bvtran

iTrader: (3)

FYI: While driving 2500miles cross country from SC to CA back to school. I took a gas survey using the A/T switch right below the stereo unit and this is what I've discovered:

On "Performance" mode:
I've filled an avg ~11.5gallons tank of 89 octanes for every 240miles.

On "Comfort" mode:
I've filled an avg ~11.5gallons tank of 88 octanes for every 300miles.
I've filled an avg ~11.5gallons tank of 89 octanes for every 310miles.
I've filled an avg ~11.5gallons tank of 92 octanes for every 350miles.

And of course, this is all HW miles and running on OD. My car was loaded of heavy stuffs too. There was only 1/10" in the back fender wheel gap. I had lowered my BTD timing to around ~7degrees knowing that once I've passed the Mississippi river, finding high octane fuel is quite hard. I drove on the avg of 88-95Mph. Yeah, I paid around $440 for the damn gas. Pricey, man!!!!!

Anyway, I am just curious if any of you wanted to know the benefits of comfort mode. It wasn't as powerful as performance mode while ramping up hills. But who cares, you're saving moneys.

So what do you guys think? Any other experiences you've discovered for improving fuel economy?

red-line-racer

iTrader: (1)

i dont feel anything when it in confort mode or when it in power i dont know about the gas but i think the button it a bunch of b.s

Wiking

- button must (!?) have been key salespoint in 90's
- gas price bs: your gas price is dirt cheap. 360mil EU ppl pay 3x...
- seek forum for mpg dis cussions: the fillup measurements are not a valid way, error margin is enormous, sorry

MrSector9

iTrader: (4)

Throttle position overrides where the button is,next time you get in leve it on normal and put it to the floor an the "P" light will light up.

I leave mine on normal all the time

vansskaterfreek

iTrader: (14)

"power mode" tells the tranny basically when to shift...which is higher RPM's, so of course you will get worse gas mileage.

91WBSE

iTrader: (1)

"Power" mode on the switch works only under part throttle situations. You can see that the transmission holds gears longer, shifting at higher rpm. If you have the switch in either of the two other positions(Normal & Comfort) and you were to quickly hit the gas pedal or floor it, the trans automatically goes into Power mode. With the switch in the middle position the car will normally drive in the Comfort mode.

Alex_V

How many tanks of each did you use? 1 isnt very accurate. 8-10 is alot more accurate.

~Alex

aw89maxSE

iTrader: (3)

That's good information. Seems as higher gas = more miles, but it seems to me that it evens out with the higher the gas, the more expensive it but then you get more miles

internetautomar

iTrader: (30)

1. comfort will increase your mileage as long as you can keep from flooring it all the time
2. run lighter /narrower wheels and tires will also increase mileage
3. lighter weight will also increase your mileage (get all the excess **** out of the trunk)

falseicon

iTrader: (2)

I just did a cross country (CO to VT) last month. Same thing, loaded car, doing 85, etc. I found that my mpg with higher octane seemed at least slightly noticeable, though oddly enough the 8 hour stint at night in the considerably cooler temps seemed to further knock up the mpg. I reasoned that there were less cars on the road (less speed change) and it was through Iowa (not so many hills), but curious if ambient temp could actually effect effiency, don't see how, though it seemed very obvious when I got an extra 60 miles between 12 gallon fill-ups that night. Coulda just been sleep deprivation though and a fickle gauge.

LvR

Ignition and fuel management is highly dependent on temp - Nissan (or the person that developed and calibrated the sensors involved in the measurement of all parameters influencing the ECU/TCU) would have us believe that they have done an absolute perfect job ..................

Sensors etc while being remarkably robust in the application on a typical vehicle do drift with age, use, etc etc so its highly likely that temp will influence the fuel economy of a vehicle.

My first reaction would always be to always drive in cooler air if at all possible, but because the calibration and current state of drift of the sensors on the specific vehicle may be such that higher temps result in more accurate fuel management strategies, then its going to be a highly individualized experience as to under what conditions you get better mileage.

DaWifey's90

iTrader: (3)

with regards to temp...also don't forget that colder ambient temps mean cooler air charger which means more dense air = more oxygen per unit volume of air = more power

so i take it no one has come up with a feasible substitute for gas yet.
i read some of the E85 posts and can appreciate the logic in either direction...anyone know where to get the stuff in jersey? i'd be up for starting a long term real life application study.

