I went to the dyno a while back and I noticed that I was running really rich(~11.5) up top. I finally got a fuel controller but I won't be able to get to a dyno for a while. So I was wondering if anybody could tell me from experience about how much percent I should take out to get to about 13:1.

 

i don't think its possible to just calculate it like that.

I would say, start at 5% leaner.

because on a single cam, 5% would bring you way up to like 14.

lots of factors. 11.5 is not that bad at all....

3-5% will be ok, as long as its 1.8 liter or more.

Jeff

 

just let it set at factory settings till you get the chance to tune it. this way you won't screw anything up.

 

Thanks,
Is there anyway I could check it with without a dyno? Something that I should be able to get at any auto parts store.

 

...you could use an OBD scan tool from your local autoparts store, or OBD software on a laptop... keeping in mind that it would be no more accurate that your primary O2 sensor... which would be ballpark if the sensor is up to snuff...

In short, you'd best be served by going somewhere that has a wideband o2... usually your local dyno post...

 

The ECU reads voltage from the O2 sensor, and AF monitors read that voltage and convert it to a ratio, right? Can the AF be monitored with a voltmeter? The only problem would be to know the equation for coverting the volt to the ratio.
Any thoughts or comments?

 

yea...but the stock O2 sensor isn't that accurate. You need to take readings from a wideband O2 sensor.

 

Any idea on the accuracy of the stock sensor and the wideband?

 

I don't have any hard numbers on the accuracy of a stock O2 vs a wideband but basically a stock O2's accuracy does not compare to the accuracy of a stock O2. Maybe someone else has some better information? But I would not try to adjust fuel based off of an A/F guage that reads from a stock O2 sensor.

 

The ECU uses the stock O2 sensor, does it use it for general adjustmenst in any way or does it actually adjusts to what the sensor puts out?

Don't think I am trying to question you, just trying to learn more.

 

From what I remember, the ecu adjusts fuel based on the O2 readings only during normal driving, ie not WOT. (I believe it reads maps for WOT and ignores the O2 readings.) As I understand it, the ecu constantly adjusts the fuel if the O2 reads rich or lean. That is why an A/F guage constantly oscillates from lean to rich during normal driving. The thing is the O2 can tell you if it is rich or lean but it isn't accurate in telling you how lean or rich it is. I believe that's the major short coming of the stock O2 when trying to tune with it.

 

are there any upgrades for the O2 sensors to get a better reading?

 

FJO enterprises makes a kit to measure AF but it costs about $700 here is their accuracy
- accuracy (standard deviation)

10:1 to 12:1 12:1 to 14:1 14:1 to 17:1 17:1 to 20:1
0.09 A/F Ratio 0.06 A/F Ratio 0.15 A/F Ratio 0.29 A/F Ratio

it is pretty good but expensive. It would only be good if alot of tunning is needed.
I have another question though, if the stock sensor is not very accurate then how accurate will engine managment systems, such as Hondata and the new AEM system, be if the O2 sensor is not as accurate. Do they come with O2 sensors? If they are good enough for them then the ohm meter should be good enough to make adjustments.





[Modified by 98401R, 8:50 AM 2/10/2002]

 

Yes there are some O2 kits out there that are very accurate but they are also expensive. Some standalones can be equipped with a wideband O2, such as Speedpro, but I think that is a little over kill for a street car. But when you have a standalone, you still tune it on the dyno with a wideband O2 to set all of the parameters correctly. The reason why standalones are better then the band aids(afc's, FMU, etc.) is that you are actually changing the parameters instead of fooling the ecu like band aids do. Also, when you have a lot of band aids, there is a greater chance of something failing then if you just had a standalone.

 

would you consider the APEX V-AFC a band aid?

 

Yes, but depending on how far one goes into engine modifications, it may prove enough to go with a V-AFC instead of a standalone.

 

Yes. It modifies signals to the ecu.(not sure which signals though)

 

then let's come back to the initial point of this story. Is it good enough to tune with an Ohmmeter and the V-AFC? This is mostly for street use and not track. It makes perfect sense to do it right (Dyno) for track use.
Also does the AEM management system or Hondata come with their own O2 sensors? because if they don't you may still be programming the ECU directly but may not be making the right adjustments if the O2 sensor is inferior..

 

Well I guess it depends on what you plan on doing. If you are staying NA and don't plan any major mods, an afc is fine. But I would still tune with a wideband O2. But in my case, I have a turbo and trying to tune off of the stock O2 would most likely result in a blown engine. About the standalones, I'm pretty sure that both the Hondata and AEM do not come with their own O2 sensors. If I wasn't going to tune with a wideband then I wouldn't get a standalone.

 

I am mostly interested in making adjustments, so far all I've got is CAI, VAFC, adjustable cam gears and a Denso plugs, last time I checked the plugs showed signs of carbon deposits which according to the Chiltons manual indicates a rich mixture or weak ignition. If it is not the AF ratio then it may be that I need to upgrade the ignition system(applying the elimination process), I would like to tune but need something to read the O2 sensor, I know, I know, best way is Dyno. I am just looking at my options and learning more about it as I go along, but of course if all else fails I will Dyno. I like to do the work, no better way to learn.

 

Yes I agree...doing things yourself is the best way to learn. You are most likely running rich because the stock ignition is very good unless it is defective. People with 300 whp turbos run stock ignitions with no problems. Our cars run rich from the factory and trimming the fuel with an afc should help out.