24's my minimum mang.... usually i get 28mpg, and have gotten 29 once. i used to get 15-20 when my o2 wasn't working.

 

Maybe I'll see about having it looked at - I would have though my car would either smell worse or run worse or the check engine light would be on if an O2 failed on me but yeah what do I know. Unfortunately I don't have a volt meter or understand anything electronic so I'm going to have to hope one of the Honda fools in my machining class can test it this month.

 

maybe some smells, probably no CEL tho. check the gen maintenence sticky to see how to check codes. a 33 is O2 sensor. my car didn't smell too bad really.. the main bad smell was from my torn vent hose but i fixed that a while back.

 

Here is some nice info on the basic operation and signals generated by a working O2

Unplugging the O2 as alternative? - Its going to be a function of what the electronics look like on that input inside the ECU ............... IMO its not that simple, but could be - experimentation will tell

 

The O2 sensor is like a oscillator already, switching between two states on small oxygen content variations. Still I guess ECU O2 input checks the average voltage and adjusts accordingly; should have the component specs.

The ECU EPROM threads might be good. And cheap. But surely time consuming... I have to dig my prommer and see if it still works ... DOS. Otherwise no dice buying expensive equipment.

Pls ppl , try to learn to READ: put your own O2 crap sensor problems on your own thread.

This is a tech thread on 14.7

Please Mr. Greeny?

 

My friend - if you are talking to me, I would suggest you first learn to speak English properly and to then make up a decent thread title excluding absolutely everything that in your opinion would not be relevant.

Note that I am not saying the O2 is the answer to your particular question, but it definitely is part of a means of tuning for running with something different than 14.7 .................... you may want the answers to all your technical questions to be given to you in short sentences, but there are few if anybody here that have already conducted the experiments you need answers for.

So iso *****ing and constantly asking questions only, why don't you do more yourself and start talking measured facts and parameters on a 3rd gen in particular iso of forever telling people they need to have a different mindset?.

You are the one wanting answers to arbitrary questions, but cannot or will not interact sensibly with your peers

 

No.

...the issue was?

 

Sorry about the 'rich' statement.. I just pointed out the obvious for the less astute..

My point was less fuel = less power.

Also, you are incorrect about the O2 sensor, the ECU assumes 14.7:1 (don't know where you got 14.7:100??) for calculating fuel from AFM readings. The O2 sensor overrides this by measuring the oxygen content of the exhaust gasses; it has no preset mixture figure.

Removing the heater wire from the O2 sensor will simply mean it will take longer to reach operating temperature (some cars don't have 'heated' O2 sensors), meaning your car will run on the ECU's 14.7:1 ratio for longer!!

I am still yet to see anyone explain why they believe burning fuel with an excess of air/oxygen will produce more power than burning with the correct amount of air/oxygen?

 

If you wanted to do this easily without opening the ecu ( which by the way would allow you to lean out higher load and rpm ranges slightly for even more fuel savings.) You could always get a innovate lc-1 wideband unit. It has a simulated narrowband with an adjustable switching point so you can trick your ecu.

 

ecu goes to open loop and stops reading the 02 sensor over 50% throttle so you have to find a way to feed it less fuel or make it read less air while it's reading the non-adjusting high-load maps. a slight resistor on the MAF wiring maybe? just so it thinks it's got less air and therefore uses less fuel, is therefore one suggestion in the el-cheapo category.

 

Well with just a "resistor mod", you will end up changing the load the ecu calculates and will effect the fuel map as well as the timing map and other related maps such as knock control.That, depending on the value of the resistor may not be a good move.

 

well if nobody tries it we'll never know. small steps are the way to go... 1 or 2 % change at a time, to see how it works out.

but it all comes down to 'you get what you pay for'... the more time and money you invest in tuning, the better your results will be.

 

Yes - that is the basic mixture map Hmmmmmmmmm - very difficult to agree with that one.

The O2 sensor generates a voltage signal and the ECU may or may not use it to change the volume of fuel injected from the "ideal pre-programmed 14.7 map value" depending on TPS/load/engine temp etc as Caped already mentioned

Think you missed the boat there completely.

If the ECU has determined that the environmental operating conditions are suitable to start using the O2 (expecting to find the O2 to supply real usable readings because of it being expected to be at normal op temp) and you have removed the O2 heater, the O2 sensor will simply output a very low voltage signal (even if the current mixture was managed to be at 14.7 because of the ECU's map) - that low voltage signal if and when used by the ECU will cause the ECU to richen the mixture because it is being incorrectly told by the O2 that there is a lean mixture condition detected in the exhaust - iow the ECU will continue to richen the mixture to reach a "O2 measured and agreed " 14.7 signal point negating the whole point of this thread until such a time as the O2 has reached normal operating temp

The theory wrt the title of the thread is that the power extracted from a given amount of fuel curve, when plotted against mixture quality, reaches a point where the curve shows a fairly broad and flat section around 14.7. That "flat" section will allow you to move the mixture around a little with very little power loss from absolute optimum (and hopefully not detectable - you can move it either richer or leaner). The theory is that if you move it just a little leaner (even though you may be required to give it a little more throttle to keep the exact same amount of power as at 14.7) you may end up effectively using less fuel.

