EGT temps?

[MattS]

So I got a Mychron 3 XG log for my 1948 BSA 500 single. I figure I can get some good tuning info from the A/F & EGT readings. But I have no idea where the EGT's should be. It has 9.5:1 comp and I'll be using the ERC 110K.
It has an 85mm bore & an 88mm stroke & redlines around 6500 rpm or so.

Anyone have any info on where it should run? Max not to exceed?
I've heard 1300 to 1500 degrees.... does that sound right?



Thanks in advance,


Matt

[landracing]

I guess the ones that would know would be the ones that have holes in the pistons...

Ask JoeA...

Jon

[Speed Limit 1000]

With our NA motors we like to keep them under 1300, but have seen 1800 without a hole in a piston  

[Dynoroom]

Hey Matt,
Kinda depends (but not as much as some would say) where the probe is in the exhaust. Most of the time it is 2-5 inches away from the exhaust valve. If your running a "K" type thermocouple and a non-supercharged engine on gasoline 1350 degrees is a safe number to use (I start to look at things after that). Keep in mind that a closed end thermocouple takes longer to react than the open tip type.
Good Luck and have a good time.

[MattS]

Hey Matt,
Kinda depends (but not as much as some would say) where the probe is in the exhaust. Most of the time it is 2-5 inches away from the exhaust valve. If your running a "K" type thermocouple and a non-supercharged engine on gasoline 1350 degrees is a safe number to use (I start to look at things after that). Keep in mind that a closed end thermocouple takes longer to react than the open tip type.
Good Luck and have a good time.

I guess I should have said NA, even though for B'ville I should be turboed. I mounted the sensor per the instructions, which said 5.9" from the edge of the exhaust port in the head. It is a "K" type thermocouple.

I have a hard time finding pistons for this engine, so I'm trying to make this one last till I have to use the 12.5:1 one I have.

Thanks,

Matt

[Harold Bettes]

Gentlemen,

The specific use of EGTs is a very shaky business as a singular tune-up tool. UNLESS one knows where the A/F ratio peaks the temps (typically at stoichiometric or chemically correct for the fuel used), any target numbers are pretty spooky. 

As an example, if the temperature where you are reading this comment is 70-75⁰F - Is that rich or lean? It is an indication of temperature. When isolating EGTs and evaluating the bell shaped curve of A/F ratios vs Temperature, one can be referencing the same temperature at two (or more) different exhaust gas temps.

Also as the thermocouples are fairly slow to react, you are looking at history more often than not.

Lots more could be said here, but sufficient to state that it is spooky business without the correct supporting inputs of other sensors.

Yours for less detonation and more fun,
Regards to All,
HB2

[dwarner]

In the movie World's Fastest Indian old Bert gives step by step instructions on how to obtain hard to get pistons.

DW

[1212FBGS]

i'm pretty sure you'll only hit 1500 once! best thing is to put her on the dyno with a sniffer up the tail. when ya get af around 13 or your best hp check your egt, remember it, then try to tune around your number. like others have said egt's are history and not a great tuning tool.
kent

[landracing]

Nahh Good for finding the dead hole fast with data acq...

Jon

[RidgeRunner]

     One advantage to running a single - no doubt which one and never have to replace more than one at a time.  Been there, even tried welding a plug in the hole for a second go round.  Didn't work.

     Hope you get in some good rides and have fun, partial to the Beeza bangers myself.

                                                                                        Ed Purinton

[MattS]

Yep, I know there's no number to just tune to, but I just want to know what to avoid. Since E.M. is so short, I might be able to get away with a higher EGT & not do any damage. Also, since my bike has a manual spark advance, I can retard the spark if the EGT starts going too high... if the sensor reacts fast enough, if I react fast enough. But that's probably a pipe dream.

It gives me something to play with.


Thanks for all the info,

Matt

[Speed Limit 1000]

EGT is ok if you start out on the rich end and watch not to go above a temp. Not all of us can go to the dyno when we want to, so we use the large white dyno to tune

[promachine]

Your egt`s are more affected by your ignition timing than by your fuel mix.
Pay more attention to your a/f and where you mount your sencers.
If your engine is blown, and your egt`s are over 1500, put some more timing
in it and you will be amazed. Use all of your information to tune, not just one
thing. Plenty of people will argue with this, so take it for what its worth.

[Bob Drury]

One point not mentioned is that if you have egt's on all cylinders, they will give you a pretty good idea of which, if any, need re-jetting which helps a lot especially if you are running alcohol and trying to read the plugs...........

[joea]

jon your killing me.........

holes is my pistons were a function of cylinder
combustion characteristics..........you can hole em
at 1100 or 1800.......if your real good.........