I wonder if one could just install a Super AFC and lean the low throttle maps way the hell out... ?

 

An AFC is never a bad idea. Even if your car isn't modded, you'll get some benfits from using an AFC. I'm still fairly new to the Maxima's, but can the Maxima factory PCM handle that much mapping? I know on my GTP I had to go to a different PCM/DHP to handle the mapping.

 

What do you mean? You don't modify the factory ECU fuel maps at all, the AFCs just modify the MAF signal to alter fuel.

In any case, the original post hasn't been updated to reflect the benefits of engine braking on decel.

 

Nice too see someone else from Finland here too!

I must say that I dislike the fact that driving schools always seem to tell you to shift through the entire set of gears on every damn corner. This will cause excessive wear on the transmission and when I got my license my parents cars did not even have fuel injection.
If you are traveling at a suitable speed and see the lights turn red at a relatively long distance it is probably good as you car will consume 0liters/100km while you slow down. (I try to shift to 2nd gear on my automatic sometimes) When just driving downhill I think neutral is the way to go. If you coast in highest gear your modern car will consume 0liters/hour in neutral less than 1liter/hour but it will not decelerate from engine friction. I think it is obvious that 700rpm is better than 2500rpm if you don't want to stop.

I agree with antti but hate when people who don't know anything about physics (like driving school teachers in Finland) exaggerate the benefits of engine braking.

 

Sounds like you've never faded your brakes to the point of uselessness.

There are a number of safety aspects associated with the use of engine braking on long or steep descents (never mind the legal one involving the posted speed limit - claiming that you were seeking improved fuel economy isn't likely to get you anywhere with the traffic court judge).

One is that you maintain a greater margin against encountering fade, since heat that is rejected into compression of the engine intake air is heat that does not end up in the rotors and pads (it's by far engine compression that provides the braking effect, with not very much due to engine friction).

Two is that the driver in the vehicle following you does not get caught off guard by any sudden increase in your braking. Brake lights only warn that some level of braking is occurring, not how severe that it is, and there is a definite time lag between the gap between two vehicles closing up and the following driver reacting to it at all.

You should never give up all control over any aspect of vehicle behavior while the vehicle is in motion. Coasting in neutral down hills leaves your speed at the mercy of the slope, and is generally comparable to driving with no hands on the steering wheel. You give up some flexibility in the manner with which you deal with unexpected situations by not having the immediate ability to accelerate at your disposal. People tend to get clumsy or panicky under stressful conditions, and it cannot be guaranteed that any given individual will engage an appropriate gear when he has only time enough for one chance to get it right.

Like many other "hypermiling" tricks, this one does not look at the whole driving picture. And before making sweeping statements concerning the relative efficiency merits of 700 rpm vs 2500, one really needs to have in-depth knowledge of the fuel cut on decel strategy that is programmed into the PCM.


Norm

 

Thank you all for the info. I find it very helpfull!

 

That is good info. Some of the points have such small impacts that they shouldn't be listed, but a combination of all of them will really make a difference.

The most important of the elements are:

-keep your right foot off the pedal as much as possible

-avoid idling (BIG TIME)

-proper tire inflation

-reduce weight..those tools, spare car parts, random other crap in the car that equates to excess weight is bad.

-on the hwy..cruising at 67 or 68 instead of 75 will make a huge difference in your mpg. If my max averages 26 at 75, it will average 31 at 67. It is that big.

Those are the main points imo.

 

Good for you Potatoman!!! Excellent info with a purpose. Wish more of us would post like you. Thank you.

 

I'll have to try these....especially getting rid of some of the junk in our trunk!

 

I don't agree with your alternator comment. The only thing that the alternator does is spin a magnet around ferric metals to create electricity. The harder it is to spin the magnet, the more load the engine takes. The more current is coming out of the battery, the more load the battery takes. An alternator is a type of generator, it is an output device, a reverse electric motor. It has no direct effect on the motor.

 

I'm not sure who or specifically what you are commenting against, and it isn't clear what you're trying to say (a quote or post reference would have been nice).

But since you cannot create additional electrical output without providing additional mechanical input power from the engine, any increase in the electrical output is directly tied to an increase in the total mechanical power that must be provided by the engine, which in turn comes from additional fuel usage. It isn't a huge number of HP worth, but it's there all the same. You might consider the use of whatever device causes the alternator to provide greater output an indirect cause of additional fuel consumption, but that's really just an argument over semantics.


Norm

 

I was commenting on the original post. He said it was an argumentive statement.