This theory can be very easily proven to work (and work well) on static load engines with manual operator mixture control abilities such as small aircraft engines (see my earlier post on this aspect).

The problem comes when you start varying the load such as a typical motor vehicle operation would dictate. The complexity and interaction of all the different engine design parameters makes it virtually impossible to define a "simple" employable lean running strategy on the 3rd gen motor with its rudimentary ECU and limited number of sensors. Sure you should be able to "force" the motor to run at something other than 14.7 under certain conditions, but as I said in my first post in this thread already, its going to be a crap-shoot method if no detail measurements and engineering design parameters are known ................... apart from that (as I also said already), your results/savings achieved will be extremely engine/driver/conditions specific

 

Thanks for the Well constructed reply LvR!!
What you said about the O2 sensors function in mixture control, is basically what I meant, the ECU doesn't have to use the O2 sensor, but the O2 sensor itself does not cause the ECU to run at the 14.7:1 ratio mentioned, in fact it just measures the O2 content of the exhaust and allows the ECU to adjust the mixture to suit.

I also agree with the O2 sensor heater, by disconnecting it, you aren't going to make the engine run leaner, once the O2 sensor heats up via exhaust gasses, it will still work the same.

As for running slightly lean, does this mean you are effectivly extracting more power for the fuel you are using (assuming static load/rpm), or are you just adding more air and using the same amount of fuel?

 

Right

Right again

Nope - in the example I posted about on the airplane motor mixture control tweaking, the amount of air consumed is constant (same engine speed and throttle position) but you tweak a mixture control **** affecting eg a ventury/jet size to allow more fuel into the air stream.

Let me try this way:

There is x amount of latent energy contained in any given amount and specific type of fuel - you cannot extract more energy than that no matter what you do or what methods you employ.

If you decide to use an internal combustion engine to make that energy available at the wheels, then you are partially (mostly) governed by the well-known Carnot cycle, partially by the friction losses in the engine etc etc, and a horde of other factors that I cannot even think of as a non-expert on the subject's finer details.

On a specific motor, under a specific load and at a specific rotational speed, you can play off the various parameters involved against each other and arrive at a point where you may be able to optimize the fuel ratio (ito the thread title - leaner) while eg retarding the timing at the same time, and by doing so arrive at an overall operating point where you get close to max or even max energy extraction from the amount of fuel injected.

............... but once again as per my first post, this will be so involved and engine specific for Joe Bloggs, that to do it right, it will simply not make financial sense - one can however take the view that Wiking has and say "but I am willing to experiment without all the knowledge and background info" - nothing wrong with that at all if you have the time, money, ability yourself because whatever you do manage to find, is just about guaranteed not to be applicable to any and all engines - not even from the same manufacturer and model in the absence of a controlled environment.

Apart from all of this:

The reality is that you may very well find (if you are really serious enough) that running at eg 11.8 under certain conditions will give you a bigger fuel saving gain than simply trying to go lean by default

 

Thank you once again for the well constructed reply.

Although I haven't had any experience with engines in a static load situation, like aircraft or Genset engines, I do understand what you are saying.
And I must totally agree that trying to replicate these tweaks on an engine in a dynamic load/rpm situation is probably not going to yield any benefit, and may very well cause damage if it isn't done very carefully.

I can probably say that Nissan would have spent $$ and a lot of time to give the best fuel economy while maintaining a 'one size fits all', as well as an economic approach to the ECU/sensor setup on the VG30E. And without spending $$ and a lot more time, we probably aren't going to see much improvement by messing with the setup to make it run leaner.

 

Yep - as an example take the situation where people are forever trying to run as much static timing as possible and then posting about it here on the forum.

For the life of me my motor simply refuses to run anything better than 16 without ping under load when hot, yet I see some people reporting as high as 20+............

Perhaps I am overly sensitive to these things but I find that the motor produces a lot more heat (quicker up to temp and faster/more often radiator fan come-on for the same driving conditions) ............... but I have yet to see any of the guys running those huge static timings mention this on their setups - to me basically indicating the typical "crap-shoot" approach to these endeavors .............

