a turbo is pretty indentical to the stock cat in terms of backpressure


Modified by digitalcongo at 3:13 PM 1/21/2006

scUba-stEve

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

why don't you go sit with the guys that said that civic could never be fast</TD></TR></TABLE>

you're basically asking to make a powerful (200+whp d16), that'll give you the gas milage of a prius (which is about 50+mpg)...that is NOT going to happen...the most gas milage you'll probably get is in the 30's or maybe 40's...and they only way you're gonna do that is going turbo...because when you're cruising, you're not boosting, so it'll be almost like driving a stock car...but getting as much gas milage as a hybrid?...i dont think that's gonna happen.

Used2beAb16

lighten the hell out of your car, use small tires super light wheels and tires.

That will help in both the performance and gas mileage aspect.

Work on aerodynamics, diffusers..

etc. that will get your mileage up because you even if you would restrict performance its gonna be tough achieving prius like numbers in the MPG dept.

civdx94

mista bones lightly massaged and tuned d15 has been getting crazy mileage for a number of years and before his monster cam install he was gettin 53mpg. with stop and go traffic i would think it would be quite hard to compete with a prius as this is where they really excel, but you as i have noticed are using the lean burn technology as your base which also has its advantages. there are much easier ways however to achieve overall efficiency. for example the vw one liter car concept achieves 238mpg with a 10hp diesel engine aside from it weighing around 800 pounds what else could be a factor..definitely the c/d of .159...if i were attempting this i would do as follows

1st gen crx hf c/d of .24,curb weight of 1713 pounds
rebuilt d15 with a milled/professionally ported y8 head(still fuel efficient but much better window of tuning) and a stock dx tranny with light flywheel
Then remove all necessary weight both on the car and engine internals(also coatings on the bearings,pistons,etc) if desired, a vacuum pump and oil scraper would be a good idea as well
Finally add a belly pan/diffuser to the underside of the car
After reading your current plans i really don t think you ll touch your goal you need to do alot more research especially in the realm of the y5 powerplant, they are very very difficult to modify/tune and by no means would i call them superior. Your car indefinitely needs to improve on aerodynamics,weight, and engine efficency but from what i am seeing you are only indentifying one aspect of the overall equation. Another variable to think of when considering adding a turbo is the significant amount of weight added vs the gains provided.


Modified by civdx94 at 10:26 PM 1/21/2006


Modified by civdx94 at 3:41 AM 1/26/2006

slofu

some good points raised here. weight isn't so much a factor for steady-state cruising, where you only have to burn enough fuel to maintain the momentum (against the wind/drag), as is aero, and the opposite holds tru for stop-and-go, where wind drag isn't high enough to make as much difference as having to accelerate more mass.

look to the Honda Insight. those rear fender-skirt things help reduce drag, as does the low, narrow, sweeping profile. the front and rear windscreens are at a fairly slight angles to the road.

i'd say that a crx is a good chassis to use, as it has some similar angles, and is also very lightweight (and cheap). make some air diffusers to route as much air around the car as possible, instead of under it, and fix areas of high-pressure stagnation, such as behind the rear bumper. keep front grill area only large enough to provide adequate airflow to the radiator, keep the car low to the ground and try to cover areas under the car which can become pressure-pockets.

you can replace some of the glass with polycarbonate, and get 13" lightweight Al wheels. you can even reduce drag by using lexan to cover the openings between the spokes on wheels to reduce drag.

beating the Prius is easy. Honda already did it in '92 with the VX, which the EPA estimated to get ~55mpg hwy. half of the stuff which makes the Prius good on gas also hurts it. (my friend has one, and it doesn't get close to the advertised mileage.) the battery and electric motors, etc. are heavy, especially since it still needs a gas engine, typical trans, a fuel tank, etc.

you also don't need to run a cat, you can bypass a turbo when it's not needed. you can drive with a lambda meter and gauge to display a/f, and egt probe and gauge, and a knock-sensor box. have 2 ***** with which you can fine tune a/f and spark on the fly when the EGT is too high, or when knock is detected. (knowing EGT will help you know when to ignore the knock-alert- e.g, due to noisy valvetrain, etc.) you might be surprised at how lean you can run sometimes without knocking or burning anything. i've heard of guys running &gt;13:1 static comp on built 2L B vtecs getting 35mpg. you should be able to get &gt;50 on your setup and run 13s in the 1/4 np.

xEnderx

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote"> you should be able to get &gt;50 on your setup and run 13s in the 1/4 np. </TD></TR></TABLE>

Bullshit. I've got $1000 that says you CANNOT build a single cam turbo honda motor that gets over 50 MPG and runs 13's.

digitalcongo

^^^ show me the money !!!
thats about all the money i need to finish the build
lol



(p.s. you are ricer trash...and humans cant end **** !!!)

scUba-stEve

slofu...do you have a link or something that shows a 13:1CR 2.0 liter, getting 35mpg? i do not know if it's impossible, but it sure seems like it.

digitalcongo

i'm using the 3-stage motor
it has vtec-e / 16 valve / wild lobe
with a reported 1.7 r/s ratio
9.4:1 cr (98+ had 9.6:1)



just ordered a skyline r33 turbo
has ceramic turbine and nylon compressor wheel - bb of course

search thru my posts to see the shell i'm using

i like how your tongue feels on my sac
j/k





bones motor is *******...have you seen the dyno...?




Modified by digitalcongo at 7:26 PM 1/21/2006

slofu

contact SGT (steve sakai). he claimed to have done it years ago.

something else to consider; hp = tq x rpm / 5252. if displacement is low enough, and you're not demanding much power from the engine, either to accelerate it or to maintain velocity through the air, you're not requiring it to burn much fuel. as long as you can configure it to carry the power longer (and keep the engine together), you can make the power by revving higher and get good mileage when you're not.

those older, lozenge-shaped Ford Taurus cars only required ~12hp to maintain ~60mph. testament to the importance of aero. they weren't exactly light, nor did they have the power to accelerate quickly, but for their size, weight, and engine displacement they got decent hwy mileage.

as to Ender's challenge: i don't have the resources at my disposal to make it worth trying anytime soon, but surely someone else will be willing to take your money. perhaps Bense, who started this thread. as i said, it would be easy enough to bypass the turbo altogether with a diverter when it would only impede exhaust flow, and as long as the driver can activate the turbo from the cockpit while the engine runs, it's still considered a turbo engine. i'm not saying that it won't take work, but Bense seems up to the task, and your negative, antagonistic attitude might do more to inspire him to prove with his project that a single cam honda turbo gas engine can run 13s in the 1/4 as well as get 50mpg or better, especially if he gets the weight down and the aero correct.

Go Bense!