From my understanding of a generating electricity using magnets and the alternator, the alternator gives an electricity output through the turning of the magnet, which is is tied to the pulley of the engine. The output electricity is a function of the engine speed. (With the 3-phase alternator, this isn't as simple as a generator) In order to keep up with "demand," that means the alternator has a feedback device, an electrical system that tells it how much it should output. I didn't see such a device on an alternator. The parts were all mechanical. The load, as with all electrical systems, are judged by the current it draws. But a magnet spinning, is like a transformer, Power in = Power out, and Power out does not effect power in without the feedback device.

 

Nice write-up. I would just add drafting/slipstreaming on the highway. This reduces wind resistance and also reduces the amount of energy used to maintain a constant speed. Ever have cruise control on at 80mph and a car doing 85-90 steady gets in front of you and suddenly your car increases speed, the ECU lets off the throttle, sometimes requiring you to brake as well?

Wouldn't recommend doing it behind semi-trucks; while their wake does provide excellent wind deflection, they kick up rocks on the highway that can chip your paint and even your windshield...

To add to that mod list, lightened flywheel and underdrive crank pulley can improve gas mileage as well. Less rotational mass means less work for the motor, more HP to the wheels and a lighter load on the motor at highway speeds. Not to mention passing cars quicker

If your really hard core about it there's that 6spd tranny swap.......

 

I just drove 75 highway miles and only used 1/8 of a tank tonight. In 6th gear with cruise control set at 60mph the whole time, the display said 31-33mpg... which is equivalent to 28-30 actual mpg. Not bad for a 255hp 3.5 Liter V6. Wimpy 4 cylinder cars brag about getting 30mpg on the highway, and our cars can hang right there with them... and still smoke them in a race if necessary! I never use cruise control or drive at that speed, but I just wanted to test it out to see how much gas I would save by slowing down and throwing it on cruise control, and wow... the difference is amazing. I'm confident I could get well over 400 miles out of that tank before the gas light came on. One thing's for sure, I'll find out next time I go on a long trip!

 

I did it! 454 miles on a tank!
Went on a trip to see a friend this weekend. I started with 110 on the tripmeter which was half highway/half city. Then drove until 454 before i was on E and put gas in. However, i wasnt near a shell so i only put in 4.018 gallons from a BP (93 octane). Then I drove until 490 when I got home and put in another 12.858 gallons from a shell (93 again). So 490mi/16.88gal = 29mpg which isnt bad

Breakdown:
Filled up tank
110 half city/half highway
drove til 454 (highway, 75mph avg) and needle was starting to fall below E
put in 4 gal
drove til 490mi
put in 12.8 gal to top it off.

Woulda been nice to hit 30mpg...my car does need to be aligned too.

 

Sorry, but as far as this discussion is concerned it does not matter what happens electrically inside the alternator. It is simply a "black box" that transforms mechanical power into electrical power, and the details are irrelevant here. More electrical power out = more mechanical power in (assuming that the belt drive can transmit that much power, which was not always the case in older cars with V-belt drives and poor control of belt tensioning). It really is as simple as that.

If you know a little something about EFI, you might also know about "stall-saver" logic that raises RPM under conditions of heavy electrical demand (turn on the seat heater, A/C, and rear window defog all at once, then shut them all off and pay attention to the tach). If you ever played with a field phone generator you'd know firsthand that it takes mechanical effort to make electrical power.


Norm

 

My '98 and '97 had better mpg than the '93

 

I am getting about 25.9 according to the reading on the dash... is that reading accurate?

 

that's one of the first things i learned on this forum... the 5th gen for sure, not sure about the others, display 3-4 mpg OVER what u actually get...

so if you are getting 25.9, sorry bud, you're getting closer to 22mpg

tested it my self, filling up, reseting trip, etc... and it's true.

 

Increasing my MPG from 21 or so to 24-25 (yeah, I drive in the city a lot) has been pretty easy with getting one of those engine cleaner jobs at Jiffy Lube and just making sure my tire pressure is good.

--Jed

 

Ok, I don't know if it was the headers, the intake spacers, timing advance, or straight through intake tube that I put on since this post, but my gas mileage has increased DRAMATICALLY with these mods. I took the same drive today (haven't had an oil change or changed tire pressure) at the same speed on cruise, and the display this time wavered between 37 and 39mpg, which pegs actual mileage around 34-36 mpg. That's a good 6 mile per gallon increase with these mods. I never thought this car was even capable of that kind of mileage! Just imagine when I get tuned and put in new spark plugs. Performance mods to increase gas mileage, FTW

 

whoa, good for u man, i've seen those #'s ( 35/36mpg) for brief periods onthe highway doing around 60mph, but that's sweet all those mods are paying dividens.

if i can ask though, what did those part cost u ? ballpark figure is goodenough.

