Efficiency

[seishuku]

My SR with out the turbo ran 25MPG, with the turbo it gets 28MPG. And I have a pretty heavy right foot.

[menassy17]

seishuku, that is good information, too.  Thanks

[JonB]

Just for the engine;
Volumetric, thermal, and mechanical efficiencies, the real one- BSFC(Brake Specific Fuel Consumtion)How much every HP costs you in gas.

Volumetric is pretty much the horse power- You can get more outta a motor with it but its gonna take more fuel.

Mechanical is the friction in the motor- A factor but not an end-all of the best motor.

Thermal I'd have to say is the biggest effect on the BSFC, and one of the hardest and one of the most expensive to improve. Won't get you the most power, but will get you more power for the gas you put in it. Nothin you can do to break records compared to the auto makers efforts though, but they are governed by accountants. I'd bet the newer the motor, the better the motor.

You'll probaly need to be as specific as possible with what you want.

We could hook you up with the largest-slowest spinning 4 we could find.  It'll have more torque than the rest, less throttle movement to get the car going, and spin slower= less mechanical wear on the motor and last forever. How about a 2.5  2-valve with an Iron head? Then we get the pistons and some other internals thermal coated! Put a taller gear and chuck as much weight off the car as possible. Little thermal loss-Iron head. Two valves run by a belt=little mechanical loss. Small cam duration matched to the torque of the motor. Hell we could get ya cruisin at 65mph at 2.2k and over 35mpg. Just messin!

Also like Julie says. Decient turbo setup. Day to day grind it's almost never on boost. A little loss in flow efficiency from the turbo down low. But when you summon the boost, It's crams the freakin' air in there, and the gas to. You can lean on the turbo from time to time and maybee even pull more mpg than a non-turbo. But I think it's really up to how you drive. Mash on it all the time, I highly doubt you'll ever get better gas milage.

There's alotta good minds on this site, Much better than me, dig deeper/be more specific maybee the Ideas will flow in.

I'd look at the out-put of the motors stock, with the MPG of their original cars. Keeping in mind the weight of the vehicals vs your car's weight and don't forget torque and where in the power band the torque and hp is at and how and where you drive.

From there getting better than stock is gonna take some money and research. Less restrictive exhaust, coatings and things. Get weight outta the car, Maybee swap the gears, (I spin at 3k at 55-60, real bad for highway mpg). Lighter wheels are a certain factor, things like that.

[WankelMonkey]

Actually Julie is on to something there about the turbo. When people think turbo, immediately they think "power adder". Well yes, it does that, but could also be used to increase fuel efficiency. Much of the automakers are relooking at using turbos to improve performance out of smaller displacement engines compared to larger naturally aspirated ones. Just they are not tuned to output a rediculus amount of boost.

Prime example: Ford's EcoBoost GTDI engines
http://www.autobloggreen.com/2008/01/06/de...injection-engi/

However from a practicality standpoint with the current offerings made available to ya. It would probably more effort than one would be willing to spend to get the setup right. So if your really just looking for something to drop in without much fuss or hassle, my post is pretty much moot. However if you don't mind the heresy, you find an engine from another manufacture! Just trying to convert a B16 to a RWD layout might be a PITA

[blue streak]

why not look at your ca that you already have,
1. cold air intake
2. cat-back exhaust
3. new, more effecient O2 sensor
4. better plugs, wires
If the question is effeciency, by letting the engine breathe easier and look at the ratios betters. that should do what your looking for. other engines are better, Im using the CA18DET, but its really up to you and what your looking for as in HP vs MPG.
thats just my 2cts

[turbos12]

my ca-det gets about 400 miles to a tank..thats about 32mpg

[Draconis]

That's dang good for a CA18DET.  My RB20 had high 20s like 27-29 until I started playing with it... Then it dropped to 19-24.

[silvia love]

i posted this in a different thread, but its more relevant to this one.
read away...
http://www.importtuner.com/tech/0711_impp_...ency/index.html

[Julie]

large vehicles such as rigs and buses use turbo diesel engines for a reason and thats gas effciency. its literally a "no waste" principal where you try to maximize every resource you can from an engine in order to increase useable power without harming how far you can go with each gallon of fuel.

now, menassy17, take a look at this link. it details a setup utilized back in the day by turbo omnis and such

http://www.gusmahon.org/html/boostcontrol.htm

[Jsvob03]

why not look at your ca that you already have,
1. cold air intake
2. cat-back exhaust
3. new, more effecient O2 sensor
4. better plugs, wires
If the question is effeciency, by letting the engine breathe easier and look at the ratios betters. that should do what your looking for. other engines are better, Im using the CA18DET, but its really up to you and what your looking for as in HP vs MPG.
thats just my 2cts

cold air intake will not yield you any more Fuel efficiency. a Colder Air charge is able to carry more molecules into the Cylinder, thus able to take more fuel. So more power sure (if its a good setup). Too cold though (below 100*F intake temp) and the fuel will condense in the intake, which leads to horrible running conditions.

definatly agree New plugs, wires, cap n rotor will help.


