plug readings vs EGT readings

Have you experienced that the data logger says a different cylinder is leaner then what your spark plugs are saying?

Are my thermocouples too slow?

 

I agree. You can get totally lost if you just follow the computer.

 

Well what about using the number it's producing. Like if it goes over 1150 degrees. But the plug shows cad still.

 

I second this, we got our first data logger in 2007 and I had my self so lost, I actually took it off.
If EGTs aren't a good thing to data log can we trust the O2 sensor for blown alky?

If so, which brand are you guys having good luck with?

 

I've been doing the spark plug reading thing religiously for about 15 years, but I figured I better not let technology pass me up. Now what you're telling me is that the EGT electronics aren't accurate?

Have you ever spoke with Superflow or Racepak about how or why this is, no doubt they have many customers counting on those readings to be accurate?

 

In our case with a TA/FC you could tell how rich or lean you were one other way...by how purple the header tips were after a run and how far up the bend it would go. After a run you would scotch brite the headers to clean them up and then recheck after the next run. A little unconventional for sure but I know some pretty good teams that take a look at stuff like that.

For those that don't know EGT's are an indicator of issues for the most part. If you see something on the EGT's you don't like immediately after a run and are trying to turn the car around in 60 minutes or less the information they provide will send you straight to the spark plug and leak down tester if something on a particular cylinder has numbers that are out of whack. Besides pulling up oil pressure on the run on the screen I immediately go to EGT's to see if any of them headed north on the screen from about 1,000 feet to finish line. If any of them did, then you know it likely have a cylinder that went into detonation or some other problem and you can to tell the guys to jump right on it to get it fixed. If you lost a pushrod, spark plug, etc., it's also a good way to pinpoint when it happened on the run because the EGT for that cylinder drops off immediately.

 

Type K thermocouples have an accuracy of about +/-2 degrees celsius.

Reading plugs gives you feedback on combustion temps, in the cylinder. EGT probes give you feedback on exhaust gas temp - not the same thing.

Response time of an EGT probe will vary with the thickness of the probe as well.

I agree they're a good tool if understood and used for what information they can provide, but I wouldn't recommend tuning entirely off of them - unless you're racing a 2 stroke maybe... lol

 

I would still use the plugs. I tuned my 2 stroke golf cart by making "hits" in the driveway and pulling the plug

So far, it looks like I can trust my egts on my blown alky bbc. 1300 was 2-3 threads. After hurting some stuff, I richened it up to 1000. At 11-1150, it just started to frost the one cylinder that's a touch hot. Gives me confidence that I can go rounds without pulling every plug every pass as long as the egts look reasonable.

 

What data logger and what thermocouples are you using?

 

Junk-ass altronics red alert unit I bought off the classifieds. Not complaining about the purchase, just saying it's far from user friendly. I had to ditch the junction box it came with. I do still get some noise on one channel, but as long as I ignore that everything else seems fine.