RB26 Abnormally high EGT on one cylinder. Individual EGT setup. Map and Log attached. Haltech 2500

Hi guys,

I just did a pull of my RB26 and upon review my data, the EGT on my 4th cylinder is HIGH, approaching 1000C, while other cylinders are about 780C, even though my AFR is 11.3

In normal driving the EGT is very normal and even across all cylinder.

Spec: Forged RB26, EFR8374, heavy built head, D585 coil with 3.6ms dwell, Haltech Elite 2500 with the TCA8 module

After discussing with my tuner, it is very possible the readout is just a glitch. The VE value is accurate as my Haltech did not do much fuel trimming.

However, what if it is not a glitch?

Attached log and map for review

5:23 second gear pull

6:08 third gear pull

6:33 third gear pull #2

The few hypothesis I have so far:

1) Clogged #4 injector. but seems unlikely?

2) Excessive dwell on the D585 coil causing it to discharge early causing knock, causing high EGT? Even though my knock sensor not picking up anything

3) Really its a dodgy EGT probe?

Either way I feel very uncomfortable to do another pull.

Another thing to add is I use cheap ebay Type K thermocouple, not the one from Haltech. The TCA8 is from Haltech, however.

OK, the AFR is the average, so won't be particularely useful for a single cylinder.

Have you pulled the spark plugs yet, they can be quite informative?

I'd suggest swapping the injector with a different cylinder, and the EGT with a different cylinder and seeing it it follows either.

Do you have access to a laser thermometer that can read to 1000c as this would help as a check against the sensors.

k types can fail internally, especially cheaper ones. Check the connections on the sensors too.

As Gord says move the sensor around and check the injectors.

Can you listen to the engine to hear if there is knock that you are not picking up?

First of all, I appreciate you guys methodological input on the situation.

Yes I have pulled all the spark plugs out and they look normal and exactly the same across the board. I use NGK Iridum 7 heat range and plug gap about 25 thou.

I have ordered the washer to re-seal the EGT probes to switch them around.

How do I use laser thermometer to check the probes? They are sealed inside the exhaust manifold? At the moment I am road tuning the car, that I start the log and do a pull then replay. So no I don't have the ability to hear the knock using special equipment.

Just point the laser thermometer at the header pipes near the EGT probes. If one is 200 deg Hotter, the pipe will also be quite a bit hotter. If the pipes all seem to be about the same temp, but he sensor is reading different -- suspect the sensor is wrong.

You can make a small mobile knock “kit” yourself, a sensor some wire to extend into the cabin, an amplifier and some headphones is all you really need.

This method there is no filtering of the sound you will hear but you can understand then if it’s knock your experiencing.

I tend to use a GM sensor with a small section of wire already attached and then extend this to an 3.5mm audio connector and a small battery amplifier; And some over ear headphones.

I can draw up a little diagram later. This is a crude method but it gets the required results without breaking the bank.