Egt's reading wrong numbers

[kingcat162]

Has anyone ever had egt probes reading wrong numbers? I thought they were super accurate and never really fail - ya wrong - they read wrong numbers and fail - I thought I had carb issues turns out I had egt issues - bye bye top end - so cheddared right now I wanna pull my hair out

 

[maxwell]

Where are the probes placed

 

[1100]

Egt’s are great. But the key to them is devoloping a baseline, through plug chops and reading your spark plugs. Depending on mounting probe location, one guys sled could be safe to run to 1230 max on a pull, the next guy might of mounted his further away and his set up might be safe up to 1350, by doing a pull and immediately killing your sled after the spark plugs will tell you what is safe for your machine.
This was a much easier task in the days of zx, and the old mighty RT 1000 days. Started running a air fuel gauge on the nytro turbo, and have continued on my xm. There’s pros and cons to each unit.

 

[kingcat162]

Where are the probes placed

Probes are as close the jug as possible - they were reading 600f when actual temp was burn down temps fml

 

[Chrisco]

Well technically you can use any measurement you want, you would just need to do some baseline runs to figure out at what temp it needs to run in that particular spot, at 8-12 inches it would be alot colder than the measurement i gave, i know from the 6" measuremnet with CS pipes it needs to run around 1200* at full temp, at 8"s it may be down to 1050 with the same jetting, theres no right and wrong really, like i said just do some baselines and figure out what it needs, as long as both are exactly the same dimension it will work.

I believe 5 to 6 inches from the piston was the norm.

 

[kingcat162]

Well technically you can use any measurement you want, you would just need to do some baseline runs to figure out at what temp it needs to run in that particular spot, at 8-12 inches it would be alot colder than the measurement i gave, i know from the 6" measuremnet with CS pipes it needs to run around 1200* at full temp, at 8"s it may be down to 1050 with the same jetting, theres no right and wrong really, like i said just do some baselines and figure out what it needs, as long as both are exactly the same dimension it will work.

I believe 5 to 6 inches from the piston was the norm.

Mine are 3" from the piston maybe that's the problem and the fact that the probes are 10yrs old or more - gonna try to get my top end unstuck today and assess the damage I wanna put my head thru the wall

 

[Bnorth]

You're hard on equipment bud

 

[kingcat162]

You're hard on equipment bud

It's an epidemic for me lol it's really awesome how the old cat has zero shut down fail safe - had my 16 yr old son on it and he didn't watch the thermometer gauge hit 122 degrees celcius

 

[slededjr]

Typical mounting location is 4”-6” from piston skirt. Single pipe is typically mounted at 4” and twin/triple pipes at 6”. Depending on type of engine, mods etc will determine egt numbers. EGT’s are a great aid in tuning but should only be used as that and not the sole tuning object. Piston wash, plug colour all good ways to aid in tuning. EGT’s can also read high if too rich in mixture not just lean as the excess fuel can actually burn inside the pipe causing a false reading. I typically tune/setup from piston wash and compare that to the RPM and egt readings. I like to be a little on the rich (safe)side and my numbers run around 1120-1170 mid range, 1100-1160 WOT. Pain in the ass constantly playing/tuning but once dialed in easy to make a small tweak here and there. Once dialed in use the egt’s as a fail safe. If you know that cruising in mid range your temps are usually 1100 and all of sudden you’re reading higher or lower, you have a problem.

 

[kingcat162]

Typical mounting location is 4”-6” from piston skirt. Single pipe is typically mounted at 4” and twin/triple pipes at 6”. Depending on type of engine, mods etc will determine egt numbers. EGT’s are a great aid in tuning but should only be used as that and not the sole tuning object. Piston wash, plug colour all good ways to aid in tuning. EGT’s can also read high if too rich in mixture not just lean as the excess fuel can actually burn inside the pipe causing a false reading. I typically tune/setup from piston wash and compare that to the RPM and egt readings. I like to be a little on the rich (safe)side and my numbers run around 1120-1170 mid range, 1100-1160 WOT. Pain in the ass constantly playing/tuning but once dialed in easy to make a small tweak here and there. Once dialed in use the egt’s as a fail safe. If you know that cruising in mid range your temps are usually 1100 and all of sudden you’re reading higher or lower, you have a problem.

Gonna order new probes and fix the one jug and piston that are nuked and mount new probes further away - I know where I should be running for Jets - for some reason I was cooked between the ears and was believing my egt's like some kind of Scientologist follower - man I'm choked at myself for being such an idiot

 

[slededjr]

Gonna order new probes and fix the one jug and piston that are nuked and mount new probes further away - I know where I should be running for Jets - for some reason I was cooked between the ears and was believing my egt's like some kind of Scientologist follower - man I'm choked at myself for being such an idiot

Pretty sure lots of have made similar mistake or worse lol.
When I first started getting into mod engines in the late 90’s I sure as hell made enough lol.

 

[Modman]

Depending on fuel and motor parameters, your EGTs may or may not show a lean condition before it gets too hot. Too much fuel in the pipe will also show an artificial high (over fueled) on your EGTs. Here are some old threads regarding this. F-Bombs website doesn't work anymore unfortunately but you should be able to glean most of how to set a baseline from these threads.

www.snowandmud.com/archive/index.php/t-83444.html
https://www.snowandmud.com/archive/index.php/t-13162.html

Anyway, without knowing a bunch more about the sled I can't say much more. Depending on the bore size, stroke etc, bigger pistons will not want to run as hot since they cannot dissipate heat to the cylinder as fast, therefore needing more fuel to keep the piston dome cooled. Your stroke length will determine how much time the piston has to cool between cycles etc etc. General rules is that 1250 is good for most 800 bores at WFO, don't push it past 1300 for any length of time or you are asking for trouble (again this is a very generic rule). I had 1 race gas sled that ran high 1300s / 1400 and ran the best up there, but as a conservative measure I ran it right around the 1300. Never burnt it down.

Hope that helps.