I think a Ka24DE is the way to go. as Draconis said, similar in power output to the VG, only a 4cyl (a little big..) so mileage will be fair. and parts are fairly easy to get should anything break.

I could see ~25 MPG out of a good running KA. Plus, if you ever get the itch for more power, just add forced induction (its not just that easy, but you get what i mean).

Also, make sure your tire pressures are right, alignment is as straight as it can be, and everything is in proper working order and well lubricated.

[jeffwins24]

a turbo engine is better then a non turbo

if you're not in boost you can get like from 25 - 30 MPG on a turbo or more (correct me if i'm wrong)

but if you mash that pedal it'll drop.

IMO a KA24E is better.

[WankelMonkey]

yeah Tire pressure can get neglected very easily and if your in a climate that can swing quite a bit, you'll have to check your pressure more often. I had to re-adjust my tire pressure here in Tx because from hot to cold real quick, which played with my tire pressure.
Also, make sure your O2 sensor is working in the right order, since that has a direct effect on how much fuel your car will be squirting into the combustion chamber.

[bleuoval64]

why not look at your ca that you already have,
1. cold air intake
2. cat-back exhaust
3. new, more effecient O2 sensor
4. better plugs, wires
If the question is effeciency, by letting the engine breathe easier and look at the ratios betters. that should do what your looking for. other engines are better, Im using the CA18DET, but its really up to you and what your looking for as in HP vs MPG.
thats just my 2cts

Unlike what Jsvob03 said in his post, a True cold air intake will improve fuel efficiency.  To a degree, More air= more power, more power= more mpg... to a degree.  Notice I said "a True cold air intake."

A lot of people, specifically in the tuner world, think slapping a cone filter in the engine bay qualifies as a cold air intake setup.  The truth is, this method can be worse than utilizing the factory air box.  The concept of a cold air intake places the filter outside the engine compartment, protecting it from the rising ambient heat of the engine.  You wouldn't put an intercooler right behind the radiator would you?  Colder air is more dense with oxygen than hot air.  More Oxygen means the ignition within the engine is more efficient, which translates to a more effective use of the fuel.  By this same basic concept, turbos produce more power by increasing the amount of air within the combustion chamber.  With the filter still in the engine compartment it gets quite hot as engine temps rise which negates the effects using an open filter.  With the factory air box, the filter is somewhat shielded from these temperatures.  Its not called a cold air intake because the air is actually cold like ice or whatever.  Its because the air being routed to the intake is cooler than if the air had been more affected by the heat in the factory air box.

A cat-back exhaust would not be the way to go in my opinion.  Depending on if you have emissions regulations or if you even have to have the vehicles inspected at all, you could do without the cat entirely.  Get a decent size(2.5"-3" depending on the engine) mandrel bent exhaust without a cat and a straight-through muffler.

As for the O2 sensor, it wouldn't hurt to get a new one if yours is old.  As for more efficient, I would think they are all pretty much the same other than different brands behaving differently.  I've never heard of someone putting a "high efficiency O2 sensor".

And for better plugs and wires, I would say go further than that and replace the cap & rotor, coils or consider doing the dual coil mod thing.    

a turbo engine is better then a non turbo

if you're not in boost you can get like from 25 - 30 MPG on a turbo or more (correct me if i'm wrong)

but if you mash that pedal it'll drop.

IMO a KA24E is better.

Jeff, do you read what you type before you post it.  When you aren't on boost its basically the same as not having a turbo at all.  I agree that turbo engines have advantages over N/A.  However, I must question why you would recommend someone to install a turbo engine and run with little boost to save gas mileage?  MPG is different for any engine, you can't just assume a turbo engine running little to no boost will get you those numbers, I know of some that will net more or less than 25-30.  Finally I must ask why after saying: "a turbo is better than a non turbo", why would you say a NA engine is better?

[Garrett76zt]

for what its worth i've had a couple dual cam ka's one of which was a 95 auto s14 which regularly got 29mpg.

[silverarrow27]

Ca18et or ka24e

I personally have both and actually prefer the ka24e in my 240sx. Smoother engine and still gets great gas mileage. I'm still on the same tank from two weeks ago. I've been almost all over the Inland Empire the last two weeks.

[menassy17]

Hmmm  Lots of information.  No surprise that some is conflicting, but it all helps to weigh the issues.

There is so much here, I can't address it all, but I do want to keep the communication open so I can learn more.

