hey guys... so i finally installed my a/f ratio and boost gauge. both by autometer. i installed the boost gauge by running the vacuum line out by the steering hub, to the manifold. and the a/f ratio, i ran the o2 sensor line to the ecu. on the ecu, i found the wire from the o2 sensor to the ecu. it's the middle clip, black wire, second fromt the right. ok here's my questions: how come the a/f ration meter jump from lean to rich and back and forth all day long? the only time it doesn't move is when i'm WOT, or when the car is idling. is this normal? it seems like i'm running really rich, i'm running a m2 stage 3 ecu.... can that be the problem?

mods : intake, cb, dp, bov, m2 stage3 ecu.

 

Yes, it's entirely normal. Your A/F ratios will vary from high teens to below 10:1 depending on rpm, boost, and throttle.

I will now get on my soapbox about using A/F gauges with the stock O2 sensor -- THEY ARE WORTHLESS. The only time an A/F gauge is going to tell you much of anything worth looking at is when it is connected to a wideband O2 sensor. I guess you can verify if your O2 sensor is working but that's about it.....

 

thanks...

 

I believe the instructions that come with the Autometer gauge state that the unit is really only "accurate" when you are at WOT or on the pedal at least pretty hard.

 

from what i've heard about a/f ratio guages, they only take readings once a second, and in between they drop back down, so they'll go up, then down. The peak of the up stroke is the actual reading. Hope that helps.

 

thanks.... ok so i guess i'm running really rich... the lights are right in the beginning and sometimes at the middle of the "rich" part... is that normal??? how can i lean it out if i have to???

 

turbocharged rotaries run much richer than N/A piston engines, most A/F gauges don't even read rich enough.

Also, narrowband O2 sensors are NOT accurate at WOT, far from it. They are only accurate under idle and cruise conditions. This is precisely why the stock ecu reverts to a pre-programmed map under boost and WOT situations. An A/F gauge using a narrowband O2 sensor will NOT give an accurate result under WOT and boost -- exactly where you need it to.

 

the cycling is from closed loop operation of the ECU. the ECU constantly reads info from the O2 sensor and adjusts fuel accordingly. this is to improve gas mileage and reduce emissions.

once you go to WOT, the ECU reverts to open loop operation where it takes various readings (TPS, boost, air intake temp, etc.) and follows "maps" for determining the amount of fuel to inject. at WOT, it doesn't even pay attention to the O2 sensor anymore because it is not accurate. readings from that can lag by as much as a second.

plus O2 sensors are reasonably accurate around 14.7:1 A/F ratios, but the further away from that point, the less accurate that they become. which for rotary's is another reason not to use it under WOT.

 

Ditto

 

wow... thanks. so in other words.. i'm ok???

 

im not sure about your A/F ratio but your gauge is working properly (well as properly as it can possibly be).

 

Is it a bad thing if the car is runnig too rich?
I have intake, dp, mp, cb on my FD and from my autometer A/F gauge the car is running very rich. Would that affect the optimal performance of the car?

 

your autometer gauge is not telling you anything!!! trust me dude, it can't. the stock O2 sensor was never made to tune! there is a reason why real wideband O2 meters cost 400 bucks alone!

as to your question, yes it is a bad thing since running too rich does increase your chance of preignition or detonation. its not as bad as running too lean but its still not that good. it also causes carbon build up although you can just rev to 8k often to get rid of it. (reving to 8k is also fun as hell and does not hurt your engine at all as long as your a/f ratio is between 10:1-11.5:1. I suggest you do it as often as you can )

 

are you sure about that? i agree that running rich is robbing hp and leads to excess carbon build up, but i've never heard of detonation from simply running too rich. (as long as everything else is in check)

 

Yep, I'm sure about that. at least thats the concensus

 

You want to be running quite rich under boost. 12:1 or richer seems about right, as mentioned previously. Running this rich is what you want, and your A/F meter will read quite rich under these conditions.

Running a lot richer than that has some downsides. Loss of power, bad mileage , and also that the extra fuel will wash the oil off the combustion chamber walls increasing wear.

Narrow band A/F meters should not be used for tuning. They are not accurate enough. It is sometimes useful to see the cycling so you know you are in fuel efficient closed loop mode on the highway.

-Max

 

I have a delfi a/f gauge and it jumps down to the 17 mark and then back to the middle, so is my car running lean because you said that it talks readings in incraments, also I have an aftermarket o2 censor.

 

Ok, so you spent Retail $124.99, sale Price $115.00 for a defi Air/Fuel Gauges, guess what, you just wasted 115-125 bucks! Don't feel bad, I wasted 40 bucks on a autometer A/F ratio gauge but I do enjoy the lightshow it puts on In the end, it dont matter if you have the defi or greddy or autometer aftermarket A/F ratio gauge, they will not tell you anything (their all crap!!!)! It don't matter if you have an aftermarket O2 sensor either, get on a wideband asap!

 

Unless you've got yourself an aftermarket ECU or fuel controller, you're definately not running rich. With intake and full exhaust, ESPECIALLY with a midpipe you're probly running lean as hell. I'd be careful with your motor, it probly won't last long with that setup.

Cavell

 

So you guys mean to tell me that no one has a air/fuel ratio gauge that reads specifically for an Fd? I know our cars run rich but, is there not a gauge out there that will read our ratios in a normal way(instead of it always showing rich)? I hope this question isn't confusing.

 

Come on dude, are you reading this post at all? What dont you get about all aftermarket A/F ratio gauges are worthless and that only a wideband O2 sensor can tell you anything usefull??????????????????????????????????

 

Sorry I guess I should have read a little more closely. Hey I understand your point of view about the crappy a/f ratio gauges, however I guess I'm clueless when it comes to this wideband stuff. Does the wideband sensor come with its own special gauge or does it make the aftermarket ones read more accuratly? Just trying to understand thats all!

 

I keep reading statements like this, and I have to jump in. The standard AFR gauges people use with the narrowband sensors are NOT useless...they're just not useful for tuning. For example, I'm having a problem with my car not entering closed-loop mode...very easy to diagnose with an AFR gauge, not so easy without it. Also, while they don't tell you what your ratio is, they are fairly consistent. If I get 2 green LEDs under a particular condition, and then one day I'm not...that's something to be alarmed about.

jds

 

I don't think anyone directly commented on this statement, but its not true. At least, its not true of any AFR gauge I've ever seen. Most of them, certainly the LED bar graph types, are analog circuits. The 02 sensor is a constant voltage that varies with the amount of O2 in the exhaust, and the bar graph display just shows the current output of that sensor. I suppose you could design a circuit that had an A/D and a microprocessor that sampled it once per second...but that would be a pretty worthless design.

jds