Wiking

- absolutely (oh eh)
- these drifting & intermittent problems with sensors & wiring have the possibility to affect mpg most. The hollywood tranny sw doest not: just keep rpm down
- Why is it so horribly difficult to ppl to get the "tank full" measurement is bs? Cannot understand... Please. Buy precision fuel measurement equipment before posting, feelings are not enough. One of the issues --->gvmt says 16% times u fill u tank, u dont get what u pay for.
- then rusty jammed hanbrake cable ruins all u nice excel tables

zillion threads on this issue, seek out, heres two latest:
http://forums.maxima.org/showthread.php?t=422161
http://forums.maxima.org/showthread.php?t=425481

LvR

Which, at part throttle that you usually cruise at, if your air volume measurement via AFM is correct, means nothing at all even if the air is colder.................

No use having "more power" if you don't use it

Ps : Long time no see Wiking

DaWifey's90

iTrader: (3)

but the afm only measures flow which is extrapolated to volume...density is not measured at the AFM so there can be a "cold air" effect. or perhaps the entire cold air induction industry is just a scam. then there's the temp sensor which i believe only affects timing and does not contribute to any density calculations - i think

LvR

Flow is by definition volume per unit time .............. no? ...............

The AFM (hot wire) according to the FSM does compensate for temp and therefore density (not by a temp measurement as such, but by means of its effect on the hot-wire transfer measurement characteristic)

I am however still convinced there is a "cold-air effect" ................ but depending on the AFM and the calibration and current status, it may be either positive or negative - thats why I said initially its going to be an extremely individual experience as to what you see economy wise with colder air.

Wiking

Yes, where have u bin? Der other side of erden?

Pls. Tell me if/when u find a source for those 5cent resistors in the empty MAF box, id' like to build my own. And/or schema...

Abs right what u say about airflow. And its just one of hundreds variables which are individually going up or down, simultaneously.

eric93SE

iTrader: (1)

newer max's have an ambient temp sensor, to more acuratley determine A/F mix.

LvR

I doubt that a dedicated induction air temp measurement would necessarily imply an improvement in accuracy.

Its what is getting done to the AFM's output (volume less the temp compensation) that will determine if its going to improve.

What effectively is happening is that whereas the VG's AFM applies a temp factor compensation via the hotwire transfer characteristic in mechanical terms which then gets fed to the ECU, the later vehicles with a dedicated AF temp sensor applies the same compensation inside the ECU to the raw uncompensated AFM signal - via mathematics deduced from a model.

Both the VGs AFM and any other AFM in combination with a dedicated induction air temp measurement in my opinion is equally capable of applying the exact same compensation to the same extent - whether the one is going to be more accurate is going to be a huge factor of the successful integration of a very complex mathematical formula for temp compensation in the ECU .............

Sure in theory with PROMs, cpus etc in the ECU things can in theory be made to be very complex to the n-th degree ............

In my experience that cost a heck of a lot of money ............. guess I am not so convinced that a more complex way of AFM is necessarily guaranteeing the best.

eric93SE

iTrader: (1)

Well I know for a fact that I get some really poor fuel economy in the winter. Sure there may be some factors, like a snow covered ground, but over all the economy is lessened. The hot wire in the MAFS is used to measure the air flow accross it, via a temperature drop (and read as a voltage accross the adjacent resistor). Now that temp drop by air flow (volume) is also affected by the ambient temperature (which is not being measure), so the sensor thinks its getting more air volume (when its really not), hence poor fuel economy in the winter (or even year round for that matter since temp varies so dramatically in some areas).

eric93SE

iTrader: (1)

One way to increase fuel economy would be to install a high energy ignition system. I'm pretty sure non of us on the org determined the ignition voltage on the VE. VG people can upgrade to an MSD ignition.

Actually a simple experiment would be to see how far the spark can jump in air. All you would need is an adjustable gap. There is a simple physics formula to apply.

LvR

In the strictest sense of looking at only the hot-wire you are absolutely correct.

There are however 2 ways of using a hot-wire to measure flow - one is the simple way where you measure only the current flowing through the hot-wire while it is sitting in the airflow it's supposed to be measuring - with this design you are indeed bound to have ambient temp influencing the flow measurements to a larger extent. (the air density is however still a function of temp and hence the volume too, so to a large extent the ambiant air temp is already compensated for because of that)

There is also a second and more commonly used method where the hot-film only forms part of a resistance bridge - one of the bridge's elements is replaced with a temp sensitive device (thermistor) to compensate for ambient temps and the signal from the bridge is then used rather than the signal from the hot-wire alone.

Now I have yet to see any diagrams of the actual MAF design on a VG to support my assertions, but am willing to bet that its design is based on the second bridge method (some experience as EE in this field)

Your poor economy in winter is most likely as a result of the A/F system running in open-loop mode for much longer than during summer - IE - rich/overly rich because of low engine temps for much longer, especially if you are driving only short distances

eric93SE

iTrader: (1)

Okay, I see what your saying, this is most likely the method being used, since there is a thin film resistor in the air flow. I forgot that there would be a temperature dependence on the current passing through the thin film resistor. Anyways the system was further improved on in the following maxima models, where they now use an ambient temp sensor in the air flow.