Btw, I do apologize for my ignorance.  I am 50 years old and have only had two cars in my life.  Both have been excellent cars and I still have them both.  The 1962 Chevy II was my parents' first car and it was passed to me through two sisters and a brother (my younger brother never got it!). The Nissan was my first and only new car.  It has been an excellent car and I have had to do little to it through the years other than normal maintenance. Though I have done much work on the Chevy II (in my younger years).  I have not been able to keep up with car mechanics in my "working" adulthood.

But as you can see... I am inclined toward longevity.

I can't remember who said what right now, and I am not sure that I have remembered everything in proper context so please be understanding if I have misunderstood what has been said.

Someone mentioned that I needed to be more specific about what I want.  I probably assumed too much in my initial post.  In regard to fuel economy I am focusing in on highway mpg.  City mpg is nice, but most of my local driving is done on a scooter.  I have one that can go 80 mph and at 55 and 65 mph gets close to 80 mpg.  My other scooter can go 100 mph and at 70-75 mph gets around 60 mpg.

Obviously, there are times when you just need a car... especially on longer trips.  I have a car and I want it to be as efficient as possible at 70-75 mpg.  Depending on how it affects other things, I would not mind having the little extra punch of power that has been mentioned for situations that may call for such (emergencies, getting out of someone's way, etc.).  For example, if a turbo engine can get better mileage at the same time of giving that "emergency power"... that is a great plus!

There is some truth to someone's statement that, to a point, more power means better gas mileage.  For example, I had a 150cc scooter that could go 60 mph., but when it was going that fast it was at full throttle so my 200cc scooter would get much better gas mileage at 60 mph than the 150cc scooter would.  I know it is not that simple, but it seems to apply in this situation.  My CA20E engine does great on fuel efficiency up until about 60 mph, but falls quickly thereafter.

I do also have some questions:

If a true cold intake is not in the engine compartment, where is it?
Btw, there are no inspections where I live.  

In regard to the exhaust, is there no need for a mod to the exhaust manifold?

Thank you to the two who gave the urls.  Those were very helpful.  Actually, the one on fuel efficiency has potential, but hopefully the next installment will give the specific modifications that will help fuel efficiency.  Do you know when that will be available?  I looked but did not see a date on the one that I read.

Garrett76zt, as I look at your info I see that your KA's are DET. What have you done to get good gas mileage?

Thanks to all.

[Julie]

once a car is moving, it needs less fuel to make power at higher speeds, thats simple physics.

a cold air intake is an aftermarket part, where the air filter is close to the ground, behind the bumper cover and infront of the wheel, typically. they draw in cold air from outside the car, unlike the typical intake that draws in warmer air from the engine bay

exhaust manifolds are iffy. since you understand v8s and such then you surely know how much of an effect of swapping to a full length tubular header on a v8 engine. improved flow improves upper rpm power (i think) but the majority of nissan engines have free flowing manifolds that dont really require mods unless youre searching for those few extra ponies

[Draconis]

If you have no inspections, make your cold air directly to the front of your car.  Something like what Signal Auto did with their R34.  It would be interesting to see what you can do.



Best idea in my opinion... do an intake, exhaust and maybe some head work if you can afford it.  Nissan is known for poor flowing of air supply.  Honda's have always had the upper hand when it came to that.  SO by doing that, you will see quite a bit of difference.  Also, play with the throttle cable just a bit to get a good balance for power a little faster so you dont spend so much time playing with the throttle to get off the ground.  Talk to Sterling.  He has made a CA20 act like nothing I've known.  It was a mixture of a couple things here and there and lightening the car where it didnt need the excess parts.  Basically, make it so the engine can breathe better will help you reap rewards.

[silverarrow27]

I would go for a bigger diameter catback exhaust & high flow cat. Exhaust manifold upgrades for these small engines probably wouldn't help much. Exhaust manifold upgrade for a forced induced engine would help some in lag/turbo response.

Remember though that with exhaust modifications, the car/engine is going to be louder and I'm not sure if you'd appreciate the louder noise for long trips.

Try a K&N drop-in filter if you do not want to modify the intake in anyway and in my opinion it's just almost as effective as a cold air intake.

[RB25sx - SLPR]

If you want efficiency, you are using the wrong fuel. Gasoline engines produce too much heat, diesel converts much more of its energy into mechanical energy, hence they run colder.

As for the turbo vs non turbo debate, its simple physics really, x amount of CFM require y amount of lbs/hour of fuel. You need to maintain a stoich mixture, however if you can get away with running a small displacement turbo charged motor with compression tipping towards the higher end of the scale, your gains will be much more noticeable than say... A high compression small displacement non turbo motor.

And for the record, my RB25det does about 17mpg. Ow.

And just to add to the conversation pot, what are people's opinions of variable compression engines? Saab was developping one that could accept almost any type of fuel and could vary its compression ratio through a fairly substantial range.

http://en.wikipedia.org/wiki/Saab_Variable...pression_engine

-Dan