I have a new o2 sensor I installed when I made my downpipe, like an idiot (maybe?) I put the o2 sensor on the inside of the curve coming down out of the turbo, but still faced up some. I'm not sure if because it's on the inside of very gradually 115* bend or so on a 3 inch pipe it will make a difference or not in the accuracy.

Anyways....

When I boost I'm getting .94v at wot, but my EGT's arn't going above 1350. I have the probe installed underneith, 1 inch away from exhaust port 4.

Can I still go leaner, or do I have a low EGT reading because my probe is underneith?

I have not heard the dreaded sound of detonation yet.

Thanks for your help.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

I dunno if this applies in your case but "Of course, If you run lean, yoru EGT's go up..........then as some people know (usu. expierenced tuners) the egt's will begin to FALL again. put 2 and 2 together. Increwasing the air/fuel ratio WILL make mre heat. If the heat isn't comming otu of the exhaust, where is it going??? All of that heat is being thermally transfered into your pistons, head, head gasket, and spark plugs via detonation."

Just a thought...

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I thought .94v was a good number for us, hell, mines usually betwen .88 and .9 and no signs of detonation, i'm hoping its just that my o2 sensor is f'd up, that and the fuel filter are gonna get changed and if that doesnt help then its time for an sfmu if i don't blow it up by then

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Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

Firstly, why are you trusting your motor to a NB02 sensor?

Secondly, why are you trusting your motor to an EGT gauge?

WB02 sensors became cheap for a reason...

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Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

I forgot to mention that above air temp is with an ambient temp of 85*F outside.

I held full boost on the highway for 8 seconds and it started to approach 1400, where it looked like is may have stayed there, but I was going to fast to find out.

How long are you guys at full boost before you take a reading from your EGT?

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

If you don't have timing control, but have WBO2, EGT is useless. If your AFR is spot-on, all that can be indicated by an EGT gauge is a timing problem. If you have a timing problem, what can you really do about it?

I don't like tuning AFR based on EGR readings, as opposite conditions have the same indication (lean is hot, rich is hot). In a perfect world, using EGT and WB02 would give you a perfect picture of what your motor is doing.

Since your only available method of setting timing is playing with the sAFC, and compensating with your FPR, I wouldn't really bother with the EGT for now.


Actually, I really believe that EGR is useless, now that I think about it.

EDIT: I'm sorry, I keep pulling this off-topic. I'll refrain from replying, as I don't really have much to add to this discussion topic. Again, my apologies.

Whoops, that was a dumb typo. Shit happens, though.

As for EGT, it is useless. Lean is hot, and rich is cool. Unless you’re WAY rich, then the mix is still burning on it’s way through the manifold. Then it reads hot.

But lean will always read hot, too, right? No. If you are WAY lean, you aren’t putting enough fuel into the mix to create an excess of heat, so leaning it out will cool it down further.

Alright, how about this… Let’s say that you are knocking from being lean, so the EGT gauge shows “Fucking hot.” The PCM pulls back a bit of timing, which cools the exhaust gas a bit, so now, the gauge reads “less than fucking hot.”

FURTHERMORE, the effect that the air:fuel ratio has on exhaust gas temperature is MINOR when compared to that of timing. This means that a hot mixture is probably the result of pulled timing, which could be any kind of input through the knock sensor (even mechanical knock).

If you don’t have knock retard for any reason, and can adjust timing independently, then EGT is a decent way to tune, and it may be possible that a NB 02 sensor would be adequate to reference it to. Otherwise, I would put no faith in it.

I wasn’t going to reply again, but some wiseass decided to point out a simple (although contextually major) typo, and disagree with what I feel is right.

Good stuff, thanks.

Can't I monitor timing then (I have a pocketlogger) and if the timing ISN'T being pulled AND my egt's are low, can I lean it out more? I definately don't trust my narrow o2 even though it has just been replaced (I haven't been able to make it read over .96 even if I have black smoke come out of the pipe). How long do you guys boost before you are taking a EGT reading? If I go out on the highway, and ride low third gear to redline, my highest EGT would be the right way to read it correct?

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

You might want to read a little bit higher than the guage does. Depending on where it is, it can be a little bit behind on warming up.

I think that you might be able to lean it out a bit, but don't quote me on that.

I would still start planning on getting a wideband at some point. The Techedge unit is nice, functional, and not all that expensive.

An EGT gauge is by no means "useless" if you dont have any means of timing control...its more accurate than the dreaded blinky light gauges, and even the digital A/F gauges...granted, you have to "know" how to use it properly....but we are all expert tuners, right??


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I'll grant that it isn't useless, but without knowing where your timing is, you are missing half of the equation. EGT is more affected by timing than AFR.

Sure, it's still better than the blinky light with it's non-linear nature, but an EGT gauge goes (from lean to right) cold, hot, cold, hot. How do you know which cold and which hot you are at? Since not everybody here is an expert tuner, many people will miss the fact that they are after-burning because of a rich mix, or running out of combustable fuel on a lean mix, and adjust their AFR in the wrong direction.