Alex_V

Im pretty sure our max's cant run on E85 (if it they do it wouldnt be worth it in any way). My s10 is a 95 but the 97 or 98 and newer with the Flexible Fuel Vehical (FFV) option can run on it. It actually uses more fuel, and has a completely diffrent map, but it uses more of it but its much cheaper. Some cars actually do get more mpg but the 2.2L 4cyl thats in the s10 sux completely.

Sabb has a new turbo car that nearly doubles the psi (its something like 14psi) and produces a big increse in tourqe while mantaining the same mpg when running on E85. Or something like that any way, I saw an add for it in a mag and I donno where it is. Id like to find out more about it but I dont have time.

I think for use to use it we'd have to change the fuel pump (because of seals and better performance, possibly) all the seals and hoses and start a fuel map from scratch, along with diffrent timing. I have no idea on power but it should be similar but with less then half the gas bill we have now ><

any way a little food for thought.

~Alex

DaWifey's90

iTrader: (3)

uhhmmmm...no...flow defines the speed of motion...say for example the speed of water in a stream...it bears no account at all to the depth and width of that stream.

seeing as to how the dimensions of our "stream" (the air induction manifolds) are fixed, this is how the afm - which detects flow - works with the engine's computer to extrapolate volume.

fuel economy will suffer in the winter because there is only so cold you can go before you fall out of the oprimal operating range of an engine. then you start affecting things like fuel atomization, oil viscosity, parasitic heat loss and so on

DaWifey's90

iTrader: (3)

how bout a different mix like E50 or so. i've also seen the results you've described in other cars which got a boost of power but lost some mileage. do you think by using a greater percentage of gasoline, one can keep it's lubricating qualities while still benefiting from the ethanol? what about ETBE?

eric93SE

iTrader: (1)

I'm pretty sure nissan says not to use it AT ALL (its in the little maintanance/info book). But we may be able to get away with it for a while, until things start falling apart.

internetautomar

iTrader: (30)

if you are really serious about using less fuel then get thinner tires, lighter wheels, reduce the cars weight (throw out the amps and subs from the trunk)
wider tires consume more fuel
as do larger/heavier rims.

DaWifey's90

iTrader: (3)

i hear what your saying but how much do you really think that stuff helps? my car is like 98% stock so i don't have much to throw out. it seems like the mods you're talking about would have the same effect as would giving one less person a ride in your car. i don't see the current crisis as a fuel efficiency matter as much as it is an economy of fuel matter. the cost per BTU breakdown of traditional gasoline just doesn't seem to add up when compared to swapping in some neoprene lines and a plastic tank.

Wiking

Helps 0,1% or more. Invest, an never get money bck... ppl who own maxima, complain seriously about mpg, are hypocrites: truly worried dont speak but go an buy diesel rabbit.

Just do the suggested maintenance on max, and be happy: your gas is dirt cheap compared to what most ppl on earth pay.

internetautomar

iTrader: (30)

not anymore it ain't
and within 2 years we'll be up to $5 a gallon. (same as the rest of the world)
we're currently at $3.50+ a gallon here in chi-town

eric93SE

iTrader: (1)

Well for all of you out there, driving around with your ORIGINAL oxygen sensor, REPLACE IT, and enjoy a 10-15% gas savings

internetautomar

iTrader: (30)

I also forgot to mention to make sure your brakes are functioning correctly as well as making sure your exhaust doesn't leak.

LvR

..............and if you want to save even more money, remove it completely and run a South African ECU - we don't use those finicky O2 sensors at all.

Wiking

sigh. Now 7.5$ per gallon. U dont know the tax ratchet system our criminals have installed.


LvR ...run a South African ECU - we don't use those finicky O2 sensors at all.
- me wants schematics

LvR

Me too ............

You offering?

I have asked allover and pleaded and offered money for a schematic/diagram - all to no avail.

Fact is they have tuned the ECU for local conditions and our cars dont have O2 sensors fitted at all - suspect the Australian guys may be in the same situation, but dont know for sure.

Anybody with details ? ....................

Wiking

I could send good schematics for a sauna...? Maybe tent sauna u may carry in max?

LvR

In our South African climate with the Midnite Blue color of my Max, the whole VG is a sauna by design .............. just turn off the AC for 2 minutes and you sweating like a pig!

nForce

iTrader: (5)

I get about 285 to 325 miles on one tank of gas. Thats with the power switch always on and 89 octane gas. I will have to try Comfort more I just like the power you get off the power switch the tanny shifts so much smoother.

Alex_V

Unless your computer isnt working right the shift speed and smoothness should be the same in any of the 3 positions. Power just means it shifts latter. My power switch is my clutch foot

~Alex