Separate post as this applies to what tool you trust more when tuning your DIY PROM.


I question how much one should rely on the output of a WB O2 since I've seen too many cases that don't follow the logic. One engine will make best power at 11:1 and another at 14:1. The EGT's will be very close between the two at best power.

Vizard has tried individual O2's on each header tube, AND EGT's on each header tube. I haven't heard this straight from the man but I think he tends to go with the EGT's for WOT tuning and the O2's for part throttle.
Any thoughts on this?

 

Only use EGTs for timing. Wideband o2 is for fuel, it's that simple.
Watch the EGTs closely, if your engine is too retarded then the EGTs will tell you in less than a second. They'll sky rocket pretty high, this is because more of the fuels energy is being released into the exhaust and less into the engines colant system.
The wideband should always be made richer than 14:1 for premium fuel if going for max power. Run closer to 15.5 for gas milage .

 

As a single indicator?.
Not at all.
It's a tuning tool, IMO, it makes getting a repeatable reading of AFR with any GIVEN tune. 830 mv with a NB can be 11.5 or 12.5, with a WB 2.5v (for a given example) is going to be 14.7.

EGT is about how close you are to the thermal limits of the enigne.
You can play with timing and AFR to move it around some.

You can move the timing around and effect the indicated AFR.

Measuring performance, and plug reading are the best indicators of actual AFR, IMO. And even then you can wind up with the wrong combo, and miss the tune. A tad too hot on plug with too much timing and fuel and you can get the perfect beige and knock the corners off the pistons.

He is getting harder and hard to contact.

 

I'm glad that you mentioned this type of scenario. Stuff like this will keep you on your toes!

Now for my question on it, how would you know that you were off, other than having a failure? Is this maybe just a case of how you can go right past where things need to be?

 

I would think that EGT readings would vary with a/f ratio. example, when using aditional fuel to cool the chamber. cooler chamber= lower EGT. I might be totally off, I've never used an EGT sensor...