I would put this mixture thing in the exactly the same category, and expect the same individualized results

 

I know, it's an old thread but interesting nonetheless. I think, this says it all:

http://en.wikipedia.org/wiki/Lean_burn

It turns out despite all the efforts the gains are fairly small and assume that we stop pushing that pedal to the floor to begin with. This would save fuel with the stock setup too but oh well .

 

rather than spending time and money screwing around with tuning the factory ECU itself, pick up a Greddy emanage or VAFC/SAFC and plug it in and go. Find yourself a QUALITY dyno tuning shop and use their wideband O2 sensor and stick the car on a dyno varying the load and speed..

The better option would be a Nistune, since you can fiddle with all the fuel maps and ignition timing and whatnot. it's probably cheaper at the end of the day with the nistune setup..

but yeah, as has been mentioned, there's lots of efficiency gains possible by leaning out the fuel mixture. (I know a guy with a built turbo VG30E that is getting about 34mpg on the highway, while making 350+whp when he puts his foot in it! ) watch out on the facotry cast pistons though. they'll die quicker than good quality aftermarket pistons due to the higher heat of running it leaner.

 

in my way, i dont think so that running your engine leaner is a good idea....it kills ur engine slowly slowly.....running rich is ok but then ur fuel economy goes BAD...i think we should stick with factory mixer or let the ECU choose wats the best for the car unless we r doing some big mode on the car like turbo and stuff.....

 

a properly built engine running leaner during light loads won't hurt the engine at all- only issue is it might increase emissions at the expense of more fuel economy.

when it hurts the engine is when you run it lean on a heavy load. That's when the heat starts to get nasty.

 

but if you've got Nistune then you have almighty control of all of that, amirite?

 

So in this article there is a paragraph...

So if you do get this appropriate mixture you could go to a inspection station to figure out how to get emmisions passable without a CAT.... less restriction better flow more HP.

 

Ding ding ding! A winner is you!

 

i can has cookie?

the thing that always bugged me about the stock ECU is that if I short-shift and use the throttle more, sometimes the ECU will snap to openloop which defeats the purpose of short-shifting to reduce pumping losses.. but i guess a nistuned ECU might still go open-loop but the default maps therein can be set leaner anyways. I guess I don't have a right to complain since i don't use 93 octane anyways...

 

Ummm no.. try again. it's saying the cat requires a certain amount of unburned fuel to operate and reduce the pollutants. running without a cat makes the problems even worse.

as I mentioned above, running the engine lean increases combustion temps to the point where NOx pollutants increase and the cat doesn't really reduce NOx as well as it does hydrocarbons.

 

most states require a Cat to be installed. in NC if you're past the point of emissions testing you STILL have to have a cat... even if you are safety-only.

 

Ahhh, i read it wrong, i thought that lean mixtures would not allow a CAT to function properly....

 

here, they will send u home without even checking ur air care if ur muffler is noisy, so whoever have after market muffler ( like me ) have to re weld stock muffler every 1 year ( 2 year for 95 up ) for air care lol....

 

you mean they refuse to inspect your car because it's too loud? or because you've done something to your cat? matt's 89 has no cat on it (his schedule doesn't line up with the muffler shop's hours ftl) so he can't get it inspected but that's just cuz the PO sold the cat cuz the car wasn't running... he wasn't doing it for MPG gains or HP gains or anything

 

5 months ago my cat was in really bad condition plus i had a stock muffler on it...soo i hardly passed aircare....then i cut the whole exhaust pipe right after O2 sensor with cat and muffler in it....and installed the whole new pipe with no cat and resonator with high flow muffler on it......it sounds awsome plus i seen gain in hp and better fuel economy....specially i really gained high end with straight pipe......

and ya they dont pass air care here AT ALL if ur muffler is too loud or if u have no cat or ur car is showing check engine light.....i don have any problem with welding stock muffler and cat again for a day for air care cuz i have things available to me....i wouldnt do all these if i have to go to muffler shop to get done all these things......

 

so when you want to pass aircare (canadian emissions standards, i assume?) you have to put a cat back on don't you? otherwise your emissions are through the roof... i know canada is cold but you don't need to warm it up that fast

that trick wouldn't work so hot on an OBD2 car tho..... post-cat o2 sensor would be like "wtf mate"

 

ya....everything is through the roof if u don't have CAT,Gentle muffler, and if u have check Engine Light thats through the roof too even for that they have big sign outside '' People who have check engine light showing on their dash,They have to fix that then come back'' lol

thats why i like OBD1 less mess...they even connect computers to cars that r equipped with OBD2 so u dont really have a choice with OBD2s....with OBD1 they dont connect anything but emission testing devices....and as far i can think since they dont connect computers with OBD1 cars u can trick many things like my buddy's 3rd gen was showing check engine light so he jus pulled the bulb from the bak LOL......