 

they werent nearly cheap enough for the increase in gas mileage to justify the cost.. lol.. just an added benefit to the performance gains.. headers were $700 something (on sale).. spacers were like $225 (birthday gift).. timing advance was $30.. intake tube and couplers were like $20 from autozone

 

are these numbers consistant or a one time thing?

 

oh yeah, i was thinking performance first, but it's nice to get more power and a more efficient car !

beyond FEELING a difference in how your engine reacts, have u done a track run/timed any 0 -60?

Mods seem fun but not srue how much i'll do to my car wtih 90 k miles on it. not sure worth the invest ment

 

i've only measured my mpg on the highway that one time since having these mods.. but believe me, i will be doing it again... while also doing a true mpg calculation my dividing miles driven by gallons of gas used.. but judging from the car's computer, it looks promising

 

no, i haven't been to the track with these mods yet.. but 90k, are you kidding me!? people buy cars at 100k and start modding.. lol.. well i guess it all depends on how long you plan on keeping the car, how much you wanna spend on mods, and how much importance you place upon improving performance

 

yeah , it's my first used car, but i'm really hoping to get my Max to at least 150K mileage before any major problems/repairs come into play, and from what i read Nissans can hang with honda/toyota in durability.

but that's a good pt. about how long do u plan to have the car, if i do get some engine upgrades, i might as well get it sooner rather than later so i can enjoy em while they last

 

definitely.. the whole point of mods is to make your car more enjoyable to drive... a simple intake, y-pipe, or exhaust will make your car noticeably faster.. a rear sway bar, shocks/struts and/or lowering springs will make your car handle alot better.. aggressive brake pads will make it stop a whole lot better.. and many of those things contribute to safety too as well as enjoyment.. the world of automobile modification is a beautiful place

 

i have a 96 maxima with a warpspeed y, magnaflow cat, pacesetter cat back. i dont drive aggresively (rpm usually under or around 2k, rarely go over 2500). keep all tires at 40psi COLD, windows down always (don't use my a/c), drive 60-65 on the highway. and i'm averaging about 27mpg right now. i would say about 60% highway 40% city. i am pretty happy with that but what i think really helps is no a/c and accelerate slowly from a stop. im still looking for some mods to increase mpg though!

 

Bumping two year old thread ftl.

No kind of "mod" will increase gas mileage, with maybe the exception of a turbocharger. But even then, the amount of driving you'll have to do in order to offset the cost of turbocharging is insane.

 

There is............ that idea of using low friction oil like 5W-20 and that thing which I think was busted on Mythbusters about adding acetone. Also keeping tires harder than the people at those **** conventions is a pretty but tiny boost. Also keeping your engine clean is a goody.

But to be honest although the newer cars these days use that wimpy baby oil 5W-20, I personally prefer the thicker stuff. My car is a man, and we... I mean it... uses the thick stuff. And plus seeing how most of our cars are old I think using something that thin will cause a lot of engine noise.

But yet again some people say it will kept your MPG figures happy, some will say its bad. I will just use what works and when I have money to buy another car if something goes a bit wrong. I will experiment with other... lubricants.

 

how has my mods NOT improved my mpg. before i was averaging about 20mpg a tank. then put that **** in, now im averaging 27-30mpg easy which is kind of ridiculous for a 96 max i think. same driving styles, same habits, same everything... actually i drive a little more aggressive my mods in and still get 27-30. so please tell me how those mods have not increased the mpg???????

 

didn't you just get these "mods" on about 20 days ago (one or two tanks of gas)... how can you accurataly say that you are getting 7-10 more miles per gallon just by changing the exhaust and driving more aggressive. not possible imo

 

Coast when you can...keep tires inflated...use 93 octane.

 

i dont think i said i got them 20 days ago but whatever. and how is that not possible. i get terrible gas mileage before ypipe,cat,exhaust. and am now getting close to 30mpg. i dont care if you think its not possible. i am getting great gas mileage in a big v6 sedan thats all im concerned with.

 

^ this is you 22 days ago... on another thread, remember?

"got my system installed today and holy **** it's great. very noticeable difference in power and overall feel in the car.. the sound is amazing imo. its nice and deep, not too loud also. im guessing this should increase my mpg?? but ill start keeping track of it"

 

oh i dont even remember but dude your a *****. like you're the typical internet know it all. i am getting 28-30 mpg in my car and your hatin. i still dont know how 21 days or whatever would make a difference. your saying the mpg will improve for about a month then go back down????? thats bull****. get some puss then get at me.

 

and i'm on my 4th tank and still averaging 28.4mpg

 

That's about average for these cars. Maybe your pre-cats were raped.