Ex. manifold or y pipe.....or other?

Which is more accurate?

 

Best place to put it would be where both banks come together at the Ypipe, that way you can't be running super lean in one bank and just fine in the other and possibly not know it.

 

That's where mine was tapped before - only problem is you're reading is off because the gases have lost heat by the time they get there -i'm currently tapped in the front bank of the y pipe - it tends to run leaner... so i feel it has more use there - it's about 2 inches below the o2 sensor.

 

Closest to the exhaust port is best... but I put mine at the collector of one bank:

 

Best is to have one EGT probe per cylinder in the runners, next best is one EGT per bank in the collector so you can tell which bank is lean, after that is where the down pipes come together. After that you say EGTs is for sissies and don't bother.

 

Nigel......I dont follow

1 EGT per runner of the exh. manifold?? 6 total?

or

1 probe on both collectors of each manifold?

 

Sure. It really helps with the aircraft cockpit look, too. Of course you need a flight engineer along to keep track of all the temperatures.

This begs a question, though. How do you correct just one cylinder or even one bank that is running lean without affecting the others?

Okay, I know the answer is most people don't. Typically you just tune based on the lean cylinder or bank. But do some piggybacks or standalones allow for tweaking of individual injector pulse widths, so that you could tune each cylinder individually?

 

Wouldn't a single cylinder running significantly hotter than the others be indicative of a problem in that cylinder? Something which you would want to rectify by fixing it, rather than just adding more fuel to lower the cylinder temperature and continuing on as if everything were ok? It would be neat to be able to tweak individual cylinders though.

 

Cylinders usually run at very slightly different afrs due to uneven air flow distribution through the intake manifold. Cylinders that get more air are going to run leaner if the injection pulse widths are the same for every cylinder. Most factory intake manifolds are engineered pretty well, so you don't see much variation in flow from one cylinder to the next.

Another cause of cylinder temperature variation is how the coolant path is designed. The cylinders towards the end of the coolant path are going to be cooled with warmer coolant and therefore less efficiently than the ones at the beginning. In this case, the temperature variation is not due to afr, but making the hotter cylinders run a bit richer can help reduce temperature and forestall detonation problems.

 

So, unless you're running an extremely powerful setup, 1 is fine huh? Does the MEVI make the flow of "uneven air flow distribution" BETTER or has it not been THAT serious of an issue?

 

Not enough to be a problem.

 

So for a one probe setup, you put it where the down pipes come together?

 

If your definition of best is the easiest... yes.
As for accuracy, it was explained in post #5 above.

 

correct. if you have only one probe and only take readings from one bank of cylinders, the readings will be accurate to run the motor, but in the event that one of the cylinders on the opposing bank starts to take a sh*t on you, you wont know until its basically too late. if you have one probe you have to take the reading somewhere where all the exhaust from all the cylinders is flowing - not half or any other fraction of them.