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A/F gauges reads the stock O2 sensor by splicing into the wiring and not very useful for tuning.
EGT's, or,exhaust gas temperature, tells you the temperature of the exhaust coming out the cylinder and requires drilling and tapping for a temp. probe, preferably in the manifold. It can tell you if your lean; When your too lean you get some knock, which leads to retarded ignition timing, which leads to late combustion, which drives up EGT's (makes sense?).
 

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a/f gauges are for those people that like to watch the little green bar go from lean to rich but not really mean anything. If you want a true guage to help you in watching what is happening spend the extra money on a Wide Band O2 setup. That with a EGT, a FPR(in dash not under hood :p) and oil pressure gauge will truely help in tuning. You can go even further with a simple palm setup with obdII cable, SAFC, and what ever more your wallet can take :p

PS EGT is very very easy to install with a cordless drill, drill bit, and a tap/die. Would highly recommend removing exhaust manifold before drilling as those little metal shards have a tendancy to mess turbo's up :p
 

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can we take this discussion a step further and talk about using an EGT in conjunction with a WB02?

It's my thinking that if you first get the fuel where you want it, you can then start increasing the timing until you see EGT's increase, indicating you've exceeded the limit and may be approaching knock. I'm not sure though, perhaps the knock sensor has a higher sensitivity threshold and is a better indicator, rendering the EGT pretty much useless.
 

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pezzonovante said:
It's my thinking that if you first get the fuel where you want it, you can then start increasing the timing until you see EGT's increase, indicating you've exceeded the limit and may be approaching knock. I'm not sure though, perhaps the knock sensor has a higher sensitivity threshold and is a better indicator, rendering the EGT pretty much useless.
EGT's aren't useless, it just easier to look at a gauge than a logger or laptop while your driving. It also kinda depends on the management system used and if it retains a "stock like" knock saftey feature (I hope this makes sense).
If your using a piggyback (S-AFC) or a system that automatically reduces timing when knock is present, it will retard timing to keep things safe. This retarted timing will be so late in the cycle that part of the cumbustion will occur in the manifold and drive up EGT's. That's your inicator somethings wrong.
Increasing ignition timing will not raise EGT's like you think and if your using a stand alone or another system that gives you control over ignition timing, knock in conjuntion with a W/B should be the threshold indicator. This is very fine tuning and I really haven't seen high timing numbers as much as getting the fuel just right.
Does this make sense?
 
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